OF PARACHUTE ON SHUTTLE AND SHUTTLELESS LOOMS · 00 i technical report -- ad _ natick/tr-87/015 comparison of the properties of parachute webbings woven on shuttle and shuttleless

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00

i TECHNICAL REPORT -- _ ADNATICK/TR-87/015

COMPARISON OF THE PROPERTIESOF PARACHUTE WEBBINGS WOVEN

ON SHUTTLE AND SHUTTLELESS LOOMS

BY

MARYANN C. KENNEYNORMAN J. ABBOT1'

'a ALBANY INTERNATIONAL RESEARCH CO.,DEDHAM, MA 02026

FEBRUARY 1987 -TFINAL REPORT FOR THE PERIOD

*MAY 1985 TO FEBRUARY 1987 &::ETMY2 2 1987SECTE o

aD

APPROVED FOR PUBLIC RELEASE;DISTRIBUTION UNLIMITED

Prepared for

UNITED STATES ARMY NATICKRESEARCH, DEVELOPMENT AND ENGINEERING CENTER

NATICK, MASSACHUSETTS 01760-5000

INDIVIDUAL PROTECTION DIRECTORATE8 5 21 598

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4 P NRRMINb OT GANIZATION RLPORI NUMBER( !, MONITORING ORQANiZATION REPORT NUMBER(SJ

NATICK/TR-87/015

t,4 NAME OF PERFORMING ORGANIZATION Tb OFFICE SYMBOL 7a NAME OF MONITORING ORGANIZATION

Albany International (if applicable) U.S. Army Natick Research, Development

RARP rnh rn and Engineering Center6C ADDRESS (OCy. State, and ZIPCOde) 7b ADDRESS(Oy. Stale. and ZIP Code)

1000 Providence Highway Kansas Street

Dedham, MA 02026 Natick, MA 01760-5019

64 NAME OF FUNDINGISPONSORING Sb OFFICE SYMBOL 9 PROCUREMENT INSTRUMENT IDENTIFCATION NUMBERORGANIZATION (If applcabe) Contract No. DAAK60-85-C-O064i

Sc ADDRESS (City. S ate. and ZIPCode) 10 SOURCE OF FUNDING NUMBERSELEMENT NO 'NO NO, ACCESSION NO

728012.12 O&MA 1

11 TITLE (Include Securty ClasubCalton)

Comparison of the Properties of Parachute Webbings Woven on Shuttle and Shuttleless

12 PERSONAL AUTHOR(S)IAR,"INT r Venry anl Nirman 7. thb'tt

13a TYPE OF REPORT 13b TIME COVERED 14 DATE OF REPORT (Year.Monh. Day) IS PAG, COUNTF1naT FROM May '8 TOeb_8a7 107 Februarv 1 T1J4

16 SUPPLEMENTARY NOTATION

I? COSATI CODES IS SUBJECT TERMS (Cotianue on reverse it necessay and identiy by block number)

FIELD T GROUP j SUBGROUP PARACHUTES, -- YLWO - SHUTTLELESS ABRASIONWEBBINGS POLYESTE OM IPCSHUTTLE ABSORPTION ",NSILE STRENGTH %NiAPPING-

AB8STRACT (Coninue an reverse it necesisaq and identity by block number) 1K\This study compares the properties of shuttle and shttleless webbings for three fiber

types: nylon 6,6, nylon 6, and polyester. Tensile strength, elongation and energy absorp-tion were measured on the original webbings and after hex bar abrasion, weathering, highspeed Impact, and edge abrasion.

For all webbing types there were no statistically significant differences in tensile prop-ertles between webbangs produced on shuttle or shuttleless loomza. Among the riber typea,

the polyester webbings showed several significant Ciffercn¢e.s. However, the polyesterconstructions were not optimized for performance, and many of the differen;e5 observedcould have been significantly affected by the construction. .Uj

Z DISTRIBUTION AVAILABILITY OF ABSTRACT 1l2 ABSTRACT SECURITY CLASSIFICATION1: UNI-ARSSIFIEORILIMITED 0 SAME AS RPT C10tlr UBRB

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All other edition% are obsotlte Unc lass if i ed

SUMMARY

This study compares the properties of webbings produced on shuttle andshuttleless looms. The narrow fabric industry is currently undergoing achange to shuttleless looms. This raises concerns for webbing supply andcost under the existing specification which requires that critical (lifesupport) applications use only nylon 6,6 webbings produced on a shuttleloom. This study compares the properties of six webbing types (Types VI,VIII, X, XIII, XIX, and XXII), in shuttle and shuttleless constructions,both uncoated and resin coated, for three fiber types: nylon 6,6, nylon 6,and polyester. Various physical properties were examined. Tensilestrength, elongation and energy absorption were measured on the originalwebbings and then after various test conditions: hex bar abrasion, weather-ing, high speed impact, and edge abrasion. High speed impact and edge abra-sion were tested by methods devised for this project.

For all webbing types, there were no statistically significant differ-ences in tensile properties between webbings produced on shuttle or shuttle-less looms. In particular, resistance to high speed impact and edge abra-sion were equivalent for both weaving methods. In addition, no differencesin the amount of edge abrasion occurring on the catch-cord and non-catch-cord edge of the shuttleless webbings were observed.

Among the fiber types, the polyester webbings showed several signifi-cant differences. However, these constructions were formed by straightsubstitution of 1000 denier polyester for 840 denier nylon, and not trulyoptimized for performance. Many of the differences observed could not beattributed directly to an inherent property of the polyester fiber, butcould h~ve been significantly affected by the construction. The most not-able differences were: original elongation of most polyester webbings wereabout 75 to 85% of the equivalent nylon 6,6 shuttle webbings. This gaveenergy values in the range of 65 to 85% of the nylon 6,6 shuttle webbingsSeveral individual coated polyester constructions showed comparatively lowtensile strength values after accelerated weathering (<85%). Polyesterwebbings showed slightly Increased napping tendency during hex bar abra-sion, and in the uncoated state showed relatively large strength reductionscompared to nylon 6,6 and nylon 6. After Impact cycling, polyester web-bings show considerable loss of tensile elongation and energy absorption.However, in all of these cases, it must be emphasized that constructionaleffects could explain some or all of the differences.

ii3

PREFACE

This report was prepared by Albany International Research Co. underU. S. Government Contract No. DAAK60-85-C-0064. The study was conductedbetween May 1985 and February 1987. Ms. Jeanine Duhamel of the Natick Cen-ter Procurement Office was the Contracting Officer. The Contracting Offi-cer's Representative was Mr. James E. Mello, Project Officer.

The authors wish to express tneir thanks to several Albany Interna-tional Research Co. co-workers who assisted in the study. Ms. Ruth Hallperformed the majority of the laboratory work with the assistance ofMs. Janet Finn and Ms. Elizabeth Page. Mr. Joseph Panto provided assist-ance in running the Weatherometer exposures. Mr. Robert Sebring designedand assembled the impact testing modifications. Also, Mr. James Tierney ofthe Aero-Mechanical Engineering Directorate at the Natick RD&E Centerprovided assistance during the impact testing at Natick.

v

TABLE OF CONTENTS

Page

SUMMARY iiiPREFACE vLIST OF FIGURES ixLIST OF TABLES xi

S.I INTRODUCTION. .. .... ....... ....... ....... I

II MATERIALS. .. .. ...... ....... ...... ...... 3

III TEST METHODS. .. .... ....... ....... ....... 5

1. Thickness .. ..... ....... ...... ....... 52. Weight .. ... ...... ....... ...... .... 53. Lateral Curvature. .. .. ...... ....... ...... 54. Construction. .. ..... ...... ....... .... 55. Tensile Testing. .. .. ...... ....... ....... 56. Accelerated Weathering. .. ..... ...... ....... 67. Hex Bar Abrasion .. .. ....... ...... ....... 88. High Speed Impact. .. .. ....... ...... ...... 89. Edge Abrasion .. .. .... ...... ....... .... 9

IV RESULTS AND DISCUSSION. .. .... ....... ........ 11

1. Thickness. .. .. ...... ....... .......... 112. Weight .. .. ....... ...... ....... .... 113. Lateral Curvature .. .. .... ....... ......... 114. Webbing Construction .. .. ....... ...... .... 115. Original Tensile Testing .. .. ....... ......... 176. Accelerated Weathering .. .. ....... ...... ... 937. Hex Bar Abrasion. .. ..... ...... .......... 978. High Speed Impact. .. .. ...... ....... ..... 106

V CONCLUSIONS AND RECOMMENDATIONS. .. .. ...... ....... 117

REFERENCES. .. .... ....... ....... ....... 119

APPENDI. ....... ...... ....... ......... 121

NTIS CRe,&IDTIC TA3 f

vii vi':o

LIST OF FIGURES

Page

I Spectral Distribution of Sunshine Carbon Are .......... 72 Spectral Distribution of Xenon Arc Lamp .... ......... 73 Edge Abrasion Test Device .... ................ .... 104 Type 6, Class 1, Uncoated, Nylon 6,6 .............. .... 215 Type 6, Class 2, Uncoated, Nylon 6,6 .............. .... 226 Type 6, Class 1, Coated, Nylon 6,6 ............... ... 237 Type 6, Class 2, Coated, Nylon 6,6 ..... ............ 248 Type 6, Class 1, Uncoated, Nylon 6 ............... ... 259 Type 6, Class 2, Uncoated, Nylon 6 ............... ... 2610 Type 6, Class 1, Coated, Nylon 6 ...... ............. 2711 Type 6, Class 2, Coated, Nylon 6 ...... ............. 2812 Type 6, Class 1, Uncoated, Polyester .............. .... 2913 Type 6, Class 2, Uncoated, Polyester .............. .... 3014 Type 6, Class 1, Coated, Polyester ............... .... 3115 Type 6, Class 2, Coated, Polyester ............... ... 3216 Type 8, Class 1, Uncoated, Nylon 6,6 .............. .... 3317 Type 8, Class 2, Uncoated, Nylon 6,6 .... ........... 3418 Type 8, Class 1, Coated, Nylon 6,6 ............... .... 3519 Type 8, Class 2, Coated, Nylon 6,6 ............... .... 3620 Type 8, Class 1, Uncoated, Nylon 6 ............... .... 3721 Type 8, Class 2, Uncoated, Nylon 6 ............... .... 3822 Type 8, Class 1, Coated, Nylon 6 ...... ............. 3923 Type 8, Class 2, Coated, Nylon 6 ................ ..... 4024 Type 8, Class 1, Uncoated, Polyester .............. .... 4125 Type 8, Class 2, Uncoated, Polyester .............. .... 4226 Type 8, Class 1, Coated, Polyester ............... .... 4327 Type 8, Class 2, Coated, Polyester ..... ............. 4428 Type 10, Class 1, Uncoated, Nylon 6,6 ..... .......... 4529 Type 10, Class 2, Uncoated, Nylon 6,6 ..... .......... 4630 Type 10, Class 1, Coated, Nylon 6,6 ............. .... 4731 Type 10, Claps 2, Coated, Nylon 6,6 ............. .... 4832 Type 10, Class 1, Uncoated, Nylon 6 ............. .... 4933 Type 10, Class 2, Uncoated, Nylon 6 .. ........... .... 5034 Type 10, Class 1, Coated, Nylon 6 ... ............ .... 5135 Type 10, Class 2, Coated, Nylon 6 ... ............ .... 5236 Type 10, Class 1, Uncoated, Polyester ..... .......... 5337 Type 10, Class 2, Uncoated, Polyester ..... .......... 5438 Type 10, Class 1, Coated, Polyester .. ........... .... 5539 Type 10, Class 2, Coated, Polyester .. ........... .... 5640 Type 13, Class 1, Uncoated, Nylon 6,6 ............ ... 5741 Type 13, Class 2, Uncoated, Nylon 6,6 ............ ... 5842 Type 13, Class 1, Coated, Nylon 6,6 ............. .... 5943 Type 13, Class 2, Coated, Nylon 6,6 ............. .... 6044 Type 13, Class 1, Uncoated, Nylon 6 .. ........... .... 6145 Type 13, Class 2, Uncoated, Nylon 6 .. ........... .... 6246 Type 13, Class 1, Coated, Nylon 6 ... ............ .... 6347 Type 13, Class 2, Coated, Nylon 6 ..... ............. 6448 Type 13, Class 1, Uncoated, Polyester ..... .......... 6549 Type 13, Class 2. Uncoated, Polyester ..... .......... 66

ix

LIST OF FIGURES (cont)

Page

50 Type 13, Class 1, Coated, Polyester ........... 6751 Type 13, Class 2, Coated, Poly6ster .......... 6852 Type 19, Class 1, Uncoated, Nyl6n 6,6 .......... 6953 Type 19; Class 2, Uncoded, Nyloi 6,6 .......... 70

5 ! Tjp 19, Clg.ss i, Coated; Nylon 6,6 .. .. .. ....... 7155 Type 19, Class 2, Coated; Nylon 6,6 ; ..... .......... 7256 Typ 19; Cliss 1, Oncoatid; Nylon 6 ...... ... .. 7357 Type 19, Class 2, Uncoated, Nylon 6 ... ........ . .. 7458 Type 19, Class 1, Coated, Nylon 6 ... ............ .... 7559 Type 19, Class 2, Coated, Nyloh 6 ... ............ 760 Typb 19; Clias 1, Uncditbd, Polyetr .................. 776i Type 19; Class 2, Uncoated; Plyester ............ .... 7862 Type 19, Class 1, Coated, Polyester ..... ........... 7963 Type 19, Class 2, Coated, Polyester ..... ........... 8064 Type 22, Class 1, Uncoated, Nylon 6,6 ......... .. 8165 Tjpe 22, Class 2, Uncoatdd; Nylon 6,6 2...........866 Type 22, Class 1, Coated; Nyloh 6,6 ..... ........... 8367 Type 22, Class 2, Coated, Nylon 6,6 ..... ........... 8468 Type 22, Class 1, Uncoated, Nylon 6 ..... ........... 8569 Type 22, Class 2, Uncoated, Nylon 6 ..... ........... 86

70 Type 22, Class 1, Coated, Nylon 6 .......... ; ...... 8771 Type 22, Class 2, Coatd Nylon 6 ... ............ .... 8872 Type 22, Class 1, Uncoated, Polyester ............ .... 8973 Type 22, Class 2, Uncoated, Polyester ............ .... 9074 Type 22, Class 1, Coated, Polyester ..... ........... 9175 Type 22, Class 2, Coited, Polyester ..... ........... 9276 Illustration of Napping from Hex Bar Abrasion ... ...... 98

Appendix

A-1 Type 6, Class 1, Coated, Polyester 124A-2 Type 6, Class 2, Coated, Polyester 125A-3 Type 8, Class 2, Coated, Polyester 126A-4 Type 10, Class 2, Coated, Polyester 127A-5 Type 13, Class 1, Coated, Polyester 128A-6 Type 13, Class 2, Coated, Polyester 129A-7 Type 19, Class 2, Coated, Polyester 130A-8 Type 22, Class 2, Coated, Polyester 131A-9 Type 26, Class 1, Coated, Polyester 132

A-10 Type 26, Class 2, Coated, Polyester 133

LIST OF TABLES

Page

1 Physical and Mechanical Requirements - HIL-W-4088J .......... 4

2 Webbing Thickness (in) ...... .. ..................... 12

3 Webbing Weight (oz/yd) ...... .. ..................... 13

4 Lateral Curvature (32nds in) ..... .................. ... 14

5 Construction .......... .......................... 15

6 Yarn Ply ......... ............................ .. 16

7 Original Tensile Strength (ib) ....... ................. 18

8 Original Tensile Elongation (%) ................... 19

9 Original Energy Absorption (ft-lb/ft) ...... ............. 20

10 Tensile Strength (ib) After Accelerated Weathering ........... 94

11 Tensile Elongation () After Accelerated Weathering ... ...... 95

12 Energy Absorption (ft-lb) After Accelerated Weathering ........ 96

13 Example of Construction Factors in Napping .............. .. 100

14 Occurrence of Napping After Hex Bar Abrasion .... .......... 101

15 Tensile Strength (lb) After Hex Bar Abrasion .... .......... 102

16 Tensile Elongation (') After Hex Bar Abrasion .... ......... 103

17 Energy Absorption (ft-lb/ft) After Hex Bar Abrasion ... ...... 104

18 Tensile Strength (lb) After Impact Cycling .............. .. 107

19 Tensile Elongation (%) After Impact Cycling .... .......... 108

20 Energy Absorption (ft-lb/ft) After Impact Cycling ... ....... 109

21 Number of Yarns Abraded after Edge Abrasion ... .......... 111

22 Tensile Strength (lb) After Edge Abrasion ............. .. 112

23 Elongation (%) After Edge Abrasion .................. .. 113

24 Energy Absorption (ft-lb/ft) After Edge Abrasion ........... 114

Appendix

A-1 Additional Polyester Webbing Constructions...... ... .. 122

A-2 Additional Polyester Webbing ConstructionsTensile Strength (lb) After Impact Cycling .............. .. 122

A-3 Additional Polyester Webbing ConstructionsTensile Elongation (%) After Impact Cycling ............ ... 123

A-4 Additional Polyester Webbing ConstructionsEnergy Absorption (ft-lb/ft) After Impact Cycling ... ....... 123

xi

COMPARISON OF THE PROPERTIES OF PARACHUTE WEBBINGS WOVEN ON

SHUTTLE AND SHUTTLELESS LOOMS

I. INTRODUCTION

The narrow fabric industry is undergoing a change from shuttle toshuttleless looms. The specification now existing for nylon 6,6 webbingsin critical (life support) applications requires the webbing to be con-structed on a shuttle type loom. Because of the decreasing availability ofwebbings produced on shuttle looms, this raises concerns for both webbingsupply and increased cost. These problems have been recognized over thelast 10 to 15 years, and several steps have been taken to address them. Onmay 10, 1974, Revision H of MIL-W-4088 allowed the use of shuttleless loomproduced webbings for non-critical use (Class 2), the same revision alsoallowed the substitution on nylon 6 for nylon 6,6 for certain webbings (13.

In 1977 and 1978 a study was conducted by Gardella and Devarakonda [23at NRDEC (then NARADCOM) comparing the properties of selected webbingswoven on both shuttle and shuttleless looms. From this study, they con-cluded that both types performed equally well in all noncritical applica-tions, but suggested further testing should be conducted for critical lifesupport applications. They also concluded at that time that cost savingsof approximately 5% could be expected from using shuttleless webbings.

The study which follows extends this work to several additional web-bing types, and further considers the use of nylon 6 and polyester in web-bing applications. One of the particular concerns is the effect of thenon-interlaced edge on a shuttleless webbing which result, from a doublepick inserted from one side only during weaving. This edge in a shuttle-less construction is typically bound together by knitting in a catch-cordyarn. The behavior of this structure when subjected to edge abrasion dur-ing use in related hardware, and during conditions of Impact loading, isthe point of concern. For example, would the catch-:grd edge show unusualedge abrasion properties, or would it "unzip" with impact? To determine ifthe shuttleless webbings would maintain the same tensile properties afteredge abrasion and high speed impact, two test methods were developed forthis project.

The study which follows compares the tensile propertleA of six webbingtypes, in shuttle and shuttleless constructions, both uncoated and resincoated, for three fiber types: nylon 6,6, nylon 6, and polyester. A num-ber of physical properties such as thickness, weight, and lateral curvatureare examined. Tensile strength, elongation and energy absorption are mea-sured on the original webbings and then after various test conditions or"treatments": hex bar abrasion, weathering, high speed impact, and edgeabrasion.

II. MATERIALS

Webbings made from nylon 6,6, nylon 6 and high strength polyesteryarn, all dyed olive drab shade 7 (OD-7) were obtained by subcontract toNarricot Industries, Inc. (Cheltenham, PA). Six webbing types were fabri-cated: Types VI, VIII, X, XIII, XIX, and XXII according to the specifica-tion requirements of MIL-W-4088J, Table 2. Selected specification require-ments are shown in Table I of this report. Each webbing was fabricated inboth a shuttle and shuttleless version, and in the uncoated and resincoated states. In the following report, all shuttle webbings are denotedClass I and all shuttleless webbings Class 2, for all fiber types. Withinthe specification, however, only nylon 6,6 shuttle loom webbings may beClass 1; nylon 6, regardless of the loom used, is Class 2; and polyester isnot approved for the current spec. In the interests of clarity, however,Class I (shuttle) and Class 2 (shuttleless) have been adopted for this re-port. A total of 72 webbings were produced. Additionally, 100 linearyards of each of the 36 rebin-coated webbings were produced to be deliveredto the Government at completion of the project.

As the specific gravity of polyester is greater than that of nylon, anadjustment in the polyester yarn denier was made so that the polyester web-bings would be expected to conform to thickness and width requirements.This was done by using 1000-denier polyester (Allied polyester Type IWTO)in place of 840-denier nylon, with the aim of substituting directly, plyfor ply, and end for end. In several of the constructions, difficultieswere encountered with this approach, as the specified number of picks perinch could not be inserted. Accordingly, the picks per Inch and/or fillingply and denier were adjusted to come as close as possible to the thicknessrequirements of MIL-W-4088. As development of optimized polyester construc-tions was not an objective of this work, we accepted these webbings as re-ceived for the required comparative testing. Details of the constructionsmay be found In the results and discussion section.

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III. TEST METHODS

1. Thickness

Determined according to FED-STD-191A, Test Method 5030 133.

2. Weight

Determined according to FED-STD-191A, Test Method 5041 [4].

3. Lateral Curvature

Determined according to MIL-W-4088J, para. 4.5.1 [l.

4. Construction

Determi,ad according to FED-STD-191A, Test Method 5050 153.

5. Tensile Testing

A method similar to FED-STD-191A, Test Method 4108 was used [6]. Thejaws, gripping procedures, and test speeds were as described in this method.Our original intention was to use an extensometer to measure elongation,rather than gauge marks, as called for in Method 410S. An extensometerwould provide a direct trace of load vs. elongation which could be analyzedby computer to give rapid and accurate measurements of energy and elonga-tion at break. Several problems were encountered with this testing proce-dure. The extensometers currently available are not rugged enough for usewith these webbings. During the break and subsequent recoil of the web-bing, the extensometer is slammed against the capstan jaws. For lowstrength webbings, this results in the constant need to tighten the exten-someter assembly, or retrieve screws and small parts. For high strengthwebbings, it results in total fracture of the extensometer arm. A numberof methods to retrieve or cushion the extensometer arm were considered withno success. We subsequently developed a procedure to measure elongationuslig a video camera and gauge marks on the specimen, which was as follows:a 5-inch gauge length is marked on the webbing at a small pre-load tension(I to 2% of breaking strength). A lightweight paper ruler graduated in0.1-inch increments is taped at one end to the 0 gauge mark on the webbingusing a narrow piece of tape (approximately 0.1 inch). The other end hangsfree over the 5-inch gauge mark. The video camera is focused on the lower5-inch mark, and follows this as the test proceeds. The upper edge of theruler stays fixed.

As the test runs, the Instron chart is pipped at various load inter-vals, and simultaneously a statement is made into the microphone input ofthe video camera. In this way, when the tape is replayed, the load may beread from the chart at the designated pips, and the elongation, at the cor-responding time, may be read from the movement of the gauge mark relativeto the ruler. The elongation may be estimated to the nearest 0.01 inchfrom the ruler. With sufficient experience, it is possible to read elonga-tion from the video camera display as the test is running, without usingthe tape replay. When necessary, the tape is replayed for the final point

5

tQ accurately determine elongation at break and match it to the correspond-ing load at break from the Instron chart. This method was used on all butthe very initial low strength webbing tests which were done with the exten-someter. A duplicate run using both methods was conducted on one webbingtype to assure the test validity, with good results.

Tensile testing in the original state, as well as after all of thefollowing treatments, was conducted by this procedure. Values are reporteo

at break for tensile strength, elongation, and energy absorption (areaunder the curve). Unless otherwise noted, all results presented are anaverage or 5 values.

6. Accelerated Weathering

The procedure used was changed from FED-STD-191A, Test Method 5804 (73to ASTM Test Method D2565-79 [8), according to contract modification P00001.The reason for the change is to obtain better correspondence with exposureto sunlight, which we assume is the degrqatiye agent which it is desiredto simulate, and, therefore, more reliable comparisons between fibers and

weaves,

The attached spectral distribution curves are copies from literatureprovided by the Atlas Company, manufacturers of the Weatherometer, Method

5804 specifies the use of a "Sunshine Carbon Arc," the spectral distribu-

tion curve for which is compared to normal sunlight in Figure 1. Note

that the carbon are emission contains a large energy peak in the 350-450 nmregion, while the curve for sunlight shows only a gradual rise through thiswavelength range. The DuPont Technical Bulletin X-189 "Light Resistance of

Industrial Fiber Products" [9) says "... the primary cause for light degra-dation of fibers is ultraviolet rayp with wavelengths between 290 and

400 nm." Consequently, they caution that "For comparative testing of

fibers, the spectral distribution in the ultraviolet portion of the radia-tion should be as close as possible to that encountered in actual use of

the fiber products. This is important because the relative rate of degra-dation of fibers varies considerably with spectral distribution, and erro-neous conclusions could be drawn even though the fibers receive the sametotal ultraviolet radiation during the test." They further say "DuPontbelieves that the carbon arc is not an acceptable substitute for outdoor

exposure since no consistent correlation either with outdoor exposure tests

or with actual weathering performances has been observed by DuPont."

For many years there has been a better source than the carbon arc for

simulating sunlight exposure, namely the Xenon arc lamp. Its spectral dis-

tribution is given in Figure 2 and can be seen to match that of sunlight

very closely, except for two small peaks between 450 and 500 nm, a regionwhich does not seriously degrade most textile fibers. It is this Xenonlamp which is specified in ASTH Method D2565-79 for exposure of plastic

specimens.

6

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*747

The specific procedures, within the guidelines of ASTM D2565-79, whichwe used are as follows: Procedure A for comparative evaluation within aseries exposed simultaneously in one instrument. For the best comparison,

we ran identical shuttle and shuttleless constructions side by side. Thetotal specimen length used was 54 in., as required for subsequent tensiletesting by Federal Standard 191A, Test Method 4108. At least 8 in. of spec-imen in the central section of the webbing was exposed to the weatheringconditions. The remaining specimen length was wrapped around the test rackand secured in tne back by means of a plastic buckle.

ASTM D2565-79 (Section 4.3) states thickness at the start and end ofthe test shall be recorded. As initial thickness has previously been deter-mined, and is fixed by the specification, and final thickness was not theproperty of interest, we chose to omit this step.

Specimen mounting was over the entire length of the test rack, andcomparison samples were alternated in position around the rack diameter.Specimen positions were not rotated during the 200 hour exposure. The testrack, however, rotated continuously.

The Weatherometer was a Type AH. The bulb was a Xenon arc withBorosilicate inner and outer filters. The filters and burners werepre-aged by the manufacturer in accordance with ASTM D2565-79. The innerfilter was changed at least every 300 hours and the outer filter at thetime the bulb was changed (at least every 1500 hours).

Wattage settings for each exposure interval were adjusted according tothe recommendations of the equipment supplier.

The black panel temperature was 1450650F. Spray water was deionized

and filtered to <20 ppm total solids. The light and spray cycle consistedof 102 minutes of light without spray and 18 minutes of light with spray.

The relative humidity conditions, as a result of the showering se-quence, were in the range of 35 to 40% RH immediately prior to the spraycycle.

7. Hex Bar Abrasion

Webbings were abraded 2500 cycles in a hex bar abrader according toFED-STD-191A, Test Method 5309 [10). The rods used for testing were ob-tained from the Narrow Fabric Institute, Inc. The quality of the firstshipment of rods was unacceptable, according to the description within theStandard. The quality of a replacement shipment was still not ideal, asthere was scale deposited on some faces. However, as this represented thebest available, we used these rods after carefully cleaning the surfacewith fine emery paper. As noted in the test method, two new edges wereused for each abrasion test.

8. High Speed Impact

Testing was conducted on an apparatus available at the Aero-MechanicalEngineering Directorate at the Natick RD&E Center. This tester is a highcapacity compressive impact device which Albany International Research Co.

(then Fabric Research Laboratories) built for Natick about 20 years ago.This device consists of two steel carriages mounted on a track structure,and propelled toward each other by pneumatic pistons. When the device isused for compression testing, the specimen is mounted on the front face ofone carriage, the carriages ere accelerated by pneumatic cylinders, andthen coast freely towards a collision at the center of the track span, com-pressing the specimen on impact.

For the tensile impacts of the current study, one carriage is removedfrom action, and the tensile specimen is secured, by means of heavy capstanjaws, as a tether between the active carriage and the stationary end of thetrack. The specimen is impacted in tension when the movable carriage ispropelled down the track, pulling the webbing taut and bringing the car-riage to a stop. The magnitude of the tensile impact depends on the kinet-ic energy of the carriage, and is controlled by varying either the mass orthe velocity of the carriages, or both. To provide impact velocities atrelevant levels, the original heavy compression carriages had to be re-placed with a new lightweight carriage structure, designed and fabricatedfor this program. The resultant carriage weight was varied from 116 to226 Ibs, and the impact velocities ranged from 15 to 25 ft/sec. Ti.: para-chutes that use the webbings tested in this study are generally designed tobe deployed at relatively low speeds, of the order of 250 ft/sec or less.However, this is an extremely high speed for tensile cycling. The veloci-ties described above still provide for a fairly high rate of speed, withoutthe construction of expensive specialized equipment.

With this apparatus, the webbings were subjected to 5 cycles to 50% oftheir breaking energy, as determined by original slow-speed tensile test-ing, then removed from the tester and returneu to the laboratory for subse-quent slow-speed tensile testing to break, as described in Section 111,5.While this approach does not permit actual measurement of breakingstrength, elongation or energy absorption at high speed, it does, however,detect any damage which might have been caused by the high speed cyclingwhich subsequently affects the tensile properties measured at standard test-ing speeds.

9. Edge Abrasion

A test device for edge abrasion of webbings was designed as part ofthis contract. The test device, shown in Figure 3, consists of a motordriven belt sander mounted in stand so that the belt surface runs horizon-tal. Five webbings are clamped between two steel plates (5 in. x2-5/8 in.), with the webbing edges carefully aligned, and protruding fromthe plates by approximately 3/8 in. The total normal force, applied fromthe weight of the plates and clamps, is 1070 gm (2.4 lb). The sander frameis designed so that the webbing and clamp assembly is lowered down onto thebelt, parallel to the belt axis, through an alignment slot. No additionalnormal force is applied. To minimize variations from sander startup, thesander is running prior to lowering the webbing.

9

Figure 3. Edge Abrasion Test Device

Each webbing edge is abraded for 30 seconds in one direction followedby 30 seconds in the other direction (parallel and anti-parallel to thebelt) for a total of one minute per side. The second side is abraded inthe same nanner. This abrasion time was selected by experiment such thatsome observable damage resulted, but not such severe degradation as wouldobviously remove a webbing from service. The abrading surface is reposi-tioned or changed every two to three tests to maintain a freh surface.Prior to tensile testing, a visual assessment is made of the number ofyarns abraded from each side. This is a rather qualitative measurement asIt is sometimes difficult to determine the exact number, and the number mayvary slightly from one webbing to another, or one spot to another. Valuesranged from I to 4 yarns. For shuttleless webbings, two values are given;the first for the non-catch-curd edge, and the second for the catch-cordedge.

10

Ij

IV. RESULTS AND DISCUSSION

1. Thickness

All webbing types, including the polyester constructions, are withinspecification limits. The results, along with specification limits, areshown in Table 2. The minimum thickness limit on the resin coated sampleshas been djtermined from the minimum uncoated specification value less 12%.The values for the polyester webbings are in agreement with the stated goalof attaining specification thickness by the substitution of 1000-denierpolyester for the normal 840-denier nylon.

2. Weight

Results and specification limits are shown in Table 3. The maximumweight specification for the resin coated samples has been determined asthe maximum uncoated value +10%. Several of the polyester shuttleless con-structions are slightly higher than the allowed specifications (from 1 to10% higher). In all cases, even those within spec, the polyester webbingsare heavier than the corresponding nylon 6,6 constructions, in most casesby approximately 10 to 20%.

3. Lateral Curvature

Results are shown in Table 4. All uncoated webbing measurements arewithin specification. While no specification is given for the resin coatedsamples, these were also tested and are well below the maximum value foruncoated samples.

4. Webbing Construction

Ends/warp, binder, and picks/inch were checked for all uncoated web-bings. (Note: In shuttleless weaving, one filling insertion lays in twoyarns, which have beer counted as 2 picks). The results are given inTable 5. The nylon 6,6 and nylon 6 webbings are all within specification.The polyester webbings, however, are all low in picks/inch (from 5 to 27%below spec for the shuttle constructions and from 11 to 36% below specifi-cations for the shuttleless). In one Case (Type XIX, shuttleless poly-ester), the end count was also 12% below spec. The polyester webbings wereconstructed to meet thickness and weight specifications, with the requiredends/warp used, and then the makimum possible number of picks inserted.Even with the reduced pick count, the filling ply used for the shuttle poly-ester webbings had to be reduced to a single ply, which, according to speci-fications should only be used in shuttleless webbings where two picks areinserted per shed. The yarn ply data are given in Table 6. Since develop-ment of optimized polyester constructions was not the objective of thiswork, we accepted these webbings for the required comparative testing. The

construction results on these polyester webbings imply that a straight1000-denier substitution for 840-denier nylon is not the ideal approach.Nevertheless, these results do not mean that a polyester webbing cannot bemade to meet all performance specifications with some small changes in con-struction, thickness, or weight. Clearly, additional construction develop-ment is necessary to utilize the polyester properties appropriately.

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which has contributed to the need for a reduced pick count in the webbing.

5. Original Tensile Testing

Measurements of tensile strength, elongation, and energy absorption onall webbings are given in Tables 7, 8, and 9. Average load-elongationcurves of these results are shown in Figures 4 through 75. Also shown forcomparison in these figures are the average load-elongation curves for anyadditional treatments. All strength values are within specification exceptfor three polyester constructions. These are Type VI, shuttleless, resincoated, 41 lb low; Type X, shuttle, uncoated, 1006 lb low; and Type X,shuttle, resin coated, 140 lb low. As discussed in Section IV,4, WebbingConstruction, the polyester constructions have not necessarily been opti-mized, and these strength differences are most likely attributed to theconstruction, rather than an inherent p operty of the polyester. Withineach material type, there are no signit cant differences between theshuttle and shuttleless constructions; ither is consistently higher instrength.

There is no specification given for elongation. When comparing thevalues for shuttle and shuttleless constructions in Tabie 8, there areagain no significant diiferences in elongation between weaving methods.Considering fiber type, the nylon 6 results scatter about the elongationsof comparable nylon 6,6 shuttle webbings. The value ranges from 86 to 130%

of the nylon 6,6 shuttle constructions, indicating no significant trend fornylon 6. For the polyester constructions, elongation values are all lowerthan the comparable nylon 6,6 shuttle webbings, in the range of 64 to 92%,with most values falling within 75 to 85% of the nylon 6,6 shuttle webbing.The polyester webbings show a real difference in elongation. Howeve-, be-cause the constructions are not optimum, the origin of this difference can-not be clearly attributed to fiber type. Also, the absence of a specifica-tion for this value, and the clear understanding of its meaning In relationto actual field use, do not presently indicate this as either an advantageor disadvantage for the polyester webbings.

17

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21

5000

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Elongation (%)Figure 12. Type 6, Class 1. Uncoated, Polyester


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32

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Figure 23. Type 8. Class 2, Coated, Nylon 6Original and After Treatment

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Figure 30. Type 10, Class 1, Coated, Nylon 6,6Original and After Treatment

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Figure 31. Type 10, Class 2. Coated. Nylon 6.6Original and Arter Treatment

48

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Figure 34. Type 10, Class 1, Coated, Nylon 6Original and After Treatment

51

15000

12000

9000

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23 High speed impact

010 20 30 40 50

Elongation (%)Figure 35. Type 10, Class 2, Coated, Nylon 6


52

10000-

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Elongation (7)Figure 37. Type 10, Class 2. Uncoated, Polyester

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Elongation (%)Figure 38. Tye10, Clas 1, Coated. Polyester


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0 10 20 30 40 50

Elongation (%)Figure 39. Type 10, Class 2, Coated. Polyester

Original and After Treatnent

56

10000

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0 10 20 30 40 50

Elongation (%)Figure 40. Type 13, Class 1, Uncoated, Nylon 6,6


57

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58

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. . , .. . . , I . .. I , . ! . . , . .

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. .. I . . . . I . . * . . I . , I . . . .

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60

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q0 10 20 30 40 50

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61

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62

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63

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0 10 20 30 40 50

Elongation (%)Figure 52. Type 19. Class 1. Unoated. Nylon 6.6


69

-------------------------------- ---------------

15000-

12000-

9000-

g 6000

o Original


a Weathering

0 10 20 30 40 50

Elongation (%)Figure 53. Ty'pe 19, Clas3 2. Uncoated. Nylon 6,6


70

15000

12000-

9000-

6000-

o Originai


a Wathering

AHigh speed impact

0 10 20 30 40 50

Elongation (%)Figure 54 Type 19. Cls .Coated. Nylon 6.6

OrignalandArter Treatment

I 71

15000

12000

9000

-0090.-

6000

o Original


a Weathering


I -I * i

0 10 20 30 40 50

Elongation (%)Figure 55. Type 19, Class 2, Coated, lylon 6.6


72

15000F[

12000

9000

-000._J

6000

o Original


a Weathering

. , I . . . I , I . . . , I *1 , . .

0 10 20 30 40 50

Elongation (%)

Figure 56. Type 19, Class 1. Uncoated, Hylon 6Original and After Treatment

73

15000

12000

9000

0

6000

o Originol

Treatment3000 x Hex bor abrasion

a Weathering

0 10 20 30 40 50

Elongation (%)

Figure 57. Type 19, Class 2, Uncoated. Nylon 6Original and After Treatment

74

1500017

120007

9000(.)

0

6000

o Original


o Weathering

* Edge abrasion4) A High speed impact

0 10 20 30 40 50

Elongation (%)

Figure 58. Type 19, Class 1. Coated. Nylon 6Original and Arter Treatment

75

15000-

12000/

9000-

6000-

o Original

3000-Treatment3000x Hex bar abrasionj a Weathering

*Edge abrasionAHigh speed impact

0 10 20 30 40 50

Elongation (%~)Figure 59. Type 19. Class 2, Coated. Nylon 6

Original and After Treatmsent

76

15000

12000--

9000

0

uC6000a

S Originaladgne l

3000 x Hex bar abrasiona Weatliering

0. 10 20 30 40 50

~Elongation (%)Figure 60. Type 19, Class I.-Uncoated, Polyester


77

15000 -

120001

/9000

0

6000

o Original

Treatment.UUU x Hex bar abrasion

a Weathering

I . . , I r ,

0 10 20 30 40 50

Elongation (%)figure 61. Type 19, Class 2. Uncoated, Polyester


78

15000

12000-

9000-

0

-J6000-

o Original

Treatment3)UUUF x Hex bar abrasion

ra Weathering

# Edge abrasion

A High speed impact

PA0 10 20 30 40 50

Elongation (%)Figure 62. Type 19. Class 1, Coated, Polyester

Original and Arter Treatenent

79

15000[

120 00

9000

0

6000-

aOriqinol3Treatment3000"

x Hex bar abrasion

a Weanering

* Edgr, abrasion

A High speed impact

0 10 20 30 40 50

Elongation (a)

Figure 63. Type 19, Class 2. Coated, PolyesterOriginal and Atter Treatment

80

15000[

12000-

9000

iN -o0

6000

3000 Treatment


a Weathering

. .. , . I . . . ! I , ! . . 1 _ , ,

0 10 20 30 40 50

Elongation (%)

Figure 64. Type 22, Class 1, Uncoated, Nylon 6,6Original and After Treatment

81

15000-

12000

9000

00

6000

a Original


a Weathering

I. . I I -

0 10 20 30 40 50

Elongation (%)

Figure 65. Type 22. Class 2, Uncoated. Nylon 6.6Original and After Treatment

82

15000

12000-

9000-

0

6000-

o Original

* Treatment

3000 x Hex bar abrosion

o Weothering

* Edge abrasion

AHigh speed impact

010 * 20 30 40 50

Elongation (%)Figure 66. Type 22. Class 1. Coated, Nlylon 6.6


83

15000

12000

9000-

6000

o Original


o Weathering

* Edge abrasionA High speed Impact

0 10 20 30 40 50

Elongation (%)

Figure 67. Type 22. Class 2. Coated. Nylon 6.6Original and After Treatment

84

15000

12000

9000

C)

0

6000

o Original

Treatment3000' x Hex bar abrasion

o Weathering

0 10 20 30 40 50

Elongation (%)Figure 68. Type 22. Class 1. Uncoated. Nylon 6


W85

15000-

12000-

9000-

6000-

o Original


a Weathering

0 10 20 30 40 50

Elongation (%)Figure 69. Type 22. Cla3s 2, Uncoated. Nylon 6


86

15000

12000

9000,C,)

0

6000

o Original


a Weathering

* Edge obrasionA High speed impact

f 10 20 30 40 50

Elongation (%)Figure 70. Type 22, Class 1. Coated, Nylon 6


87

15000-

12000

7

9000

V. 0

6000

o Original


a Weathering

* Edge abrasion& High speed impact

ito I . I . . . . I . ., . .

0 10 20 30 40 50

Elongation (%)

Figure 71. Type 22, Class 2, Coated, Nylon 6Original and After Treatment

88

15000-

12000

9000

j 06000-

o Original


o Weathering

6 0 ~~Elongation3() 405

Figure 72. Type 22. Class 1. Uncoated, Polyesteroriginal and After Treatment

89

15000

12000

9000-o

00.- I

6000

o OriginalTreatment

x Hex bar abrasion

o Weathering

. .. . , . . . . . I . , I . . . , -

0 10 20 30 40 50

Elongation (%)Figure 73. Type 22, Class 2, Uncoated. Polyester


90

15000

12000-

9000-

00

600

o Original

3000 Treatment3000x Hex bar abrasion

a Weathering# Edge abrasion

,L High speed impact

0 1 10 210 3 10 40 50

Elongation (%Figure 74I. Type 22, Class 1, Coated. Polyester

Original and AfLer Treatm~ent

91

15000-

12000

9000

0-.J

6000

o Original

Treatment3000-x Hex bar abrasion

a Weathering


. . . I . , , I . . . , . . I . , . . *. . .

0 10 20 30 40 50

Elongation (%)

Figure 75. Type 22, Class 2, Coated. PolyesterOriginal and At er Treatment

92

Results for energy absorption at break are given in Table 9. There isagain no spec for these values. The energy value is computed as the areaunder the load-elongati~n curve up to the breaking point, and is presumablythe amount of energy which a webbing can absorb at failure. As thesevalues are a product of strength and elongation, the results are similar tothose noted above: no significant differences between shuttle and shuttle-less constructions, no significant difference between nylon 6,6 andnylon 6, and somewhat reduced values of energy absorption for the polyesterconstructions. Most of the polyester energy absorption values fall within65 and 85% of the comparable nylon 6,6 shuttle values. The same provisionsapply to interpretation of these results - they cannot be clearly attrib-uted to fiber type because of construction variations, and the implicationsof energy absorption data in relation to actual use are not clearly known.

6. Accelerated Weathering

All three of the fiber types studied ere well known to exhibit somedegradation in properties after exposure to sunlight [11]. For nylon, thedegradation can occur by direct disruption of C-N bonds, or by abstractionof hydrogen atoms from the carbon adjacent to the NH group. For polyester,degradation can occur by absorption at the ester carbonyl. The performanceof both nylon and polyester is influenced by many factors such as the pres-ence of stabilizers, dyes, yarn denier or fabric construction. Acceleratedweathering, as an attempt to simulate actual outdoor exposure of these web-bings, is subject to much variability and has historically been difficultto interpret with great accuracy. For this reason, as described in theTest Methods section, we have chosen to weather matched pairs of shuttleand shuttleless constructions for the best comparison of constructionaleffects,

Values for tensile strength, elongation and energy absorption afteraccelerated weathering are shown in Tables 10, 11 and 12. There is a speci-fication of 95% of original strength for all resin coated samples, and no

specification for uncoated webbings. Many values within the nylon 6,6 andnylon 6 groups are slightly below spec, with averages of the coated valuesranging from 91 to 94%. The behavior of the nylon 6,6 and nylon 6 to theaccelerated weathering exposure is stastically equivalent. No nylon web-bings show less than 85% strength retention, and on an absolute, ratherthan normalized basis, all show tensile strengths greater than the minimumoriginal spec. A large part of this departure from spec may be attributedto the particularly variable nature of weathering, and also to the factthat weathering was conducted with a Xenon bulb Weatherometer as an ap-proved replacement for the carbon arc. The Xenon bulb spectrum, as dis-cussed in Test Methods, better corresponds to the exposure to sunlight,which is assumed to be the degradative agent in accelerated weathering.

The coated polyester webbings show average values for strength reten-tion of 88 and 89% for the 3huttle and shuttleless constructions, but thesevalues are statistically equivalent to the nylon values. Several Indi-vidual coated polyester constructions did show values below 85% (Type XIXshuttleless resin coated had the lowest value at 81.8%) but because of thelack of optimum construction, this cannot clearly be attributed to a charac-teristic of the polyester, but may be a function of the construction. Theconstruction might, for example, provide more severe exposure of the warpyarns, or shrinkage imbalance during the wet cycle.

19 ~93

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For all types (nylon 6,6 and nylon 6 and polyester), there is no signi-ficant difference between the average strength retention of shuttle andshuttleless constructions. Although there is a weathering specificationfor resin coated webbings only, the presence of the coating does not appearto affect weathering performance. Coated and uncoated webbings performequivalently, as may be seen from the separate averages at the bottom ofTable 10. At this level of exposure, coating cannot be considered to im-prove weathering performance.

For all webbing types, elongation remains close to the original valuewith some slight departures. The lowest elongation retention was 86.7% forType XIX shuttle, uncoated polyester; and the highest retention was an in-crease to 117.7% for Type XIII shuttleless, resin coated nylon 6,6. Theaverage values for each fiber type and weaving method were statisticallyequivalent.

Retention of energy absorption after accelerated weathering followsfrom the strength and elongation measurements. As noted previously, slightdecreases in strength and elongation can bring reductions in energy whichare, in a number of cases, in the 70 to 80% range. (A value as low as 66%was measured for the Type VI shuttleless, resin-coated nylon 6,6). The

averages of each coated fiber type and weaving method, shown at the bottomof Table 12, range from 81 to 90% retention. As found for many other treat-ments, there are no significant differences in average behavior among fibertypes or weaving methods.

7. Hex Bar Abrasion

All webbings were abraded 2500 cycles in the Hex Bnr Abrader as speci-fied in Method 5309 of Federal Standard 191A. This abrasion procedure in-volves both rubbing and flexing and can, in some instances, result in aphenomenon which we have called "napping," which is a roughening of thesurface which is not in contact with the hex bar. This surface has manyprotruding yarn loops giving it the appearance of a napped fabric, and anincrease in webbing thickness in the napped area. An example is given inFigure 76 which shows a Type XIX shuttle, uncoated, polyester. Figure 76ashows the original webbing cross section. Figure 76b shows the webbingafter hex bar abrasion. The left side was in contact with the bar andshows some evidence of "normal" abrasion with broken or damaged fibers.The right side clearly shows large protruding loops, giving an overallthickness increase. Figure 76c shows the napped surface. In this case,the napping has occurred at the outer edges as evidenced by the long wavyloops. Warp yarns protruding from the webbing plane after abrasion werealso observed by Gardella and Devarakonda [2]. They attributed this to a"raking" action which increased warp yarn crimp.

Napping has been studied in some detail C12]. It is caused by buck-ling of the warp yarns, and can be induced solely by flexing, without anadditional rubbing component. Napping of the surface occurs only when thewebbing construction happens to permit it. The critical parameters are thetightness of the weave and, more importantly, the relationship between the"wavelength" of the warp yarn twist and the weft yarn spacing. When a

97

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match between these dimensions exists, and when the filament yarn span be-tween restrictions (filling interlacings) is between certain limits, condi-tions for the development of warp yarn loops is optimum. The construc-tional limits within which this becomes clearly evident are relatively nar-row, though it occurs to varying degrees over fairly broad limits.

Table 13 is a detailed example of these constructional factors for theuncoated, shuttle version of each weboing type. This illustrates the con-trolling factor is the number of warp yarn turns per weft yarn intersection.This is obtained by dividing the warp twist by the pick count, and thenmultiplying by a spacing factor dependent on the weave: I for the plainweave, or 2 for the 2 up 2 down twill. The double twill weaves ofTypes XIX and XXII are more complicated and an approximate value is givenbased on a factor of either 5 or 3, respectively.

Of these constructions, those with a greater number of turns per inter-section show a greater tendency to form warp yarn loops. For the examplegiven, webbings above approximately 0.3 turns between intersections (consid-ering the higher factor in the more complex weaves) tend to nap. Table 14describes the presence or absence of napping for all webbing types. Thedouble plain weaves (Types X and XIII), with low turns between intersec-tions, do not nap, while the twill weaves are more prone to napping. Thepolyester webbings, with slightly higher warp yarn twist and lower pickcounts show an increased napping tendency. These results should not implythis is a characteristic of the polyester, as results would differ withdifferent weave constructions.

Tensile strength, elongation and energy absorption were measured afterhex bar abrasion. Results are shown in Tables 15, 16, and 17. Strengthretention after hex bar abrasion is generally good. There is a specifica-tion value of 80% original tensile strength retention for all resin coatedsamples; and for one uncoated sample (Type XXII), a value of 90% of theminimum original tensile strength (as opposed to the measured originalvalue) For all nylon 6,6 and nylon 6 webbings for which there is a speci-fication, results are within spec. For the polyester webbings, three ofthe resin-coated versions are marginally below the spec. These are Type Xshuttleless at 76.9%, Type XIII shuttleless at 74.0%. and Type XIX at 78.9%.The Type XXII uncoated polyester gave values far below the 90% spec at 56.4and 43.4% for shuttle and shuttleless webbings, respectively. Two generalobservations may be made from these strength data. First, there is no sta-tistically significant difference for any webbing material (nylon 6,6,nylon 6 or polyester) between the average shuttle and shuttleless construe-tions in their resistance to tensile strength reduction by hex bar abrasion.Secondly, the Type XXII uncoated webbings. while being uuiquely subjectedto a 90$ of minimum spec, in comparative testing, perform similarly to theother uncoated webbings when normalized to original measured values.

99

---------- ----------- --

TABLE 13. Example of Constructional Factors in Napping

Uncoated, Shuttle Webbings

Warp TurnsWebbing Fiber Twist Ends/ Picks/ tpi/ Between NappingType Type (tpi) Warp Inch ppL Intersections Tendency

VI Nylon 6,6 2.7 114 22 .123 .246 02 up 2 down Nylon 6 2.9 114 22 .132 .264 0Herringbone Polyester 3.3 114 20 .165 .330twill

VIII Nylon 6,6 2.7 166 18 .150 .300 N-2 up 2 down Nylon 6 2.9 166 19 .153 .306 NHerringbone Polyester 3.3 165 15 .220 .440 N+twill

X Nylon 6,6 2.7 258 22 .123 .123 0Double Nylon 6 2.9 257 24 .120 .120 0plain Polyester 3.4 257 16 .213 .213 0

XIII Nylon 6,6 2.7 284 24 .113 .113 0Double Nylon 6 2.9 277 26 .112 .112 0plain Folyester 3.4 282 18 .189 .189 0

XIX Nylon 6,6 2.7 282 18 .150 .150 N5 up I down .750twill Nylon 6 2.9 280 20 .145 .145 N

.725Polyester 3.3 280 14 .236 .236 N.

1.18

XXII Nylon 6.6 2.8 264 18 .156 .156 0

(1/3 twill) .468

Nylon 6 2.9 259 19 .152 .152 N.456

Polyester 3.5 259 11 .250 .250 N.750

0 - No napping

11 - Slight napping

N - Napping

N- - Extensive napping

100

TABLE 14. Occurrence of Napping after Hex Bar Abrasion

Webbing Nylon 6,6 Nylon 6 Polyester

Type Treatment SH SL SH SL SH SL

VI none 0 0 0 0 N+ N+

resin 0 0 0 0 0 0

VIII none N- N- 1 N N+ N+

resin N N 0 N 0 0

X none 0 0 0 0 0 0

resin 0 0 0 0 0 0

XIII none 0 0 0 0 0 0

resin 0 0 0 0 0 0

XIX none N N N+ N N+ N+

resin N 0 0 N 0 0

XXII none 0 0 N 0 N N

resin 0 0 0 0 0 0

$H - Shuttle SL - Shuttleless

0 - no "napping"

N+ - extensive "napping"

N - "napping"

1- - slight "napping"

101

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For those uncoated webbings for which there are no specificationvalues, the uncoated polyester webbings generally show significantlygreater strength reductions after hex bar abrasion than either nylon 6,6 ornylon 6. This may be seen more clearly when the averages are separatedinto two groups, uncoated and coated, at the bottom of Table 15. The lowstrength retention values after hex bar abrasion for the uncoated polyesterwe.bbings cannot be directly attributed to the inherent abrasion propertiesof the fiber, but are much more likely caused by the construction. Asnoted previously, these polyester constructions are often lower in end orpick counts and are thus somewhat more flexible. This increased flexibil-ity makes them more subject to the flexing action of the abrader. Presum-ably, the resin coating acts to immobilize the webbing and the coated poly-ester webbing average values are much closer to the nylon 6,6 and nylon 6.

Considering the strength retention results in light of the nappingphenomenon discussed above, those constructions which exhibit napping gen-erally show the most strength reduction. However, this is neither a neces-sary nor a sufficient condition for strength reduction, as several Aamplesshow 50% retention with no napping and others show 80 to 90% with napping.Resin coating, in most all cases, reduces the tendency to nap by immobiliz-ing an otherwise mobile structure. This is particularly evident inType XIX which is a 5 up I down twill weave which naps, sometimes extensive-ly, for all webbings in the uncoated state, and is eliminated in all buttwo of the resin-coated versions (see Table 14).

Elongation values after hex bar abrasion are given in Table 16. Elon-gation is generally comparable to the original tensile elongation, withoverall averages for each material type and construction method rangingfrom 85 to 97% of original. There are no statistically significant differ-ences among fiber types (nylon 6,6, nylon 6 or polyester) or between weav-ing methods (shuttle or shuttleless) in average elongation retention. With-in the individual webbings, however, results are quite variable, rangingfrom 67% for a Type XIX, shuttle, uncoated nylon 6,6 to 123% for aType XIII, shuttleless, uncoated polyester.

The relation between napping and elongation is somewhat more clearlydefined than that for tensile strength. All samples that showed residualelongations of <80% displayed napping, and all samples that showed greaterthan 100% elongation did not. Napping is not always sufficient to signifi-cantly reduce elongation, however, as napped values ranged from 67 to 98%of original. One potential reason for the decrease in elongation with nap-ping is a structural rearrangement which, on tensioning, produces a strainimbalance. Because of this imbalance, not all of the warp yarn loops canbe pulled straight and premature failure results. For all uncoated polyes-ter webbings, regardless of napping, the load-elongation curves after hexbar abrasion are shifted to the right, to higher elongations at equivalentloads (see, for example, Figures 12 and 13). This shift is presumablycaused by structural rearrangement during flexing of the mobile polyesterconstructions. Some, but not necessarily all, of these rearrangements arepulled free during tensioning, leading to premature failure in some cases.However, the exact nature of these changes would require more careful studyto explain fully.

105

Energy absorption after hex bar abrasion is shown in Table 17. Asobserved for tensile strength and elongation, there is no significant ef-fect of shuttle vs. shuttleless construction, and notably for the polyesterwebbings, resin coating is particularly effective in raising the measuredvalues. When considering only the averages of resin coated samples, thepolyester constructions show energy absorption retention comparable toeither nylon 6,6 or nylon 6. One point should be noted on energy absorp-tion. As energy absorption is the product of strength and elongation, asmall reduction in tensile strength (still within the 80% original spec)along with a small reduction in elongation can result in substantially re-duced energy absorption. Many values of energy absorption for all materialtypes fall within the 60 to 70% range. Again, the importance of energyabsorption values to actual use should be interpreted with care.

8. High Speed Impact

Results for tensile strength, elongation and energy absorption afterhigh speed impact cycling are shown in Tables 18, 19 and 20. Webbings weresubjected to 5 impact cycles to 50% of the original measured breakingenergy, and then tested to failure in a regular, slow speed, tensile test.Impact cycles and tensile testing were conducted on coated webbings only.Nylon 6,6, nylon 6, and polyester webbings all showed excellent strengthretention after cycling. All webbings, regardless of fiber type or weavingmethod, retained >94% of original strength, with averages for each fibertype and weaving method ranging from 97 to 100%. There were no significantdifferences among nylon 6,6, nylon 6, or polyester nor between shuttle andshuttleless constructions.

Values for elongation after impact are quite variable, as shown inTable 19. Averages for all types within the nylon 6 shuttle and shuttle-less constructions, and within the nylon 6,6 shuttleless are greater than90%. Individual types within these sets range from 85 to 105% elongationretention. The nylon 6,6 shuttle webbings retain, on average, 84% of origi-nal elongation, because of the variability in these results, however, it isnot possible to conclude that the nylon 6,6 shuttle constructions are signi-ficantly different from the shuttleless or nylon 6 constructions.

Elongation of polyester webbings after impact show a significant drop.They retain, on average, 75 and 76% of original for shuttle and shuttlelesswebbings, respectively, with no significant difference in the behavior be-tween the two weaving methods. Examination of the load-elongation curvesfor the coated polyester webbings suggests a reason for this drop in elon-gation. All curves after impact cycling show a pronounced reduction of theinflection point, or shoulder, observed in the original polyester curves(see, for exa.Aple, Figure 14 and 15). This inflection point is normallyassociated with crimp interchange. Potentially, a sizable component of theinitial elongation in the polyester webbings results from crimp interchangeduring tensioning, rather than straining of the individual fibers. It isthis component which is exhausted during impact cycling. If crimp inter-change is a significant factor, then the less than optimum constructions ofthe polyester webbings make it impossible to form any conclusions on theinherent Impact resistant properties of the constituent polyester fibers.

106

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Energy absorption after impact is shown in Table 20. Because of thedrops observed in strength and elongation, average values of energy foreach weaving method and fiber type show moderate reductions ranging from80 to 94%. Because of the relatively high variability in these measure-ments, however, the absolute value of these reductions, and particularlythe significance of differences between them, must be interpreted with cau-tion.

One additional feature of the impact testing which should be pointedout, Is that the impact energy applied to each webbing is based on theoriginal measured breaking energy. Accordingly, those webbings with loweroriginal breaking energy, for example many of the polyester constructions,received lower impact energies. This factor should be considered in anyfurther interpretations of this data.

9. Edge Abrasion

During use within a harness system, the edges of a parachute webbingare exposed to a variety of hardware components. As the webbing travelsback and forth within the hardware, the ability to withstand repeated abra-sive cycling at its edges could become an important factor in performance.In particular, any differences in the edge construction, such as the pres-ence or absence of a catch-cord in shuttleless or shuttle weaving should beconsidered. For this reason, a test method was designed to subject thewebbing edge to a moderate degree of abrasive wear, producing a small, butnoticeable degree of damage, and webbings were subsequently tested forchanges in tensile properties.

As described in the Test Methods section, webbings were abraded, insets of file, for one minute on each edge. Prior to tensile testing, avisual assessment was m3de of the number of yarns abraded from each edge.These results are given in Table 21. For the shuttleless webbings, twovalues are given; the first for the non-catch-cord edge, and the second forthe catch-cord edge. Values ranged from 1/2 to 4 yarns abraded at eitheredge. Although this is a rather qualitative measure, there appeared to beno significant differences between shuttle and shuttleless webbings, orbetween the catch-cord and non-catch-cord edges of the shuttleles3 web-bings.

Tensile properties, after one minute abrasion on each side, are shownin Tables 22, 23 and 24. Strength retention after abrasion ranges from80 to 100% of original. The thinner, lighter weight webbings (Types VI andVIII) generally show the most strength loss after abrasion, from 80 to 93%.The most likely reason is that, for the thinner webbings, loss of a singleyarn represents a larger fraction of the total load-bearing members. Also,thinner webbings experience an increased stress at the edge, as a smallercross section must support the same normal load. The thinner webbings tendto lose more threads during abrasion, as shown in Table 21, but this isonly a very general trend, and no direct correlation can be observed forall cases between the number of threads abraded and strength loss. Thereare no significant differences observed between the averdge strength reten-tion of shuttle vs. shuttleless constructions, or among fiber types.

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114

Elongation after edge abrasion is given in Table 23. Values rangefrom 73.9% to 111.2%, with most values falling between 75% and 95%. Thegeneral reduction in elongation most probably results from premature fail-ure at slightly lower strengths. Because of the drop In both strength andelongation, the energy absorption values, given in Table 24, show averagevalues for the three fiber types (nylon 6,6, nylon 6 and polyester) rangingfrom 70.8% to 92.4%, with fairly large variability within fiber types.Because of this variability, it is not possible to determine any signifi-cant differences between shuttle or shuttleless constructions. Of thethree fibers, the polyester may be marginally better in energy absorptionretention, related to a marginally higher elongation retention. As statedpreviously, this is not necessarily a feature of the polyester itself, butrather of the construction, which is generally looser and more flexible.However, the number of comparisons is small, and these observations shouldbe considered with care.

115

V. CONCLUSIONS AND RECOMMENDATIONS

The primary goal of this study has been to compare the tensile proper-ties of shuttle and shuttleless webbings. Tensile properties were comparedoriginally and after various treatments to determine what effects, if any,the use of a shuttleless weaving method has on performance. Fiom all ofthe results of this study, there were no significant performance differ-ences detected between the shuttle and shuttleless weaving methods. Orig-inal Lensile p,operties, and tensile properties after accelerated weather-ing, hex bar abrasion, impact cycling and edge abrasion are statisticallyequivalent for both weaving methods. This conclusion applies to tensilestrength, tensile elongation and energy absorption at break. Of particularimportance are the impact and edge abrasion properties. No evidence of thecatch-cord edge "unzipping" with impact was observed, and no unusual sus-ceptibility to edge abrasion of the catch-cord edge was detected. In alllaboratory testing, Class 2 shuttleless webbings performed equivalent toClass I shuttle webbings. Based on these results, shuttleless webbingsshould be considered for use in Class 1 (critical life support) applica-tions. However, as a final precaution, we would re-ortiend actual drop test-Ing of shuttle and shuttleless webbings before altering the Class I spec toinclude shuttleless webbings.

A second goal of this study was to comp,'re the tensile properties ofthree fiber types: nylon 6,6, nylon 6, and polyester. Of these, onlynylon 6,6 is currently approved for use in Class I 6ebbings. From all re-sults of this study, we found no significant differences In the behavior ornylon 6,6 and nylon 6. The original tensile properties and afteraccelerated weathering, hex bar abrasion, impact cycling, and edge abrasionwere equivalent for the two fiber types. One difference between nylon 6,6and nylon 6 not addressed in this study is the difference in melting point;2650C for nylon 6,6 and 225

0C for nylon 6. These temperatures are far in

excess of any developed as a result ,f the testing in this study. The po-tential for heat buildup during use or exposure to adverse conditionsshould be examined, however, before considering the~e materials equivalentfor field use.

For the polyester webbings, several significant dirferences were noted.However, these constructions were formed by straignt substitution of1000-denier polyester for 840-denier nylon, and not truly optimized forperformance. Many of the differences observed could not be attributed di-rectly to an inherent property of the polyester fiber, but could have beensignificantly affected by the construction. The most notable differenceswere: original elongation of most polyester webbings were about 75 to 85%of the equivalent nylon 6,6 shuttle webbings. Thi3 gave energy in therange of 65 to 85% of the nylon 6,6 shuttle webbinga. Several individualcoated polyester constructions showed comparatively low tensile strengthvalues after accelerated weathering (<85%). Polyester aebbings showedslightly increased napping tendency during hex bar abrasion, and in theuncoated state showed relatively large strengt; reductions compared tonylon 6,6 and nylon 6. After impact cycling, polyester webbings show con-siderable loss of tensile elongation and energy absorption. In all ofthese cases, it must be emphasized that constrecticnal effects could ex-plain some or all of the differences. Clearly, additional study of opti-mized polyester constructions is recommended.

117

In many of the results observed in this study, small decreases in ten-sile strength and elongation after various treatments can lead to signifi-cant decreases in energy absorption. It is the former, tensile strengthretention, which is used in all current specifications. The importance ofa change in energy absorption is not at all clear. The interpretation ofenergy absorptio data could become even more important if webbings, forexample polyester, are constructed to meet all tensile strength specifi-cations but at a lower elongation, and consequently lower energy absorption.It is worth noting that KevlarTM webbings have a very low elongation, andsignificantly lower energy absorption to break than nylon webbings, yet aretotally satisfactory for use in parachutes. In view of this, it may bedesirable to consider more carefully the meaning of the energy absorption

values by analysis of the conditions occurring during use, and by actualfield drops.

Many of the webbings studied exhibited the phenomenon called "napping."The occurrence of napping relates to the nature of the test which providesboth abrasion and flex, and is dependent on the webbing construction. Mostof the problems encountered from napping do not relate to fiber type, andcould presumably be reduced by constructional changes.

As a final point, accelerated weathering by Xenon burner, as conductedin this study, provides weathering more closely approximating the exposureto natural sunlight, which is assumed to be the degradative agent in accel-erated weathering. Because the Xenon arc more closely approximates thespectrum of natural sunlight and represents the most current technology asspecified in ASTM D2565-79 for exposure of plastic specimens, this proce-dure should be considered as a replacement for the current carbon arc weath-ering requirement.

This document reports research undertaken incooperation with the US Army Natick Research,Development and Engineering Center underContract No. 1 4 'C ' " y and has beenassigned No. ", ej/1 .io~s in the seriesof reports approved for publication.

11A

REFERENCES

1. Military Specification MIL-W-4088J, Webbing, Textile, Woven Nylon,December 22, 1981.

2-. Gardella, J.W., Devarakonda, V.K., "Laboratory Evaluation of NarrowFabrics Woven on Shuttleless Looms," Technical Report NatickTR-78/030, ADA 060 963, October 1978.

3. Federal Standard FED-STD-191A, Test Method 5030, Thickness of TextileMaterials; Determination of, July 20, 1978.

4. Federal Standard FED-STD-191A, Test Method 5041, Weight of TextileMaterials, Small Specimen Method; Determination of, July 20, 1978.

5. Federal Standard FED-STD-191A, Test Method 5050, Yarns per Unit Length(Inch or Centimeter) in Woven Cloth, July 20, 1978.

6. Federal Standard FED-STD-191A, Test Method 4108, Strength and Elonga-tion, Breaking; Textile Webbing, Tape and Braided Items, July 20, 1978.

7. Federal Standard FED-STD-191A, Test Method 5804, Weathering Resistanceof Cloth; Accelerated Weathering Method, July 20, 1978.

8. ASTM Standard D2565-79, Standard Practice for Operating Xenon Arc-Type(Water-Cooled) Light-Exposure Apparatus With and Without Water forExposure of Plastics.

9. Light Resistance of Industrial Fiber Products, DuPont Technical Infor-mation Bulletin X-189, April 1964.

10. Federal Standard FED-STD-191A, Test Method 5309, Abrasion Resistanceof Textile Webbing, July 20, 1978.

11. Ranby, B., Rabek, J.F., "Photodegradation, Photo-oxidation and Photo-stabilization of Polymers," John Wiley & Sons, New York, 1975.

12. Toney, H., Schoppee, M.M. and Skelton, J., "Cumulative GeometricChanges in Woven Fabrics with Repeated Flexing," Textile Research Jour-nal, 56 (6), pp. 370-378, June 1986.

119

APPENDIX

During the course of this study, ten additional webbings, produced bya polyester supplier, became available for impact testing. Through a modi-fication of the existing contract, these webbings were tested on the impactcycling device at the Natick laboratories. The webbings and test time werefurnished at no expense to the Government, and the impact results are sup-plied as a part of this Final Report. All test methods used for these re-sults are the same as described in the Test Methods section of the mainreport.

The ten polyester webbing constructions are shown in Table 1A. Theseare the same types as in the main study, with one additional, Type XXVI.All webbings tested for impact cycling were resin coated. Webbings weretested in the normal manner for original tensile properties and then impactcycled for 5 cycles to 50% of the measured breaking energy. Results fortensile strength, elongation and energy absorption are shown in Tables 2A,3A and 4A. All webbings show good retention of original tensile strength.Results range from 95 to 102% of original values. Three of the webbingtypes did give absolute values of strength which were below the specifica-tion value for an original webbing, however. Two of these (Type XIIshuttle, and Type XXVI shuttleless) were below spec in the original values,and Type XIII shuttleless was only marginally above spec to start. Fromthe limited number of comparisons available, there is no significant differ-ence in tensile strength retention after impact between the shuttle andshuttleless constructions.

Tensile elongation after impact shows a significant drop. Shuttle andshuttleless constructions retained, on average, 78% and 77% of their orig-inal values, respectively. There again appeared to be no difference inbehavior between the two construction methods, shuttle or shuttleless.Values were quite variable, however, ranging from 62.5 to 86.5% of original.The load-elongation curves shown in Figures 1A through IOA exhibit the samereduction of the original inflection point observed in the main report. Asdescribed in the main report, this inflection point Is normally associatedwith crimp interchange. Potentially, a sizable component of the initialelongation in these webbings results from crimp interchange during tension-ing, rather than straining of the individual fibers. It is this componentwhich is exhausted during cycling, and is substantially Influenced by theconstruction.

The loss of elongation after Impact is also evident In the tensileenergy absorption which, on average, is 79% or 80% of original shuttle orshuttleless constructions, respectively. Again there is no significantdifference between shuttle and shuttleless types. However, the above ob-servations are based on a very limited number of tests, and the absolutevalue of the reductions should be considered with care.

All of the above results are quite consistent with the polyester speci-men results in the main report.

121

-- - - - - - - - - - - - - - -

TABLE A-1. Additional Polyester Webbing Constructions

Webbing Weaving MethodType Shuttle Shuttleless

VI X X

VIII X

X X

XIII X X

XIX X

XXII X

XXVI X X


Tensile Strength (lb) After Impact Cycling(average of 5 values)

Webbing Shuttle Shuttleless

Type* % Original % Original

VI 3043 99.7 3103 101.0

VIII 4186 98.8

X 10040 102.4

XIII 6160 95.4 6980 97.3

XIX 10180 100.5

XXII 9690 99.4

XXVI 14630 100.2 15660 102.4

Average 98.4% 100.3%

Std Dev 2.6 1.9

*All webbings resin coated.

122


Tensile Elongation (%) After Impact Cycling(average of 5 values)


Type* % % Original _ % Original

VI 11.8 86.6 12.8 86.5

VIII 14.6 88.5

X 20.4 75.8

XIII 18.6 70.7 17.4 76.3

XIX 19.2 62.5

XXII 17.6 75.9

XXVI 17.2 77.5 19.6 73.7

Average 78.3 77.0Std Dev 8.1 8.6



Energy Absorption (ft-lb/ft) After Impact Cycling(average of 5 values)


Type* _ % Original _ % Original

VI 169 82.6 182 81.7

VIII 282 85.4

X 864 85.0

XIII 521 71.3 522 76.0

XIX 889 69.6

XXII 778 80.0

XXVI 1055 82.2 1346 83.8

Average 78.7 80.2Std Dev 6.4 5.7


123

5000-

4000-

3000 fter Impact-

-Original

0

2000-

1000-

0 10 20 30 40 50

Elongation (%)Figure A-1. Type 6. Class 1, Coated, Polyester

Original Tensile and Arter Impact

1241

5000-

4000-

After Impact-3000-

U) -Original

0

2000

1000

I __j

0 10 20 30 40 50

Elongation (%)Figure A-2. Type 6. Class 2. Coated, Polyester

Original Tensile and After Impact

125

10000-

8000-

6000:

00

4000 After impact-

-Original

2000

fe

~pc,

0 10 20 30 40 50

Elongation (%)Figure A-3. Type 8. Class 2, Coated. Polyester


126

15000

12000-

After Impact-

9000_Oiia

C)

0-j

6000-

3000-

0 1 10 2 0 3 10 .4 0 5 10

Elongation (%)Figure A-4t. Type 10, Class 2, Coated, Polyester


127

100007

8000-

600 After Impact-

__ -Original

00

00

N 00

Elongation ()Figure A-5. Type 13, Class 1. Coated, Polyester


10000-

8000-

After Impact- -Original

6000--o

0

4000-

2000-

0 10 20 30 40 50

Elongation (%)F'igure A-6. Type 13. Class 2. coated. Polyester

Original Tensile and After Im~pact

129

15000

12000

After Impact--Original

9000

")

0-J

6000

3000

, .. I _ *. . . .I ... . , *. ,

0 10 20 30 40 50

Elongotion (%)

Figure A-7. Type 19. Class 2. Coaed, PolyesterOriginal Tensile and Arter Impact

130

15000-

12000

After Impact-

9000 .- original

0

6000

3000-

0 10 20 30 405

Elongation (%)Figure A-8. Type 22. Class 2. Coated. Polyester

Original Tensile and After Impaet;

131

20000-

15000After Impact-

-Original

. 10000

5000

0 10 20 30 40 50

Elongation (%)

Figure A-9. Type 26, Class 1. Coated, Polyester


132

20000-

15000-After Impact-

-original

-100000

5000-

0 10 20 30 40 50

Elongation (%)Figure A-10. Type 26, Class 2, Coated, Polyester


133

Documents

OF PARACHUTE ON SHUTTLE AND SHUTTLELESS LOOMS · 00 i technical report -- ad _ natick/tr-87/015 comparison of the properties of parachute webbings woven on shuttle and shuttleless