Testing Progress Report

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October 14, 2009

To: Mark WeitzFrom: Justin WalshSubject: Material Testing Report Tensile, Compressive, Impact and Shear

Evaluations of Boat Hull Laminates

Introduction

Combined efforts of Kennon and EdgeWater Boats seek to reduce the weight of boat hulls whilemaintaining or improving boat performance. Boat hulls are commonly made from chop-glass/polyester using an open mold spray layup. Kennon and Edgewater Boats are exploring theeffects of Vacuum Assisted Resin Transfer Molding (VARTM), developed for boats byEdgeWater as Single Process Infusion, SPI, and a variety of laminate schedules on hull weightand performance. It has been requested for the material properties of laminates made by the SPIinfusion process to be measured relative to laminates made from chop glass. Panels provided byEdgeWater Boats for material testing are designated as given below. Panels 1-7 were provided

in 24 inch by 24 inch cross sections varying from 0.05 to 0.125 inches in thickness. The 3DIpanel was provided as a 6 inch by 12 inch cross section measuring 0.3 inches in thickness.Images of the panels received are given in Appendix A.

Panel Designation

Panel 1: Open mold (chop glass) blended resins

Panel 2: SPI blended resins (80% PE and 20% VE)

Panel 3: SPI 100% VE

Panel 4: SPI epoxy

Panel 5: Ultra 1 epoxy

Panel 6: Ultra 2 epoxy Panel 7: Ultra 2 100% VE

Panel 8: 3DI

Contained within are tensile, compressive and in-plane shear results (*shear tests still to be

completed) for panels 1-7 as well as tensile, compressive and Izod impact results (*impact

tests still to be completed) for panel 8. Density was also measured for each of the panels to

allow for calculations of fiber volume fraction, specific strength and specific modulus. In-plane

shear tests were only explored for panels 1-7 because the thickness of panel 8 was not within the

specified thicknesses of the corresponding ASTM standard. Similarly, Izod impact tests were

not performed for panels 1-7 due to failure to meet thickness standards.

Test Methods

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Material testing was conducted in accordance with current ASTM standards. The standards used

for each test are given below. Each test was conducted on five specimens of every panel.

Tensile Properties

ASTM standard: D 638-08 Tested 0 and 90 directions for panels 1-7 Tested 0 direction for panel 8

Compressive Properties ASTM standard: D 695-08 Tested 0 and 90 directions for panels 1-7 Tested 0 direction for panel 8

Izod Pendulum Impact Energy

ASTM standard: D 256-06a Tested 0 direction for panel 8

V-Notch Shear (In-Plane Shear) ASTM standard: D 5379-05 Tested 0 direction for panels 1-7

Test Specimens

Test specimens were cut, with exception of the notch in the Izod specimen, using a CNC

controlled OMAX. The notch in the Izod test specimens was machined by the University of

Wyoming machine shop in accordance with ASTM standard D-256. Images of these test

specimens are provided in Appendix A. Test specimens were dimensioned to meet ASTM

standards for each of the given tests. Dimensioned drawings of the specimens are also given in

Appendix A.

Tension Results

Average tensile strength and tensile modulus results for the eight materials are given in Table 1.

The elastic modulus of each tensile specimen was calculated for initial linear region of the stress-

strain relation. For comparative purposes the results in Table 1 and corresponding standard

deviations are plotted in Figures 1-4. Individual results for each specimen are given in AppendixB. Stress-displacement plots and images of the specimens after loading are given in Appendices

C and D respectively. Selected stress-strain plots are provided in Figures 5 and 6 below to

display differences in material behavior. However, stress-strain plots for each of the tests ran are

not provided because extensometer slipping occurred, altering the stress-strain trend. Although

problems were encountered with the extensometer slipping, sufficient strain data was still

available for complete tensile characterization of the material.

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Table 1: Average Tensile Strengths and Moduli

Panel 1 Panel 2 Panel 3 Panel 4 Panel 5 Panel 6 Panel 7 Panel 8

Axial

modulus E1,GPa (Msi)

11.2

(1.62)

15.0

(2.18)

14.3

(2.08)

15.2

(2.20)

22.0

(3.19)

29.3

(4.24)

30.8

(4.47)

19.4

(2.82)

Transverse

modulus E2,

GPa (Msi)

12.7

(1.84)

13.6

(1.97)

12.8

(1.86)

15.3

(2.22)

35.5

(5.15)

39.5

(5.73)

40.0

(5.80)---

Axial

tensile

strength XT,

MPa (ksi)

139

(20.2)

224

(32.5)

222

(32.3)

255

(37.0)

389

(56.4)

521

(75.6)

492

(71.3)

335

(48.6)

Transverse

tensile

strength YT,

MPa (ksi)

168

(24.4)

217

(31.4)

200

(29.0)

211

(30.7)

628

(91.1)

671

(97.2)

636

(92.3)---

Figure 1: Axial Tensile Strength (psi)

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Figure 2: Transverse Tensile Strength (psi)

Figure 3: Axial Tensile Modulus (psi)

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Figure 4: Transverse Tensile Modulus (psi)

Figure 5: Panel 1 Tensile Stress-Strain Behavior

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Figure 6: Panel 6 Tensile Stress-Strain Behavior

Tensile properties of the SPI laminates were all similar in magnitude and exhibited superiortensile behavior as compared to the open mold laminate, which is to be expected. The SPIlaminate consisting of an epoxy resin appeared to show a slight (on the order of 10%) advantagein axial strength as compared to the other SPI laminates. Also, the blended resin SPI laminateappeared to exhibit slightly better properties than the 100% VE SPI laminate. Because of thedeviation of the measured data and the small differences between tensile properties of laminate2-4, no clear advantage between resins observed from the results. However, during loading oflaminates 1-3, laminates made with VE, cracking was observed both visually (Figure 7) andaudibly (acoustic emissions from cracking).

Figure 7: Cracking Prior to Failure (Panel 3)

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Failure

MicroCracking


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Cracking at the micro scale, as depicted in Figure 7, occurred for laminates 1-3, but not for thelaminate manufactured using an epoxy resin (panel 4). Cracking was observed to occur atroughly half the load at failure. Although these specimens exhibited strength on the same orderas the epoxy SPI laminate, cracking of the matrix prior to failure has certain implications on theendurance of the material.

3DI tensile specimens exhibited significantly higher strengths and moduli than the SPI and openmold glass-reinforced specimens. The average strength and modulus of 3DI was approximately20% greater than the SPI laminate infused with an epoxy resin (panel 4), which exhibited thehighest properties of the three SPI laminates. Difference in tensile properties between thesespecimens is most likely largely attributed to differences in fiber volume content. Stress-strainrelations of panels 1-4 were non-linear as displayed in Figure 5. This suggests that panels 1-4are matrix dominant laminates, which correlates to a low fiber volume. Panels 5-8 all exhibitedhookean stress-strain relations similar to results displayed in Figure 6. Therefore, the 3DIlaminate is likely to have a larger fiber volume fraction than the other glass-reinforced laminates.Actual fiber volume fractions are calculated in the Analysis of Results section.

3DI tensile specimens did not experience complete failure. Failure only occurred on one side ofthe laminate as displayed in Figure 8. The material cracked up to the CFM layer anddelaminated along the CFM.

Figure 8: Delamination of 3DI Tensile Specimen

The 3DI laminate is not symmetric. It consists of differing number of plies on each side of theCFM layer. Failure occurred on the side of the CFM containing less plies. The CFM layer actsas a material with effectively no strength separating the two sides of the laminates. Therefore,strength of this laminate is limited by the ply of CFM.

Ultra 1 and Ultra 2 laminates (panels 5-7) exhibited the highest tensile properties of the materialstested. Of the two carbon-Kevlar hybrid laminate schedules, the Ultra 2 exhibited the greatertensile properties. The Ultra 2 laminate infused with an epoxy resin (panel 6) exhibited a highertensile strength than the vinyl ester infused Ultra 2 laminate (panel 7). Difference in thesestrengths is approximately 5%. Elastic Moduli of the two Ultra 2 laminates were similar inmagnitude. Consistent with results from the SPI laminates, a clear advantage in strength can beseen in using an epoxy matrix over a vinyl ester matrix for the Ultra 2 panels.

Ultra laminates exhibited lower strength and stiffness in the axial direction than in the transversedirection. This suggests that more reinforcing material is oriented at 90 than at 0. Significant

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FailureDelaminationAlong CFM


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scatter was also observed in the results of the Ultra panels. This is attributed to the heterogeneityof the material, which can be seen in Appendix A. Due to the heterogeneity, each test specimenhad a different composition of reinforcing material. The Ultra laminate schedule is also non-symmetric with Kevlar placed on only one side of the laminates. Lack of laminate symmetrycalls into question the validity of the calculated elastic modulus for the Ultra laminates.

Compression Results

Average compressive strength results for the eight materials are given in Table 2. Forcomparative purposes the results in Table 2 and corresponding standard deviations are plotted inFigures 9 and 10. Individual results for each specimen are given in Appendix B. Stress-displacement plots and images of the specimens after loading are given in Appendices C and Drespectively.

Table 2: Average Compressive Strengths

Panel 1 Panel 2 Panel 3 Panel 4 Panel 5 Panel 6 Panel 7 Panel 8Axial

compressive

strength XC,

MPa (ksi)

230

(33.7)

245

(35.5)

268

(38.8)

228

(33.0)

179

(25.9)

213

(30.9)

134

(19.5)

303

(43.9)

Tranverse

compressive

strength YC,

MPa (ksi)

250

(36.3)

225

(32.7)

208

(30.2)

218

(31.7)

202

(29.3)

208

(30.2)

168

(24.3)---

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Figure 9: Axial Compressive Strength (psi)

Figure 10: Transverse Compressive Strength (psi)

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Compression strength results for glass-reinforced laminates are greater than carbon-reinforced

laminates. Of the glass-reinforced laminates, the 3DI laminate exhibited the largest strength.

The Ultra 2 laminate infused with an epoxy resin achieved higher strength than the Ultra 2

laminate infused with a vinyl ester resin. This again displays the advantage of infusing a

laminate with epoxy over a vinyl ester.

3DI compression specimens differ in geometry from the other compression specimens. Panel 1-

7 compression specimens were cut as dog bone specimens while panel 8 compression specimens

are rectangular. Differences in the geometries can be seen in Appendix A. These geometries

were created to meet ASTM standard D-695.

In the compression tests two types of failure were observed. Failure either occurred through the

center of the specimen or by brooming/crushing that occurred at the either the applied load or the

fixture base. Both of these failures are likely due to fiber buckling. Failure due to brooming is

displayed in Figure 11.

Figure 11: Brooming/Crushing of 3DI Compression Specimen

Brooming occurred for all of the 3DI compression specimens and was also the cause of a largenumber of failures in the Ultra compression specimens. Individual specimens that failed frombrooming are noted in Tables 8 and 9 in Appendix B. Specimens that failed through the center(displayed in Appendix D) exhibited strengths similar in magnitude to specimens that failed dueto brooming.

Analysis of Results

Because the goal of this project is to reduce weight while maintaining or improving performance,

it is useful to provide density normalized properties such as specific strength and specificmodulus. These normalized properties allow for a direct comparison between materials in terms

of strength-to-weight and stiffness-to-weight performances respectively. Composite material

mechanical properties are also greatly contingent upon fiber volume fraction. Thus, fiber

volume fractions are also calculated in that which follows.

In order to calculate density normalized properties and fiber volume fractions the density of the

composite is required. Densities of each of the materials were calculated from measured test

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specimen masses and volumes. Calculated densities, specific strengths and specific moduli are

provided in Table 3. For comparative purposes, specific modulus was plotted versus specific

strength for both axial (Figure 12) and transverse (Figure 13) tensile results. These figures serve

as a useful tool for material selection

Density of the constituents was also required to calculate fiber volume fractions. Tabulated

constituent densities were used for this purpose. Fiber volume fraction is defined as,

vf=VfVc

where Vfis the volume of the fiber and Vc is the volume of the composite. The following

equation was used to solve for fiber volume fractions:

c= cvc= fvf+mvm

where vm is the matrix volume fraction and can be written as

vm=1-vf.

By satisfying the above equations fiber volume fractions given in Table 3 were calculated.

Table 3: Physical and Density Normalized Properties

Panel 1 Panel 2 Panel 3 Panel 4 Panel 5 Panel 6 Panel 7 Panel 8

Density,

g/cm3 1.47 1.47 1.48 1.479 1.37 1.39 1.39 1.73

Fiber

volume

fraction vf,

(carbon)

(Kevlar)

0.25 .025 0.25 0.23

0.43

(0.25)

(0.18)

0.46

(0.30)

(0.16)

0.50

(0.35)

(0.15)

0.41

Specific

axial

strength,

kNm/kg

95 152 151 173 265 354 335 228

Specific

transverse

strength,

kNm/kg

114 148 136 144 427 456 433 ---

Specific 7.6 10.2 9.7 10.3 15.0 19.9 21.0 13.2

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axial

modulus,

MNm/kg

Specifictransverse

modulus,

MNm/kg

8.6 9.3 8.7 10.4 24.1 26.9 27.2 ---

Figure 12: Axial Specific Moduli vs. Specific Strength

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Figure 13: Transverse Specific Moduli vs. Specific Strength

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Figures 12 and 13 display the clear advantage of carbon-reinforced composites over glass-

reinforced composites. SPI produces a laminate with better strength-to-weight and stiffness-

weight properties than a laminate manufactured using an open mold process. The 3DI laminateexhibits the highest weight normalized mechanical properties of all the glass-reinforced

materials. This is due to differences in fiber volume fraction. The fiber volume fraction of the

3DI laminate is approximately 40% as compared to 25% for the other glass-reinforced

specimens. 15% is a significant difference in fiber volume fractions and is the reason that the

3DI laminate exhibited a higher tensile strength and modulus. Although increase in fiber volume

fraction increases the density, the increase in strength and stiffness from the increased fiber

content outweighs the negative effect of an increase in laminate density.

Conclusions

Glass-reinforced SPI infused laminates performed better in tension and compression than theglass-reinforced laminate made from an open mold process. The Ultra 2 exhibited the greatest

tensile strength and modulus. Compressive properties of glass-reinforced laminates were higher

than that of carbon-reinforced laminates. This is to be expected as carbon-reinforced composites

typically perform poorly in compression. In both tensile and compression results epoxy infused

laminates proved to perform slightly better than laminates infused with vinyl ester.

In terms of specific strength and specific modulus, carbon-reinforced laminates are ideal. The

3DI laminate was also shown to be advantageous over the other glass-reinforced laminates. This

was largely due to differences in fiber volume content. By increasing the fiber volume fraction

in the SPI laminates would likely perform similarly to the 3DI laminate. One disadvantage ofthe laminate schedule for the 3DI laminate is the inclusion of the CFM layer. This layer is a

limiting factor in the performance of the laminate due to delaminations shown to occur along the

layer in tensile testing. It is of the opinion of the author that the CFM layer will also be a

performance limiting factor in other loading scenarios (i.e. flexure).

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Appendix A: Material and Test Specimens

Section A.1: Materials as Received

Figure 14: Panel 1 (2'x2')

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Figure 21: Panel 8 (6"x12")

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Section A.2: Panels 1-7 Test Specimens Prior to Loading

Figure 22: Panels 1-7 (Left to Right) Tensile Specimens

Figure 23: Panels 1-7 (Left to Right) Compression Specimens

Figure 24: Panels 1-7 (Left to Right) Shear Specimens

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Section A.2: Panel 8 Test Specimens

Figure 25: Panel8 Tensile (Left) and Compression (Right) Specimens

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Section A.3: Test Specimen Dimensioned Engineering Drawings

Figure 26: Tensile Specimen Geometries (ASTM D 638)

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Figure 27: Compression Specimen Geometries for Panels 1-7 (ASTM D 695)

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Figure 28: Compression Specimen Geometries for Panel 8 (ASTM D 695)

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Figure 29: Shear Specimen Geometries for Panels 1-7 (ASTM D 5379)

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Figure 30: Izod Impact Specimen Geometries for Panel 8 (ASTM D 256)

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Appendix B: Tabulated Results for Each Sample

Section B.1: Axial Tensile Results

Table 4: Axial Tensile Strength Results

Sample

Panel1XT

(ksi)

Panel2XT

(ksi)

Panel3XT

(ksi)

Panel4XT

(ksi)

Panel5XT

(ksi)

Panel6XT

(ksi)

Panel7XT

(ksi)

panel8XT

(ksi)

1 17.5 29.4 31.7 42.1 57.8 70.4 64.7 48.1

2 23.4 32.4 33.2 35.0 60.2 72.6 72.9 44.2

3 20.4 34.4 31.2 36.3 58.8 79.6 71.1 47.8

4 17.0 32.1 33.1 35.5 59.6 78.5 73.0 51.0

5 22.8 34.3 32.3 35.9 45.6 76.9 74.8 51.7

Ave 20.2 32.5 32.3 37.0 56.4 75.6 71.3 48.6

StDev 2.9 2.0 0.9 2.9 6.1 4.0 3.9 3.0

Table 5: Axial Tensile Modulus Results

Samp

le

Panel1E1

(Msi)

Panel2E1

(Msi)

Panel3E1

(Msi)

Panel4E1

(Msi)

Panel5E1

(Msi)

Panel6E1

(Msi)

Panel7E1

(Msi)

panel8E1

(Msi)1 1.36 1.87 1.85 2.13 3.19 3.77 5.67 2.95

2 1.54 2.21 1.91 2.34 3.39 3.98 3.48 2.61

3 1.76 2.13 2.08 2.33 3.12 4.45 4.83 2.89

4 1.46 2.11 2.34 2.01 2.93 4.26 3.42 ---

5 1.99 2.57 2.21 2.20 3.34 4.76 4.94 ---

Mean 1.62 2.18 2.08 2.20 3.19 4.24 4.47 2.82

StDev 0.25 0.25 0.20 0.14 0.18 0.39 0.98 0.18

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Section B.2: Transverse Tensile Results

Table 6: Transverse Tensile Strength Results

Sample

Panel

1YT(ksi)

Panel

2YT(ksi)

Panel

3YT(ksi)

Panel

4YT(ksi)

Panel

5YT(ksi)

Panel

6YT(ksi)

Panel

7YT(ksi)

1 23.1 33.0 30.2 30.3 78.4 100.5 93.2

2 23.7 30.6 28.8 30.5 86.0 102.8 95.0

3 24.4 32.5 29.4 32.0 107.2 108.5 93.9

4 25.7 28.4 27.1 26.7 93.2 87.2 92.6

5 25.1 32.8 29.7 34.0 90.9 87.2 86.8

Ave 24.4 31.4 29.0 30.7 91.1 97.2 92.3

StDev 1.0 2.0 1.2 2.7 10.6 9.6 3.2

Table 7: Transverse Tensile Modulus Results

Sample

Panel1

E2(Msi)

Panel2

E2(Msi)

Panel3

E2(Msi)

Panel4

E2(Msi)

Panel5

E2(Msi)

Panel6

E2(Msi)

Panel7

E2(Msi)

1 1.74 2.32 1.36 2.03 5.12 6.27 5.74

2 1.81 1.64 2.09 2.03 5.14 6.30 5.80

3 1.92 2.10 1.74 2.24 4.90 5.64 5.59

4 1.74 1.94 1.67 2.44 --- 5.13 5.53

5 1.97 1.87 2.44 2.35 5.47 5.32 6.31

Ave 1.84 1.97 1.86 2.22 5.16 5.73 5.80

StDev 0.10 0.25 0.41 0.19 0.23 0.54 0.31

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Section B.3: Axial and Transverse Compression Results

Table 8: Axial Compressive Strength Results

Sample

Panel1XC

(ksi)

Panel2XC

(ksi)

Panel3XC

(ksi)

Panel4XC

(ksi)

Panel5XC

(ksi)

Panel6XC

(ksi)

Panel7XC

(ksi)

panel8XC

(ksi)

1 31.8 35.7 37.4 38.0 26.2 29.2 19.9* ---

2 32.8 32.3 35.6 32.3* 28.4 31.5* 18.0* 40.8*

3 33.1 37.0 41.4 32.7* 25.3 33.1 20.5* 44.9*

4 35.5 35.2 43.6 30.4* 26.6* 33.8* 18.6* 43.1*

5 33.6 37.4 36.1 31.8* 23.1 26.9* 20.4* 46.9*

Ave 33.4 35.5 38.8 33.0 25.9 30.9 19.5 43.9

StDev 1.4 2.0 3.5 2.9 2.0 2.9 1.1 2.6* Crushing/brooming occurred at applied load or support base

Table 9: Transverse Compressive Strength Results

Sample

Panel1

YC(ksi)

Panel2

YC(ksi)

Panel3

YC(ksi)

Panel4

YC(ksi)

Panel5

YC(ksi)

Panel6

YC(ksi)

Panel7

YC(ksi)

1 36.3 31.4 31.9 28.1 29.3 31.9* 22.7*

2 37.1 30.2 28.0 32.9 29.0 30.9* 24.2*3 32.7 33.9 30.9 33.3 29.7 30.4* 26.3*

4 36.6 36.7 26.7 31.9 29.1 29.2 23.0

5 38.8 31.2* 33.5 32.1 --- 28.3 25.5*

Ave 36.3 32.7 30.2 31.7 29.3 30.2 24.3

StDev 2.2 2.6 2.8 2.1 0.3 1.4 1.6* Crushing/brooming occurred at applied load or support base

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Appendix C: Stress-Displacement Figures

Section C.1: Tension Results

Figure 31: Panel 1 0 Tensile Stress - Displacement

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Figure 34: Panel 2 90 Tensile Stress Displacement


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Figure 37: Panel 4 0 Tensile Stress Displacement

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Section C.2: Compression Results

Figure 46: Panel 1 0 Compressive Stress Displacement

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Appendix D: Test Specimens after Loading

Section D.1: Axial Tensile Specimens after Loading

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Figure 61: Panel 1 Axial Tensile Specimens after Loading

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Figure 67: Panel 7

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Axial Tensile Specimens after Loading


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Section D.2: Transverse Tensile Specimens after Loading

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Figure 69: Panel 1 Transverse Tensile Specimens after Loading

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Section D.3: Axial Compression Specimens after Loading

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Figure 76: Panel 1 Axial Compression Specimens after Loading

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Section D.1: Transverse Compression Specimens after Loading

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Figure 84: Panel 1 Transverse Compression Specimens after Loading

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Documents

Testing Progress Report