Comparison of strength behavior of unidirectional HMC and HSC composite

subjected to biaxial loading

J. Krystek, R. Kottner, L. Bek

19th Conference on Materials and Technology; 22 and 23 November 2011, Portorož, Slovenia

Outline

• Introduction• Material model• Mechanical properties• Failure criteria• Experiments• Numerical analysis• Summary

Introduction

– Currently, the failure of composite is well predictable only in basic cases

– Biaxial tests shown dependence of specimen strength on the ratio of tension and compression

Wrapped pin joint

Mechanical propertiesTensile test

Type of

fibers[GPa] [GPa] [ - ] [GPa] [GPa] [ - ] [MPa] [MPa] [MPa] [MPa] [MPa] [ ° ]

HSC 120.0 8.0 0.337 4.8 110.0 1.11 1800 850 55 213 82 59

HMC 200.0 6.8 0.290 6.5 128.0 1.28 1770 685 42 160 60 57

1E 2E 12 012G

012 12 n T X CX T Y C Y L S

Elasticity and strength parameters of composite

0 α

Compression test – type I Compression test – type II( E1, E2 , ν12 , XT, YT ) ( YC, α0 ) ( XC, Y C, α0 )

ASTM D 3410ASTM D 3039

Material modelo Unidirectional composite material

66

66

2322

222312

232212

121211

00000

00000

002000

000

000

000

C

C

CC

CCC

CCC

CCC

C

Stiffness matrix of transverse isotropic material

– 5 independence components of stiffness matrix (C11 , C12 , C22 , C23 , C66)– 5 independence material constants (E1, E2 , G12 , υ12 , υ13)

1212

11

012

12012

012

1212

1nn

τ

γG

GγG

– Nonlinear function with constant asymptote was used for shear modulus G12 :

– This material model is not standard part of used FEM system MSC.Marc, therefore it was implemented into MSC.Marc system.

Force and extension dependencies

Failure criteria

o FIBRE FAILURE

1T1 X

FI

12L

213

212

2

T1

SXFI

1T1 X

FI

1f

T1

PX

FI

01

o MATRIX FAILURE

– Maximum stress

– Hashin

– LaRC04 #3

– adjusted LaRC04 #3

– Maximum stress

– Hashin

– LaRC04 #2

– adjusted LaRC04 #2

01

01

01

1C3 Y

FI 03

12

12 2L

213

212

2T

32223

2

T32

C32

2

T

C

SSSYS

YFI

032

12

nLL

L2

nTT

T

SS

FI

0 ;0 13 12

1nLL

L2

1nTT

T

MM PSPS

FI

0 ;0 13

Schema of biaxial test

Testing machine

– Biaxial test

– Standard testing machine Zwick/Roell Z050 was supplemented by second loading axis for the localized compression

– The second loading axis consisted of power machine vice VMC-130 and HBM C9B compact force transducer

Experiments

– Loading was applied in two basic steps

Loading steps

– Specimens were cut using water jet from unidirectional composite plates, which were made from 8 layers of prepreg

– Geometry parameters of specimens

HSC composite

b = 5.0 mm, h = 2.2 mm, l = 240 mm

HMC composite

b = 4.8 mm, h = 2.0 mm, l = 240 mm

– Geometry parameters of compression element:

w = 20 mm, v = 10 mm, R = 1 mm

– Specimens were supplemented with aluminium pads on both sides.

– All pads were bonded on the specimens by Araldit AV 138M + HV 998 adhesive

Geometry parameters

Specimens with aluminium pads

Specimens

Experiments - results

Dependences of specimen strength on the combination of tensile and compression forces

HSC HMC

Failure of matrix in biaxial test Failure of fibres in biaxial test

– Compressive strength (matrix failure) is increasing with the tensile force

– Tensile strength (fibre failure) is decreasing with the compressive loading

b = 5.0 mm, h = 2.2 mm b = 4.8 mm, h = 2.0 mm

Numerical analysis

o FEM system: MSC.Marc

Boundary condition

– Regarding symmetry of the specimen, only one quarter of the specimen was modelled

– Loading was applied in two basic steps which correspond with experiment

– Compressive loading was applied by force acting on contact surface which represented compressive element

– Friction was neglected

Modeled quarter

Numerical analysis

Failure index for Hashin - fibre failure

Failure index for LaRC04 #2 - matrix failure Failure index for Maximum stress - matrix failure

o HSC composite

Summary

– Selected stiffness and strength parameters of composites were identified

– Composites had high modulus carbon (HMC) fibres and high strength carbon (HSC) fibres

– Strength analysis of the composites subjected to biaxial loading was performed

– Experimental specimens were loaded in two perpendicular directions

– Specimens were exposed to the combination of the tension in the fibre direction and the localized compression in the transverse direction

– Loading was applied in two basic steps

– Experiments showed similar dependence of specimen strength of both types of composite on the ratio of tension and compression

– Compressive strength is increasing with the tensile force

– Tensile strength is decreasing with the compressive force

– Predictive capabilities of different failure criteria for composite materials were tested in the failure analysis - Maximum stress, Hashin, LaRC04