Jan KrystekTomáš KroupaRadek Kottner

Identification of mechanical properties from

tensile and compression tests of

unidirectional carbon composite

Introduction

Tensile test

Two compression tests

Identification of material properties

Summary

Outline

Introduction

Aim:

o 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 component of stiffness matrix (C11 , C12 , C22 , C23 , C66)

– 5 independence material constant (EL, ET , GLT , υLT , υTT´)

– strength parameters (XT, XC, YT, YC, SL, α0)

o Identification of mechanical properties using numerical simulation of tensile and

compression test in FE system MCS. Marc and optimization algorithm in

optiSlang software– Material: carbon fibers Tenax HTS 5631 and epoxy resin

Tensile test

Measured properties:o EL, ET , νLT , XT, YT

Tensile specimens Fracture of specimens

Compression test - type I

Measured properties:o YC, α0

Fracture of specimen C-I_a → α0 = 57°

Labelling Length Width Thickness YC

[mm] [mm] [mm] [MPa]

C-I_a 4.9 9.9 2.2 210

C-I_b 9.9 4.9 2.2 220

C-I_c 9.9 10.0 2.2 220

C-I_d 17.8 4.9 2.2 203

C-I_e 4.9 17.8 2.2 245*

C-I_f 9.9 17.8 2.2 272*

* incorrect fractureCompressive strength

Compression test - type II

Measured properties:o XC, YC, α0

Labelling Length Gage length Width Thickness Fiber angle YC XC Failure

[mm] [mm] [mm] [mm] [ °] [MPa] [MPa] identification code

C-II_a 165 5.0 25.0 1.1 90 185 - HAM

C-II_b 170 10.0 25.0 2.2 90 175 - AAT

C-II_c 165 5.0 9.8 1.1 0 - 987 TAM

C-II_d 170 10.0 9.8 2.2 0 - 853 HAM

Fracture of specimens

Failure identification codes

First character

Failure mode Code

Angled A

Brooming B

end-Crushing C

Delamination D

Euler buckling E

tHrough-thickness H

Kink bands K

Lateral L

Multi-mode M(x,y,z)

long.-Splitting S

Transverse shear T

eXplosive X

Other O

Second character

Failure area Code

Inside grip/tab I

At grip/tab A

Gage G

Multiple areas M

Tab adhesive T

Various V

Unkwnow U

Third character

Failure location Code

Bottom B

Top T

Left L

Right R

Middle M

Various V

Unkwnow U

ASTM International: D 3410 Standard Test Method for Compressive Properties of Polymer Matrix Composite Materials with Unsupported Gage Section by Shear Loading. ASTM International, USA.

Compression test specimen three-part identification codes

Identification of material parameterso From experiment:

LTTL νE E , αA

CFC, Y

A

C_F

CX ,A

T_F

T,YA

T_F

TX ,,,max0

max90

max0

max0

o In case of specimens with fibre angles between 15° and 75°, the nonlinear dependence of tensile force on displacement is obvious

o Nonlinear function with constant asymptote was used for shear modulus GLT in the process of identification:

LTLT nn

LT

LTLT

LTLTLT

τγG

GγG 1

1

0

0

0

1

Comparison between linear and nonlinear models

j jiei

ijinjie

,θuF

,θuF,θuFR

max

2

o By means of otimization algorithms , the following function was minimized L

LTLTLT S nτG and,, 00

o Parameters of optimization

o The strength criterion LaRC04 was used for identification of shear strength SL

Identification of material parameters

Schema of identification process

oEL – elastic modulus in the longitudinal direction

oET – elastic modulus in the transverse direction

oνLT – Poisson´s ratio

oGLT – shear modulus

oG0LT – initial shear modulus

o τ0LT – asymptote value of shear

onLT – shape parameter

o XT – tensile strength in the longitudinal direction

oXC – compressive strength in the longitudinal direction

oYT – tensile strength in the transverse direction

oYC – compression strength in the transverse direction

oSL – shear strength

oα0 – angle of the fracture plane in pure transverse

compressionLinear model Nonlinear model

EL ET υLT GLT G0LT τ0

LT nLT XT XC YT YC SL α0

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

120.0 8.0 0.337 4.0 4.6 115.0 1.2 1480 850 55 213 82 57

Identified material properties

Summary

Specimens with different geometric properties were tested in tensile test and two types of compression tests

The material parameters were identified with the use of numerical simulation of tests in finite element system MSC.Marc and optimization algorithms included in optiSlang software

Failure criterion LaRC04 was used for the identification of strength parameters

The nonlinear function with constant asymptote had to be used for description of material behavior up to fracture in the process identification

In case of small displacement, the linear relationship can be used with sufficient accuracy