Delamination damage of carbon fiber-reinforced polymer composite laminates under cyclic shear-induced loading conditions
Interface delamination is a major failure mode induced by in-plane shear stress frequently encountered in carbon fiber-reinforce polymer (CFRP) composite laminates structures. This failure process under monotonic loading has been successfully described using cohesive zone model (CZM). Many previ...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English |
| Published: |
2018
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| Subjects: | |
| Online Access: | http://eprints.uthm.edu.my/699/1/24%20p%20MUHAMMAD%20A%27IMULLAH.pdf |
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| Summary: | Interface delamination is a major failure mode induced by in-plane shear stress
frequently encountered in carbon fiber-reinforce polymer (CFRP) composite laminates
structures. This failure process under monotonic loading has been successfully
described using cohesive zone model (CZM). Many previous CZM approaches for
cyclic case were considering damage parameters based on a crack growth relation which
has some disadvantages for predicting a non-linear crack growth. In addition, the
previous CZM approach lacks ground in understanding the physics underlying the
delamination process and effect of stress ratio. The objective of the study is to extend
the existing CZM to account for the delamination damage evolution of CFRP composite
laminates under cyclic shear-induced loading conditions named as cyclic cohesive zone
model (CCZM). In this respect, the fatigue damage response and the residual interfacial
properties associated with the development of the CCZM are established under cyclic
shear-induced loading condition. A series of Mode-II-type tests were performed on prefatigued
end-notched flexural (ENF) beams of CFRP composite laminates, [0]8 for
different applied load ratio conditions (R = 0.1, 0.15 and 0.25) to induce only
interlaminar damage at the pre-existing delamination interface crack front. Subsequent
quasi-static test to catastrophic failure establishes the characteristic residual strength
responses of the damaged specimen. A hybrid experimental-computational approach
was introduced to obtain the residual interlaminar properties for all the loading cases.
A normalized gradual degradation rule was used to present the degradation for
interlaminar shear strength ( ), penalty stiffness ( ) and the critical Mode-II energy
release rate (
) which cover the wide range of interlaminar failure mode from wear
PTTA
out to sudden death. This interlaminar properties degradation model can describe the
characteristic evolution of the interlaminar damage response and the degradation of
CCZM properties under cyclic shear-induced loading case. The interlaminar properties
degradation model together with the CCZM model is coded by using user-define
material model (UMAT) subroutine to implement in ABAQUS finite element analysis
(FEA) software. This model had been used to simulate under 3-point bending cases and
compared with the experiment results. Result had shown that the comparison between
the FE simulation and the experiment fatigue load-life cycles for CFRP composite
laminate interfaces are close with the difference of less than 1% and shows a very
successful verification of the modified CCZM model to simulate the interlaminar
damage evolution and failure response. Besides that, an independent validation had
been run to validate the performance of interlaminar properties which were obtained in
the study. A load-deflection response under 3-point bending case was simulated based
on [0]16 ENF specimen under identical load cycle parameters and compared with the
measured experiment results. Result shows that the peak load differences between the
experiment and simulation is less than 6%. From the study, the capability of CCZM
model for cyclic case has been demonstrated by linking interlaminar properties
degradation with damage mechanics approach. This will help in understanding the
physics underlying the delamination process and effect of stress ratio. |
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