Joshi, Sukanya Pravin
(2016)
Study of interface delamination in uni-directional CFRP laminate under static loading condition: Experiments and cohesive zone modelling.
Masters thesis, Indian Institute of Technology Hyderabad.
Abstract
Interface delamination is reported to be the dominant mode of failure in the stepped lap joints in
CFRP composites. The load transfer between the patch and panel takes place through thin adhesive
layer. And it being weak link makes it prone to damages. However, not much work was reported in
literature to understand the complex mixed-mode delamination of adhesive layer in CFRP laminates.
Our study aims at modelling mixed-mode delamination under quasi-static loading conditions for
single and double stepped lap unidirectional CFRP composite joint. Modified Cohesive mode-1
Crack and Mixed mode cohesive zone modelling developed by Benzeggagh and Kanane (1995) are
used to model the ductile adhesive failure. The mode-1 and 2 fracture toughness required for
Beneggagh-Kanane model are obtained through standard experiments. We calibrated the numerical
DCB under opening mode loading with the cohesive crack (in method-1) and the mixed mode
delamination (method-2) to obtain the cohesive crack length and mixed mode parameter. Through
the calibration we showed that the mixed-mode delmaination modelling can be either modelled
using the modified cohesive crack or Benzeggagh-Kanane model. The calibrated quantities is used
in understnading the single and double stepped lap joint. Modified cohesive crack is superior of
Benzeggagh-Kanane model in estimating the damage intiation load and ultimate failure load.
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