Extrinsic/intrinsic cohesive zone modelling and experiments on interface failure of multi-walled carbon nanotube reinforced adhesively bonded joints under mode II loading

Abstract

The present work is primarily concerned with determining mode II cohesive zone parameters for eliminating the crack tip stress-field singularity for constant, linear, and parabolic extrinsic cohesive zone models (CZMs). A semi-analytical approach is used to estimate the stress intensity factor (SIF) associated with the cohesive zone ahead of the physical crack tip. Simultaneously, the obtained SIF is compared with the popular Interaction integral technique results considering the influence of crack face traction. The influence of the order of the traction-separation law (TSL) on the global load–displacement responses is numerically investigated using a crack propagation methodology based on the nullification of SIF. The effectiveness of the proposed approach has been demonstrated through a series of experiments involving the failure of epoxy-based adhesively bonded modified compact tension specimens (CTS) subjected to pure mode II loading. The adhesives are reinforced with different multi-walled carbon nanotubes (MWCNTs) reinforcement of 0.1 wt%, 0.2 wt%, and 0.3 wt%, and its effect on the global load vs displacement responses are recorded. Specific cohesive zone parameters are obtained for the experimental problem to model the failure behaviour for a broad spectrum of cases considered using extrinsic and intrinsic TSLs.