Axisymmetric defect originated Al–CFRP interface thermo-elastic fracture study of type-III composite vessel and inverse identification of cohesive zone parameters

Abstract

Debonding existence at the interface of Al liner and overwrapped CFRP laminates may endanger the structural integrity of type-III composite vessel. In this study, CFRP and GFRP wound composite pressure vessels with Teflon sheet inserted artificial axisymmetric defect in Al–CFRP interface and without any defect were manufactured and nitrogen gas inside cooling experiments of the vessels were conducted. During the cooling axial strain and temperature responses at distinct locations of outer GFRP hoop surface were monitored to study the thermoelastic crack growth along Al–CFRP interface. The nonlinear strain response obtained under temperature change in the defect bearing specimen was considered as a result of Al–CFRP interface crack growth. Furthermore, to expose the Al–CFRP interfacial cross section of post-cooling specimen, destructive cutting and optical microscopy were performed. The Al–CFRP cross sectional microscopic observations at cutting planes showed Al–CFRP interface crack growth due to cooling in the defective specimen. Afterwards, the GFRP hoop surface axial strain experimental data fitted inversely to the surface based cohesive zone modeling (CZM) simulation results to estimate the Al–CFRP interface cohesive strength, and fracture energy.