Influence of extremely cold environmental conditions on interfacial fracture phenomenon of aerospace grade unidirectional composites

Abstract

An investigation of interfacial fracture modelling of carbon fibre reinforced plastic (CFRP) laminates at the atmosphere similar to the cruise condition of an aircraft has been carried out in this article. The Mode I & Mode II fracture tests are carried out using specimen of aerospace grade composite (AS4/914) at - 550C. Compliance based methods for estimation of crack growth have been adopted for monitoring during the fracture tests. A new set of thermally influenced interfacial fracture properties are evaluated for AS4/914 laminates. A modified traction ? separation law has been derived for Mode-I loadings considering the influence of fibre bridging under influence of extremely cold environmental conditions. This law has been evaluated from the superposition of traditional bilinear law and derived bridging law. A significant reduction in interlaminar fracture toughness has been observed due to the fragile nature of the matrix under cold environment. Experimentally obtained interfacial fracture properties are implemented into the numerical formulation. Extended Isogeometric Analysis augmented with Cohesive Zone Modelling (XIGA-CZM) for unidirectional CFRP laminate has been enhanced and enriched with thermally influenced fracture toughness properties for further investigation. Results obtained from the present XIGA-CZM formulation shows a good agreement with experimentally obtained results. Scanning Electron Microscope (SEM) observation of fractured surfaces are carried out to investigate the nature of crack propagation in CFRP laminate at - 550C.