Determination of J-R curves by load separation criterion in highly ductile TP-based composites under high temperature conditions

Abstract

This work was aimed at determining the J-integral in 5-harness satin weave carbon fabrics reinforced PolyPhenylene Sulphide (PPS) structures at 120°C>Tg (glass transition temperature). The use of the linear elastic fracture mechanics (LEFM) framework to investigate the fracture behavior is not relevant in C/PPS laminates whose angle-ply stacking sequence is characterized by a highly ductile behavior. Thus the corresponding strain energy release rate (denoted J) in angle-ply laminates can be evaluated by means of the J-integral to account for the elastic-plastic fracture mechanics (EPFM). To this aim, a particular attention was paid to determine ηel- and ηpl-factors which are key points in the evaluation of J. ηel is classically evaluated using the compliance method, whereas, ηpl is determined by means of the load separation method applied to both elastic and total displacements. The comparison between initial crack length calculated using plastic and total displacement allows us to conclude that ηpl-factor based on total displacement leads to more accurate results. Using the Sij parameter, it is therefore possible to estimate transverse crack growths for different initial notch lengths. The predicted crack growth is in a good agreement with the experimental evolution obtained using Digital Image Correlation (DIC). Finally, the present work provides the J-R curves of highly ductile composite systems for different initial crack length over width ratios (a/w).