AN ENERGY-BASED ANALYTICAL PUSH-OUT MODEL APPLIED TO CHARACTERIZE THEINTERFACIAL PROPERTIES OF KNITTED GLASS-FIBER-REINFORCED PET

In this study, the interfacial properties of weft-knitted glass fibre (GF)-polyethylene terephthalate (PET) composites were examined. On thi n polished cut-outs of knitted GF/PET composite parts, push-out experi ments were carried out at different temperatures using a push-out devi ce set up in a SEM. Load-displacement curves were digitally recorded. FEM results suggested that crack initiation was located at or near the top of the free specimen surface. To interpret the load-displacement curves from the push-out experiments a new energy-based model was prop osed. The model follows the principle of minimal energy and includes t he effects of friction, Poisson expansion of the fibre, and energy rel ease of the debonded part of the fibre. Crack progression was calculat ed applying the concept of interfacial surface fracture energy. With t he proposed analytical model, the interfacial properties of GF/PET wer e extracted. The model is compared with existing approaches. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.