The hygrothermal behaviour of glass-fibre-reinforced thermoplastic composites: a prediction of the composite lifetime

A study in an accelerated environment of the mechanical properties of glass -fibre-reinforced thermoplastic composites based on polyamide 66, poly(ethy lene terephthalate) and poly(butylene terephthalate) is reported. Results s howed a decrease of -90% to -50% in ultimate stress to failure and impact s trength with ageing according to the nature of the matrix. Increasing the a geing temperature resulted in a faster degradation rate. Depending on the m atrix nature, the mechanisms of ageing seemed to be different. Polyamide 66 and poly(butylene terephthalate) composites showed effects of both physica l ageing through plasticisation and chemical degradation through chain scis sion. Poly(ethylene terephthalate) composites did not give evidence of any plasticisation. The extent of hydrolysis was quantified through end-group a nalysis and gel permeation chromatography measurements. Scanning electron m icroscopy observations showed that hygrothermal ageing reduced the effectiv eness of the interfacial bonds. (C) 2001 Elsevier Science Ltd. All rights r eserved.