Influence of moisture on the fatigue behaviour of a woven thermoplastic composite used for automotive application

• An extended database on the fatigue life of a woven PA6,6 composite for three moisture conditions is provided.
• The influence of moisture conditions is reported to be less important for low fatigue stress levels.
• SEM observations showed both ductile and brittle matrix failure regardless of the moisture conditions.
• A fatigue life model is developed and show good correlation with experimental data.

Effect of moisture conditions on the fatigue lives of woven glass-fibre-reinforced polyamide 6,6 composite was investigated. Fatigue tests were conducted at a stress ratio of R = 0.1 on specimens of different stacking sequences, namely [(0/90)3], [(90/0)3] and [(± 45)3] and different moisture contents (RH0, RH50 and RH100). Although moisture content highly affects the fatigue life for high stress levels, this effect tends to lessen for lower stress levels. As this phenomenon was unexpected, additional fatigue tests in climatic chamber were performed. These tests support initial results and confirm the fact that the effect of moisture tend to decrease for low stress levels. In addition, this study proposes an enhanced fatigue life model to predict accurately the fatigue lives of this material for any moisture content and fibre orientation. This model shows a good correlation with experimental data.

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