The Tensile Fatigue Behaviour of Glass Fibre Reinforced Plastic Composites based upon a Rubber-Modified Epoxy Matrix

A thermosetting epoxy polymer was modified by incorporating 9 wt.% of a carboxyl-terminated butadiene-acrylonitrile (CTBN) rubber, essentially in the form of well-dispersed micro-particles. The stress-controlled constant amplitude (CA) tensile fatigue behaviour at a stress ratio, R = 0.1, for both the neat (i.e. unmodified) and the rubber-modified epoxy polymer was investigated. The addition of the rubber particles increased the fatigue life of the bulk epoxy polymer by a factor of about three to four times. Cavitation of the rubber particles, which then enabled further plastic deformation of the epoxy matrix to occur, was the mechanism which was observed to account for the enhanced fatigue life of the bulk rubber-modified epoxy polymer. The neat and the rubber-modified epoxy resins were then infused into a quasiisotropic lay-up of E-glass fibre non-crimp fabric. A resin infusion under flexible tooling (RIFT) production method was employed to fabricate the glass fibre reinforced plastic (GFRP) composite panels. Stress-controlled CA tensile fatigue tests, at a stress ratio, R = 0.1, were performed using these GFRP composites, and the extent of matrix cracking and stiffness degradation were continuously monitored during the cyclic fatigue tests. As for the fatigue behaviour of the bulk epoxy polymers, the fatigue life of the GFRP composite was increased by a factor of about three times due to the presence of the rubber particulate phase in the epoxy matrix. Suppressed matrix cracking and

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