Flexural fatigue behaviour of random continuous-fibre-reinforced thermoplastic composites

Static and fatigue tests have been performed in four-point bending an a random continuous-fibre-reinforced polypropylene. The data obtained were used to assess a closed-form formula, previously presented, aimed at the prediction of the fatigue response of a composite material, and explicitly accounting for the effect of the stress patio. Comparing the experimental results with similar data available in the literature for thermoset-based composites, it was shown that the presence of an inherently, ductile, thermoplastic matrix does not sensibly affect the fatigue sensitivity of the material, probably because of the constraint action of the reinforcement. From the fatigue model, a statistical model was developed, assuming a distribution of the static strength according to a two-parameter Weibull distribution. The data were in excellent agreement with theoretical pi predictions, indicating that a fatigue characterisation for probabilistic design can be achieved by a minimum of experimental tests. (C) 1998 Elsevier Science Ltd. All rights reserved.