FLEXURAL FATIGUE BEHAVIOR OF RANDOM CONTINUOUS-FIBER-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, an d 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 constrai nt action of the reinforcement. From the fatigue model, a statistical model was developed, assuming a distribution of the static strength ac cording to a two-parameter Weibull distribution. The data were in exce llent agreement with theoretical pi predictions, indicating that a fat igue characterisation for probabilistic design can be achieved by a mi nimum of experimental tests. (C) 1998 Elsevier Science Ltd. All rights reserved.