ON FLEXURAL AND TENSILE-STRENGTH FOR COMPOSITES MANUFACTURED BY RTM

The difference between tensile and flexural strength for a composite consisting of vinylester reinforced with continuous E-glass fibres arranged in a random pattern has been investigated. Both tensile tests and three- and four-point bending tests have been performed. It was found that the Weibull theory can be applied to explain the difference between ultimate strength in tension and bending provided that the theory is applied on fibre stress and not on some average composite stress. In addition it was found that influences of friction at the supports and large deflections has to be taken into account as well as nonlinear elastic material behaviour when glass fibre reinforced plastics are tested in bending. Simple closed form expressions which take these effects into account have been derived. A suggestion for proper evaluation of bending tests is presented in summarized form in Appendix A.