New Test Method to Determine the Compressive Strength of Fiber-ReinforcedComposites

摘要

The measured compression strength of advanced composites is sensitive to specimeninhomogeneities, loading geometry, and test conditions. Consequently, the reported strength is not an intrinsic material property, but simply the failure stress under compression loading, and varies widely for a given composite system. To obtain a more accurate measure of the material property, premature failure must be avoided, and a specimen was specifically designed for this purpose. The specimen is a miniature sandwich beam with identical composite skins on either side of a neat resin core, and can be tested in axial compression as well as four-point flexure. The axial compressive properties of epoxy composites reinforced with carbon, glass, and boron filaments, and composites of carbon fibers in a polyetheretherketone (PEEK) matrix have been evaluated with this specimen in an IITRI test fixture. Failure occurred predominantly in the gage section for unidirectional composites at composite stresses and strains substantially higher than those observed with all-composite test coupons and with substantially less variation in the data. Multidirectional laminates also displayed higher strengths with the sandwich specimen.