Evaluation of Aluminum Foil-Interlayed High-Modulus K13CU Pitch Fiber-Siloxane-Modified Resin Composite Panels

摘要

A contractor is currently fabricating flat panels of high-modulus fiber K13CU/siloxane-modified polycyanurate matrix resin composites. Mechanical testing at a commercial lab showed that the interlaminar shear strengths and the flat-wise tensile properties were below that expected. We evaluated the degree of consolidation and cure to verify that incorporated foil layers were not causing premature failure. A number of composite panels were analyzed using dynamic mechanical analysis and optical microscopy. The measured glass- transition temperatures (Tg's) of the samples all suggested that they were properly cured. A solvent exposure test developed in our laboratory also corroborated these results. Optical micrographs of cross-sections for the different composites indicated good consolidation and no observable foil debonds. All of the samples exhibited similar failure modes from our testing. The focus of the lower-than-expected strengths was then placed on the sample preparation procedure for mechanical testing. Sample preparation of the test specimens at the testing laboratory was identified as the cause for the lower- than-expected strengths. Subsequent tests on articles with proper sample preparation yielded acceptable mechanical strengths.