Damage characterization of high temperature composite laminates

High temperature polymer composites are receiving increasing attention because of their potential applications to high speed transport airframe structures and aircraft engine components exposed to elevated temperatures. The objective of this study is to characterized the behavior of a typical carbon/epoxy composite proposed for high temperature applications. The mechanical properties of this unidirectional laminate were first characterized both at room and high temperatures. Damage mechanisms of transverse cracking in cross-ply laminates were studied by X-ray radiography at room temperature and in-test photography technique at high temperature. Monte Carlo simulation technique based on experimentally obtained parameters was applied to predict transverse cracking at different temperatures. Experiments and simulation showed that they agree well both at room temperature and 149°C (stress free temperature) in terms of applied stress vs. crack density. Finally, a generalized master curve that predicts the normalized applied stress vs. normalized crack density for various lay-ups and various temperatures was established.