Shape Instabilities in Composites Resulting from Laminate Anisotropy

Abstract

Experimental results show that mid-plane symmetric composite laminates of semi-cylindrical, curved geometry warp during manufacture and continue to change shape with changing temperature throughout their service life. A mathematical model is presented which predicts the observed shape change and yields results which compare closely with the experimentally obtained values. Further, a method of modifying the lami nate stacking sequence to counter the environmentally induced shape instability is sug gested and a predictive model, based on classical laminated plate theory, is developed. Measured instabilities of optimized laminates indicate that the proposed technique does modify the shape stability of test laminates as predicted. Thus, this technique allows the design and manufacture of curved composite laminates which are shape stable over a wide temperature range.