Flexural strength of a composite cylinder incorporated with thermal residual stresses

Continuous fiber reinforced composite cylinders are frequently fabricated at higher than working temperatures and are used as a primary load-carrying element in general. The purpose of this paper is to investigate the ultimate bending strength of a polymer composite cylinder and to compare the estimated results with and without thermal residual stresses incorporated. In order to figure out the progressive bending failure process generated in the cylinder, it is discretized into a number of lamina layers with different widths and is analyzed as a laminated structure. Whereas the failure of an individual lamina ply with combined flexural load and thermal residual stress effect can be understood in terms of the bridging microsmechanics model, a critical deflection condition has to be employed to determine the ultimate failure and thus the ultimate bending strength of the cylinder. An experiment has been carried out to measure the load-deflection of a polymer composite cylinder subjected to three-point bending until ultimate failure. The measured results have been used as benchmark to validate the analysis accuracy. It has been found that the present thermal residual stresses only had a marginal effect on the later part of the load-deflection curve of the composite cylinder. By ignorance of them, however, the prediction was less accurate. (C) 2003 Elsevier B.V. All rights reserved.