Residual stress measurements in fibre reinforced titanium alloy composites

The residual stresses in two Ti/SiC unidirectional composite panels with thick cladding were measured using two experimental methods. The variation of in-plane residual stresses in the cladding of the materials was measured by using a crack compliance method, and the average fibre stresses were inferred from the results. The applicability of a simple bending theory for the calculation of the residual stresses from curvature measurements was confirmed by a finite element analysis. Using a matrix etching method, the longitudinal fibre strains were measured from the relaxation of fibres upon dissolving the matrix in a part of the composite. The stresses in the fibre and the matrix were then calculated using a concentric cylinder model. By combining the results of both methods, the out-of-plane stresses were also determined, so that the full stress state in the reinforced section of the material could be obtained. (C) 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.