ON THE NONLINEAR VISCOELASTIC BEHAVIOR OF POLYMER-MATRIX COMPOSITES

The non-linear viscoelastic response of a unidirectional carbon-fibre- reinforced polymer composite has been studied, For the needs of the pr esent study, creep and recovery tests in tension for different stress levels were executed while measurements were made of the creep and rec overy strain response of the composite system. For the description of the viscoelastic behaviour of the material, Schapery's non-linear visc oelastic model was used. For the description of the non-linear viscoel astic response of the material and the determination of the non-linear parameters, an analytical method, based on a modified version of Scha pery's constitutive relationship where a viscoplastic term was added, has been developed. The method has successfully been applied to the cu rrent tests and an estimation of the non-linear parameters was success ful. useful results and conclusions for the applicability of the new m ethod were also extracted. (C) 1998 Elsevier Science Ltd. All rights r eserved.