RELIABILITY OF COMPOSITES IN A RANDOM STRESS STATE

A general problem of reliability evaluation of an anisotropic material in a random 2-D or 3-D stress state is considered. Here, reliability is defined as a probability of the material non-failure. Strength char acteristics of the material are also considered as random ones and det ermined by the respective mean values and all possible correlations. I n contrast with the existing numerical or approximate methods, a simpl e analytical approach is offered for evaluating the main statistical c haracteristics of the reliability. A fundamental idea of the approach consists of analysis of the material's failure envelope in the form of a random linear function of certain non-linear combinations (products ) of applied random stresses, instead of the traditional consideration of the envelope as a random non-linear function of the stresses. Thus , the approach allows one to take into consideration all possible kind s of failure envelopes in the simplest analytical form. Analytical exp ressions regarding calculation of necessary statistical characteristic s are presented. Numerical examples of reliability evaluation are cons idered for unidirectional and laminated composites. (C) 1998 Elsevier Science Ltd. All rights reserved.