A critique on the theories predicting the thermoelastic properties of unidirectional fibrous composites is presented. The method of approach in these theories varies from netting analysis to complex statistical methods. This critique provides a concise description and evaluation of those theories which are instructive or illustrate an interesting approach in the prediction of the thermoelastic proper ties. It is intended to contribute to better understanding and judicious application of these theories, to familiarize the researcher with the state of the art and to provide him with a basis for future effort. Thermoelastic properties predicted by the various theories are arranged in check-list form for quick reference. Typical results are included for comparison purposes and current trends are dis cussed. References and publications which provide working equa tions and/or result comparison of these theories are cited.

A unified set of composite micromechanics equations is summarized and described. This unified set is for predicting the ply microstresses when the ply stresses are known. The set consists of equations of simple form for predicting three-dimensional stresses (six each) in the matrix, fiber, and interface. Several numerical examples are included to illus trate use and computational effectiveness of the equations in this unified set. Numberical results from these examples are discussed with respect to their significance on microcrack formation and, therefore, damage initiation in fiber composites.

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As a part of a world-wide study, a commercial code (General Optimization Analyzer), based on multi-scale (micro–macro) progressive failure analysis (PFA), is used to provide theoretical predictions for damage development for a set of challenging 13 test cases proposed in the Third World-Wide Failure Exercise (WWFE-III). Multiple failure criteria were utilized aimed at tackling issues related to a wide range of damage modes, being addressed by the WWFE-III. The critical damage events/indexes predictions tracked translaminar and interlaminar composite failures, namely matrix cracking/crack density, damage initiation/propagation, delamination initiation/growth, and their interaction with fiber failure. The composite laminates analysed were both with and without a central hole and the predictions were made using constituent fiber properties and matrix properties based on materials data or identification from ply stress–strain curve inputs. Loadings included uniaxial tension or compression, biaxial, bending, thermal, and loading–unloading.