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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.

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A new procedure for fitting fatigue models (consisting of a deterministic equation defining the shape of the S-N curve and a probabilistic description of the data scatter) is presented. The procedure consists of (1) transforming the fatigue data into equivalent static strength data by using the deterministic equation in the fatigue model with unknown parameters, (2) obtaining the maximum-likelihood estimates for the parameters of the (two-parameter Weibull) distribution describing the equivalent static strength data, and (3) repeating Steps 1 and 2 until the largest maximum-likelihood estimate of the shape parameter is obtained. The procedure can handle runouts and tab failures through progressive censoring. Finally, the procedure is well defined when small fatigue data samples are available.

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