Micromechanics for Performance Simulation

Abstract

The manner in which mechanics should be used to describe strength is not firmly established for homogeneous materials, and is less well understood for composite materials. Moreover, if one wishes to describe the degradation of strength over long periods of time (say, during the engineering use of such materials) this fundamental weakness precludes definitive systematic use of mechanics for that purpose as well.

The use of various local mechanics approaches seems to offer hope of overcoming these limitations. Present efforts suggest that it is possible to describe the strength of composite materials using micromechanical representations of the failure modes that control the strength of those materials. In fact, it appears that it may be possible to construct such micromechanical models in such a way that the changes in the parameters in those models during long-term loading can be measured and used to estimate the changes in the strength of the global composite. In addition, those parameters may be related, in many cases, to the manner in which the composites were synthesized and manufactured, so that a means of “designing” material systems for specific long-term performance may be provided by this approach.

The present paper outlines one example of such an approach. The performance discussed is tensilc-strength-controlled remaining strength and life of fiber reinforced composite laminates with typical constituent properties. The sensitivity of the predicted results to various micro-parameters (including some statistical ones) will be described, and related observations will be compared to the results.