THE INFLUENCE OF INCLUSION GEOMETRY ON THE ELASTIC PROPERTIES OF DISCONTINUOUS FIBER COMPOSITES

Simplifying assumptions are used to reduce micromechanical treatments to compact expressions which directly reveal the role of the inclusion shape and aspect ratio in establishing the elastic behavior of hetero geneous materials. Attention is directed to the comparison of aligned ellipsoidal and cylindrical inclusions that exhibit transversely isotr opic behavior characterized by five independent elastic constants. The se comparisons show that the effective transverse in-plane moduli (E(T ), kappa* and G(TT)* are essentially independent of inclusion shape f or aspect ratio greater than approximately 20; ellipsoidal inclusions provide higher longitudinal reinforcement than cylindrical inclusions of equivalent aspect ratio. Comparison of predictions with measured el astic moduli shows that both the cylindrical and ellipsoidal shape mod els for isolated inclusions overpredict longitudinal elastic constants for systems which exhibit evidence of inclusion agglomeration. The no tion of an effective aspect ratio based on clusters of filaments respo nding as a coherent unit appears to provide a means for reconciling a wide range of experimental observations.