Fiber packing and elastic properties of a transversely random unidirectional glass/epoxy composite

Image analysis was used to characterize the microstructure of a unidirectio nal glass/epoxy composite which was found to be transversely randomly packe d. Starting from a measured distribution of fiber diameter, a Monte Carlo p rocedure was employed to generate periodic computer models with unit cells comprising of random dispersion of a hundred non-overlapping parallel fiber s of different diameter. The morphology generated in this way showed excell ent agreement with that of the actual composite studied. An ultrasonic velo city method was used to measure a complete set of composite elastic constan ts and those of the epoxy matrix. On the basis of periodic three-dimensiona l meshes, the composite elastic constants of the Monte Carlo models were ca lculated numerically. Numerical and measured elastic constants were in good agreement. It was shown numerically that the randomness of the composite m icrostructure had a significant influence on the transverse composite elast ic constants while the effect of fiber diameter distribution was small and unimportant. The predictive potential of the Halpin-Tsai and some other mod els commonly employed for predicting the elastic behavior of unidirectional composites was also assessed. (C) 2000 Elsevier Science Ltd. All rights re served.