A parallel-supercomputing investigation of the stiffness of aligned, short-fiber-reinforced composites using the Boundary Element Method

摘要

Computational experiments are carried out in three-dimensional, multi-fibre specimens with the objective of determining the influence of fibre volume fraction (φ) and aspect ratio (ar) on the effective tensile modulus of aligned, discontinuous fibre-reinforced composites. The Boundary Element Method (BEM), implemented on a 1840-node Intel Paragon parallel supercomputer using a torus-wrap mapping, enables the prediction of the tensile behaviour of composite specimens consisting of up to 200 discrete aligned short fibres, randomly dispersed in an elastic matrix. Statistical averages of the computed effective longitudinal moduli are compared with the predictions of the Halpin-Tsai equation and are found to be in good agreement for low values of ar and φ. However, as ar and/or φ increase, the predictions of the Halpin-Tsai equation fall below the computed moduli. Consideration of the finite packing efficiency of the fibres as proposed by Lewis and Nielsen results in a generalized form of the Halpin-Tsai equation whose predictions are in very good agreement with the BEM calculations for the entire range of φ and ar examined. The scatter in the computed moduli decreases with increasing number of fibres, reflecting the homogenization of the specimen brought about by consideration of larger numbers of smaller fibres. This scatter grows with increasing and ar, reflecting an increase in the magnitude and complexity of inter-fibre interactions.