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

Computational experiments are carried out in three-dimensional, multi-Þbre specimens with the objective of determining the inßuence of Þbre volume fraction (/) and aspect ratio (a3 ) on the e¤ective tensile modulus of aligned, discontinuous Þbre-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 Þbres, randomly dispersed in an elastic matrix. Statistical averages of the computed e¤ective longitudinal moduli are compared with the predictions of the HalpinÐTsai equation and are found to be in good agreement for low values of a3 and /. However, as a3 and/or / increase, the predictions of the HalpinÐTsai equation fall below the computed moduli. Consideration of the Þnite packing e¦ciency of the Þbres as proposed by Lewis and Nielsen results in a generalized form of the HalpinÐTsai equation whose predictions are in very good agreement with the BEM calculations for the entire range of / and a3 examined. The scatter in the computed moduli decreases with increasing number of Þbres, reßecting the ÔhomogenizationÕ of the specimen brought about by consideration of larger numbers of smaller Þbres. This scatter grows with increasing / and a3 , reßecting an increase in the magnitude and complexity of inter-Þbre interactions