Prediction of overall tension behavior of short fiber-reinforced composites

The bridging stress of fibers along the crack surface plays an important ro le in analyzing the tension behavior of short or long fiber-reinforced comp osites. This paper uses the inclusion theory to obtain the expression of br idging stress for short fiber reinforced composite (SFRC). A simplified mod el with periodically distributed fibers is proposed to estimate: the averag e fiber spacings. The total fracture resistance is calculated as an energy summation including interface debonding energy dissipation, frictional slid ing work between fibers and matrix, strain energy increment of fibers and m atrix. The bend over point (BOP) stress is calculated by this fracture resi stance. The necessary conditions of the fibers and matrix for the multiple cracking in SFRCs are discussed and the expression of ultimate external str ess is derived. The critical fiber volume fraction for the strain hardening response is determined by an iteration method. In the meanwhile, the avera ge spacing between two short fibers is proposed by a periodical distributio n assumption. The theoretical prediction is compared with experimental data . (C) 1999 Elsevier Science Ltd. All rights reserved.