MODELING OF THE MECHANICAL-PROPERTIES OF DISCONTINUOUS-ALIGNED-FIBER COMPOSITES AFTER THERMOFORMING

Specimens made of unidirectional and bidirectional discontinuous-align ed-fiber (DAF) composite material were elongated to different states o f deformation by thermoforming. Tension tests were performed on pre-st retched specimens. The thermoforming behavior was modeled by using the Herschel-Bulkley model. The effect of fiber orientation during thermo forming was described by applying the Jeffrey equation. The combinatio n of both the Herschel-Bulkley model and the Jeffrey equation enabled, under consideration of thermal stresses, the determination of the ult imate tensile strength of thermoformed unidirectional and bidirectiona l DAF materials. These results correlated well with those of the exper imental tensile rests. (C) 1997 Elsevier Science Limited.