Modeling of the mechanical properties of discontinuous-aligned-fiber composites after thermoforming

Specimens made of unidirectional and bidirectional discontinuous-aligned-fiber (DAF) composite material were elongated to different states of deformation by thermoforming. Tension tests were performed on pre-stretched specimens. The thermoforming behavior was modeled by using the Herschel-Bulkley model. The effect of fiber orientation during thermoforming was described by applying the Jeffrey equation. The combination of both the Herschel-Bulkley model and the Jeffrey equation enabled, under consideration of thermal stresses, the determination of the ultimate tensile strength of thermoformed unidirectional and bidirectional DAF materials. These results correlated well with those of the experimental tensile tests.