Effect of Fiber Length on Hysteretic Heating of Discontinuous Fiber-Reinforced Polypropylene

Abstract

Fatigue application of a polymeric material is limited due to its hysteretic heating behavior. In this work, effort has been made to understand the effect of fiber reinforcement and length of the reinforcing fibers on hysteretic heating behavior and its mechanisms. Unreinforced, 20% short glass fiber-reinforced and 20% long glass fiber-reinforced polypropylene materials have been injection-molded and subjected to a finite number of fatigue cycles. The load required for constant deflection and the surface temperature of materials during testing was measured and correlated with the hysteretic heating mechanism. During material deformation, the presence of the reinforced fibers and fiber-matrix interface in the reinforced material contributed more internal friction, and resulted in higher heat generation than unreinforced material. Higher fiber density and the inferior fiber-matrix bonds existing in the short fiber-reinforced material generated higher heat than that of long fiber-reinforced material during testing.