Effects of Fatigue Damage on the Impact Energy-Absorption Property of Talc-Reinforced Polypropylene Copolymers
Hidetoshi TAKEDA, Mikiko NAKAJIMA and Tetsuo SHOJI
Abstract:Fatigue tests were conducted using talc-reinforced Polypropylene copolymers. Then, high-speed tensile tests were conducted using the fatigue-damaged samples to reveal the effect of fatigue damage on the impact energy-absorption. The fatigue damage progression mechanism was investigated due to fracture surface observation, density measurement, and local elastic property. The following conclusions have been drawn from the experimental results: 1) The residual impact resistance decreases significantly with an increase in the lifetime ratio. 2) The fracture surfaces in a high-speed tensile test show prominent talc exposure, differing greatly from the surfaces of undamaged materials or creep-damaged materials. This state may have arisen due to the separation of talc portions from the matrix as a result of fatigue loading. 3) From the variation of density and local elastic modulus, we clarified that fatigue damage differs from creep-induced damage, which is caused by the large accumulation of voids, and is in fact caused by the talc separation described above. 4) The local elastic property measurement was shown to be an appropriate non-destructive method, capable of detecting reductions in the residual impact resistance of working products. Key Words:Talc-reinforced polypropylene copolymer, Injection process, High-speed tensile test, Residual impact resistance, Stress concentration, Notch, Fatigue damage, Fracture surface, Density, Lifetime ratio, Local elastic property, Void ratio