Effects of Environmental Temperature and Recycling onTensile Strength and Fracture Behavior for Notched GF/PP Plate
Toshihiro YAMAMOTO and Hidetoshi TAKEDA
Abstract:The effects of environmental temperature on the tensile strength and fracture behavior of notched plates made from virgin material and recycled material were investigated. The virgin material was a short-glass-fiber-reinforced polypropylene (GFPP). GFPP plates, each containing 30 % E-glass fiber by weight, were made by injection molding. The pellets were kneaded again, and an injection-molded plate was made. This plate is referred to as recycled GFPP (R-GFPP) plate. The mean fiber lengths of GFPP and R-GFPP were 3.5 and 0.4 mm, respectively. The notch-root radius was 0.5, 1, and 2 mm. The tensile test was carried out in thermostatic chamber at temperatures of 22, 40, 60, 80, 100, 120, and 140 for a constant crosshead speed. The process of initiation and growth of damage near the notch root during tensile test was measured by means of the luminance measuring technique using a CCD camera. The experimental results show that the configuration of the damaged zone and that of the fracture surface were dependent on the environmental temperature. At temperatures lower than a certain value, the initial formation of the damaged zone was observed only near the notch root. The specimen failed in a brittle manner at the maximum load. In this temperature range, the fracture criterion could apparently be applied on the basis of the severity near the notch root. The effect of the notch geometry on the tensile strength decreased with an increase in the environmental temperature. Furthermore, over a certain temperature range, the maximum nominal stress of the notched specimen was approximately equal to that of the smooth specimen. Damage was also observed outside the stress concentration zone in the notch root. The specimen failed in a ductile manner. R-GFPP showed a more remarkable deterioration in strength with an increase in the environmental temperature. Key Words:Fiber reinforced plastics, Notch, Tension, Temperature, Recycle, Nondestructive evaluation, Luminance