Instrumented impact testing of glass reinforced polypropylene

The impact response of a glass fiber reinforced polypropylene was studied in a 3‐point drop‐weight impact test between −15 and 85°C and at a constant impact velocity of 2.2 m/s (5 mph). The response is a combination of tension and shear and can be expressed in terms of an apparent modulus, E A : 1\documentclass{article}\pagestyle{empty}\begin{document}$$\frac{1}{{E_A }} = \frac{1}{{E_{11} }} + \frac{6}{{5G_{12} }}\left({\frac{d}{l}} \right)^2$$\end{document} . Where E 11 is the tensile modulus, G 12 : shear modulus, d : specimen thickness, and l : specimen length. For a 40 weight‐percent glass reinforced polypropylene, E 11 was found to have a room temperature value of 5.8 GPa, and shear modulus of 0.43 GPa. Both decreased with temperature increase, with the shear modulus showing greater sensitivity to a temperature change. The fracture initiation and propagation energies were relatively independent of temperature. The fracture initiation energy per unit deformed volume was of the order of 1 MJ/m 3 . The total fracture energy was found to be sensitive to l / d : about 7 MJ/m 3 at l / d of 5.3 and about 1.7 MJ/ m 3 at l / d of 16.