Effect of strain rate on tensile behavior of polypropylene and carbon nanofiber filled polypropylene

In the present paper, vapor-grown carbon nanofibers were mechanically dry-mixed with polypropylene powder and extruded into filaments with a single screw extruder. Then tensile tests were performed on the single filament at a strain rate range from 0.02 min−1 to 2 min−1. Results indicate that both neat and nanophased polypropylene were strain rate-strengthening material. The tensile modulus and yield strength both increased with increasing strain rate. Results also show that infusing polypropylene with nanofibers increases tensile modulus and yield strength, but decreases ductility. Finally, based on the tensile test results, a nonlinear constitutive equation was developed to describe strain rate-sensitive behavior of neat and nanophased polypropylene.