Mechanical characteristics, constitutive models and fracture behaviors of short basalt fiber reinforced thermoplastic composites under varying strain rates

Mechanical properties and fracture behaviors of polypropylene (PP) and short basalt fiber reinforced polypropylene (BFRPP) composites were studied at varying strain rates ranging from 0.001 s-1 to 400 s-1. Full-field strain analyses were performed via Digital Image Correlation (DIC) methods to evaluate the entire progressive failure process. The strain localization phenomenon caused by the strong toughness of PP matrix is found. Based on Halpin-Tsai model, the tensile strength prediction model of BFRPP composites was established, and the tensile strength under different fiber content and strain rate was predicted. Based on Cowper-Symonds model, a onedimensional phenomenological constitutive model related to the strain rate of BFRPP composites was established by introducing strain rate related functions. It reveals the strain rate dependent behavior of the stressstrain curve of BFRPP composites. Results show that the tensile strength of PP and BFRPP has strongly positive strain rate sensitivity. Microscopic failure modes of BFRPP composites mainly include matrix cracking, interfacial debonding, fibers pulled out and fibers breakage. As the strain rate increases, the fracture behavior of PP matrix in BFRPP composites changes from ductile to brittle, however basalt fiber is always brittle fracture from relatively flat transverse fracture to oblique fracture with an angle.