Tensile mechanical and perforation impact behavior of all-PP composites containing random PP copolymer as matrix and stretched PP homopolymer as reinforcement: Effect of β nucleation of the matrix

All polypropylene (all-PP) composites were manufactured by exploiting the polymorphic forms of PP, in which alpha (α)-PP homopolymer tapes worked as reinforcement and β-nucleated random PP copolymer (β-rPP) as matrix. Both unidirectional (UD) and cross-ply (CP) laminates were prepared by tape winding technology combined with a film stacking method followed by hot pressing. To study the efficacy of using β-rPP as matrix, all-PP composites were also prepared with α-PP tape as reinforcement and alpha random PP copolymer (α-rPP) as matrix and their properties were compared. The mechanical performance of the composites was investigated by dynamic mechanical thermal analysis (DMTA), static flexure and dynamic impact tests. The volume fractions of the reinforcement and the void content were estimated by using optical microscope images. Both the DMTA and the static flexural bending tests revealed that the α-PP tape acted as a more effective reinforcement for the β-rPP matrix than for the α-rPP, especially for all-PP composites of UD lay-up. The perforation impact properties were determined from instrumented falling weight impact (IFWI) tests, performed at room temperature. It was found that transcrystalline layer is responsible for the stress transfer from the β-rPP matrix to the α-PP reinforcement.