Effect of the cooling rate on the mechanical properties of glass fiber reinforced thermoplastic composites

For the manufacturing of the polymer based composite materials, the understanding of appropriate manufacturing process is important to improve the productivity and manufacturing process. In this study, the effect of cooling rate on the mechanical properties of glass fiber reinforced polypropylene (GFPP) composite was investigated including the tensile, interlaminar shear strength (ILSS), fracture toughness and also the impact properties. To observe the crystallinity of the polypropylene (PP), the X-ray diffraction (XRD) and the differential scanning calorimetry (DSC) analysis were employed. Based on the experimental results, it was found that the tensile strength of GFPP was decreased in the higher cooling rate due to the insufficient adhesion strength between the glass fiber and PP. Nevertheless, the fracture toughness, ILSS and impact properties of GFPP were much improved as the cooling rate increased because the adhesion strength between PP spherulites could be enhanced due to the higher crystallinity. It is expected that the investigated relationships between the cooling rate and the mechanical properties of GFPP will be widely used to optimize the manufacturing process.