Experimental investigation on mechanical properties, shrinkage and warpage of injection molded short glass fiber reinforced polypropylene

Polymer composites have remarkable popularity in the aerospace and automotive industries due to their high strength-to-weight ratio and ease of production. In this study, the effects of the glass fiber (GF) and maleic anhydride grafted polypropylene (PP-g-MA) as coupling agent on mechanical properties, shrinkage and warpage of polypropylene (PP) were investigated. Tensile, flexural, shrinkage and warpage tests were performed according to relevant standards. Results indicate that the strengths and moduli of composite specimens have been significantly improved compared to pure PP. Also, the shrinkage and warpage of composite specimens were reduced. Analysis of variance showed that both GF and PP-g-MA had a significant effect. In composite with a 40% weight fraction of GF, the tensile and flexural strengths were increased by 91% and 62%, respectively. A micromechanics model was proposed to predict the tensile modulus of composites. A good agreement between experiments and the model was achieved.