A Novel Technique for Manufacturing Polypropylene Based Functionally Graded Materials

Abstract

This article proposes a first of its kind manufacturing route to fabricate thermoplastic based functionally graded materials (FGMs). FGMs and homogeneous composites are fabricated by means of an especially designed mold and a punch. The punch acts as an integral rotating member of the mold and has a cavity where the material is filled to produce the desired samples. The punch rotates at 1 800 min⁻¹ for two minutes to create deliberate segregation of fibers towards the periphery of the punch cavity. Polypropylene filled with 15 wt% and 30 wt% glass fibers is used to fabricate FGMs and homogeneous composites. Unfilled Polypropylene is also fabricated for comparative study. Gradation in FGM is verified by scanning electron microscopy (SEM) analysis and Shore D hardness measured in four different zones of the fabricated specimens. Gradation in FGM is also verified by ignition loss test method. It is observed from SEM that fibers tend to conglomerate towards the circumference due to inherent effects of centrifugal force. The hardness of FGMs is found to be high as compared to homogeneous composites. This route shows a promising potential for fabrication of thermoplastics based FGMs which otherwise are difficult to make because of their rapid solidifying characteristics.