Lightweighting of PP/GF: foamed composites for automotive applications

Abstract

Lightweight construction is one of the main strategies conducted by carmakers in order to reduce fuel consumption and greenhouse gas emissions. Since the demand of plastic and composite materials for automotive applications is continuously growing, lightening approaches like foaming techniques are being introduced with the aim of decreasing their weight. The present work aims to compare the morphology and mechanical properties of plastic foams obtained by two different foaming technologies: MuCell® and IQ Foam®. Solid and foamed plates of glass fiber reinforced-polypropylene (PP/GF) were injection molded by using MuCell® and IQ Foam® processes combined with the complementary tool technology Core Back expansion molding. The morphology analysis of the obtained plates was carried out through Scanning Electron Microscopy (SEM) and Computed Tomography (CT) techniques, and the mechanical properties were assessed by means of tensile, flexural and impact tests. The morphology analysis revealed the presence of solid skin-foamed core structure in the foamed samples. The mechanical properties decreased gradually with the apparent density of the microcellular plates. By increasing the thickness of the part because of the expansion of the cavity, the apparent density decreased but the flexural stiffness was greatly enhanced. Foamed samples obtained by IQ Foam® technology exhibited lower cell density than that of the MuCell® ones, but consequently higher resistant area, and thus, slightly higher mechanical properties. The new IQ Foam® technology is able to produce foamed parts with properties comparable to that of the MuCell® process, offering additional benefits such as cost-effectiveness, easy to use and machine-independence.

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