The effect of fibre-content gradient on the mechanical properties of glass-fibre-mat/polypropylene composites

Glass-fibre-mat reinforced polypropylene (PP) composites have been manufactured with spatially-graded distributions of fibre content. Flexural and impact tests were carried out to investigate the effect of these fibre distributions on the load-direction-dependent mechanical properties of the composites. Isotropic composites with uniform fibre content distribution through the specimen thickness were also prepared for comparison with the spatially-graded composite. When the face of a sample with high glass fibre content was loaded, the flexural strength and the impact energy of the composite showed improved values by comparison with those of the isotropic composite. On the other hand, poor flexural strength and impact energy were observed when the face of the sample with low fibre content was loaded. Finite-element analysis was performed to investigate the stress/strain distribution of the deformed model structure with the variation of moduli through the thickness. Despite having the same fibre content, the glass-fibre-mat/PP composites could have the characteristic mechanical properties with different spatial distributions of fibre content.