Enhancing the tribological performance of polymeric laminated composite materials by adopting the functionally graded materials technique

The concept of functionally graded materials was adopted to experimentally enhance the wear resistance and hardness of the traditional laminated composite materials made of long glass fibers and epoxy resin in this work. The laminated composite structure consisted of twelve layers. The redistribution of fibers through the width of the specimens produces three distinct functionally graded patterns: linear, non-linear, and stepwise. A Shore-D hardness tester was used to get the hardness of each pattern, while their wear and friction coefficients were measured through a Pin-On-Disc tester according to ASTM standards for applied load varied from 10 to 40 N and sliding speed ranged from 0.2 to 0.8 m/s. The study also considered the effects of fiber orientation relative to the sliding direction, i.e., parallel, anti-parallel, and normal. The worn surfaces of the composite were inspected using an optical microscopy microscope, X-ray diffraction analysis, and scanning electron microscope. The results indicated that the wear rate, friction coefficient, and temperature of a functionally graded composite are influenced by several factors, including sliding speed, applied load, sliding distance, and fiber orientation. The composite demonstrated superior wear performance in the normal orientation compared to parallel and anti-parallel ones. The linear patterns improved the wear resistance rate and coefficient of friction of conventional composites with an average of 15% and 3%, respectively, in the normal orientation in all manners of applied forces and sliding velocities. Meanwhile, the stepwise patterns enhanced both of them by up to 25% and 8% in parallel and anti-parallel orientations for the same cases.