Mechanical properties of non-woven composite material

In recent years, the interest in recycled and sustainable materials in engineering applications has grown due to the need to reduce environmental impact and industrial scrap wastes, especially in composite material applications. Among the reinforcements that can be used in composite production, non-woven random mat carbon fibers are one of the most interesting solutions, since they allow the use of the scraps coming from the production of carbon fibers using a very easy and low energy consuming method. In this study, the mechanical properties of non-woven carbon fiber/epoxy matrix composites have been investigated by means bending, compression, tensile, and shear tests. Composite laminates were manufactured using the vacuum infusion process. Specimens were cut at four different angles (0°, 30°, 60°, 90°) with respect to the resin flow direction using a water jet cutting system. For tensile and shear tests, Digital Image Correlation (DIC) was used to map the strain on the surface of the specimen during the test, whereas, for compression and bending test, the strain was measured by means of strain gauges. The elastic modulus and the ultimate tensile stress of the considered specimens were computed and compared, considering different orientations. Finally, in order to analyze the orientation of the fibers inside the epoxy matrix, an optical analysis of the fracture surfaces was conducted using a digital microscope. Experimental results showed that for bending and tensile tests, the maximum stress and the maximum modulus were obtained for the specimens oriented at 90° while the maximum strain was obtained for the specimens along the longitudinal direction. By contrast, for compression and shear tests, the maximum stress and maximum modulus were obtained for the specimens oriented at 60°and 90°, respectively. Therefore, experimental results verify that the mechanical properties of non-woven carbon composites are affected at different angles with respect to the resin flow direction.