Flexural properties of unidirectional hybrid composites of three layers, carbon fibers/epoxy, aluminafibers/epoxy and low elastic layers

An elastic layer was introduced into unidirectional composites laminarily reinforced with carbon (CF) and alumina (AF) fibers to analyze its effect on the flexural properties. When the hybrid ratio of CF-reinforced layer was below 60%, both of the hybrid composites (INL) having an elastic (polyester fiber reinforced) layer between the CF- and AF-reinforced layers and the corresponding hybrid composites (NOL) without the elastic layer started to fracture from the AF-reinforced layer (tension side). When the hybrid ratio of CF-reinforced layer was higher than 60%, small cracks were formed in the CF-reinforced layer both in the NOL and INL that was allowed to yield under a low bending load. The presence of the elastic layer can relieve the negative effect of hybrid lamination, sometimes preventing the fracture that is often observed in NOL. Furthermore, the deflection at the initial fracture and the streess at initial fracture increased significantly in INL compared with those of NOL,because of the decreased stress arising between the CF- and AF- reinforced layers in the formers.