Study On Interface Parameters Of Composite Materials With Noncircular Cross-Sectional Reinforcing Fiber

The mechanical property of the matrix is significantly different from the fiber in the fiber-reinforced composite. The discontinuity of mechanical property occurs at the interface between matrix and fiber, which results in the phenomenon of stress concentration. The stress concentration is an important reason for the internal injuries, defects and damage. Neutral reinforcing fiber does not disturb the stress field in the surrounding elastic matrix and can remove the stress concentration phenomenon. Therefore, it is meaningful to investigate the interface parameters in case that the fiber reinforced composite satisfies the situation of neutral reinforcing fiber.In the traditional research, it is always assumed that the interface between matrix and fiber is perfect. However, the neutral reinforcing fiber does not exist in the case of perfect interface, while possibly occurs when interface is imperfect. Here, an imperfect interface model that based on the zero thickness of the line-spring is proposed. The three-phase model involving matrix, reinforcing fiber and interface is simplified, and therefore a two-phase model that involves matrix and reinforcing fiber and satisfies the imperfect condition of zero thickness of the line-spring is obtained. According to the imperfect interface condition and theory of elastic mechanics, the interface parameters of neutral reinforcing fiber in isotropic and transversely isotropic material are derived respectively with consideration of anti-plane shear and plane deformation.The influences of shapes of reinforcing fiber involving circle, ellipse and intersectant circle on the interface parameters are discussed. It indicates that the interface parameters are related to shapes of reinforcing fiber. It also reveals that the interface parameters are not influenced by the magnitude of the stress field or displacement field acting on the matrix, but influenced by the loading mode. The interface parameters of neutral reinforcing fiber in isotropic and transversely isotropic material have similar form of expression. With consideration of plane deformation, unified forms of the interface parameter in conditions of plane stress and plane strain are made in isotropic and transversely isotropic material respectively.In this paper, we study the effects of loading, component material properties and cross-section geometry of reinforcements etc. on interface parameters which meet neutral conditions, providing a basis for the interface performance design of non-circular neutral reinforcing fiber.