Off-axial Compressive Properties of 3-axially Reinforced 3D Composites

Mechanical properties of multi-axis three-dimensional fabric composite materials are considered to be influenced by molding condition and molding defects. Off-axial compressive properties, which are sensitive to defects, have been studied for rod piercing type threeaxially reinforced threedimensional (3D3A) composites. The following results are obtained. (1) Initial failure on the off-axial compression of the 3D3A composites was detected as drifts of apparent Poisson's ratio. And that of composites without defects was found to be generated as interfacial debonding at the definite corners of rod at which tensile stress concentrates. On the other hand, in the case of the composite having molding defects, the initial failure was developed from the defects as starting points. (2) The compressive modulus was depressed by the presence of defects. The stress at the initial failure depended mainly on the defects and slightly on the molding pressure of the composite. Interfacial strength between rod and matrix, however, had little influence upon the off-axial compressive properties.