Mechanical properties of woven laminates and felt composites using carbon fibers. Part 2: interlaminar properties

This paper compares interlaminar shear strength, interlaminar fracture toughness and compression-after-impact strength of epoxy resin matrix composites reinforced with carbon fiber woven fabrics and carbon fiber felts, and investigates the influences of weave pattern and needle-punching density. With regard to the weave pattern of fabric layers in woven laminates and felt/resin composites, plain weave with a smaller radius of curvature of yarns is preferable for obtaining higher damage tolerance of the composites. Felt/resin composites have improved interlaminar and damage tolerant properties as compared with woven laminates. These properties of the felt/resin composites improve with increasing needle-punching density. The compression-after-impact strength of the woven laminates and felt/resin composites can be uniquely related to the mode I interlaminar fracture toughness regardless of the types of composites, and the result has been interpreted by applying the equation derived by Ilic and Williams [Theoret. Appl. Fract. Mech. 6 (2) (1986) 121]. Damage tolerance of the felt-reinforced composites utilizing more brittle carbon matrix has also been investigated.