Fracture toughness of SCF-reinforced composites

The incorporation of short fibers into polymers greatly affects their fracture behavior. Several modes of failure would occur in the short fiber reinforced polymer composites including fiber breakage, crack deflection, crack bridging, fiber pullout and matrix deforraa- 

Brittle polymers such as epoxy resin are mostly toughened with CFs, thus their fracture toughness can be well characterized by Kjq. The fracture toughness of CFRP composites can be determined experimentally using compact tension specimens under a plane strain condition. In this case, the specimen thickness should obey the following equation  

Microcracks form at stress singularities. Main crack reaches the first fiber and interface fracture starts. 

Interface fracture is completed. Propagation to the second fiber begins, starting interface fracture. 

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