Effect of reinforcement fiber cross section geometry on interfacial debonding behavior of composites

Interfacial properties between matrix and reinforcement in composite materials are important because the material properties of composites depend on the interfacial properties. In this study, we conducted Single Fiber Pull-out tests of the model composites with round-shaped and gear-shaped reinforcements to evaluate the effect of the reinforcement cross section geometry on the interfacial properties. After the Pull-out test, we observed interface of the gear-shaped wire and found that debonding occurred along the outer surface of the wire and did not progress to the concave area of the gear. This unique interfacial debonding process of irregularly-shaped reinforcement may affect the increase of interfacial properties of composite materials by an effect like mechanical interlocking. Then we conducted stress analysis by Finite Element Method and found that stress distribution of the model with gear-shaped reinforcement is so unique. From both of experimental and numerical results, we expect that the gear-shaped reinforcement causes good interfacial properties by the mechanical interlocking effect. We discuss the cross-sectional geometry of the irregular-shaped reinforcement to induce the mechanical interlocking effect.