Considerations on branching phenomenon of fatigue crack along the interface of epoxy plates with different Young's moduli.

Abstract

Fatigue cracks growing perpendicularly to the interface of dissimilar materials often arrested or branched at the interface, This branching crack phenomenon seems to be important to improve the fatigue life of composite material or to evaluate the fatigue life. In this paper, the branching crack phenomenon is investigated in detail using epoxy dissimilar plate specimens with various Young's modulus ratios (E2/E1) and different bonded strengthes. It is found that the branching crack along the interface can occur in only limited conditions. That is, Young's modulus ratio E2/E1 is higher than 1.14 and an applied displacement range ΔV (or load range) is higer than a critical value, which becomes large with increase of E2/E1 and becomes lower in the case of iow bonded strength. A new model to explain these branching crack phenomenon is proposed and discussed based on linear fracture mechnics.