Brittle to Ductile Transition in a Fiber Bundle with Strong Heterogeneity

Abstract

We analyze the failure process of a two-component system with widely different fracture strength in the framework of a fiber bundle model with localized load sharing. A fraction 0\leq α\leq 1 of the bundle is strong and it is represented by unbreakable fibers, while fibers of the weak component have randomly distributed failure strength. Computer simulations revealed that there exists a critical composition α_c which separates two qualitatively different behaviors: below the critical point the failure of the bundle is brittle characterized by an abrupt damage growth within the breakable part of the system. Above α_c, however, the macroscopic response becomes ductile providing stability during the entire breaking process. The transition occurs at an astonishingly low fraction of strong fibers which can have importance for applications. We show that in the ductile phase the size distribution of breaking bursts has a power law functional form with an exponent μ=2 followed by an exponential cutoff. In the brittle phase the power law also prevails but with a higher exponent μ=9/2. The transition between the two phases shows analogies to continuous phase transitions. Analyzing the microstructure of the damage, it was found that at the beginning of the fracture process cracks nucleate randomly, while later on growth and coalescence of cracks dominate which give rise to power law distributed crack sizes.

8 pages, 9 figures

References in corpus (5)

• Statistical Models of Fracture
• Local load sharing fiber bundles with a lower cutoff of strength disorder
• From Brittle to Ductile Fracture in Disordered Materials
• Universality class of fiber bundles with strong heterogeneities
• Onset of Localization in Heterogeneous Interfacial Failure

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• Brittle to quasibrittle transition in a compound fiber bundle
• Size scaling of failure strength at high disorder
• Failure process of fiber bundles with random misalignment
• Stability in fiber bundle model : Existence of strong links and the effect of disorder