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Published November 2018 | public
Journal Article

Stress fluctuation, crack renucleation and toughening in layered materials


It has been established that contrast in the elastic properties can lead to enhancement of fracture toughness in heterogeneous materials. Focussing on layered materials as a model system, we show that this enhancement is a result of two distinct phenomena – first, fluctuations in stress leading to regions where the stress intensity at the crack is considerably smaller than that of the macroscopically applied value; and second, the lack of stress intensity when a crack is at a compliant to stiff interface thereby requiring renucleation. Using theoretical, computational and experimental methods, we study two geometries – a layered material and a layered material with a narrow channel – to separate the two phenomena. The stress fluctuation is present in both, but renucleation is present only in the layered medium. We provide quantitative estimates for the enhanced toughness.

Additional Information

© 2018 Elsevier. Received 22 December 2017, Accepted 18 April 2018, Available online 23 April 2018. This work draws from the doctoral thesis of Chun-Jen Hsueh at the California Institute of Technology. We thank Suzanne Oliver for assisting with the determination of the properties of the homogeneous materials. We gratefully acknowledge the support of the US National Science Foundation through the Graduate Research Fellowship DGE-1144469 (Avellar) and Award no. DMS-1535083 and DMS-1535076 under the Designing Materials to Revolutionize and Engineer our Future (DMREF) Program (All authors). Author contributions: Hsueh and Avellar contributed equally to this work. Hsueh took the lead in developing the theoretical framework and the computational portion of the work. Avellar proposed the layers with and without stripe configuration and took the lead in the experimental portion of the work. All authors were involved in the conception of the project, analysis of the results and the drafting of the manuscript.

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