Experimental characterization and phase-field modeling of anisotropic brittle fracture in silicon

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We employ experiments and phase-field modeling to characterize the four-fold anisotropic elastic and fracture response of solar-grade monocrystalline silicon on the macro-scale using thin silicon wafers. Tension tests on unnotched and double edge-notched specimens are performed to characterize the in-plane four-fold symmetric elastic behavior of the material and its fracture toughness along the weak directions. Single edge-notched tension tests with the notch oriented along the strong direction are performed to induce crack zigzagging and qualitatively capture the inherent stochastic nature of crack propagation in this setting. With the experimental results, we calibrate two deterministic anisotropic fourth-order phase-field models considering anisotropy in both elastic and fracture energies, as well as their stochastic extension proposed in our previous work. Overall, the very good agreement between experimental and numerical results demonstrates the ability of phase-field modeling to quantitatively predict anisotropic brittle fracture in monocrystalline silicon. Remarkably, very different zigzagging crack patterns obtained on nominally identical specimens are naturally reproduced by the stochastic model.