Brittle crack behaviors could help design stronger materials

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Crack in concrete

Published in journal Nature Physics is a new study by Northeastern University researchers and colleagues revealing how brittle crack behaviors could help design stronger materials.

Through the study scientists have discovered the mechanism that causes cracks and how they behave strangely when they spread very rapidly in brittle materials. Researchers say their findings could pave way for greater understanding of fragile materials including glass, ceramic, polymers, and bone and how they break. This understanding will eventually help scientists to develop stronger materials that could withstand severe stress and sheer.

In principle cracks should develop within material in a straight line, but that’s not always the case and they race through a material in unpredictable ways. This is because cracks become unstable when their speed is high and this instability causes the crack tip to wobble from side to side and trace out a wavy path through the material.

Scientists were able explain how the nonlinear relationship between stretch and force produces oscillations with a well-defined period that can be related to materials properties.

Through this research scientists developed a novel theory to help researchers predict, through large-scale computer simulations, the dynamics of a crack under varying conditions, which has the potential to help understand why and how certain materials fail.

With more work, scientists are optimistic they will be able to continue on to more related work.

“This study used very thin sheets of quasi-2D materials. We plan to extend this study to 3D bulk materials. In bulk, the instability that prevents cracks from breaking at the speed of sound happens at a lower crack velocity than in 2D but the mechanism is not understood,” one of the authors said.

To elucidate this mechanism, the team plans to investigate the 3D phenomenon of micro-branching, when the main crack splits into many micro-cracks, to understand its origins in bulk samples of brittle materials.

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