How regularity in the microstructure of composite can improve their fracture resistance?

What is it about?

Natural selection helps creatures develop features that help them survive. For example, both seashells and chalk are made of the calcium carbonate, but seashells are incredibly strong and tough. Their excellent properties come from the precisely stacking mineral building blocks that are glued together by thin interfaces. This structure allows them to spread out damage over a large area, effectively delaying failure and improving the toughness. Replicating this damage delocalization behaviour in man-made composites remains challenging. In this study, we assembled silica rods synthesized at room temperature into densely packed, highly ordered colloidal crystals in centimeter-scale using a template. With the flexible interfaces holding the rods together, this man-made material present toughness up to 100 times higher than glass, through building blocks sliding to spread damage over millimeters.

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Photo by Second Breakfast on Unsplash

Photo by Second Breakfast on Unsplash

Why is it important?

Packing more mineral into a material usually makes it stiffer but more brittle. Inspired by highly mineralized natural materials, we demonstrate a highly ordered microstructure containing 80% regular building blocks triggers damage delocalization and prevent cracks from spreading easily far better than disordered materials or materials with less mineral. This provides a design principle for high-performance composites in health care, energy storage and structural materials for extreme environments.