A composite material is provided including a polymer matrix and undercooled liquid metallic core-shell particles disposed in the matrix, wherein the particles each have an outer shell and a liquid metallic material as a core contained within the outer shell. The outer shell is frangible such that the liquid metallic material is released from at least some of the particles in response to a mechanical load applied to the composite and solidifies in-situ in the polymer matrix. As a result, the composite material can be self-strengthening and self-healing and can be reconfigurable in shape at ambient temperature.
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