Mechanical Behaviors of Soft Elastomers Filled with Low Melting Alloys

Soft elastomers with mechanical properties similar to biological tissues have shown encouraging potential in applications of biomedical devices and stretchable electronics. With the ability to enhance electric and thermal conductivity, embedding low melting alloys into soft elastomer matrix has received considerable attention in recent years. However, the mechanical properties, especially the fatigue behaviors of these soft composites, have not been extensively investigated. Here, we fabricate two silicone elastomers filled with eutectic gallium-indium, a liquid metal alloy, which has a melting temperature around room temperature. The cyclic loading-unloading tests are first performed on the composites with low melting alloys in either solid or fluid state. The results show that the modulus and energy dissipation density of the composite increase with the ratio of the alloys when the deformation temperature is below the melting temperature, while these properties decrease with the ratio of alloys when they are in the fluid state. In contrast, the failure strain shows an opposite trend. Mechanical tests are further performed on specimens with a precut to measure the fracture energy and fatigue threshold. It is demonstrated that both fracture energy and fatigue threshold are significantly enhanced in the presence of low melting alloys regardless of their states. Finally, we apply a continuum damage model to describe the Mullins effect of the soft composites observed in the loading-unloading cycles, which further reveals the change of mechanical properties with deformation for different compositions of soft composites.

Automated summary

This study investigates the mechanical properties of soft composites containing low melting alloys. The results show that increasing the ratio of the alloys enhances the modulus and energy dissipation density of the composites when the deformation temperature is below the melting temperature, while these properties decrease when the alloys are in the fluid state. However, the fracture energy and fatigue threshold are significantly enhanced in the presence of low melting alloys regardless of their states.