Molecular dynamics study for self-sensing/self-healing materials to simulate damage detection and repair in thermoset polymer matrix

The mechanochemical response of a novel cyclobutane-based mechanophore (force-sensitive molecule) covalently bonded with an epoxy-based thermoset polymer matrix is characterized by experiments and modeling. This new mechanophore consists of one cyclobutane (stress-sensitive molecular unit) and six amine groups (epoxy curing agents) that enable the cyclobutane to be connected to epoxy network chemically. Thereby the external force applied to mechanophores directly through the epoxy network, which makes the sensitivity of mechanophore to the external stimulation improved. Furthermore, the mechanical properties of epoxy can be preserved since mechanophores are connected to the host materials chemically, not embedded physically. The experimental results indicated that the yield strength slightly increased compared to the neat epoxy with improved optical response of mechanophore to the external mechanical loads. In parallel, molecular model of this new mechanophore embedded thermoset polymer system has been developed. Numerical simulations correctly capture the effect of the new mechanophore on the improvement in sensitivity of mechanophore activation and mechanical properties; the modeling framework is validated experimentally.