Adhesion and stiffness matching in epoxyvitrimers/strain sensor fiber laminates

Hybrid networks, i.e. including physical and chemical crosslinks, were synthesized from biosourced fatty acid fragments, linked to each other by a controlled number of nonexchangeable ether bonds, exchangeable ester bonds and non-covalent hydrogen bonds. The mechanical properties of these networks are tuned by the ratio di-versus tetra-epoxide, and the stoichiometry acid/epoxy. Creep tests and insolubility demonstrated the vitrimer or vitrimer-like nature of the resulting materials. The thermo-stimulated welding ability of the materials was exploited to incorporate strain sensors by embedding electrically conductive fibers into the rubbery vitrimer matrix. The efficiency of the welding procedure at moderate temperatures (80 °C) and the tunability of mechanical properties are both attractive assets for effective incorporation of thermodegradable conductive fibers while preserving their mechanical and electrical integrity. Mechanical and electrical behavior of the sensor composites were simultaneously tested, either in quasi-static or in cyclic tensile experiments, at room temperature and at distance from the Tg of the matrices. The study emphasizes the importance of matching Young's moduli of components in composite samples, which is strongly temperature-dependent.