Nanopowder-Reinforced Thixotropic Interface Enabled High-Filling Functional Epoxy Composites with Enhanced Impact Resistance and Mechanoluminescence Properties.

High-filling epoxy composites possess indispensable and pivotal performance in structural materials and functional devices; However, owing to their intrinsic brittleness and inevitable interface defects, potential stress concentration and structural damage may result in unacceptable losses. Here, a nanopowder-reinforced thixotropic interfacial design strategy was proposed, in which different morphologies of nanosized calcium carbonate were used to reinforce guanidinoacetic acid-modified polyborosiloxane (GPBS), which was then introduced into the organic-inorganic interface of epoxy composites. Owing to the frequency-dependent O→B dynamic bonds and guanidyl-carboxylate structure, the obtained GPBS exhibits an enhanced shear-thickening behavior, with its storage modulus (G') increasing sharply from 34.89 Pa at 0.1 Hz to 69.87 MPa at 100 Hz (an increase of 20,026.51 times). As a result, the corresponding epoxy composites exhibited improved mechanical properties (a 385.6% increase in tensile stress) and impact resistance performance (a force attenuation rate of up to 80%). Meanwhile, SrAl2O4:Eu2+, Dy3+ was incorporated into the composites for stress visualization, and a machine learning-assisted analysis system was developed for signal analysis. This study provides an insight into high-filling functional epoxy composites, holding great application potential in intelligent protection engineering.