Progressive stiffening in GFRP composites with low-concentration, non-functionalized SiC microparticles: An experimental–computational approach

This study investigated the mechanical response of composite materials based on polyester resin and fiberglass, doped with large silicon carbide (SiC) particles (100–250 µm). The research included bending tests (ASTM D7264), nanoindentation, and multiscale computational homogenization to describe the mechanical behavior across scales. SiC doping was applied at 1.5%, 3%, and 5% by weight, using two fiberglass configurations: continuous laminates and a mixed arrangement of continuous and discontinuous laminates, with 13 fiberglass layers per sample. Scanning electron microscopy (SEM) analyzed porosity and SiC distribution at the interface, while nanoindentation tests examined the matrix, fibers, SiC particles, and their interfaces. Long laminate stacking provided the best mechanical performance due to uniform reinforcement distribution at the fiber/matrix interface. Increasing the SiC content in long laminates improved flexural strength by 17.5% compared to undoped samples. In contrast, mixed laminates exhibited a 41% strength reduction due to SiC particle agglomeration and stress concentrations. Bending curves of SiC-doped samples showed three stiffness zones, attributed to hierarchical mechanical behavior with progressive reinforcement activation. The large SiC particle size and low fraction enhanced deformation capacity below 50 MPa while increasing flexural strength. This balance of strength and deformation represents a novel finding in composite performance.