Enhanced fracture toughness and controlled curing of basalt fiber/epoxy composites via PPE powder modification

The effect of polyphenylene ether (PPE) on Mode-I fracture behavior, mechanical performance, curing characteristics, and rheological response of basalt fiber/epoxy (BF-EP) composites was investigated. Laminates containing 0–7 wt% PPE were fabricated and evaluated using double cantilever beam (DCB), flexural, compression, impact, and interlaminar shear tests. Thermal and curing behaviors were further analyzed by dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and rheological measurements. The results indicate that PPE significantly enhances delamination resistance at moderate concentrations. The laminate with 3 wt% PPE exhibited the highest fracture toughness, with an average value of 1.334 kJ m−2, representing an increase of approximately 55% compared to the reference composite. Mechanical tests demonstrated that low PPE contents (1–3 wt%) provide the most balanced performance, while higher loadings gradually reduce stiffness and interfacial strength due to particle agglomeration and matrix heterogeneity. Rheological measurements showed that PPE decreases the initial viscosity of the uncured resin and slightly delays gelation, indicating improved processability. DSC kinetic analysis revealed that PPE incorporation does not significantly alter the curing mechanism of the epoxy system, although a slight reduction in activation energy at early conversion stages was observed. In summary, the incorporation of 3 wt% PPE serves as a dual-function modifier, improving matrix ductility and subtly affecting curing behavior, thereby enhancing the damage tolerance of basalt fiber/epoxy composites.