Frontal polymerization of high-performance glass fiber epoxy composites with high fiber volume fraction

Manufacturing high-performance glass fiber epoxy composites (GFRP) through radical-induced cationic frontal polymerization (RICFP) is challenging. Achieving high fiber content is difficult due to low resin levels and inadequate chemical reactivity. This study systematically investigates the effects of ultraviolet (UV) light and local thermal initiation on RICFP using bisphenol A diglycidyl ether (BADGE) epoxy resin as the substrate. The preferred initiation method was identified, and the enthalpy change and thermal equilibrium of the resin's RICFP reaction were effectively controlled by optimizing preheating conditions, resin composition, and the initiator ratio. A method for preparing high-fiber-volume GFRP via RICFP was also proposed. Experimental results revealed that GFRP prepared by UV-initiated RICFP exhibited a 13.8 % increase in flexural strength, alongside an 11.8 % reduction in frontal temperature compared to local thermal initiation. By optimizing the resin composition for the RICFP process, a fiber volume fraction of up to 52 % was achieved. The frontal polymerization specimen's flexural strength increased by 27.7 % and 28.7 %, while its interlaminar fracture toughness improved by 11.9 % and 50.9 %, respectively, compared to the two thermal curing specimens (SEP-Heat Cured and BADGE-Heat Cured). Furthermore, dynamic thermomechanical analysis (DMA) demonstrated significant enhancements in the glass transition temperature, with increases of 69.14 % and 139.53 %, respectively. This study provides both a theoretical foundation and technical guidelines for the RICFP process, aiming to produce high-performance GFRP with a high fiber volume fraction.