Effect of Silane-Modified Nano-Al2O3-Reinforced Vinyl Ester Resin on the Flexural Properties of Basalt Fiber Composites

This study incorporated silane coupling agent KH550-modified nano-alumina (KH550-Al2O3) into vinyl ester resin (VER) for modification. The effect of KH550-Al2O3 on the flexural properties of VER and basalt fiber-reinforced vinyl ester resin (BF/VER) composites was investigated. In addition, dynamic mechanical analysis (DMA) and long-term elevated temperature aging of the composites were performed. The surface functionalization of KH550-Al2O3 was confirmed by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and energy-dispersive X-ray spectroscopy (EDS). It was revealed by scanning electron microscopy (SEM) that the aggregation of KH550-Al2O3 had been reduced within the VER matrix, the resin was effectively enhanced, and the fiber-matrix interfacial bonding was improved. Based on the experimental results, the optimal filler loading of KH550-Al2O3 was 1.5 wt%. Compared with the control group, the resin matrix exhibited 18.1% and 22.7% improvements in flexural strength and modulus, respectively, while the composite showed increases of 9.3% and 7.6% in these properties. At 30 °C, the storage modulus of the composites increased by 11.5%, with the glass transition temperature rising from 111.0 °C to 112.5 °C. After 60 days of thermal aging at 120 °C, the retained flexural strength and modulus were 64.3% and 87.4%, respectively.