Interlaminar mechanical properties and heat resistance of silicone modified epoxy resin composites

The research on improving the interlayer mechanical properties and heat resistance of epoxy resin matrix composites through toughening modification of epoxy resin matrix has important engineering application value. Modified resin (ES) was prepared by condensation reaction of hydroxyl terminated polydimethylsiloxane and epoxy resin, and glass fiber reinforced epoxy resin matrix composite (ES-GF) was prepared by vacuum introduction method. The interlaminar mechanical properties of the composite were measured by double cantilever beam and short beam shear tests. The thermal resistance of the composite was evaluated by thermogravimetry and dynamic mechanical thermal testing. The interlaminar mechanical properties and thermal resistance of the corresponding glass fiber reinforced unmodified epoxy matrix composites (EP-GF) were also tested for comparative analysis. In order to analyze the physical mechanism of strengthening the interlaminar mechanical properties and improving the heat resistance of the composite, the tensile strength, tensile modulus, flexural strength, flexural modulus, tensile elongation at break, pendulum impact strength and microstructure characteristics of the epoxy resin before and after modification were also measured and characterized. The experimental results show that, compared with EP-GF, the release rate of type I critical strain energy (fracture toughness) of ES-GF is increased by 98.1%, and the interlaminar shear strength is increased by 13.3%. The strengthening of interlaminar mechanical properties is attributed to the comprehensive effect of Si—O bond flexible chain segment, "ductile points" playing a "nail anchor" role and improvement of fiber/matrix wettability. The maximum thermal weight loss rate of ES decreased by 33.1%, and the final residue at 800 ℃ increased by 13.5 times. Before T_g, the storage modulus of ES GF is 1.3 GPa higher than that of EP GF, and after T_g, the storage modulus of ES GF is nearly 1.3 GPa higher than that of EP GF, and the glass transition temperature of siloxane modified epoxy resin is slightly increased.