Effects of reactive diluent on processing, structure, and properties of epoxy foams and their sandwich composites

Foam sandwich composite (FSC) has recently been widely used in transportation, aerospace, shipping, and construction because of its lightweight, high specific strength, stiffness, and fatigue resistance characteristics. This study aimed to prepare, characterize, and test FSC with different diluent addition amounts. Benzyl glycidyl ester was added to the epoxy foam (EF) as a reactive diluent. Then, the EF was introduced into the three-dimensional hollow composite (3DHC) by vacuum introduction process to prepare the FSC. Fourier transform infrared spectroscopy and thermogravimetric analysis demonstrated that increased diluent content enhanced Si-N bond formation, augmenting thermal stability in resin molecules. The effects of different diluents on the mechanical properties of FSC showed that the mechanical properties of FSC were the best when the diluent content was 5 wt%. Compared with 3DHC, the flat compressive strength, flat tensile strength, and shear strength were increased by 7.2, 6.4, and 2.9 times, respectively.Highlights Diluent improves foaming agent dispersion by lowering resin viscosity. Diluent makes the EP easier to be introduced into 3DHC. FSC demonstrates a 723% increase in flat compression strength. Foam sandwich composite preparation process. image