Influence of humid and hot environment on the interlayer fracture toughness of composite materials and its mechanism

Abstract

Interlayer fracture toughness is the main indicator of the ability of composite materials to resist interlayer delamination propagation. The humid and hot environment is the main harsh environment faced by aircraft composite structures. Studying the interlayer fracture toughness in humid and hot environments is of great significance in the aviation field. In this paper，the microstructure of type Ⅰ and type Ⅱ interlayer fracture toughness experiments under different wet and thermal conditions are analyzed，and the effect of wet and thermal environment on the interlayer fracture toughness of resin matrix composites is obtained. The research results indicate that the humid and hot environment has a completely opposite effect on the interlayer fracture toughness of type Ⅰ and type Ⅱ resin composite materials. As the temperature increases，the interlayer fracture toughness of type Ⅰ resin composite laminates shows an upward trend，while the interlayer fracture toughness of type Ⅱ resin composite laminates shows a downward trend. During type Ⅰ delamination，a large number of fiberbridging phenomena occur. In humid and hot environments，the resin softens and fiber bridging phenomena increase，leading to an increase in type Ⅰ interlayer fracture toughness with increasing temperature；In a humid and hot environment，as the temperature increases，the shear strength of the resin gradually decreases，and the interfacial shear strength between the resin and fibers also gradually decreases，resulting in a decrease in type Ⅱ interlayer fracture toughness with increasing temperature.

Keywords

• composite materials
• interlayer fracture toughness
• humid and hot environment
• resin