湿热环境对复合材料层间断裂韧性的影响规律及其机理

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

层间断裂韧性是表征复合材料抗层间分层扩展能力的主要指标,湿热环境是飞机复合材料结构面临的主要严酷环境,研究湿热环境下的层间断裂韧性在航空领域具有重要意义。通过不同湿热环境条件下的Ⅰ型和Ⅱ型层间断裂韧性实验,分析其微观结构,获取湿热环境对树脂基复合材料层间断裂韧性的影响规律和湿热环境对层间断裂韧性的影响机制。结果表明:湿热环境会对树脂基复合材料Ⅰ型和Ⅱ型层间断裂韧性产生截然相反的影响,随着温度上升,树脂基复合材料层压板Ⅰ型层间断裂韧性呈上升趋势,而Ⅱ型层间断裂韧性呈下降趋势;Ⅰ型分层时会出现大量纤维桥联现象,湿热环境下树脂发生软化,纤维桥联现象增多,导致Ⅰ型层间断裂韧性随温度升高而增大;湿热环境下随着温度的升高,树脂的剪切强度会逐渐降低,树脂与纤维的界面剪切强度也会逐渐降低,导致Ⅱ型层间断裂韧性随温度升高而降低。

Interlayer fracture toughness is the main indicator of the ability of composite materials to resist interlayer de⁃lamination 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 avia⁃tion field.In this paper,the microstructure of typeⅠand typeⅡinterlayer fracture toughness experiments under dif⁃ferent wet and thermal conditions are analyzed,and the effect of wet and thermal environment on the interlayer frac⁃ture toughness of resin matrix composites is obtained.The research results indicate that the humid and hot environ⁃ment has a completely opposite effect on the interlayer fracture toughness of typeⅠand typeⅡresin composite mate⁃rials.As the temperature increases,the interlayer fracture toughness of typeⅠresin composite laminates shows an upward trend,while the interlayer fracture toughness of typeⅡresin composite laminates shows a downward trend.During typeⅠdelamination,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 typeⅠinterlayer 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,re⁃sulting in a decrease in typeⅡinterlayer fracture toughness with increasing temperature.