ダブルラップ複合材接着継手の強度に及ぼす極低温環境の影響

抄録

Low-temperature environments may cause strength degradation of composite bonded joints. Regardless, the method employed for synthesizing these joints has the potential to be effective. In this study, experimental and numerical investigations were conducted to determine the influence of a low-temperature environment on the strength properties of double-lap composite bonded joints. The strength properties and fracture modes of these joints at different temperature levels, ranging between the room and cryogenic temperatures, were studied using a cryogenic testing system with a refrigerator. The experimental results indicate that the strength of the bonded joints is significantly reduced as the temperature decreases. Finite element analysis (FEA) of the double-lap composite bonded joints was conducted to elucidate the cause of strength reduction of the bonded joints at low temperatures. In the FEA, the temperature dependency of the elastic constants, thermal contractions, and elastoplastic properties of the adherend and adhesive materials were considered. These factors were then used to calculate the stress distribution in the adhesive layer and energy release rates at the interface between the inner adherend and the adhesive layer. Numerical results revealed that the mode I energy release rates at the interface significantly increased with a decrease in plastic behavior, owing to the low-temperature environment. A reduction in the plastic characteristics of adhesive materials is, thus, a dominant factor for the strength reduction of double-lap composite bonded joints in a low-temperature environment.