车用胶粘接头机械性能的湿热老化与恢复

Hygrothermal degradation and recoverability of mechanical properties of epoxy adhesive joints for automotives

汽车轻量化推动胶接技术在车身中的应用,但湿热的汽车服役环境对胶粘接头的力学性能存在不利影响。该研究利用试验方法揭示一种环氧胶黏剂及其接头的湿热老化规律,制作了单向拉伸和缺口拉伸形式的胶黏剂本体试样,以及双悬臂梁剥离和十字拉伸剥离形式的胶粘接头试样,比较了本体和接头的初始、湿热老化和恢复性能。结果表明:胶黏剂本体的弹性模量、峰值应力、失效应变和能量吸收均随湿热老化而降低;烘烤除湿后,各性能恢复程度不一;湿热老化导致胶黏剂与母材界面的粘接强度降低,但在烘烤除湿后显著恢复。因而,在对湿热老化后粘接车身的强度进行分析时,要考虑胶本体和界面,并按最坏情形设计。

Automobile lightweight requires the adoption of adhesion technology. However, the hot-humid service environment poses a threat to the mechanical properties of structural adhesives. This experimental study uncovered the effect of hygrothermal degradation（HTD） and drying on an epoxy adhesive and its joint. The tests for uniaxial tensile, notched tensile, double cantilever beam peel and cross tensile peel were conducted to explore the performance of adhesive bulk and joint of varied HTD histories. The result shows that 1） HTD reduced bulk adhesive properties, such as elastic modulus, peak stress, failure strain and energy absorption; 2） Upon drying, elastic modulus and peak stress almost fully recovered; failure strain further decreased; energy absorption hardly restored; 3） HTD reduced the interfacial strength between adhesive and aluminum substrate leading to interfacial failure; 4） Upon drying, the interfacial strength significantly recovered. Therefore, it is suggested to design a bonded vehicle body per the worst case of hygrothermal degradation.