Spiral tunneling cracks induced by environmental stress cracking in LARC-TPI adhesives
Spiral tunneling cracks induced by environmental stress cracking in LARC-TPI adhesives
复制标题
LARC-TPI 粘合剂中环境应力开裂引起的螺旋隧道裂纹
DOI：
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发表时间：
1994
期刊：
影响因子：
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通讯作者：
T. L. Clair
中科院分区：
文献类型：
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作者：
D. Dillard;J. Hinkley;W. Johnson;T. L. Clair
摘要 LaRC™-TPI（一种最初由 NASA-Langley 开发的热塑性聚酰亚胺）的一些现有配方被发现在暴露于丙酮、甲苯、二甘醇二甲醚和甲基乙基酮等溶剂时非常容易受到环境应力开裂的影响。应力和溶剂的结合导致该材料系统的薄膜和粘合剂层快速破裂。当 LaRC-TPI 用作粘合剂或涂层时，在存在溶剂的情况下会产生残余冷却应力，从而形成密集的“泥裂纹”图案，从而释放部分存储的能量。由于这些贯穿整个厚度的裂纹无法释放被粘物附近储存的能量，因此在每个粘合剂碎片内会引发并向内生长奇怪的螺旋隧道裂纹形式的额外裂纹。给出了螺旋断裂的显微照片，以及对在粘合剂和涂层中观察到的失效过程的定性解释。
Abstract Some currently-available formulations of LaRC™-TPI, a thermoplastic polyimide originally developed at NASA-Langley, were found to be highly susceptible to environmental stress cracking when exposed to solvents such as acetone, toluene, diglyme and methyl ethyl ketone. The combination of stress and solvent led to rapid cracking in films and adhesive layers of this material system. Residual cool-down stresses induced when the LaRC-TPI is used as an adhesive or coating led, in the presence of a solvent, to dense “mud crack” patterns which relieve a portion of the stored energy. Because these through-the-thickness cracks are not able to relieve the stored energy in the vicinity of the adherends, additional fractures in the form of curious spiral tunnel cracks initiated and grew inward within each adhesive fragment. Micrographs of the spiral fractures are given, along with a qualitative explanation for the failure process as observed in adhesives and coatings.