Interfacial toughness quantifies resistance to crack growth along an interface and in this investigation the toughness of an aluminum/epoxy interface was measured as a function of surface roughness and test temperature. The large strain response of the relatively ductile epoxy adhesive used in this study was also characterized. This epoxy adhesive exhibits intrinsic strain-softening after initial compressive yield and then deforms plastically at a roughly constant flow stress until it rapidly hardens at large compressive strains. We find that interface toughness scales as the product of the temperature dependent epoxy yield strength and a length scale that characterizes surface roughness. The proposed scaling is based upon dimensional considerations of a model problem that assumes that the characteristic length scale of both the roughness and the crack-tip yield zone is small relative to the region dominated by the linear elastic asymptotic crack-tip stress field. Furthermore, the model assumes that interfacial failure occurs only after the epoxy begins to harden at large strains. The proposed relationship is validated by our interfacial toughness measurements.

中文翻译：

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界面韧性：取决于表面粗糙度和测试温度

界面韧性量化了沿界面裂纹扩展的阻力，在本研究中，铝/环氧树脂界面的韧性作为表面粗糙度和测试温度的函数进行测量。还表征了本研究中使用的相对延展性环氧树脂粘合剂的大应变响应。这种环氧树脂粘合剂在初始压缩屈服后表现出固有的应变软化，然后在大致恒定的流动应力下塑性变形，直到在大压缩应变下迅速硬化。我们发现界面韧性是随温度变化的环氧树脂屈服强度和表征表面粗糙度的长度尺度的乘积。建议的缩放基于模型问题的尺寸考虑，假设粗糙度和裂纹尖端屈服区的特征长度尺度相对于由线性弹性渐近裂纹尖端应力场主导的区域较小。此外，该模型假设只有在环氧树脂在大应变下开始硬化后才会发生界面失效。我们的界面韧性测量验证了所提出的关系。