Deformation and failure of adhesive bonds under shear loading
Deformation and failure of adhesive bonds under shear loading
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剪切载荷下粘合剂的变形和失效
DOI：
10.1007/bf00361160
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发表时间：
1993
影响因子：
4.5
通讯作者：
H. Chai
中科院分区：
文献类型：
--
作者：
H. Chai
实验表明，当材料在严格的空间约束下受到应力时，某些机械性能可以大大增强。在这项工作中，后屈服行为的脆性和韧性环氧树脂用作薄胶粘剂债券确定使用“餐巾环”剪切试验。实时观测的变形在债券以及SEM失效后分析，以获得信息的破坏过程。完整的应力-应变历史的粘合剂的粘结厚度范围从微米级的值大到足以暴露的散装性能。最显著的变化发生在极限剪切应变γf;对于脆性粘合剂，当粘合厚度t减小到几微米时，γ f相对于本体材料增加了30倍以上。实验证据和分析结果表明，γ f与t的下降是由于加载过程中夹层中形成的拉伸微裂纹或空隙引起的过早粘结破坏，特定的γ f与t的关系仅仅反映了裂纹尖端应力集中程度的变化。在微米厚度范围内，脆性环氧树脂的γf值非常大（即2.8-3.4），据信这代表了该材料的固有剪切应变。
Experiments have shown that certain mechanical properties can be greatly enhanced when a material is stressed while under tight spatial constraint. In this work, the post-yield behaviour of brittle and ductile epoxy resins used as thin adhesive bonds was determined using the “napkin ring” shear test. Real-time observations of the deformation in the bond as well as SEM post-failure analysis were employed to gain information on the failure process. The complete stress-strain histories of the adhesives were established for bond thicknesses ranging from the micrometre level up to values large enough to expose the bulk properties. The most dramatic variations occurred for the ultimate shear strain, γf; for the brittle adhesive, γfincreased by over 30-fold relative to the bulk material when the bond thickness,t, was decreased to a few micrometres. Experimental evidence and analytical considerations suggest that the decline of γfwithtwas due to premature bond failure caused by tensile microcracks or voids that were formed in the interlayer during loading, with the specific γfversustrelationship being a mere reflection of the variations in the degree of stress concentration at the tip of the flaws. The astonishingly large value of γf(i.e. 2.8–3.4) found for the brittle epoxy in the micrometre thickness range, is believed to represent the intrinsic shear strain of this material.