Study on the fatigue crack and secondary crack growth in the adhesive layer under Modes I, II and Mixed mode loadings

I型、II型及混合模式载荷下粘合层疲劳裂纹及二次裂纹扩展研究

• 批准号: 11650105
• 负责人: FUJII Toru
• 金额: $ 1.6万
• 依托单位: Doshisha University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1999
• 资助国家: 日本
• 起止时间: 1999 至 2001
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11650105/
• 关键词: Adhesively bonded joints; Model I loading; Model II loading; Mixed mode loading; Stress singularity; Crack growth; Secondary crack growth; Water absorption; 接着剤; pseudo-threshold; 破壊じん性値; 水

Bumpy surface is formed on the fractured surface of adhesively bonded DCB joints under mixed mode loading in conjunction with a crack cohesively propagates. The mechanism for formation of such bumpy fractured surface can be explained based on the stress analysis at the crack tip in conjunction with the criterion for an occurrence of crazes. The crack propagation resistance increases under cyclic mixed mode loading with an increase of mode II component. An increase in threshold is appreciable.The crack for epoxy adhesive under mode I loading propagates from cohesively to interfacailly as the energy release rate range, ?G_I decreases. Mixed mode failure appears between to cohesive and interfacial failure modes. The crack once is arrested at a certain ?G_I. Its magnitude depends on the surface condition (surface treatment) as well as other conditions such as cyclic load frequency. The crack resumes to propagate after a while under the normal laboratory condition, which is named as "Second … More ary crack growth". No secondary crack growth occurs when the fatigue tests are conducted under extremely dry condition. The characteristics of fatigue crack growth are strongly influenced by loading mode, such as Mode I, Mode II or mixed mode. The secondary crack growth occurs even at 65 % relative humidity at room temperature.Small amount of water absorption also affects the failure of carbon fiber epoxy composites appreciably. When the composite is fabricated under the laboratory condition, the tensile strength decreases 20 % lower than that of the sample fabricated with less moisture. At high cyclic fatigue, a small amount of moisture in air also strongly affects the fatigue failure of the composite. Little epoxy resin can be identified on the broken fibers. For single lap joints subjected to a tensile shear load, cracks occur at the bond termini where the stress singularity exists. With increasing the applied load, the crack interfacailly grow inward, then, they change their direction into the adhesive layer. It happens during the stable crack propagation period. The total energy release rate criterion can be used to estimate where and when such crack deflection occurs. The effect of residual stress due to adhesive shrinkage during consolidation could be one of major reasons why single lap joins become strong when the adhesive layer becomes thin. Less

在复合型载荷作用下，DCB胶接接头的断裂面上会形成凹凸面，裂纹在此凹凸面内聚扩展。根据裂纹尖端的应力分析和银纹发生的判据，可以解释这种凹凸断口的形成机理。在复合型循环载荷作用下，裂纹扩展阻力随Ⅱ型分量的增加而增加。环氧树脂胶粘剂在I型载荷作用下，裂纹从内聚向界面扩展的能量释放率范围为？G_I降低。混合模式失效出现在内聚失效模式和界面失效模式之间。裂纹一旦被逮捕在一定的？G_I.其大小取决于表面条件（表面处理）以及其他条件，如循环载荷频率。在正常的实验条件下，裂纹在一段时间后恢复扩展，称为“第二裂纹 ...更多信息 ary crack growth”。在极端干燥条件下进行疲劳试验时，没有出现二次裂纹扩展。疲劳裂纹扩展特性受加载方式的强烈影响，如模式I，模式II或混合模式。即使在室温相对湿度为65%的条件下，碳纤维/环氧树脂复合材料的二次裂纹也会发生扩展。在实验室条件下制备的复合材料，其拉伸强度比含水量少的试样降低了20%。在高周疲劳下，空气中的少量水分也强烈影响复合材料的疲劳失效。断裂纤维上几乎没有环氧树脂。对于承受拉伸剪切载荷的单搭接接头，裂纹发生在应力奇异性存在的粘接端。随着载荷的增加，界面裂纹向内扩展，然后改变方向进入胶层。它发生在稳定裂纹扩展期间。总能量释放率准则可用于估计裂纹偏转发生的位置和时间。在固结过程中由于粘结剂收缩而产生的残余应力的影响可能是当粘结剂层变薄时单搭接接头变强的主要原因之一。少

项目成果

H. Hirakata and T. Fujii: "Failure transition in fatigue crack propagation of epoxy adhesives and their secondary crack growth below threshold"Journal of Japan Soc. for Mech. Engineers Series A. Vol. 67, No. 662. 1647-1655 (2001)

H. Hirakata 和 T. Fujii：“环氧粘合剂疲劳裂纹扩展中的失效转变及其低于阈值的二次裂纹扩展”Journal of Japan Soc。

T.Saito, K.Okubo, T.Fujii: "Fatigure crack propagation of structural adhesives under Mode I loading The effect of moisture on fatigue crack propagation"Proc.of the 23th Annual Meeting of the Adhesion Soc.(American Adhesion Soc.). 103-106 (2000)

T.Saito、K.Okubo、T.Fujii：“I 型载荷下结构粘合剂的疲劳裂纹扩展水分对疲劳裂纹扩展的影响”Proc. of the 23th Annual Meeting of the Adhesion Soc.(American Adhesion Soc.)

大窪和也, 吉光寛晃, 藤井透: "混合モード荷重下における高じん性化エポキシ系接着剤の静的および疲労き裂進展特性"日本機械学会論文集A編. 67. 1514-1519 (2001)

Kazuya Okubo、Hiroaki Yoshimitsu、Toru Fujii：“混合模式加载下增韧环氧树脂粘合剂的静态和疲劳裂纹扩展特性”日本机械工程师学会汇刊，A 版 67. 1514-1519 (2001)。

K.Tanaka, K.Okubo, T.Fujii: "Novel approach on strength degradation of bonded joints using epoxy adhesives due to water absorption"Proc.of the 24th Annual Meeting of the Adhesion Soc.(American Adhesion Soc.). 400-402 (2001)

K.Tanaka、K.Okubo、T.Fujii：“由于吸水导致使用环氧粘合剂的粘合接头强度下降的新方法”第 24 届粘合协会年会（美国粘合协会）会议记录。

T.Matsui, K.Okubo, T.Fujii: "Effect of intensity of stress singularity on strength of adhesively bonded joints (Effect of fillets and bond terminus configuration on the ultimate strength of single lap and but joints)"Proc.of Adhesion 99:7th Int.Conf.on Ad

T.Matsui、K.Okubo、T.Fujii：“应力奇点强度对粘合接头强度的影响（圆角和粘合末端配置对单搭接和对接接头极限强度的影响）”Proc.of Adhesion 99