复合材料单搭接胶接头破坏声发射监测

采用声发射技术对单向拉伸载荷作用下复合材料单搭接胶接头的剪切破坏试验进行实时监测的方法,研究搭接长度对单搭接胶接头损伤破坏的影响规律及其相应的声发射响应特征。结果表明,随搭接长度的增加,引起单搭接胶接头的受力不均匀性增加,损伤易发生在胶层边缘应力集中区域,胶接头承载能力不断上升的同时,平均剪切应力逐渐降低;胶层边缘应力集中更明显,从而出现较多的声发射信号,且幅度在60~80 dB的声发射信号明显增多,声发射撞击累积数有上升趋势。声发射相对能量、幅度分布等声发射信号与胶层的损伤破坏过程相对应。     

间隙长度与间隙位置对单搭接接头强度的影响

研究了间隙长度和间隙位置对不同单搭接接头强度的影响。结果表明,随着间隙长度的增加,接头的承载能力趋于下降,但在适当的条件下,间隙连接接头并没有大幅度地减小其强度。研究中发现间隙所处的位置对接头的拉剪强度有较大的影响,间隙位置对接头实际剪切强度的影响大于间隙长度的影响。文中还论述了同一长度间隙位于不同位置时对强度的影响。     

折曲单搭接胶接接头应力分布探讨

在同轴单搭接胶接接头的基础上,设计了一种新型折曲单搭接胶接接头。通过有限元方法研究了折曲胶接接头和同轴胶接接头的应力分布规律。研究结果表明:折曲单搭接胶接接头搭接区两端的应力峰值下降幅度均超过40%,并使搭接区出现应力峰值的位置从搭接区端部转移到中部,从而显著地提高接头的承载能力。当L1=7.5 mm时,胶层中应力分布较为理想,各应力呈对称分布,是一种优于普通同轴的胶接接头形式。     

同轴单搭接胶接接头力学性能的研究

利用有限元方法研究了偏轴单搭接胶接接头和同轴单搭接胶接接头的力学性能,结果表明：同轴单搭接胶接接头可以使接头趾部的弯矩为零,进而有效地降低剥离应力的峰值和减轻剪切应力的集中程度,是一种极为合理的胶接接头形式。     

基于结构胶种类及搭接长度变化的胶接接头剪切强度及应力测试分析

通过对3种类型(双组分丙烯酸酯结构胶、双组分环氧树脂结构胶、单组分环氧树脂结构胶)共9款结构胶的搭接长度–剪切强度曲线测试及回归方程拟合,获得搭接长度–剪切应力曲线并对比分析曲线差异,基于结构胶种类及参数提出匹配不同搭接长度的选胶建议。结果表明:对此3种类型的结构胶单搭接满黏结接头,随搭接长度延长,平均剪切强度减小;低模量胶的搭接长度–剪切强度曲线形态与高模量胶的相反,前者为由缓降转为陡降,后者为由陡降转为缓降最后稳定;单组分环氧树脂结构胶适用于承受静载结构;用于承受动载的接头,建议选用双组分结构胶,搭接长度30mm以下选用丙烯酸酯型,搭接长度30mm以上选用环氧树脂型。     

搭接长度对钛合金-芳纶纤维复合材料单搭接接头胶接性能的影响

采用钛合金与芳纶纤维复合材料制备不同搭接长度的单搭接接头。利用数字图像相关技术(DIC)、万能试验机等表征方法,对接头拉伸应变与极限载荷进行表征,研究了搭接长度对异质材料单搭接接头胶接性能与破坏模式的变化规律。结果表明,随着搭接长度的增加,单搭接接头极限载荷提升,胶接强度降低,高搭接长度接头出现渐进损伤;偏心弯矩引起的接头偏移减少,搭接部位纵向应变区域面积占比降低;芳纶纤维复合材料层间破坏模式增多,钛合金-胶层界面破坏模式减少,剥离复合材料层数增加。     

含镶嵌块单搭接接头应力分布的数值分析

利用有限元方法研究了金属镶嵌对单搭接接头应力分布的影响。结果表明,采用镶嵌块组成混合连接接头,改变了接头的应力流线分布,镶嵌块承载,降低了搭接区中部胶层中的应力;同时使被粘物中部的应力增大,提高了接头搭接区中部的承载能力;在重要部件或承载较大等情况下使用胶接接头,建议采用金属镶嵌方式对接头增强,具有更强的承载能力和可靠性,有重要的实用价值。     

异质被粘物新型单搭接接头应力分析

利用有限元分析软件ANSYS建立了异质被粘物用2种胶分段粘接的单搭接接头的力学模型,分析了胶层中剪切应力的分布情况。结果表明,合理地布置高弹性模量胶粘剂及低弹性模量胶粘剂的位置,可以有效地降低刚度不对称接头胶层中应力的峰值,避免胶层因小刚度侧应力过高而导致接头过早地失效。     

温度变化对复合材料双面搭接接头拉伸强度的影响分析

介绍了复合材料三种连接方式之一——胶接。对双面搭接接头进行了有限元建模,在不同的高温环境下进行拉伸试验,运用相关的失效准则,分析判断复合材料胶接接头的破坏形式,确定温度对破坏形式的影响。通过试验,验证了分析的正确性,对复合材料胶接接头的强度校核及设计改进有重要的指导作用。     

单搭接胶接接头的拓扑优化

在有限元方法的基础上，利用变密度法对单搭接胶接接头搭接区域的被粘物形状进行了拓扑优化，通过曲线拟舍得到了较为合理的轮廓。拓扑优化的结果表明：在体积减少20％的情况下。胶接结构的强度不会降低；经拓扑优化后，胶层中剪切应力的峰值比优化以前增加不大，约1％。     

第二代丙烯酸酯结构胶拉伸剪切强度测试浅析

拉伸剪切强度实验方法是国内外标准中经常采用的胶黏剂力学性能测试方法,可以公平客观的反应出胶黏剂力学性能指标。文章通过实验,就目前国内实施的HG/T3827-2006《通用型双组分丙烯酸酯胶黏剂》,引用的GB/T 7124-2008《胶粘剂拉伸剪切强度测定方法（刚性材料-刚性材料）》对第二代丙烯酸酯结构胶粘剂测试结果影响因素做了进一步分析和讨论。     

Effect of Adhesive Type and Thickness on the Lap Shear Strength

The effect of the adhesive thickness on the bond strength of single-lap adhesive joints is still not perfectly understood. The classical elastic analyses predict that the strength increases with the adhesive thickness, whereas experimental results show the opposite. Various theories have been proposed to explain this discrepancy, but more experimental tests are necessary to understand all the variables.

The objective of the present study was to assess the effect of the adhesive thickness on the strength of single-lap joints for different kinds of adhesives. Three different adhesives were selected and tested in bulk. The strain to failure in tension ranged from 1.3% for the most brittle adhesive to 44% for the most ductile adhesive. The adherend selected was a high-strength steel to keep the adherends in the elastic range and simplify the analysis. Three thicknesses were studied for each adhesive: 0.2, 0.5, and 1 mm.

A statistical analysis of the experimental results shows that the lap shear strength increases as the bondline gets thinner and the adhesive gets tougher.     

胶接接头正拉强度和剪切测试装置的研制

作者研制出可用于金属胶接接头正拉和剪切强度测试的新装置，其结构简单、操作方便、成本低、精度高，适于生产现场的质量控制。     

Tensile Strength of Single Lap Joint and Scarf Joint between CFRP and Carbon Steel

The strength of single lap joints and scarf joints between carbon cloth laminated plastics (CFRP) and carbon steel bonded with epoxy resin was investigated both analytically and experimentally. The stress and strain distributions under tensile loads of the joints were analyzed by applying the elastic finite element method.

The strength of the joints was predicted by applying the strength law of CFRP, metal, adhesive layer and their interfaces to the calculated stress distributions. The predicted strength was compared with the experimental strength of the joints. The critical positions of the joints and the effects of the overlapped length on the joints were examined.     

拉伸强度与弯曲强度的关系及弯曲强度尺寸效应

本文研究了材料的破坏发生区、拉伸强度与弯曲强度的关系及弯曲强度的尺寸效应。拉伸及弯曲强度的关系为σ_t=σ_b(1-△/h),弯曲强度尺寸效应表现为σ_(bo)/σ_b=(1-△/h)/(1-△/h_0)。本文研究为精确测试材料拉伸强度提供了简便的方法,同时提供了破坏发生区的测试方法。     

Stress Analysis of Adhesively Bonded Electroprimed Steel Lap Shear Joints

Structural applications for adhesive bonding have been increasing in recent years due to improvements in the types of adhesives available and in improved knowledge of bonding procedures. Consequently, there exists a demand for precise numerical modeling of adhesive joint behavior, particularly along bondline interfaces where low surface energy adhesives contact high surface energy metallic oxides. The purpose of the present study is to determine the effect of electrodeposited organic paint primer (ELPO) on the stress and strain distributions within an adhesively bonded single-lap-shear joint. Initial experimental studies have shown that bonding to ELPO-primed steel adherends has enhanced strength and durability characteristics compared to conventional bonds to unprimed steel surfaces. Recent studies based on finite element analysis of varied single-lap-shear joint moduli and thicknesses, and subsequent testing of joints with two different adhesive moduli, have indicated the mechanisms involved in this phenomenon. The presence of the ELPO-primer reduced peak peel and shear stresses and allowed for more uniform stress distribution throughout the joint.     

Stress Analysis of Adhesively Bonded Electroprimed Steel Lap Shear Joints

Structural applications for adhesive bonding have been increasing in recent years due to improvements in the types of adhesives available and in improved knowledge of bonding procedures. Consequently, there exists a demand for precise numerical modeling of adhesive joint behavior, particularly along bondline interfaces where low surface energy adhesives contact high surface energy metallic oxides. The purpose of the present study is to determine the effect of electrodeposited organic paint primer (ELPO) on the stress and strain distributions within an adhesively bonded single-lap-shear joint. Initial experimental studies have shown that bonding to ELPO-primed steel adherends has enhanced strength and durability characteristics compared to conventional bonds to unprimed steel surfaces. Recent studies based on finite element analysis of varied single-lap-shear joint moduli and thicknesses, and subsequent testing of joints with two different adhesive moduli, have indicated the mechanisms involved in this phenomenon. The presence of the ELPO-primer reduced peak peel and shear stresses and allowed for more uniform stress distribution throughout the joint.