Pyrex/A1多层静电键合界面力学特征分析

采用公共阳极法实现了多层Pyrex玻璃与铝箔晶片的静电键合,采用MSC.MARC非线性有限元分析软件,对两层和3层Pyrex/Al键合件的界面残余应力及变形等力学特征进行对比分析。由于玻璃/铝/玻璃3层阳极键合试件的对称结构,键合界面附近的残余应力和应变均呈对称分布而有利于减缓变形。试件最大等效应力值均位于靠近连接界面的过渡层,使该部位成为阳极键合的薄弱环节。研究结果对于MEMS器件的精密封装工艺质量控制具有重要的意义。     

带有消声瓦的潜艇耐压壳的稳态振动和横向应力

采用混合分层理论和Ressiner混合变分原理，在壳的厚度方向取二次插值函数来描述位移沿厚度方向的变化规律；采用三次和四次插值函数来描述横向应力沿厚度方向的变化，线形处理筋条的变形，推导出粘弹加筋层合圆柱壳的动力学方程和协调方程组，并采用拉普拉斯变换，得出简支粘弹加筋层舍圆柱壳稳态振动的响应解。对于自由阻尼层合圆柱壳，所给出的振动频率和结构损耗因子与解析解吻合良好．结果表明，较高的层间横向正应力是引起潜艇消声瓦脱落的主要因素，而采用较高模量的粘弹性阻尼材料将降低层间横向应力的幅值．     

光纤布拉格光栅监测复合材料固化

复合材料层合板在固化成型过程中形成的残余应变和应力是影响材料质量的重要因素,它与预浸料铺层在固化工艺过程中产生的应变密切相关。在研究和测试了光纤布拉格光栅应变和温度传感器传感特性的基础上,将二者埋入复合材料预浸料铺层,在热压釜成型工艺过程中监测了材料内部的温度和应变发展历程,由此获得对称正交层合板的宏观残余应变。监测结果表明,单向和对称正交层合板在固化结束后都将产生收缩,对称正交层合板铺层内的残余应变平行于纤维方向为压应变,垂直于纤维方向为拉应变。光纤光栅传感器为复合材料固化监测及层合板残余应力分析提供了一种新的工具,为实现复合材料从制造到服役的全寿命、一体化监测提供了可能。      

Si3N4/SiC层状结构陶瓷摩擦磨损性能研究

利用Falex多重样品球-三块式的摩擦磨损试验机,重点研究了单层Si3N4陶瓷,9层和5层Si3N4/SiC层状结构陶瓷在不同的外加载荷、不同的界面应力分布大小、不同的表面组成与层状结构陶瓷的摩擦磨损性能的关系.结果表明:随着外加载荷逐渐加大,材料的耐磨损性能降低,表现为达到磨损突变点的时间缩短,磨痕直径变大;界面残余压应力对层状结构陶瓷耐磨损性能的提高起着重要的作用,9层结构陶瓷的界面残余压应力高出5层结构的层状陶瓷20%左右,表现出更高的耐磨损性能;SiC Si3N4两相复合陶瓷极大地提高了材料表面的耐磨损性能,在同样外加载荷下,表现为达到磨损突变点的时间更长,磨痕直径更小.     

Pyrex玻璃／铝多层阳极键合界面结构与力学分析

采用公共阳极法实现了Pyrex玻璃与铝多层晶片的静电键合,对玻璃/铝/玻璃阳极接舍界面的组织结构及其连接机理和力学特征进行了重点研究.分别利用微拉伸测试设备和ANSYS软件分析了连接区的力学性能和残余应力分布特征.分析认为键合区由玻璃一过渡层一铝组成,过渡层为Al2O3-SiO2复合氧化物.玻璃/铝界面的微观组织和元素分布均以铝为对称轴呈对称分布.在玻璃/铝/玻璃多层连接区,键合界面附近的残余应力和应变呈对称分布,多层结构的对称性有利于缓解接头应变和应力,表明应用公共阳极法可实现多层玻璃/铝/玻璃的良好键合.     

残余应力对陶瓷/硬质合金复合片硬度的影响

分析了残余剪应力对材料硬度的影响,导出了残余剪应力与硬度压头下最大剪应力的关系式．分析表明,残余剪应力与残余正应力不同,无论其方向如何,总是使材料硬度下降．通过实验证明,陶瓷／硬质合金热压复合片界面附近,残余剪应力使硬度下降的值大于由于残余压应力使硬度升高的值．据此分析认为,当陶瓷层热膨胀系数比硬质合金层小,而且太薄时,虽然可以在陶瓷层形成较大的残余压应力,但因残余剪应力的影响,表层的硬度不仅不会升高,反而会降低．     

涂层基体条件对梯度涂层残余应力影响研究

采用有限元法，对结构一定的Al/Ni-ZrO2梯度涂层在基体条件改变时涂层的残余应力进行了分析，结果表明，基体材料的热膨胀系数对涂层的残余应力有显著的影响，对于基体为圆柱形的涂层，其基体与涂层界面的残余应力梯度，最大轴向拉应力均随热膨胀系数的增大而线性增大，表面纯陶瓷层与次层界面残余应力梯度则随之减小，增大基体的直径和厚度，可缓和涂层残余应力，并在基体直径为36mm,厚度为20mm时各残余应力基本稳定。     

环氧树脂—玻璃界面层的残余应力

把电阻应变丝埋入树脂界面层并作为一臂接入一直流电桥,测定等温固化时电桥的不平衡电压可以求取因固化反应树脂体积收缩而引起的残余应力。由此测定了环氧树脂-三乙醇胺体系和环氧树脂-咪唑体系与玻璃之间界面层的残余剪切应力。在0.25mm界面层内残余应力随远离界面的距离单值地减小,环氧树脂-咪唑体系与玻璃之间界面层的残余应力值比环氧树脂-三乙醇胺体系大。     

多铁性非均匀空心层合柱圆弧界面的反平面断裂分析

讨论反平面载荷作用下多铁性非均匀空心层合柱的圆弧界面裂纹问题,层合柱由梯度铁电层和梯度铁磁层粘接而成,界面处存在圆弧型裂纹。采用分离变量和Cauchy核奇异积分方程方法求解该断裂问题。通过讨论断裂参数的数值解,分析了梯度非均匀参数、几何与材料参数变动等对应力强度因子的影响。     

陶瓷/金属钎焊接头内残余应力计算

用有限元法计算了陶瓷/金属钎焊接头内的残余应力,结果表明,在陶瓷一侧轴向残余应力的最大值位置在靠近连接界面的陶瓷表面,而不在连接界面上.最大主应力在接头内的变化规律与σzz的变化规律相似.σyy在陶瓷一侧表现为较大的压应力,在金属一侧表现为较大的拉应力.给出了接头最可能断裂的轮廓线.     

高温下短纤维增强金属基复合材料界面的微观结构和热残余应力状态研究

利用透射电镜观察了δ-Al₂O₃短纤维增强Al-5.5Mg合金复合材料界面在不同环境温度下的微观结构特征。 同时, 基于该类复合材料的单纤维模型, 利用弹塑性有限元分析方法, 研究了在不同温度下界面热残余应力的大小和分布情况, 并讨论了热残余应力对界面行为的影响。 最后, 讨论了界面的微观结构和热残余应力特征对复合材料整体性能的影响。 研究表明, 不同环境温度下, 界面具有不同的微观结构和热残余应力特征, 这些特征的变化将引起复合材料整体性能的明显变化。     

Effect of thermal misfit stress on crack deflection at planar interfaces in layered systems

Deflection of a crack at a planar bi-material interface in a layered system was investigated by considering the effects of the in-plane residual thermal misfit stress. A new parameter based on strains due to mismatch of thermal expansion coefficients was introduced to describe residual stress state independent of length scale. From a numerical analysis, it was predicted that introducing compressive residual stress in the stiffer intact layers of a composite laminate ahead of a growing primary crack would favour crack deflection by allowing advantageous energetic conditions, which indicates that stronger interfaces can be introduced in layered systems this way to improve overall mechanical properties. It was also predicted that the residual stress effect is negligible if the intact layer is more compliant than the cracked layer supporting a previous analysis and discussion reported elsewhere.     

等离子喷涂ZrC基涂层逐道逐层沉积残余应力模拟与实验验证

采用商用ANSYS14.5软件, 依据复合梁增层力学模型, 采用逐道逐层累积模型模拟了C/C复合材料表面等离子喷涂ZrC基涂层沉积残余应力的特征, 分析了SiC过渡层、第二相(SiC, MoSi₂)和涂层厚度对ZrC基涂层残余应力的影响, 并进行了实验验证。结果表明, SiC过渡层有效缓解了涂层与基体的热失配应力。涂层体系的应力随着涂层厚度的增加逐渐减小, 符合应力松弛和叠加规律。在涂层内部的径向应力以拉应力为主, 基体中主要为压应力, 且在界面边缘存在压应力集中的极限区域, 易使涂层产生裂纹并沿界面扩展。该模拟采用逐道逐层累积的方法更逼近实际喷涂过程, 能更准确预测涂层的残余应力。     

Ti/CFRP超混杂复合材料残余应力研究

由于组成Ｔｉ／ＣＦＲＰ超混杂复合材料层板的炭纤维、钛合金薄板及树脂的热膨胀系数的差异,以及树脂固化过程的收缩,在层间有残余应力形成,残余应力的存在会对材料的力学性能及加工性能产生影响。因此采用应变片包埋法和非对称层板法对该Ｔｉ／ＣＦＲＰ的残余应力进行了研究,推导出计算层板残余应力的计算公式,经修正后的计算结果与测试结果基本吻合。     

Effect of damage levels and curing stresses on delamination growth behaviour emanating from circular holes in laminated FRP composites

This paper deals with the study of the effect of drilling induced delamination damage levels and residual thermal stresses (developed during manufacturing process of cooling the laminate form curing temperature to room temperature) on delamination growth behaviour emanating form circular holes in graphite/epoxy laminated FRP composites. Two sets of full three dimensional finite element analyses (one with the residual thermal stresses developed while curing the laminate and the other without residual thermal stresses i.e. with mechanical loading only) have been performed to calculate the displacements and interlaminar stresses along the delaminated interfaces responsible for the delamination onset and propagation. Modified crack closure integral (MCCI) techniques based on the concepts of linear elastic fracture mechanics (LEFM) have been used to calculate the distribution of individual modes of strain energy release rates (SERR) to investigate the interlaminar delamination initiation and propagation characteristics. Asymmetric variations of SERR obtained along the delamination front are caused by the overlapping stress fields due to the coupling effect of thermal and mechanical loadings. It is found that parameters such as ply orientation, drilling induced damage levels and material heterogeneity at the delaminated interface dictate the interlaminar fracture behaviour of laminated FRP composites.     

Simultaneously improving strength and ductility through laminate structure design in Mg-8.0Gd-3.0Y-0.5Zr alloys

The laminate structure was applied to improve the mechanical properties of Mg-8.0Gd-3.0Y-0.5Zr alloys.Two types of laminate structures only with different distribution positions of fine grains were produced by friction-stir processing.Results show that the trilayer structure sample exhibits an excellent strengthductility synergy compared to the homogenous structure and bilayer structure.The enhanced mechanical properties are resulted from the hetero-deformation induced (HDI) stress strengthening and strain hardening which would be enhanced by increasing the quantity of interface.These observations suggest a crucial role of the number of interfaces in designing the laminate structure.     

反平面载荷作用下带界面裂纹的不同正交异性层板的应力分析

本文对含有边缘界面裂纹的不同正交各向异性平板在反平面载荷作用下的位移场与应力场进行了分析,得到了满足所有基本方程以及裂纹面边界条件与交界面连续条件的位移场与应力场展开式,本文进一步应用变分原理决定应力场展开式中奇异项系数—应力强度因子,计算结果表明,应力强度因子的收敛性是令人非常满意的.      

SiO2-Si3N4复合材料的力学性能及其增韧机理

采用热压工艺制备了ＳｉＯ２－Ｓｉ３Ｎ４复合材料，其抗弯强度和断裂韧性达到１４３ＭＰａ和１．７ＭＰａ．ｍ＾１／２，比基体ＳｉＯ２材料分别提高１０７％和７０％，复合材料改善是由于高弹性模量的Ｓｉ３Ｎ４引入以及ＳｉＯ２和Ｓｉ３Ｎ４热膨胀系数不匹配导致的残余应力。     

A multi-objective optimization approach for design of blast-resistant composite laminates using carbon nanotubes

A reliable process for the design of blast-resistance composite laminates is needed. We consider here the use of carbon nanotubes (CNTs) to enhance the mechanical properties of composite interface layers. The use of CNTs not only enhances the strength of the interface but also significantly alters stress propagation in composite laminates. A simplified wave propagation simulation is developed and the optimal CNT content in the interface layer is determined using multi-objective optimization paradigms. The optimization process targets minimizing the ratio of the stress developed in the layers to the strength of that layer for all the composite laminate layers. Two optimization methods are employed to identify the optimal CNT content. A case study demonstrating the design of five-layer composite laminate subjected to a blast event is used to demonstrate the concept. It is shown that the addition of 2% and 4% CNTs by weight to the epoxy interfaces results in significant enhancement of the composite ability to resist blast.     

Microstructure and thermal behaviour of plasma sprayed zirconia/alumina composite coating

In thermal barrier coatings (TBC), failure occurs near or at the interface between the metallic bondcoat and topcoat. On high temperature conditions, an oxide scale which is named thermally grown oxide (TGO) occurs along the bond/topcoat interface. For diminishing the creation of TGO, a dense coating with low residual stress and thermal stress buffer layer was preferable. High hardness ceramic coatings could be obtained by gas tunnel type plasma spraying, and the deposited coating had superior property in comparison with those deposited by conventional type plasma spray method. In this study, the gas tunnel type plasma spraying system was utilized to produce a zirconia/alumina functionally graded thermal barrier coating and discussed its physical and mechanical properties, thermal behavior and high temperature oxidation resistance of the coating are discussed. Consequently, the proposed system exhibited superior mechanical properties and oxidation resistance at the expenses of a slightly lower thermal insulating effect. This interlayer is preferred in order to minimize the detrimental effect of the phase transformation of gamma-Al2O3 to alpha-Al2O3.