热强-290/SC-13复合材料试样厚度对力学试验数据的影响

研究了热强-290纤维/SC-13改性酚醛树脂复合材料的力学试验设计与试样厚度对其力学试验数据的影响,确定SC-13粘结剂的力学测试试样的厚度的最佳范围为4.0～5.0mm.     

胶层厚度对拉伸试样应力分布影响的数值分析

运用弹塑性有限元法研究了胶层厚度对承受拉伸载荷的对接接头胶层内应力分布的影响．三维有限元法数值分析的结果表明，随胶层厚度减小，胶层中正应力SZ与剪应力SYZ的分布趋于均匀；而对正应力SY而言，胶层厚度为0．15mm时，其边缘峰值应力最低。     

聚硫密封剂剥离强度测定影响因素分析

本文对聚硫密封剂剥离强度测定过程中的影响因素进行了理论上的分析以及试验验证。试验表明:试验环境条件、金属试片表面状态、密封剂试样胶层厚度、试验拉伸速度对聚硫密封剂剥离强度测定具有一定的影响,因此在实际操作过程中应加以注意。     

影响BOPET薄膜厚度的因素探讨

针对影响BOPET薄膜厚度的因素进行了研究。结果表明,不同拉伸比、拉伸温度、铸片条件及APC系统的控制方式对厚度偏差影响较大。通过选择合适的工艺、控制条件可以改善薄膜的厚薄均匀性。     

试样尺寸变化影响拉伸性能试验结果的探讨

以乙醇胺为起始原料，经酯化和磺化两步反应制得牛磺酸，总收率为８３％。     

试样厚度对聚乙烯拉伸性能的影响

通过对不同厚度聚乙烯试样的拉伸试验进行分析.结果表明,试样厚度对聚乙烯的强度、应变、拉伸模量均有较大影响,对单位面积的屈服吸收能没有影响;现有塑料制品设计中,材料的拉伸性能和制品厚度为独立参数的做法存在隐患.     

底涂剂对聚氨酯密封剂粘接性能的影响

以异氰酸酯(TDI)和聚醚多元醇(如N-220、N-330和EP-330N等)为主要原料,合成了高性能双组分PU(聚氨酯)密封剂。采用不同底涂剂对水泥基材进行表面涂敷,以增强PU密封剂/水泥基材胶接件的粘接性能。结果表明:当D1[环氧树脂(EP)类底涂剂]作为PU密封剂/水泥基材胶接用底涂剂时,其粘接效果低于D2(PU类底涂剂);用硅烷偶联剂改性D1,可有效增强EP/PU间的界面结合力,提高PU密封剂/水泥基材胶接件的耐水性和耐热性;在D3(由EP、KH-550硅烷偶联剂和二乙烯三胺组成)未干时浇铸PU密封剂,则PU密封剂/水泥基材胶接件的性能满足JC/T 976—2005标准要求。     

复合材料表面密封剂与抗静电涂料在燃油中稳定性研究

研究了复合材料表面上HM108B4密封剂和H06—1020HD抗静电涂层材料在航空煤油中的质量变化、密封剂的180°剥离强度和破坏模式。研究结果表明：随着时间的延长,HM108B4密封剂／复合材料和抗静电涂层／密封剂／复合材料在航空煤油中质量变化率均先下降后上升,最后趋于稳定,抗静电涂层／密封剂／复合材料在煤油中质量变化率小于密封剂／复合材料。未浸油老化和60±2℃浸油老化7天密封剂／抗静电涂层试样的180°剥离强度分别为10．9KN／m和11．1KN／m,试样的破坏模式为内聚破坏。     

PS哑铃形试样拉伸性能的影响因素及断裂位置研究

利用自行研制的不溢式压模,制备了不同过渡段结构的PS哑铃形压制试样。通过冲击实验和偏光显微镜观察分析了试样的微观形态,研究了试样不同过渡段结构以及应力集中对拉伸强度的影响,并统计了拉伸断裂位置。研究结果表明:不同过渡段结构的哑铃形压制试样聚集态结构是均质的;拉伸强度随拉伸速率和过渡段圆弧半径的增大而增大;应用应力集中系数修正公式计算拉伸强度更接近材料的真实强度。分析结果表明,哑铃形试样拉伸断裂位置发生在距平直段与过渡段切点1～3mm的应力集中区域。     

Shear strength tests of glass ceramic sealant for solid oxide fuel cells applications

Different approaches are used for the integration of ceramic components in solid oxide fuel cells stacks, where dissimilar materials (ceramics and metals) have to be joined and coupled for a reliable long term operation. This work focuses on the mechanical characterisation of a glass ceramic sealant used for the joining of Crofer22APU metallic interconnect samples as well as the interaction with a preoxidised Crofer22APU. Crofer22APU–glass ceramic sealant joined samples are tested by two different mechanical tests. Hourglass samples with different geometries were tested using an in-house developed torsion test machine at room temperature. In addition, their mechanical strength was also evaluated according to the ISO?13124 standard. The comparison of the two different testing methods, with particular focus on the shear strength of the joined samples, are reviewed and discussed.     

硅烷改性聚醚密封胶剪切强度的研

以MS聚合物为粘料,添加填料、脱水剂、偶联剂、催化剂等助剂,制备一种单组分硅烷改性聚醚密封胶。研究了MS聚合物、填料、固化条件、胶层厚度对剪切强度的影响。     

An experimental study on the dependence of the strength of adhesively bonded joints with thickness and mechanical properties of the adhesives

Adhesive bonding joints are widely applied in many engineering fields. Their overall strength is much dependent on the thickness of adhesive layers. Many previous experimental studies have found that the ultimate failure strength of the bonding structure increases with the decrease of the adhesive thickness. However, few of them consider the effect of adhesive intrinsic material parameters on the relation between the overall strength and adhesive thickness. In the present investigation, the effect of the adhesive thickness on the overall strength of the lightweight metallic adhesive bonding joints was experimentally studied, considering the effect of the adhesive toughness. The results show that the variations of overall strength resulting from the adhesive thicknesses have remarkable discrepancy due to the toughness of the adhesive, which is in agreement with the previous model prediction.     

Effects of thermal aging on thermo-mechanical behavior of a glass sealant for solid oxide cell applications

Thermo-mechanical properties of a silicate based glass and its potential use for sealing application in intermediate temperature solid oxide cell (SOC) are presented in this paper. Effects of thermal aging are discussed on structural and microstructural evolution, thermal expansion, viscosity, modulus of elasticity, and high-temperature deformation of the glass. The balance between the viscosity and viscous flowing behavior was explored for the non-aged and aged glasses as it is essential to have a successful sealing for a SOC stack. The results reveal a temperature dependence of Young's modulus in which a transition between a slow softening (elastic) regime and a rapid softening one was observed. Crystallization induced by thermal aging led to higher creep resistance, but lower capability of crack healing when inspected by electron microscopy. However, potential of stress relaxation in the aged material was confirmed by the constitutive mechanical models of viscoelasticity.     

Effect of Adhesive Thickness on Joint Strength: A Molecular Dynamics Perspective

Recent studies suggest that adhesion in thin joints depends on several factors including temperature, interface toughness, strain rate, surface roughness of adherends, bondline thickness of adhesives, and many others. Influence of thickness on joint properties is surprising but experimentally well documented without reasonable explanations. In this study, we attempt to address the mechanical behavior of polymer adhesives by molecular dynamics (MD) simulation. We show that interfacial strength of the joints in tensile, shear, or combined loading significantly depends on the coupling strength between adhesives and adherends. Failure of joints is always at the interface when coupling strength is weaker. With stronger interfaces, cohesive failure occurs by cavitation or by bulk shear depending on the loading condition. When joints are loaded in tension, it requires an exceedingly stronger interface to realize pure shear failure, otherwise failure is through interface slip. Under a mixed mode condition, interface slip is difficult to avoid. As long as failure is not at the interface alone, the yield strength of joints improves significantly with the reduction of thickness. Increase in bulk density and change in polymer configurations with the reduction of adhesive thickness are believed to be the two key factors in improving mechanical behavior of adhesives.     

浅谈高分子聚合物的拉伸性能

分析了高聚物的拉伸过程,讨论了外力作用速度对高聚物拉伸性能的影响。     

Effects of Processing Parameters on Tensile Strength of Thin-Wall HDPE Parts Injection Molded by Ultra High-Speed Process

This study explores how ultra high-speed processing parameters affect the melt flow length and tensile strength of thin-wall injection molded parts. A spiral shaped mold with a specimen thickness of 0.4 mm and a width of 6 mm was first constructed to test the melt flow length as an index of process capability for ultra high-speed injection molding. It was observed that the flow length increases with increasing injection speed. High-density polyethylene (HDPE) tensile test specimens with different thicknesses (0.6 mm and 2 mm) were also molded for tensile tests. Both single gate and double gates were used to form parts without and with weldlines. Injection molding trials were executed by systematically adjusting related parameters setting including mold temperature, melt temperature, and injection speed. The parts’ tensile strengths were measured experimentally. It was found that tensile strengths of 0.6 mm thick parts both with and without weldlines were higher than those of 2 mm thick parts. The tensile strength of 0.6 mm thick specimens increases with increasing mold temperature, melt temperature and injection speed, whereas tensile strength in 2 mm thick specimens was only weakly dependent on the corresponding processing parameters. Furthermore, 0.6 mm thick specimens with weldlines had tensile strengths lowered about 9.6% compared to parts without weldlines. For 2 mm thick part the corresponding reduction is 4.3%.     

Effects of Al2O3 nanoparticles on the properties of glass matrix composites for sealant applications

Glass matrix composites (GMCs) have better mechanical properties than glass, which is beneficial for applications as sealants. This application scenario requires the GMCs sealants to withstand extreme service conditions for extended periods of time. In this study, a borosilicate glass as the matrix was filled with Al₂O₃ nanoparticles to prepare the GMCs through powder technology, and the effects of Al₂O₃ nanoparticles on the phase composition, thermal behavior, coefficients of thermal expansion (CTE), microstructure, wettability, viscosity and mechanical properties were systematically investigated. X-ray diffraction (XRD) patterns and thermal analysis results revealed that the Al₂O₃ particles, which were thermodynamically stable in the borosilicate glass after heat treatment, could be considered as rigid inclusions. As the mass fraction of Al₂O₃ nanoparticles increased, the CTEs of the GMCs and the wettability to metal surfaces gradually decreased, and an increasing viscosity was also observed with the addition of Al₂O₃ nanoparticles, which was attributed to the inhibition effect of the Al₂O₃ nanoparticles on glass viscous flow and apparently contributed to the residual voids. The mechanical properties of the heat-treated GMCs were enhanced by the Al₂O₃ nanoparticles but limited by structural defects such as residual voids and swollen bubbles, especially when the mass fraction of Al₂O₃ nanoparticles was large. The results thus demonstrate that an increased heat treatment temperature was expected to reduce the viscosity of the melts and promote the elimination of residual voids, but will inevitably cause the undesired bubble growth at the same time. Therefore, the content of Al₂O₃ nanoparticles in the glass matrix should be limited to a certain extent to ensure that the reinforcements can fully exert their strengthening effect.