聚氨酯复合泡沫塑料的动态压缩力学性能

针对几种不同密度、不同玻璃微珠填充比的聚氨酯复合泡沫塑料进行了动态压缩实验，研究了这类材料的宏观动态力学性能。结果表明，动态应力-应变曲线与准静态压缩加载下的应力-应变曲线具有相同的特征，也分为弹性区、平台区和致密区；在较大的应变率范围内，复合泡沫塑料的应变率效应是明显的，高密度复合泡沫塑料的屈服强度随应变率的增加而增加，而中、低密度材料的屈服强度则先随应变率的增加而提高，然后在某一高应变率下强度反而下降，材料表现出软化现象。     

基于SHPB的塑料动态压缩力学性能实验研究进展

从塑料类聚合物软材料目前力学性能研究现状及性能表征的不足,讨论了塑料类软材料在高应变率动态加载条件下霍普金森杆(SHPB)实验装置及实验用杆系的选取、应力应变信号的采集方式以及目前对塑料材料在高应变率加载条件下动态力学性能的实验研究,总结了SHPB高应变率动态实验时塑料材料的特性、提高实验数据精度的方式等方面。     

纤维增强光弹性复合材料应变-光学定律的探讨

本文根据无弹性复合材料的等倾线更接近于主应变方向而并不表征主应力方向的设想,讨论了纤维增强复合材料的应变-光学定律。利用应变-光学定律的概念,在进行正交各向异性材料平面应力的光弹性分析时,只需要测定光弹性材料的四个独立的弹性常数和任一正轴方向的材料条纹值。本文对Pipes等人提出的应变-光学定律进行了实验验证,发现模型材料所提供的数据与应变-光学定律相当吻合,等倾线参数与计算所得的主应变方向也相当接近。     

基于材料基因工程的AP/Al/HTPB推进剂单轴拉伸性能及脱湿过程计算

为克服传统"经验型"材料研发模式和"唯象法"构建材料计算模型的不足,构建了一种基于材料基因工程的复合固体推进剂单轴拉伸性能预估方法;以高氯酸铵/铝/端羟基聚丁二烯(AP/Al/HTPB)推进剂为例,将填料堆积微结构定义为材料基因之一,建立了可反映推进剂配方的填料微结构最小代表性单元,分别确定了决定填料、基体、填料-基体界面力学性能的材料基因,并建立了材料基因与推进剂单轴拉伸性能之间的构效关系,获得了单轴拉伸条件下推进剂内部的损伤演变规律及应力—应变响应。结果表明,AP/Al/HTPB推进剂的应力—应变曲线可分为弹性段、黏弹性段和损伤段3个阶段;基体的黏弹性形变和填料脱湿会导致推进剂黏弹性模量下降;应变大于15.37%时,脱湿首先发生在粗粒径颗粒上方,随后以先快速、后平稳的趋势沿粗颗粒周向扩展;应变大于21.19%时,中等粒径颗粒开始脱湿;在0～25%的应变范围内细颗粒与基体始终黏接完好。     

正交异性光弹性复合材料的研制及性能测定

本文介绍了用于正交异性光弹性实验的双折射玻璃纤维增强复合材料的制作及其性能测试方法。对测试的基本原理——应力-光学定律和应变-光学定律作了概括论述。给出了所测定的材料性能数据。这种材料用特制的光学玻璃纤维和环氧树脂常温固化制成,其透明度较好,光弹性效应灵敏。适于制作二维和三维复合材料光弹性模型。     

高体分比颗粒增强复合材料弹塑性力学分析

高体分比颗粒增强复合材料被广泛应用于工程领域。本文通过建立该类复合材料的弹塑性细观力学模型,系统研究了该类材料在单轴拉压情况下的宏观弹塑性力学性能。在有效模量预测方面,分别采用Mori-Tanaka模型和Ju等提出的相互作用细观力学模型研究了高体分比颗粒增强复合材料的宏观有效模量,指出了Mori-Tanaka模型的局限性。针对高体分比颗粒增强复合材料弹塑性力学性能,采用Hill定理和场扰动方法建立了宏观应力与基体等效应力的关系,分别采用Mori-Tanaka模型和Ju模型研究了颗粒增强复合材料在不同体分比下的宏观弹塑性力学性能,并将理论预测与实验数据和有限元模拟结果进行了对比分析。结果表明,针对高体分比颗粒增强复合材料宏观弹塑性力学性能预测,本文方法相比传统模型结果更准确,可为工程领域中该类材料的弹塑性力学性能预测提供一定的理论参考。     

HTPB推进剂疲劳特性试验研究

针对HTPB推进剂开展了不同加载应力和加载频率下的疲劳试验,并结合红外热成像系统实时监测疲劳试验中材料的表面温升,分析疲劳损伤对HTPB推进剂力学性能的影响。结果表明,随着循环次数的增加,HTPB推进剂应力—应变曲线滞回圈逐渐右移,表明峰值点和谷点的应变都在不断增加,疲劳峰值应变呈现三阶段的发展规律:初始变形阶段、稳定发展阶段和加速阶段;非弹性效应会造成不可逆的热力学现象,产生的能量绝大部分以黏性耗散的形式释放,是造成推进剂温度变化的主要原因;HTPB推进剂的初始弹性模量、屈服应力和最大抗拉强度随循环加载次数越多衰减越大,微观层面上主要是由于疲劳过程中颗粒与基体粘结界面出现"脱湿"现象,逐渐形成微孔洞和微裂纹,最终发展汇聚成宏观裂纹而失效。     

基于DIC方法的车用PP+EPDM-TD10材料动态力学性能研究

结合改性聚合物材料的实际使用工况,结合数字图像相关法(DIC),对车用前保险杠外罩材料聚丙烯+三元乙丙橡胶(PP+EPDM-TD10)进行应变率为准静态(0.000 6 s~(-1))、1 s~(-1)、25 s~(-1)、90 s~(-1)的拉伸试验。得到材料在各应变率下的应力-应变信息。分析该材料的拉伸破坏过程,以及应变率对其力学性能影响。结果表明,应变率对黏弹性材料聚丙烯(PP)+三元乙丙橡胶(EPDM)-TD10的断裂应力、断裂应变、屈服应力和流变应力影响较大。根据改进的Erying理论模型,结合试验数据得出该材料的屈服应力与应变率之间函数模型。     

水泥沥青砂浆力学性能的温度敏感性

研究了不同温度条件下不同沥青含量的水泥沥青砂浆的抗压性能,以揭示该类有机–无机复合材料力学性能的温度敏感性规律。在–40～80℃范围内选择不同环境温度,采用电液伺服控制材料万能试验机测试了水泥沥青砂浆静态单轴抗压荷载下的应力–应变全曲线,获得了峰值应力和弹性模量随温度变化的基本规律。结果表明:随温度的降低,应力–应变曲线的上升段斜率增大,峰后下降段逐渐变陡,力学特性逐渐出现韧–脆转换。一般而言,水泥沥青砂浆的弹性模量和峰值应力随温度的升高和沥青含量的增大而降低,其温度敏感性随沥青含量的增大而增大。沥青含量较大的水泥沥青砂浆,其弹性模量和峰值应力随沥青含量变化幅度不大。建立的经验关系式成功描述了不同沥青含量的水泥沥青砂浆力学性能随温度变化的定量关系,且拟合结果表明以温感因子表征其力学性能对温度的敏感性具有一定的合理性。温感因子随着沥青含量的增大而增大,峰值应力的温感因子大于弹性模量的。     

典型建筑玻璃力学性能的SHPB实验

基于建筑玻璃冲击荷载作用下的实验研究,利用分离式霍普金森压杆(SHPB)技术对比研究了建筑玻璃的冲击力学性能,分析实验结果发现钢化玻璃在应力、应变率、抗冲击性能等方面力学性能比浮法玻璃优异,进一步研究发现钢化玻璃的应力应变曲线除出现类似于浮法玻璃的线弹性段,还表现为有别于金属的屈服现象,并根据Grifith能量平衡原理进行了解释.     

固体催化剂力学性能研究

本文评述了固体催化剂力学性能研究的进展,介绍了催化剂强度失效和数据统计关联等力学基础,给出了固体催化剂力学研究体系。并指出催化剂力学研究的目标是形成催化剂填充床力学可靠性模型。     

橡胶轻骨料混凝土的物理力学性能

本文以内蒙古地区天然浮石作为粗骨料,测定了20目橡胶微粒掺量(0％、3％、6％、9％、12％、15％)和不同橡胶微粒粒径(20目、80目、120目,掺量为6％)的橡胶轻骨料混凝土工作性、3d、7d、14 d、28 d、90d、180 d抗压强度、轴心抗压强度、弹性模量,并对其受压破坏形态进行研究,结合微观结构分析了橡胶微粒对其力学性能的影响.结果表明:相对于基准组,随着橡胶掺量增加(相同粒径)和粒径减小(相同掺量),橡胶轻骨料混凝土的力学性能发展趋势基本相同,坍落度、抗压强度、轴心抗压强度均逐渐减小,但是可以增强轻骨料混凝土的塑性特征.根据物理力学性能的稳定性和强度,其中橡胶粒径为20目,掺量为6％性能最佳.     

低钾型乙苯脱氢催化剂机械强度的优化

考察了各种因素对低钾乙苯脱氢制苯乙烯催化剂机械强度的影响。实验结果表明,通过优化催化剂的化学组成,改进催化剂的制备条件,完全可以开发出机械强度好的低钾乙苯脱氢催化剂。     

不同水胶比的塑钢纤维橡胶混凝土力学性能研究

在水胶比分别为0.36、0.42、0.48的情况下,分别对普通混凝土、橡胶混凝土、塑钢纤维橡胶混凝土进行了抗压强度、劈裂抗拉强度、抗折强度等力学性能的试验研究.试验结果表明:掺入橡胶颗粒后,混凝土强度有所降低,塑钢纤维有助于提高橡胶混凝土的抗压强度.相同水胶比下,塑钢纤维对橡胶混凝土的抗折强度和抗拉强度的提高作用明显,折压比和拉压比均呈现先增大后减小趋势,塑钢纤维掺量宜控制在6 ～8 kg/m3之间.     

Mechanical stability of monolithic catalysts: Factors affecting washcoat adhesion and cohesion during preparation

Alumina‐washcoated cordierite monoliths are prepared to investigate the effects of the preparation process factors on the mechanical stability of monolithic catalysts. It is shown that the agent for pretreating substrates, properties of the washcoating solution (solid content, additive, and amount of additive), and washcoating times all have great effects on the washcoat loading and on the washcoat adhesion and cohesion. There is a great possibility of improving the mechanical stability through the optimization of these factors. If multiple washcoating is performed, the two‐time washcoating after calcination is recommended in this case. It is also pointed out that the minor variation of the washcoat loading with monolithic mini‐specimen increases the scatter of the washcoat adhesion and cohesion, resulting from fatigue failure of active material. Furthermore, the previously proposed mechanical failure mechanism is confirmed to be an effective tool to factors analysis of the mechanical stability of cordierite monolithic catalysts. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2765–2773, 2014     

Polyurethane‐solid wood composites prepared with various catalysts. I. Mechanical properties and dimensional stabilities

Polyurethane (PU)‐solid wood composites were prepared by impregnating PU prepolymer into low‐density fast‐growing poplar solid wood and controlling the prepolymer cured or foamed within wood voids in the presence of the catalysts triethanolamine (TEA), diethylenetriamine (DETA), triethylenediamine (TEDA), and N‐methyl morpholine (NMM), respectively. A scanning electron microscope (SEM) was used to observe the morphologies of the cured PU resin and the wood voids, and the effects of catalyst species on the mechanical properties and dimensional stabilities of PU‐wood composites were evaluated. The results indicated that the PU prepolymer cured in the presence of various catalysts resulted in different morphologies and distributions within wood voids, and therefore led to various mechanical properties and dimensional stabilities of the PU‐wood composites. Because of the fact that wood cell walls in the surface layer had apparently collapsed in the presence of catalyst DETA and therefore the wood was densified, the PU‐wood composite prepared with DETA had the best mechanical properties and dimensional stabilities. The PU prepolymer was well impregnated and evenly foamed within the wood in the presence of catalyst NMM, giving the PU‐wood composite prepared with NMM much better dimensional stability as the foamed PU blocked the water transfer between the cells. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

硅烷偶联剂浓度对再生塑料混凝土力学性能影响

硅烷偶联剂浓度对改性再生塑料混凝土的力学性能影响较大.本实验通过选取不同浓度的硅烷溶液来处理再生塑料颗粒,并将其掺入混凝土中,制成所需规格的试件,测定其立方体抗压强度、劈裂抗拉强度、轴心抗压强度以及抗折强度.实验结果显示,再生塑料颗粒含量较少时,硅烷浓度对力学性能影响不大;随着再生塑料颗粒含量越多,硅烷浓度对力学性能影响越大,且硅烷浓度大于1％时其力学性能增大幅度最大,之后随浓度增加基本保持不变.     

Dynamic Mechanical Thermal Analysis and Rheological Properties of Synthesized Polypropylene Reactor Blends Using Homogeneous Binary Metallocene Catalyst

A homogenous binary metallocene catalytic system comprising of isospecific rac-Me₂Si(2-Me-4-Ph In)₂ZrCl₂(I) producing high molecular weight isotactic polypropylene and oscillating (2-Ph In)₂ZrCl₂(II) precursor producing low isotactic elastomer polypropylene at three varying molar ratios of two types of catalysts was used to synthesize polypropylene reactor blends. Dynamic mechanical thermal analysis and rheological properties along with molecular weight of synthesized polypropylene reactor blends were studied and correlations among these properties were established. It was found that molar ratio of catalysts is a significant factor in determination of molecular weight and its distribution. The produced polymers with unimodal molecular weight distribution showed intermediate modulus during dynamic mechanical thermal experiment, while the ones with bimodal molecular weight distribution exhibited a kind of phase separation at low temperature. Depending on strength of the developed structures, determined by the presence of interfacial connectors, the modulus could be adjusted. Origins of other types of relaxations and their differences for each type of the developed products were discussed in detail. From rheological results and particularly the relaxation curves, the characteristics of the chain structure of the synthesized reactor blends could be resolved. It was revealed that one of the synthesized polymers had long chain branches unlike the rest of the samples having linear chain structure.     

Influence of Catalyst Content on the Thermal and Mechanical Properties of Epoxy Resins Initiated by a Cationic Latent Thermal Catalyst at Elevated Temperatures

The effect of catalyst content on the thermal and mechanical properties of diglycidyl ethers of bisphenol A (DGEBA)/BPH system was investigated at elevated temperatures. The contents of the catalyst, N‐benzylpyrazinium hexafluoroantimonate (BPH), examined were 0.5, 1, and 3 wt.‐% and the elapsed heating time was varied from 0 to 1 024 h. As a result, the thermal‐oxidative resistance and mechanical properties, including flexural strength, elastic modulus in flexure, and impact strength showed a maximum value at 1 wt.‐% BPH. By increasing the elapsed time to 4 h, the thermal and mechanical properties of the specimens were also improved. These results showed that the internal structure of the epoxy system was stabilized and post‐cured as the elapsed time increased, resulting in an improvement of the thermal and mechanical properties of the specimens.

Impact strength of the DGEBA/BPH system as a function of BPH content and elapsed heating time.     

含有潜伏性催化剂的环氧树脂/酸酐体系的研究

使用固态聚胺与疏水性微粒子WS-12制备出一种潜伏性催化剂,评价了该催化剂在环氧树脂/甲基六氢苯酐固化体系中的催化固化作用。在25～50℃的范围内本固化体系长时间黏度变化平稳,而在150℃以上时具有高效的催化效果,显示出该催化剂具有优异的潜伏功能。该催化固化体系能适合于各种黏度的环氧树脂,当使用一种低黏度环氧树脂时,即m(环氧树脂6002):m(甲基六氢苯酐):m(潜伏性催化剂)=100:70:3时,其固化物显示出最佳的力学性能。