复合材料的强度和稳定性理论中的几个近代问题

本文论述了复合材料的强度和稳定性理论中的三个近代问题:复合材料迭层板的强度准则,多层复合材料圆柱壳的非线性稳定性理论,以及复合材料板的动力稳定性理论。关于迭层板的强度准则,论述了目前以张量多项式形式所表述的唯象性破坏准则,着重讨论和比较了各种近代理论在确定耦合系数方面的特点和差别。提出了近代理论中所存在的困难和发展趋势。在多层复合材料圆柱壳的非线性稳定性理论分析中,主要的问题在于如何研究和考虑那些非线性因素,诸如由材料的剪切模量所引起的物理非线性,横向剪切变形的影响,壳体结构的初始缺陷和几何非线性,以及前屈曲变形和边界支承条件的影响等。本文指出了考虑这些因素的方法以及它们的影响程度。复合材料板的动力屈曲性能研究是一个重要的近代研究方向。本文提出了关于复合材料本身的阻尼系数,纵向和转动惯性力影响,横向剪切效应,迭层板的初始几何缺陷,以及增强纤维的铺设方向等因素对于动力屈曲性能的影响。同时提出了计算这些影响的方法,指出这些因素在复合材料板的动力稳定性分析中有着重要作用。     

随机取向短纤维复合材料的拉伸强度(英文)

以茅人杰提出的单向短纤维复合材料的模型为基础,得出单向短纤维复合材料轴向拉伸强度的计算方法．考虑到单向短纤维复合材料的横向拉伸强度、面内剪切强度,利用两对坐标轴间应力转换关系,导出单向纤维复合材料受任意方向拉伸时的应力;由无规高聚物材料分子链主轴和取向方向间夹角θ＝５４°４４′,利用一等价关系,最后导出随机取向短纤维复合材料的拉伸强度表达式．     

拉压实验与纯扭转实验的互补特性

由金属材料的单一拉伸与纯扭转实验结果的比较可见,拉伸所测等效应变值仅对不可压缩材料才成立,对可压缩材料并不成立,纯扭转实验中所测等效应变值不受压缩性影响。用纯扭转实验来初步研究材料的性能,再用拉伸实验来做压缩性修正,说明拉伸实验和纯扭转实验的互补性。利用这种互补关系,用纯扭转实验资料建立材料的本构关系,再考虑材料的压缩性,推导出可压缩材料的本构关系。     

Experimental research on behavior of composite material projectile penetrating concrete target

Projectile made of carbon fiber composite material shell and metal warhead penetrates concrete target at speeds of 336 m/s, 447 m/s and 517 m/s. The angles between the perpendicular of target surface and projectile axis are 0° and 30° . The thickness of concrete target is 200 mm and the compression strength is 30 MPa. The experimental results indicate that the strength of composite material structure is high. Composite projectile can go through concrete target without fiber segregation and breakage. The percent fill is 18.5% in the composite material projectile. It is about twice as that of metal projectile, if the density of metal is taken as 7.8 g/cm^3. Comparing with metal projectile, low-density, high-strength composite material can lessen projectile weight, improve charge-weight ratio of detonator and enhance destructive powder.     

用原位拉伸研究复合材料的机械性能

用扫描电镜原位拉伸的方法研究了碳化硅纤维增强镁铝复合材料的机械性能. 通过对材料中裂纹的起源、扩展、断裂过程的观察研究, 发现在拉伸状态下, 裂纹最初起源于碳化硅纤维; 在碳化硅纤维与基体结合较强时, 裂纹首先在碳化硅纤维中扩展, 同时裂纹附近的碳化硅纤维亦开始产生微观裂纹、镁铝金属基体发生塑性变形, 最终断裂; 而在碳化硅纤维与基体结合较弱的状态下, 材料的韧性较高.     

材料力学中组合梁组合变形的一种通用解法

两种或多种不同材料制成的组合梁是工程实际中的一种常用结构。本文基于材料力学中的平面假设、胡克定律等基本假设和概念,给出了组合梁组合变形分析的一种通用解法,建立轴力、弯矩与拉伸位移和弯曲挠度的关系,推导出拉伸位移和弯曲挠度满足的微分方程。该分析方法简单易懂,适合材料力学教学和工程实际应用。     

双峰中密度聚乙烯/纳米碳酸钙复合材料的流变行为与力学性能

研究了双峰中密度聚乙烯(BMDPE)与纳米碳酸钙不同配比复合物的流变行为与力学性能.讨论了复合物的组成、剪切应力和剪切速率以及温度对熔体粘度和膨胀比的影响,测定了不同配比熔体的非牛顿指数(n)、熔体流动速率(MFR)、粘流活化能以及习用屈服应力,断裂应力和断裂伸长率,用扫描电镜观察了纳米碳酸钙在复合材料中的分散情况.结果发现:纳米碳酸钙可以均匀地分散在BMDPE中,少量的纳米碳酸钙就可以明显提高材料的力学性能,在较高的剪切速率下还可以改善材料的加工性能.     

基于Matlab的铝合金材料拉伸试验曲线拟合研究

以2A11铝合金材料为例，采用美国MTS公司生产的MTS810 Material Test system对棒材试样作简单拉伸试验。运用Matlab的多项式运算函数对拉伸试验真应力．自然应变曲线非线性均匀变形阶段进行拟舍，建立了真应力一自然应变本构方程；误差分析表明，精度较高。研究结果为铝舍金材料真应力一自然应变本构方程的建立提供了新的方法，对工程实际应用具有很好的指导意义和参考价值。     

羧甲基纤维素与短切稻草的热压复合研究

为了探索新的稻草利用途径,开发一种基于稻草的环保复合材料,对羧甲基纤维素与稻草的热压复合进行了研究。将稻草进行短切,以水为混合及复合助剂,先使羧甲基纤维素与稻草在常温常压下进行混合,然后在热压机上进行加热加压复合。研究了羧甲基纤维素用量、热压温度、热压时间对复合材料拉伸力学性能及硬度的影响。结果表明,复合材料的拉伸强度随羧甲基纤维素的用量的增加而增加,随热压时间及热压温度的增加先增加后减小,在羧甲基纤维素用量50%,热压温度120℃,热压时间10 min时,复合材料的拉伸强度为1.52 MPa。复合材料的硬度受加工条件的影响较小。     

AZ91D变形镁合金板温热拉伸性能研究

在应变速率为10-3～10-1S-1、温度为150℃～400℃的条件下,在万能试验机上对AZ91D镁合金板材进行了在线加热拉伸试验,获得了各成形条件下0°、45°、90°三个方向的应力应变曲线。试验结果表明,当拉伸温度增加或拉伸速率降低时,板料的屈服强度和抗拉强度降低,而其塑性变形能力提高;板材具有明显的各向异性,45°方向塑性变形能力最高,90°方向时最低。     

钛合金丝材剪切强度影响因素试验研究

为满足钛合金丝材工程化研究以及剪切性能复验的需求,针对某牌号紧固件用钛合金丝材开展了剪切方法的试验研究。通过对比试验,全面系统地研究了剪切强度的主要影响因素:试验设备、剪切夹具、刀口间隙、试样与剪切孔间隙、剪切速度以及试样的表面机加工对钛合金丝材剪切强度的定量影响。这不仅有助于规范和完善钛合金丝材的剪切试验方法,减少试验误差并提高数据的可比性,同时也为改进其它金属材料的剪切试验方法提供参考。     

Continuum damage mechanics based modeling progressive failure of woven-fabric composite laminate under low velocity impact

A continuum damage mechanics （CDM） meso-model was derived for both intraply and interply progressive failure behaviors of a 2D woven-fabric composite laminate under a transversely low velocity impact.An in-plane anisotropic damage constitutive model of a 2D woven composite ply was derived based on CDM within a thermodynamic framework,an elastic constitutive model with damage for the fibre directions and an elastic-plastic constitutive model with damage for the shear direction.The progressive failure behavior of a 2D woven composite ply is determined by the damage internal variables in different directions with appropriate damage evolution equations.The interface between two adjacent 2D woven composite plies with different ply orientations was modeled by a traction-separation law based interface element.An isotropic damage constitutive law with CDM properties was used for the interface element,and a damage surface which combines stress and fracture mechanics failure criteria was employed to derive the damage initiation and evolution for the mixed-mode delamination of the interface elements.Numerical analysis and experiments were both carried out on a 2D woven glass fibre/epoxy laminate.The simulation results are in agreement with the experimental counterparts,verifying the progressive failure model of a woven composite laminate.The proposed model will enhance the understanding of dynamic deformation and progressive failure behavior of composite laminate structures in the low velocity impact process.     

Dissolved oxygen sensor based on sol-gel matrix doped with tris(2,2’-bipyridine)ruthenium dichloride

To establish a immobilization method of oxygen sensitive dye, a dissolved oxygen sensor based on a sol-gel matrix doped with ruthenium complex ([Ru(bpy)3]2+) as the oxygen-sensitive material is reported. The results indicate that the I0 /I100 value of the [Ru(bpy)3]2+-doped in tetraethylorthosilane (TEOS) composite films are estimated to be 10.6, where I0 and I100 correspond to the detected fluorescence intensities in pure nitrogen saturated water and pure oxygen saturated water, respectively. Also, the Stern-Volmer plot shows a very good linearity at low dissolved oxygen concentrations. The response time of the composite films is 5 s upon switching from nitrogen saturated water to oxygen saturated water and 10 s from oxygen saturated water to nitrogen saturated water. The dissolved oxygen sensors based on the ruthenium complex/TEOS composite films exhibit greater sensitivity, stability and faster response time as compared to the existing ones. Furthermore, the thin films possess greatly minimized dye leaching effect.     

玉米淀粉-Ti-Si复合材料的制备、表征及吸附性能研究

以玉米淀粉、钛酸正丁酯和γ-氨丙基三乙氧基硅烷为原料,通过化学键合法制备出玉米淀粉-Ti-Si复合材料,通过FTIR、SEM等方法对其进行了表征,考察了其对水溶液中Hg2＋、Cu2＋、Pb2＋及Cd2＋等重金属离子的吸附性能。研究结果表明,钛、硅无机氧化物与淀粉发生了键合作用,并均匀分布在淀粉中;淀粉-Ti-Si复合材料对金属离子具有较好的吸附性能,与淀粉及淀粉-Ti复合材料相比,淀粉-Ti-Si复合材料的吸附性能得到了明显改善。     

Formwork lateral pressure of precast normal-concrete composite shear walls infilled with self-compacting concrete

Wall cracking and mold expanding due to concrete vibrations can be effectively solved through the application of precast normal-concrete composite shear walls infilled with self-compacting concrete (SCC). However, the high liquidity of SCC will induce a higher lateral pressure. Therefore, it is important to obtain a better understanding of the template lateral pressure. In this work, nine composite shear walls were experimentally investigated, focusing on the effects of two parameters, i.e., the casting rate and the section width of the formwork. The time-varying pressure was monitored during the SCC pouring. It is found that the increase of casting rate from 3.2 m/h to 10.3 m/h resulted in a higher maximum lateral pressure. The higher casting rate led to a longer time required for the lateral pressure to drop to a steady value. There was no correlation between the section width and the rate of decrease in the initial formwork pressure and stable value. Based on the test results, a formula considering the effect of casting speed for the calculation of SCC formwork pressure was established to fill the gap in the current standards and for engineering applications.     

Thermal Response Test by Improved Test Rig with Heating or Cooling Soil简

An improved test rig providing both the heat and cold source was used to perform thermal response test(TRT), and the line source model was used for data analysis. The principle of determining the temperature difference between the inlet and outlet of test well can keep the heating or cooling rate constant, along with a reduced size of test rig. Among the influencial factors of the line source model, the temperature difference was determined as the most important, which agreed with the test results. When the gravel was taken as the backfill material, the soil thermal conductivities of heating and cooling at the test place were 1.883 W/(m·K) and 1.754 W/(m·K), respectively, and the deviation of TRT between heating and cooling soil was 6.8%. In the case of fine sand, the thermal conductivities of heating and cooling were 1.541 W/(m·K) and 1.486 W/(m·K), respectively, and the corresponding deviation was 6%. It was also concluded that different velocities of water had less influence on TRT than the temperature difference.     

小直径薄壁管直接拉伸方法研究

大学材料性能实验教学通常以棒料单向拉伸为主要内容,而未能兼顾各种型材在服役状态下的几何属性对材料属性的影响。研究小直径薄壁管直接拉伸实验技术和方法,并将其引入实验教学,使学生通过实验自主地分析塞头装配、试样类型及加载速率对拉伸结果的影响,取得了良好的实践教学效果,对管形状态下材料力学性能的准确获取与促进管材塑性成形理论研究具有重要学术意义。     

钢桥面环氧沥青铺装的界面行为

通过引入一个新参数膜劲度,在部分共同作用原理的基础上,建立了描述钢桥面环氧沥青混凝土铺装复合梁在负弯矩作用下的界面行为模型,用以分析钢-环氧沥青混凝土之间的界面滑移与应变.推导了弹性工作状态下复合梁的界面滑移与应变的表达式,编制了数值计算程序并用2根复合梁进行了校核.然后采用该程序分析了界面滑移与应变沿复合梁纵向的分布特征,以及铺装层中的最大拉应力、层间剪应力对材料参数的敏感性.结果表明,界面效应削弱了钢桥面铺装复合梁的整体抗弯刚度;中低温条件下,采用劲度更大的粘结层材料有利于改善沥青铺装层的受力;粘结层的损伤累积将加剧沥青铺装层的破坏.     

柔性环氧树脂/石墨复合材料双极板的制备

采用了E-44环氧树脂与柔性固化剂邻苯二甲酸酐和粉末石墨混合且加热模压同时进行的成型工艺制备出复合材料双极板。该方法采用流体环氧树脂且加热模压同时进行一次性完成复合材料双极板的成形。本研究利用万能材料测试机采用三点弯曲法对不同混合比例样品做了力学性能分析;热重实验验证了该样品在工作条件下的稳定性;SEM扫描电镜分析观察了其微观组织情况。结果表明本文工艺方案所制备样品性能要优于采用聚酰胺固化剂制备所得样品。     

复合交联型深部调驱体系应用研究

以安达奥瑞特石油装备有限责任公司生产的复合交联型深部调驱剂作为主要药剂。采用布氏粘度计检测流变性、物理模拟实验以及矿产实验等方法,从温度、矿化度、抗剪切性以及矿场施工等方面对复合交联型深部调驱剂进行评价测定。室内实验表明：使用复合交联型深部调驱剂配制而成的深部调驱液对温度、矿化度的影响不大,抗剪切能力强,突破压力达到1．7Mpa时,堵塞率达90％以上。