生物基全降解复合材料

淀粉/聚乳酸复合具有相对较好的力学性能和生物降解性能,价格也与石油基塑料最为接近,是极具应用前景的全生物降解塑性材料。在分析国内外聚乳酸、淀粉及其复合材料研究现状的基础上,对该类材料的技术发展方向和工业化前景进行了展望。     

SiCP/Al复合材料的拉伸性能

对高体积分数碳化硅颗粒增强铝基(SiC_P/Al)复合材料的拉伸强度进行了试验研究。发现在较高应力水平下经过2次卸载的试件与未做卸载的试件相比,拉伸强度变化很小,说明加载-卸载过程对材料的拉伸强度影响不大。在试验研究的基础上,使用ANSYS软件建立了有限元模型,对SiC_P/Al复合材料的拉伸特性进行了仿真模拟。研究结果表明,低体积分数SiC_P/Al复合材料的力学性能更接近塑性材料;而高体积分数SiC_P/Al复合材料的力学性能则接近于脆性材料。拉伸强度模拟计算误差非常小,基体破坏是导致高体积分数SiC_P/Al复合材料破坏的主要因素。     

2D-C/SiC高速深磨磨削特性及去除机制

采用树脂结合剂金刚石砂轮, 通过对2D-C/SiC复合材料高速深磨磨削加工, 并对磨削表面形貌和亚表面损伤进行了观察。提出了2D-C/SiC摩擦层(表面)的磨削力理论公式, 讨论了磨削加工用量对磨削力和磨削力比的影响。实验结果表明, 2D-C/SiC复合材料的高速深磨材料去除机制与其自身的微观结构相关, 既不同于塑性材料, 也不同于普通脆性材料, 而是以脆性断裂去除为主。     

高体积分数 SiC P / Al复合材料的拉伸、 压缩与弯曲特性

对高体积分数碳化硅颗粒增强铝基(SiC P/ Al)复合材料的拉伸、 压缩和三点弯曲特性进行了实验研究。结果表明 : 高体积分数 SiC P/ Al 复合材料与低体积分数 SiC P/ Al复合材料相比 , 没有明显的线性屈服阶段。进一步的加载2卸载实验表明 , 在外载荷作用下 , 材料宏观上呈现一种类似金属材料的塑性 , 卸载后留有较大的残余应变 , 再次加载时沿上次卸载路线上升 , 而且拉应力导致的残余应变大于压应力。三点弯曲时材料内部产生残余塑性变形的潜力最大 , 切线模量更稳定。宏观断口分析表明 , 金属基体的非均匀分布导致产生局部渐进的微屈服 ,是使材料性能宏观上类似塑性材料的主要原因。制备过程中的残余应力和基体内部的微缺陷是拉应力比压应力产生更大残余应变的主要原因。     

曲母线双向锥体形状零件的旋压工艺研究

对低塑性材料曲母线双向锥体形状零件的旋压成形工艺进行了大量试验和深入分析；确定了采用先缩旋再扩旋最后整形的联合成形工艺，并相应设计出可行的工艺装置；对缩旋、扩旋及整形进行了试验研究。     

超塑性材料研究的新进展

介绍了超塑性的基本概念和超塑性材料的研究历史,叙述了金属、精细陶瓷的超塑性及其加工方法。     

搅拌摩擦焊焊缝横截面塑性材料迁移行为分析

在搅拌摩擦焊过程中,焊缝塑性材料的迁移是保证焊缝的冶金完整性的重要因素.本研究通过采用镶嵌标示材料的方法,焊后观察焊缝横截面上塑性材料的迁移行为.研究结果表明:在焊缝横截面上,探针附近的塑性材料沿带左旋螺纹的探针表面从焊缝上表面螺旋迁移至焊缝底部,从四周向焊缝表面迁移,在厚度方向上形成一个连续迁移的循环路径.塑性变形的区域关于焊缝中心不对称,塑性材料在焊缝中心形成类似于倾斜"花瓶"状的形貌.从焊缝表面至底面,塑性变形区宽度逐渐减小,前进边塑性材料向焊缝表面迁移的距离小于返回边,前进边塑性变形区小于返回边.     

组织结构对三维整体中空复合材料压缩性能的影响

为了研究整体中空复合材料的压缩性能,制作了满足要求的测试件.选取不同面板组织的整体中空复合材料进行侧压性能对比实验,对不同芯材结构的整体中空复合材料进行平压性能对比实验.借助ORIGIN软件对上述几类材料的压缩特性进行分析,研究了组织结构对材料压缩性能的影响.结果表明:面板组织为平纹的整体中空复合材料的压缩性能比经重平结构材料好；芯材结构为“细长X型”的整体中空复合材料压缩性能比“扁平X型”结构材料好.     

零吸胶炭纤维增强高温固化环氧复合材料预浸料研制

针对大尺寸、大厚度复合材料构件对“零吸胶”预浸料的需求,对低树脂含量炭纤维增强高温固化环氧复合材料预浸料进行了研制,并对预浸料的外观和物理性能、复合材料基本力学性能及成型工艺性能进行了研究.通过对预浸料制造工艺参数的优化,研制出了低树脂含量炭纤维增强高温固化环氧复合材料预浸料,其外观和物理性能满足要求;采用低树脂含量预...     

形状记忆聚合物复合材料的研究进展EI北大核心CSCD

形状记忆聚合物复合材料已成为形状记忆材料的研究热点和重点,文中针对近年来形状记忆聚合物复合材料的最新研究进行了综述。分别对颗粒增强、纤维增强和颗粒纤维混合3类增强材料制备的形状记忆聚合物复合材料的结构与性能特点进行了分析和评述;着重阐述了形状记忆聚合物复合材料形状记忆效应的机理以及影响形状记忆行为的因素;分析了形状记忆聚合物复合材料研究中存在的问题,同时对形状记忆聚合物复合材料的应用前景进行了展望。     

6061Al／SiC层合复合材料在交变温度场作用下热应力的有限元分析

对 60 61Al/ Si C层合复合材料在交变温度场作用下的热应力进行数值分析。采用ANSYS有限元分析软件中的结构单元 ,将金属铝视为弹塑性材料 ,且采用 Mises随动强化塑性模型 ,同时计及温度对材料性能的影响 ,计算了不同温度下的残余塑性变形和热应力 ,并给出了2 0 5℃至 2 0℃交变温度场作用下的残余热应力循环曲线 ,数值计算结果与实验数据复合较好。本文的研究工作为该复合材料的疲劳寿命的预报提供良好的理论基础。     

Material characterization of laminated composite plates via static testing

A minimization method for material characterization of laminated composite plates using static test results is presented. Mechanical responses such as strains and displacements are measured from the static tests of the laminated composite plates. The finite element method is used to analyse the deformation of the laminated composite plates. An error function is established to measure the differences between the experimental and theoretical mechanical responses of the laminated composite plates. The identification of the material elastic constants of the laminated composite plates is formulated as a constrained minimization problem in which the elastic constants are determined by making the error function a global minimum. A number of examples are given to illustrate the feasibility and applications of the proposed method.     

超薄金属内衬复合材料压力容器的结构分析

采用有限元方法对超薄金属内衬复合材料压力容器结构进行分析。在分析中, 几何模型中的封头段考虑了复合材料铺放角度和厚度沿平行圆半径变化, 材料模型中的复合材料层和内衬层分别选用复合材料层合板理论和弹塑性理论进行分析, 二者之间的界面变形协调性及不可贯入性引入接触分析进行考虑。数值结果表明:在工作压力下, 容器复合材料层纵向应变均为拉应变, 环向存在部分压应变, 内衬层发生塑性变形; 卸载后, 容器的复合材料层处在拉应力状态, 内衬层处在压应力状态。在此基础上, 利用容器的简化模型, 根据内衬层最大变形点荷载位移曲线实现了容器内衬层局部屈曲模拟。容器水压应变测试和内衬局部屈曲观测结果与数值模拟结果吻合较好, 验证了本文中分析的可靠性。      

Al2O3 / 3Y-TZP 层状复合材料的制备及其超塑性能

采用流延制膜和热压烧结工艺制备了Al₂O₃ / 3 Y-TZP 层状复合材料。用SEM 观察显微组织, 并采用高温深拉实验对该材料进行了超塑性能研究。结果表明: 1550 ℃热压烧结制备的材料晶粒细小, 界面结合良好;当应变速率一定时, 变形温度对Al₂O₃ / 3Y-TZP 层状复合材料的超塑性能具有重要影响, 1500 ℃时得到深拉成形最大高度, 温度较高和较低时超塑性能均会降低。      

Thermal post-buckling and flutter characteristics of composite plates embedded with shape memory alloy fibers

It is investigated that the composite plate embedded with shape memory alloy (SMA) fibers is subject to the aerodynamic and thermal loading in the supersonic region. The nonlinear finite element equations based on the first-order shear deformation plate theory (FSDT) are formulated for the laminated composite plate embedded with SMA fibers (SMA composite plate). The von Karman strain–displacement relation is used to account for the large deflection. The incremental method considering the influence of the initial deflections and initial stresses is adopted for the temperature-dependent material properties of SMA fibers and composite matrix. The first-order piston theory is used for modeling aerodynamic loads. This study shows the effect of the SMA on the critical temperature, thermal post-buckling deflection, natural frequency and critical dynamic pressure of the SMA composite plate.     

Experimental and Theoretical Studies on the Nonlinear Stress-Strain State of a Laminated Ceramic Composite

The mechanical response of a laminated ceramic composite specimen to static bending was studied experimentally. A procedure for solving the inverse problem with experimental data on the deformation of a laminated ceramic composite specimen in the form of a beam was developed, which allowed one to evaluate its mechanical characteristics. The nonlinear stress–strain curve for the material of the specimen as a quasi-homogeneous structure was plotted, and similar curves for each of the two materials of the layers forming the composite were also obtained. The stress-strain state of this composite was investigated theoretically, and the results were analyzed.     

Pull-out steel fasteners from a laminated composite subjected to external pressure

Single steel fasteners of circular cross-section have been pulled out of predrilled laminated glass/epoxy composite cylinders located in a pressure cell in which external pressures of up to 56 MPa were applied. An analysis is presented which relates the external pressure, p_o, to the interfacial pressure, p_i, in terms of the elastic properties of the fastener and the composite and the radial clearance between them in the absence of an external pressure. The value of the coefficient of static friction, μ = 0·1, calculated from these experiments suggests that the observed axial pull-out forces of 2·5 kN for similar fasteners fired directly into the composite material, cannot be accounted for solely in terms of interfacial friction. Some evidence is presented which suggests that plastic deformation of the fastener surface into interstices within the surrounding material during impact penetration contributes to the initial resistance to pull-out.     

Ti-Cu层状复合材料静态载荷下变形与失效机制

利用水下爆炸焊接法制备了Ti-Cu层状复合材料。为研究Ti-Cu层状复合材料静态荷载下变形和失效机制，对Ti-Cu层状复合材料进行了室温条件下单轴拉伸实验和预制裂纹的三点弯曲实验，并与Ti单层板和Cu单层板进行对比分析，采用SEM观察断口形貌。通过拉伸和三点弯曲实验后的微观分析表明:在拉伸实验中，Ti-Cu层状复合材料的破坏是由于多方向应力耦合作用，加工硬化和界面效应使其拉伸强度远高于Ti单层板和Cu单层板；在预制裂纹的三点弯曲实验中，Ti-Cu层状复合材料的断裂是多重损伤失效相互作用的结果。Cu层形成大量的滑移带和变形带，Ti层产生大量的微裂纹，Ti-Cu层状复合材料由于多种损伤累积，形成一种特有的沿基体和界面交替传播的裂纹形态；相对于均质金属，Ti-Cu层状复合材料复杂的变形和失效行为是其力学性能提高的重要原因。      

Smart control of nonlinear vibrations of doubly curved functionally graded laminated composite shells under a thermal environment using 1–3 piezoelectric composites

This paper addresses the active control of geometrically nonlinear vibrations of doubly curved functionally graded (FG) laminated composite shells integrated with a patch of active constrained layer damping (ACLD) treatment under the thermal environment. Vertically/obliquely reinforced 1-3 piezoelectric composite (PZC) and active fiber composite (AFC) are used as the materials of the constraining layer of the ACLD treatment. Each layer of the substrate FG laminated composite shell is made of fiber-reinforced composite material in which the fibers are longitudinally aligned in the plane parallel to the top or bottom surface of the layer and the layer is assumed to be graded in the thickness direction by way of varying the fiber orientation angle across its thickness according to a power law. The novelty of the present work is that, unlike the traditional laminated composite shells, the FG laminated composite shells are constructed in such a way that the continuous variation of material properties and stresses across the thickness of the shell is achieved. The Golla-Hughes-McTavish (GHM) method has been implemented to model the constrained viscoelastic layer of the ACLD treatment in time domain. Based on the first-order shear deformation theory (FSDT), a finite element (FE) model has been developed to model the open-loop and closed-loop nonlinear dynamics of the overall FG laminated composite shell under a thermal environment. Both symmetric and asymmetric FG laminated composite doubly curved shells are considered for presenting the numerical results. The analysis suggests that the ACLD patch significantly improves the damping characteristics of the doubly curved FG laminated composite shells for suppressing their geometrically nonlinear transient vibrations. It is found that the performance of the ACLD patch with its constraining layer being made of the AFC material is significantly higher than that of the ACLD patch with vertically/obliquely reinforced 1-3 PZC constraining layer. The effects of variation of piezoelectric fiber orientation in both the obliquely reinforced 1-3 PZC and the AFC constraining layers on the control authority of the ACLD patch have also been investigated.     

Structural design of Cross Laminated Timber (CLT) by advanced plate theories

Cross Laminated Timber enjoys great popularity in structural engineering and is one of the upcoming building materials in the timber construction sector. To support the favorable development of this high-performance wood product and to strengthen its competitiveness towards other mass building materials, the mechanical behavior and its implications for the structural design are addressed here. From the mechanical point of view CLT is a multilayer, highly anisotropic and shear compliant laminated composite. Owing to the analytical solutions for laminated composites and sandwich plates, the actual deformation behavior of CLT will be presented, and the accuracy and computational efficiency of common and advanced plate theories will be demonstrated. Comprehending the effects of laminate lay-up, anisotropic material behavior and cross-sectional warping will lead to an enhanced understanding of its mechanical behavior and will contribute to trustworthy deformation and stress prognoses as well as to reliable structural design.