关于PP木塑型材的性能及生产研究

PP木塑型材具有对人体无害,低消耗、全环保、全循环等特点,能充分合理利用资源,降低能源消耗,节约木材,保护森林资源和促进资源循环利用,大力发展循环经济。因此,主要分析PP木塑型材的性能和生产研究。     

木塑型材与木塑复合材料抗弯性能比较研究

对目前常用的4种木塑型材和从木塑型材中取下实心方形小试样的抗弯性能进行了测试比较,同时还研究了木塑复合材料的抗弯性能与跨高比之间的关系.结果表明:木塑复合材料自身的抗弯强度和抗弯弹性模量均小于木塑型材的抗弯强度和抗弯弹性模量;木塑复合材料抗弯强度随着跨高比的加大,变化不明显;但抗弯弹性模量均随着跨高比的加大而明显下降.因此,在木塑复合材料标准制定中,需结合实际,使用重点考虑测试抗弯弹性模量时的跨高比.     

车辆型材结构的隔声性能优化研究

高速列车现在已经成为人们出行时相当重要的一种交通方式,但是随着列车速度的不断提升,控制车厢内噪声也变得越来越困难。车厢内的噪声不但会影响乘客乘坐的舒适度,严重情况下还会伤害乘客的健康。构成车厢的主要型材结构为双层且带有加筋夹层的铝合金板,对该结构的隔声性能进行优化,以求达到提高车厢整体的隔声性能,降低车厢内噪声的目的。根据典型车体型材结构建立三维几何模型,通过声学有限元方法分析其隔声量。以型材的隔声量作为评价其隔声性能的主要参数,基于列车噪声的特点将声辐射的频率范围限定为100 Hz～2 500 Hz,并且重点关注100 Hz～1 000 Hz频率范围内的隔声量。分析型材结构的尺寸,包括面板厚度、面板间距离、加筋粗细、加筋与面板间角度等对结构隔声量的影响。研究结果发现仅依靠改变尺寸结构对型材隔声量的优化是十分有限的,并且会极大影响结构的面密度或刚度,因此基于优化的型材结构,对蜂窝-型材结构进行声学有限元分析,结果显示优化后的蜂窝-型材结构具有更优异的隔声性能。研究成果可以为实际应用中对于车体型材结构的设计或隔声性能优化提供参考。     

基于ANSYS的托盘弯曲承载特性分析及试验验证

以非标准托盘为研究对象,通过建立托盘的有限元模型,对其施加特定载荷,模拟了其在静态承载弯曲试验时的受力情况,在ANSYS环境下进行有限元模拟分析,分别计算出了托盘长度方向和宽度方向的挠度值。借助托盘通用试验方法,验证了采用ANSYS对托盘弯曲性能进行理论分析的技术可行性,结果表明此方法具有较高的应用价值。     

特定结构木塑托盘静态弯曲性能的研究

以一款特定结构的木塑托盘为研究对象,基于托盘结构和连接方式两方面考虑,以托盘实验过程中的实际承载条件为依据,分析了其可能存在的失效模式,通过实验研究确定了其评价指标。在Ansys Workbench环境下建立结构模型,对2种失效模式进行了模拟,分析了整体结构及螺栓连接在静态弯曲下的承载特性。通过进一步分析比较,验证了材料结构的性能要求和设计的合理性。     

半刚接钢框架-内填剪力墙结构滞回性能的数值模拟

为了系统研究半刚接钢框架-RC剪力墙结构的滞回性能,编制了非线性有限元程序SRCWNP。对两层单跨半刚接钢框架(柱弱轴)-RC剪力墙结构试验试件的滞回性能进行有限元模拟。分析了RC墙裂缝开展;混凝土压溃过程;结构的内力分配;滞回曲线和破坏模式。模拟结果与试验结果基本吻合。     

不同密度木塑结构板材的可靠性分析

聚乙烯基木塑结构板材作为弹药箱包装材料,为了其使用安全性,研究了其可靠性。通过试验获得了其动态弹性模量和静态弹性模量,并运用一次二阶矩方法分析了该种木塑结构板材的可靠性。结果表明:密度大的木塑结构板材可靠性较高,而密度小的木塑结构板材可靠性较低。为木塑结构板材的广泛应用提供了合理依据。     

结构对变形镁合金减振性能的影响

采用有限元模拟对不同筋板布置方式的AZ31镁合金型材进行了瞬时动态数值模拟,并通过激励响应特性对AZ31镁合金型材的减振效果进行评估。结果表明:相同激励下,三角形筋板布置的镁合金型材减振性能优于其他形状筋板布置的型材,其中矩形筋板布置的镁合金型材减振性能最差。而后对模拟结论进行实验验证,实验结论与模拟相一致。最后,结合实验结果,对矩形筋板的布置方式提出优化改进方案,通过进一步的模拟计算发现型材整体变形、受力等都得到有效改善。     

空腹式型钢混凝土异形柱中框架受力机理的有限元分析

在试验研究的基础上, 采用通用有限元软件ABAQUS对空腹式型钢混凝土(SRC)异形柱中框架在单调荷载作用下的受力机理进行了研究。计算和分析了该结构的水平荷载-位移骨架曲线;对结构整体及节点核心区等关键位置在加载结束时的变形进行分析, 并与试验结果进行对比。分析表明, 有限元计算曲线与试验实测曲线吻合较好, 结构有限元模拟的最终变形与试验结果较为一致, 验证了建立的有限元模型的合理性。对结构受力全过程典型时刻、典型位置处的混凝土及型钢截面应力分布和发展规律进行了分析, 揭示了空腹式SRC异形柱中框架的受力机理, 可为这类结构的设计及其工程应用提供参考。     

复杂截面型材力控制拉弯成形数值模拟分析

复杂截面挤压型材的高精度拉弯成形是制造框架式车身的关键技术.本文基于动态显式有限元软件PAM-STAMP,针对一种典型的框架武车身用复杂截面挤压型材,对其力控制方式的直进台面式拉弯成形进行了数值模拟研究,对比分析了两种截面形状的型材截面畸变和回弹随补拉力增大的变形规律,并得到了摩擦系数对成形精度的影响.数值模拟结果表明,增加型材截面的变形刚度,可以显著地减小截面畸变和回弹;增加补拉力,增大了截面畸变但减小了回弹;增大摩擦系数,截面畸变量减小而回弹增加.     

Design analysis of three-layered structural composites based on post-consumer recycled plastics and wood residues

Three-layered structural composites were produced from municipal plastic wastes and wood flour residues to investigate the effects of design parameters on their flexural and impact performance. The studied parameters include wood content, thickness of individual composite layers, as well as stacking sequence and configuration (symmetric and asymmetric structures). The results indicate that the core layer has a lower influence on the flexural properties of structural beams in comparison with the skins. But depending on beam configuration (stacking sequence), different flexural characteristics can be obtained using the same composite layers. The classical beam theory was used to predict the flexural modulus with high precision. In addition, performance of the beams under impact tests was shown to be independent from their stacking sequences and layer thicknesses for each configuration.     

基于3D打印的木材细胞壁仿生设计

木材中起骨架作用的纤维素是以不同螺旋结构的微纤丝形式存在于细胞壁中。本文通过将3D打印技术与仿真模拟相结合,研究木材细胞壁的纤维螺旋增强结构。使用微晶纤维素(MCC)/聚乳酸(PLA)复合材料,在对MCC/PLA复合材料各项性能进行测试的基础上,借助3D打印技术构建木材细胞壁螺旋结构,通过改变纤维取向和纤维孔状结构编程合成结构的力学功能。有限元仿真则用于强调纤维在刚性单元之间的载荷传递机制中的关键作用。结果表明：通过编程纤维的取向和结构可以宏观调控结构的性能,其中纤维的交叉结构作为一种优化设计可以用于提高结构成型制品的力学性能。这些结构可以被组装成更大的系统,用于构建具有优化特定功能的模块化复合材料;在异质结构设计和新型复合材料制造领域中均具有潜在的应用价值。     

塑料托盘的有限元分析及实验验证

目的基于Workbench设计和分析塑料托盘结构的可靠性和可行性。方法通过建立塑料托盘的有限元模型,对其施加相应载荷,模拟塑料托盘试验时的受力情况,分别计算托盘在均载堆码、叉举、底铺板、弯曲下的挠度值,并与实验结果进行比较。结果塑料托盘4个挠度值的实验结果和模拟结果相对误差在10%以内。结论采用Workbench对托盘进行受力分析具有可靠性和可行性。     

不同截面形式柱状薄壁结构的缓冲性能比较

不同截面形式的柱状薄壁结构,其缓冲性能存在一定差异。基于ABAQUS/Explicit程序,对不同截面形式的柱状薄壁结构动态变形过程进行了有限元仿真,并在结构材料用量相同的条件下,简单比较了各种截面形式对动能吸收能力的差异。研究方法对缓冲包装设计等具有一定的参考价值。     

Development of pigmentable engineered cementitious composites for architectural elements through integrated structures and materials design

Integrated structures and materials design (ISMD) represents a new design approach that combines materials and structural engineering for the purpose of more effectively achieving targeted performance. Performance based design of structures provides flexibility and incentive to select composite materials with properties that efficiently meet the structural performance target. In this paper, ISMD concept was applied to develop pigmentable engineered cementitious composites (ECC) for architectural applications. Finite element analysis was carried out to relate structural performance (load capacity and energy absorption) to composite mechanical properties (tensile and compressive) under live and dead loads. Subsequently, white (and therefore highly pigmentable) ECC was developed to meet the desired composite properties. This paper details the structural performance—composite properties analyses, and test data on white ECC designed for the large form-factor panels. Through this research, the effectiveness of ISMD is revealed.     

界面改性增强塑木复合材料力学性能的研究进展

综述了国内外界面改性增强塑木复合材料力学性能的研究进展,包括界面改性增强的作用机理、木纤维的表面改性、塑料的表面改性和添加界面相容剂等,并展望了塑木复合材料界面改性研究的未来趋势。     

基于截面轴力与弯矩屈服面本构积分的梁-柱单元

梁-柱单元模型是杆系结构有限元分析的基础,现有的塑性铰模型和纤维模型无法兼顾计算精度与效率。该文依托Euler-Bernoulli梁理论,并以塑性理论和数值方法为基础,选用截面组合思想构建截面的轴力与弯矩的屈服面,提出了在截面内力空间上基于轴力与弯矩屈服面进行截面本构积分的平面梁柱单元。通过一悬臂柱的静力弹塑性分析和框架柱的动力弹塑性分析算例,验证了所提出的截面轴力弯矩(NM)耦合单元模型,在计算精度上接近纤维模型,在计算效率上远高于纤维模型。     

Wood based PLA and PP composites: Effect of fibre type and matrix polymer on fibre morphology,dispersion and composite properties

This study presents a comparison of the effect of various wood fibre types in polylactic acid and polypropylene composites produced by melt processing. The study also reveals the reinforcing effect of pelletised wood fibres compared to conventionally used wood flour or refined fibres. Composites containing 30 wt.% of chemical pulps, thermomechanical pulp and wood flour were produced by compounding and injection moulding. Fibre morphologies were analysed before and after melt processing. The dispersion of the fibres and mechanical performance of the composites were also investigated. Fibre length was reduced during melt processing steps, reduction being higher with longer fibres. Wood fibres provided clearly higher plastic reinforcement than wood flour. Comparing the wood fibre types, TMP fibres provided the highest improvement in mechanical properties in polylactic acid composites with uniform fibre dispersion. In polypropylene composites, fibre selection is not as crucial.     

Influence of additives on the global mechanical behavior and the microscopic strain localization in wood reinforced polypropylene composites during tensile deformation investigated using digital image correlation

The structural integrity of polypropylene (PP) matrix composites reinforced by natural wood fibers is investigated by digital image correlation (DIC) coupled with tensile tests. The use of the material as an alternative construction material requires extensive understanding of its micromechanical properties, which primarily define its performance. Addition of several additives such as coupling agents is common practice for such materials. These ingredients improve the performance of these materials mainly by improvement of the chemical and physical interactions between the nonpolar matrix and the polar wood fibers. These interactions facilitate the transfer of the applied deformation particularly in the interphase region between the polymer matrix and the reinforcing fibers. Such localized changes can influence the performance of the material specially its micromechanical behavior. The DIC via photogrammetry was used to study the spatial distribution of the accumulated plastic surface strain, which is based on pattern recognition of the surface before and after straining. The heterogeneous strain distribution reveals a structural inhomogeneity of the material. The magnitude of local strain was much higher than the global strain, suggesting preferred regions for plastic deformation formed by the microstructure.     

Design of μ-CNC machining centre with carbon/epoxy composite–aluminium hybrid structures containing friction layers for high damping capacity

The focus of this paper is on the design of machine tool structures, such as columns and spindle holders, for a 3-axis μ-CNC machining centre. Carbon/epoxy composite–aluminium hybrid structures with friction layers were used to increase structural damping. Two types of hybrid column structures were proposed. Finite element analyses were carried out to calculate both the static deflection of columns due to deadweight and also the first natural frequency of machine tool structures as a function of the stacking angle and thickness of the carbon/epoxy composites. To increase damping capacity, a friction layer was inserted between the aluminium-composite interface. For the design of the structures the stacking angle and the thickness ratio of the composites were considered as major design variables. And the most appropriate stacking sequence of the composite–aluminium hybrid structure employing a friction layer was determined using finite element analyses and vibration tests.