考虑纤维初始位错的复合材料轴向压缩性能

通过试验及模拟对复合材料的轴向压缩失效过程进行了研究。试验中,采用高速摄像机对失效过程进行捕捉,并对最终破坏模式进行光学显微镜分析。基于纤维初始位错、纤维随机强度及基体Ducker-Prager塑性本构,通过有限元软件ABAQUS建立了复合材料轴向压缩的有限元模型,并对比分析剪切型及拉伸型两种不同初始位错模型的模拟结果。研究结果表明,复合材料轴向压缩包含弹性变形及塑性变形阶段,离散的纤维基体二维有限元模型能够有效模拟压缩的渐进损伤过程,且模拟结果与试验结果相吻合。复合材料轴向压缩强度是纤维初始位错及塑性基体剪切屈服共同作用的结果,其随着纤维初始位错幅值的减小、波长的增加及纤维体积分数的增加而增加。     

经编间隔织物静态缓冲性能的研究

经编间隔织物是一种由2片独立编织的经编织物和间隔丝(纱)组成的3层结构织物,是一种新型缓冲包装材料.通过经编间隔织物的静态压缩试验,对其缓冲性能进行了研究,绘制出经编间隔织物的σ-ε曲线和C-σm曲线,其中的缓冲系数曲线为经编间隔织物在缓冲包装领域的应用奠定基础,并与聚氨酯泡沫的缓冲性能进行了比较.     

炭纤维复合材料及与钢内衬复合管状件轴向压缩性能研究

研究了不同材料体系、不同工艺条件制备的炭纤维复合材料管状件轴向压缩性能以及钢内衬外加炭纤维复合材料复合管状件的动态和静态压缩性能对比,结果表明,采用单向预浸料纵向(或轴向)铺层与纤维缠绕相结合的成型工艺较纤维缠绕工艺制备的管状件轴向压缩强度更高;钢内衬外加复合材料复合管状件的动态轴向压缩强度明显高于静态压缩强度,钢内衬...     

轴向变厚度星形管吸能特征及多目标优化研究

提出了一种新型的轴向变厚度星形管,采用软件ABAQUS/Explicit对该结构有限元建模,并验证了模型的精度。系统研究了该结构在轴向冲击下的变形模式、力-位移和能量吸收等耐撞性能并分析了其关键耐撞性指标,开展了不同角数星形管在保持相同质量下的耐撞性能研究,采用多目标优化方法开展了星形管的优化研究。结果表明,所提出的轴向变厚度星形管相比常规的等壁厚星形管在降低初始峰值载荷和提升结构冲击载荷效率方面具有很大优势,多目标优化得到的最优设计相比原始设计的耐撞性能得到了有效改善,比能量吸收最大提升了6.02%,初始峰值载荷最高减少了39.56%。该研究能为轴向变厚度吸能结构设计提供参考。     

基于多尺度方法的蜂窝夹层复合材料结构轴向压缩稳定性

为有效预测蜂窝夹层复合材料结构压缩失稳载荷和破坏模式,本文基于层压板宏细观多尺度数值分析模型,研究蜂窝夹层复合材料结构在轴向压缩载荷下的屈曲稳定性。基于改进的通用单胞理论模型,并结合ABAQUS用户自定义子程序接口,建立蜂窝夹层复合材料结构宏细观数值模型,预报蜂窝夹层复合材料结构失效载荷和破坏模式,并与试验结果对照,验证了模型的有效性。结果表明:通过本文建立的数值模型可以有效预测蜂窝夹层复合材料结构在压缩载荷下的失稳载荷和破坏模式,其一阶失稳载荷为128.12 kN,与试验结果误差为4.58%,蜂窝夹层复合材料结构破坏模式为先发生屈曲失稳,然后迅速破坏。      

全芳香族共聚酯纤维轴向压缩变形结构的研究

借助偏光显微镜、扫描电子显微镜及Ｘ射线衍射等方法研究了全芳族共聚酯（ＷＡＰＥＴ）纤维轴压缩变形行为。在变形初期，因局部晶面滑移而形成与纤维轴约呈６０～６５°角的变形带。变形带内链分子受剪切作用而折断或挫屈。随着变形程度增加，变形带堆积厚度增大，并且在原有变形带周围还产生许多新的较小的变形带，表明在这些区域出现应力集中。最后，微原纤间的滑移导致大分子发生剧烈侧向位移，使纤维轴向长度明显缩短，纤维破坏。     

摩托车车架多轴向多激励道路模拟试验方法研究

为在室内比较全面考核摩托车车架在实际道路行驶载荷作用下的疲劳可靠性,结合车架有限元分析建立了摩托车车架道路载荷谱采集方法,并对道路载荷谱进行了采集和分析。在分析摩托车车架实际行驶受力情况基础上,基于远程参数控制技术,结合美国MTS液压伺服作动器和控制系统,设计并搭建了一套多轴向多激励摩托车车架道路模拟试验平台,并提出了力-位移混合控制的道路载荷谱模拟迭代方法。结合所采集的摩托车车架道路载荷谱,采用力加载控制和惯性加载控制混合加载控制方式,在室内对摩托车车架道路载荷谱进行了高效准确的模拟,并建立了摩托车车架多轴向多激励道路模拟试验方法,为在室内考核摩托车车架的疲劳可靠性提供了一种行之有效的方法。     

编织复合材料圆管准静态轴向压缩吸能特性的试验研究

通过二维三向编织复合材料圆管的轴向准静态压缩试验, 分析了编织复合材料圆管的压缩破坏机理和吸能特性, 并探讨了编织参数对吸能特性的影响。试验中观察到4种破坏模式: 分瓣破坏、 局部屈曲、 块状断裂和突发破坏。在纤维体积分数相同的情况下, 随着编织层数的增加和编织角的减小, 圆管的吸能能力有所提高。二维三向编织复合材料圆管是一种较好的吸能材料, 具有较高的单位质量吸能特性。      

闭孔泡沫铝压缩性能研究

闭孔泡沫铝作为一种新型多孔金属材料,被应用于各个领域,但其压缩力学性能受到孔隙率、孔洞结构参数、相对密度及材料基本力学性能等的影响,因此针对某闭孔泡沫铝企业研究出的一款新型产品,在确定其相关参数后进行10组试样的压缩力学试验,确定其应力-应变曲线,分析各段曲线意义和产生机理,并针对其特有的压缩力学性能,研究在外力作用下的吸能表现,为该型号的闭孔泡沫铝材料在各个行业中的应用提供技术支持和参考依据。     

织物预成型体的可压缩性研究

研究了预定型织物在压实阶段的可压缩性,涉及压缩过程中纤维体积含量的变化特点.结果表明,预定型织物对压缩载荷的响应方式与织物层数及定型剂含量有关,织物层数的增加,相同载荷作用下易于获得较高的纤维体积含量;预定型处理降低了织物的可压缩性,随定型剂含量的增加,最终获得的纤维体积含量表现出下降的趋势;在实验施加的压缩载荷作用下,预定型织物的压实后纤维体积含量趋于一致,与压缩织物的层数关系不明显,但仍然受定型剂含量影响.     

泡沫金属多向承载行为的研究意义

泡沫金属具有优良的物理性能和综合力学性能,在很多场合都可用作轻质结构材料.在简要介绍该类材料用途的基础上,指出了多向载荷研究对于泡沫金属应用的实际意义,分析了以往工作在该类材料力学性能研究方面的不足,以期推进相关领域的研究者在该方面的突破.在此基础上,提出了一条研究该类材料在多向载荷作用下有关数理关系的思路.     

3D Warp Interlock Fabric Structure and their Applications in Soft and Hard Armour Protections

Applied Composite Materials - Textile materials can be used as a soft solution to protect the human body of the soldier and as a hard solution to provide more efficient armour for various types of...     

Mechanical Behavior of a Triaxial Woven Fabric Composite

The results of an experimental and finite-element investigation on a single-ply triaxial woven fabric composite loaded in tension are presented. The fabric is made of graphite yarns oriented in the 0 degrees and plus/minus 60 degrees directions and a thermoset resin. It is used by EMS Technologies Canada Ltd. for the manufacturing of super-lightweight spaceborne antenna reflectors. Two types of tensile test specimens were evaluated, straight and dog-bone, as well as three methods for bonding the strain gauges to the specimen. The effects of the specimen shape and bonding methods were evaluated. A finite-element model was developed to predict the behavior of the specimen under tensile conditions. The measured data provide information on the elastic properties and ultimate strength of the composite when subjected to loads acting either along the axial yarns or perpendicular to them.     

Effect of Frictions on the Ballistic Performance of a 3D Warp Interlock Fabric: Numerical Analysis

3D interlock woven fabrics are promising materials to replace the 2D structures in the field of ballistic protection. The structural complexity of this material caused many difficulties in numerical modeling. This paper presents a new tool that permits to generate a geometry model of any woven fabric, then, mesh this model in shell or solid elements, and apply the mechanical properties of yarns to them. The tool shows many advantages over existing software. It is very handy in use with an organization of the functions in menu and using a graphic interface. It can describe correctly the geometry of all textile woven fabrics. With this tool, the orientation of the local axes of finite elements following the yarn direction facilitates defining the yarn mechanical properties in a numerical model. This tool can be largely applied because it is compatible with popular finite element codes such as Abaqus, Ansys, Radioss etc. Thanks to this tool, a finite element model was carried out to describe a ballistic impact on a 3D warp interlock Kevlar KM2? fabric. This work focuses on studying the effect of friction onto the ballistic impact behavior of this textile interlock structure. Results showed that the friction among yarns affects considerably on the impact behavior of this fabric. The effect of the friction between projectile and yarn is less important. The friction plays an important role in keeping the fabric structural stability during the impact event. This phenomenon explained why the projectile is easier to penetrate this 3D warp interlock fabric in the no-friction case. This result also indicates that the ballistic performance of the interlock woven fabrics can be improved by using fibers with great friction coefficients.     

Compressibility of Salts

The mechanism of tablet compression of the chloride, bromide and iodide salts of sodium, potassium and ammonium was studied, by obtaining their force-displacement curves. The area under these curves, which represents the work done on the tableting mass during compaction, was calculated. The effect of duration of the compressive force, of applied pressure on tablet strength and of pressure on the relative volume for potassium bromide were also studied.     

Spherical-cymbal换能器端帽自由胀形回弹预测与控制

为更经济地制造出质量更高的Spherical-cymbal换能器端帽,在其成形中用自由液压胀形工艺取代传统的冲压工艺,并对其自由胀形中的回弹问题进行了重点研究。采用ANSYS/LS-DYNA软件对端帽的自由胀形回弹量进行了预测,并根据约束条件及有限元模拟结果提出了回弹控制措施。实验结果验证了采用有限元数值模拟进行Spherical-cymbal换能器端帽自由胀形回弹预测与控制的可行性。     

Nonlinear Compression Behavior of Warp-Knitted Spacer Fabric: Effect of Sandwich Structure

Compressibility of warp-knitted spacer fabrics is one of their important mechanical properties with regard to many special applications such as body protection, cushion and mattresses. Due to specific structural features of the fabric and a non-linear mechanical behavior of monofilaments, the compression properties of this kind of fabrics are very complicated. Although several studies have been performed to investigate their compression behavior, its mechanism has not well been understood yet. This work is concerned with a study of compression mechanism of a selected warp-knitted spacer fabric with a given sandwich structure. Both experimental and numerical methods are used to study the effect of the material's structure on the overall compression mechanism. Compression tests are conducted to obtain force-displacement relationships of the fabric. A micro-computed tomography system is used to analyze specimens under different levels of compression displacement to investigate the change in material's structure during the compression process. At the same time, finite element models are developed separately to simulate the initial geometric structure and the compression behavior of the fabric. Three finite element models based on beam elements are firstly developed to simulate the effect of manufacturing process on shapes of monofilaments within the fabric and to determine their morphologies, which are used to assemble a geometry part of the finite element model of the overall fabric. Then the finite-element model is developed using beam and shell elements to describe the compression behavior of the fabric by introducing the effect of its complex microstructure and real non-linear mechanical properties of the monofilaments. A comparison of the obtained experimental and CT data, and results of simulation is carried out, demonstrating a good agreement. With this study, a compression mechanism of the warp-knitted spacer fabric can be better understood.