Quasi-static compression and compression–compression fatigue characteristics of 3D braided carbon/epoxy tube

This study presents an experimental study of the quasi-static axial compression and compression–compression fatigue behavior of a three-dimensional braided carbon/epoxy composite tube. Three kinds of tubes with different braiding angles, i.e. 25º, 35º, and 45º were used to examine the dependence of fatigue behavior on the braiding parameters. Quasi-static compression and compression–compression cyclic loadings were carried out on the braided composite samples. The S–N [stress and number of cycles to failure] curves, strain–N (number) curves, and damage observation were used to evaluate the behavior of the braided tubes under fatigue loading. The test results showed that braiding angle had significant effect on the ultimate compression strength (UCS) and the number of cycles per stress level that the sample could withstand. The tube with 25º braiding angle had the highest UCS while the tube with 45º braiding angle accumulates high number of cycles for the same stress level as compared to other samples. Damage occurred along the braid angle for 25º tubes while matrix crack plus bulging occurred in the tubes with 35º and 45º braiding angles.     

形状记忆复合编织圆管的制备及其热致回复性能

为分析编织角、回复温度对形状记忆编织圆管力学性能与形状回复性能的影响,采用改进的双螺杆挤出工艺制备连续碳纤维/形状记忆聚氨酯复合长丝,通过二维编织技术制备得到编织角为15°、30°、45°、60°、75°的圆管,对比分析了其径向支撑力和形状回复率。结果表明:制备的复合长丝中连续碳纤维被形状记忆聚氨酯均匀包覆,且基本位于复合长丝中心位置;编织圆管的径向支撑力与编织角大小成正比关系,编织角为45°时圆管的形状回复率最高,编织角度越接近45°形状回复率越高;回复温度对形状记忆性能有一定的影响,回复温度越高圆管的回复速率越快,形状回复率越大;该圆管结构具有优异的形状回复率,最高可达96%。     

碳纤维增强编织复合材料圆管制备及其压缩性能

为进一步探究编织结构与长度对复合材料圆管压缩性能的影响,采用树脂传递模塑成型工艺复合二维编织铺层与三维四向编织圆管,通过轴向准静态压缩试验获取了4种复合材料圆管试样的压缩力学行为。结合高速摄影记录,分析了编织复合材料圆管的破坏过程及失效模式,探索其压缩失效机制。结果显示:试样均表现出弹塑性特征,但三维编织圆管呈现出更好的压缩承载特性,其压缩模量与载荷峰值分别达到5.91 GPa与14.23 kN;试样呈现出纤维断裂、基体开裂脱黏、瓣状破坏、剪切以及挤压屈曲等破坏模式中的几种或全部的组合;二维编织复合材料圆管的渐进失效特征更为明显,具有较好的吸能特性,且其压缩模量随管件长度的增加而有所提升,但是吸能效果与试样长度呈非线性关系。     

Finite element analyses on longitudinal compressive behaviors of 3D braided carbon /epoxy composite with different braided angles at low temperatures

This paper presents a numerical study on the effect of temperature and braided angle on quasi-static longitudinal compression of 3D braided carbon fiber/epoxy composites. The 3D braided composites with different braided angles, i.e. 26°, 35° and 48° were analyzed to examine the temperature-dependent longitudinal compressive behaviors with finite element method (FEM) based on the full-scale meso-structure model. Three temperatures (20, ?50 and ?100 °C) were used to investigate the influence of temperature on the longitudinal compression behaviors. In addition, the imperfect interface and the fiber waviness were combined into the FEM model. Both interfacial properties and fiber waviness were closely associated with compression modulus of 3D braided composites. The FEM results revealed thermal stress distribution and its influence on stress evolution in braided composites with different braided angles. The influence of temperature on stress distribution manifested the temperature-dependent damage of 3D braided composite.     

Numerical analyses of thermo-mechanical behaviors of 3-D rectangular braided composite under different temperatures

This paper reports numerical analyses of thermo-mechanical behaviors of three-dimensional (3-D) 4-step rectangular braided basalt fiber/epoxy resin composite materials under different temperatures from 60 to 210°C. In the braided composite, the basalt fiber tows were assumed as thermal insensitive material and the mechanical behaviors of the epoxy resin under different temperatures were tested and introduced in microstructure model of the 3-D braided composite. The thermal stress distributions in fiber tows and resins were numerical calculated based on the microstructure model. The influences of fiber tow orientations and braided architectures on the stress distribution along the axial direction and resins have been discussed to characterize the thermal stress under different temperatures. The residual stress in the braided composite induced from the temperature change is also analyzed for the application of the braided composite to different temperature environments. It is expected that such a numerical investigation could be extended to the design of 3-D braided composite applied to high temperatures.     

开孔三维编织复合材料的压缩性能

为研究机械开孔对三维编织复合材料压缩性能的影响,测试了2种三维编织复合材料试验件的压缩性能。1种为基本编织(100%编织纱)结构,另1种为含有编织纱/轴向纱(58/42)的结构,试验件编织角约为±12°。根据相关标准要求,分别进行有开孔和无开孔的复合材料试验件准静态压缩试验,并与层合板的压缩性能进行对比。研究结果表明:2种三维编织结构无缺陷材料的压缩强度较为接近,但引入开孔后,无增强纱结构可保留更高比列的压缩强度;引入开孔后,2种三维编织复合材料保留的压缩强度均高于层合板;在失效形式上,2种三维编织复合材料的宏观失效形式较为相似,均为剪切失效,表现出横向断裂且无分层现象。     

碳/芳纶混编三维编织复合材料拉伸性能

为分析三维编织复合材料拉伸性能和失效机制,分别以碳纤维和芳纶纤维为轴纱和编织纱织造了三维五向、三维六向碳/芳纶混编复合材料。采用数字图像相关法采集试样在单轴拉伸过程中表面全场应变信息得到的泊松比。结果表明：三维编织复合材料泊松比受编织结构的影响较大,同种编织结构下,碳纤维为轴纱的复合材料基本保持了碳纤维三维编织复合材料的拉伸强度和模量,同时提高了断裂伸长率;芳纶纤维为轴纱的复合材料则显著提高了断裂伸长率,但拉伸强度和模量损失较为明显;同种混编方式下,三维五向编织复合材料的拉伸强度和拉伸模量较三维六向高,断裂伸长率无明显差异。编织纱分别为碳纤维和芳纶纤维的三维编织复合材料高应变区分别类似点阵分布和波浪线分布,三维五向和三维六向编织复合材料高应变区分别呈均匀分散分布和横向分布。     

三维多向编织复合材料T型梁抗弯应力分析

针对三维多向编织复合材料结构件承载细观结构优化设计的问题,以三维编织复合材料T型梁为对象,对其抗弯性能进行模拟分析。基于细观结构单胞模型,采用刚度体积平均法计算具有不同编织角的三维四向、五向和六向编织复合材料的弹性常数;利用有限元软件Patran/Nastran计算T型梁承受弯曲载荷的应力与应变,分析纤维束交织结构和细观结构参数对T型梁抗弯性能的影响。结果表明,纤维体积含量一定时,三维六向较三维四向、五向编织复合材料的弹性性能更接近各向同性,同时选择比较大的编织角,可提高T型梁抗弯的承载能力。此方法可为异型三维编织复合材料构件细观结构的选型与参数设计可供参考。     

三维编织复合材料压缩损伤声发射特性分析

论述了声发射技术在三维编织复合材料压缩过程中的应用及实验方法,给出了声发射在三维编织复合材料中压缩过程的特征。结果表明,声发射参数可描述复合材料在不同情况下内部变形的损伤机制。表面编织角是影响三维编织复合材料力学性能的主要参数,编织角小于30°,三维编织复合材料具有较好的压缩性能;编织角大于40°,三维编织复合材料压缩力学性能明显降低。为分析复合材料的力学性能,改善材料复合工艺提供理论基础。     

嵌入碳纳米线的三维编织复合材料损伤监测

为实现对三维编织复合材料制件损伤情况进行实时监测,提出了通过三维五向四步法在三维编织复合材料中嵌入碳纳米线传感器的方法,由于碳纳米线传感与碳纤维具有相似性,因此碳纳米线嵌入三维编织复合材料制件的对其承载性能几乎没有影响。通过三点弯曲实验分析了碳纳米线在三维编织复合材料制件遭受外界应力时其电阻变化率与应力应变的相关性。实验结果说明显示其相关性为指数拟合关系,因此,三维编织复合材料的损伤状况可通过嵌入其中的碳纳米线传感器的电阻变化率与制件所承载的应力应变函数映射关系来进行实时监测。     

光纤布拉格光栅在复合材料连续状态健康监测中的应用

为实现三维编织复合材料状态健康连续监测,根据三维编织复合材料的编织工艺,将光纤布拉格光栅(FBG)传感器嵌入到复合材料制件中,分析拉伸承载下的制件内部应变与FBG传感器信号变化的关系.实验结果表明,FBG传感器信号与制件应变具有较好的线性关系,复合材料的表面编织角对FBG的信号具有一定影响,嵌入FBG传感器对复合材料的...     

嵌入三维编织复合材料的碳纳米线应变传感特性

为实现三维编织复合材料的原位结构健康监测,研制了嵌入碳纳米线的三维五向编织复合材料预制件,建立了基于三维编织复合材料试件的碳纳米线应变传感实验系统,分析了嵌入三维编织复合材料中的碳纳米线应变传感特性。结果表明：在单调拉伸和循环加载卸载过程中,嵌入三维编织复合材料的碳纳米线传感器电阻变化与试件应变的线性相关性较高;在较大载荷循环加载卸载后,碳纳米线传感器产生的残余电阻可用于检测试件的损伤或累积损伤;引入电阻应变相关系数建立了电阻变化净差值与机械应变净差值的应变传感方程,可实现基于碳纳米线传感器的三维编织复合材料原位结构健康监测。     

碳纤维增强编织复合材料圆管的扭转力学性能及其损伤机制

为研究编织层数对编织复合材料圆管的扭转力学性能和失效模式的影响,采用二维编织铺层(Over-Braiding)工艺及真空辅助树脂灌注成型工艺分别制备了2、3和4层的碳纤维/树脂编织复合材料圆管.通过搭建扭转试验-非接触全场应变测试平台,研究了3种编织层数的复合材料圆管的扭转力学响应.基于扫描电子显微镜与微计算机断层扫描...     

Finite element analyses of compressive behaviors of biaxial warp-knitted composite material under various strain rates with a simplified geometrical model

This paper reports the compressive behaviors of biaxial warp-knitted (BWK) composite material under compression with various strain rates. The compression stress–strain curves and the failure modes along three orthogonal directions were obtained from split Hopkinson pressure bar (SHPB) apparatus. A finite element analysis (FEA) model based on a simplified model of BWK composite was also carried out to verify the experimental results. In the simplified model, an equivalence resin (ER) combined tricot yarns with resin, and the stiffness matrix was derived from the mechanical parameters of the tricot yarns and the resin. A good agreement between experimental and FEA demonstrates that the simplified method is applicable of modeling the high strain-rate behaviors. By comparing the experimental damage morphologies with the damage development and morphologies observed from the model, it was found that the FEA model offers a better understanding to the compression damage mechanisms. The model can also be extended to design the impact performance of the BWK composite with high efficiency.     

智能复合材料中碳纳米管纱线参数设计及其变化特征

为将碳纳米管纱线传感器嵌入复合材料中, 利用三维编织技术构建了智能三维编织复合材料。针对三维六向编织复合材料编织结构,构建了编织机携纱器运动数学模型;提出了智能复合材料嵌入碳纳米管纱线的数量、长度的计算方法;分析了碳纳米管纱线在承载下的电阻变化特征。实验证明：通过Bezier 曲线计算的碳纳米管纱线长度值与实际长度的误差小于1%;当拉伸应变超过2%时,嵌入的碳纳米管纱线的应力与应变开始出现非线性;试件的加载－ 卸载对碳纳米管纱线的电阻变化具有一定影响,试件承受大负荷卸载后,碳纳米管纱线会产生剩余电阻。     

大尺寸三维编织复合材料结构损伤指数特征

为实现大尺寸三维编织复合材料内部损伤实时监测,针对三维六向编织复合材料的编织特点,将布拉格光栅（ＦＢＧ）传感器嵌入三维编织复合材料预制件中,提出了大尺寸智能复合材料的制作方法。研究了大尺寸复合材料内部ＦＢＧ 传感器的拉伸特性,基于主成分分析方法提出了制件结构损伤检测算法,分析了相同损伤的４ 个制件的损伤指数表现特征。试验结果表明：ＦＢＧ 传感器能准确测量复合材料内部损伤变化;损伤指数可描述试件结构损伤程度。损伤指数Ｔ２ 和综合损伤指数Ｐｈｉ 能迅速诊断制件内部损伤的存在性,对于制件的同一个损伤Ｐｈｉ 指数计算值大于Ｔ２ 指数值,是其２ 倍以上,Ｐｈｉ 指数可用于及时判断制件内部是否产生损伤,Ｑ 指数和Ｉ 指数描述损伤的详细参数更加准确。     

三维四向和五向编织复合材料冲击断裂行为的多尺度模拟

为对三维编织复合材料的结构特性进行模拟预测分析,采用一种多尺度和细观结构结合的方法,建立三维编织复合材料的等效拼接组合模型,进一步揭示编织复合材料在微观结构水平下的冲击损伤演化、裂纹扩展和能量吸收。设计制备三维四向和三维五向2种编织结构的碳/环氧树脂三维编织复合材料,根据编织参数建立等效拼接组合模型;通过落锤式冲击试验仪结合高速摄影系统记录2种编织复合材料在低速冲击下的断裂行为,与等效拼接组合模型在有限元数值模拟结果相对比,验证等效拼接组合模型的有效性。模拟结果表明,相同的体积分数下轴纱表现出最高的能量吸收,由于轴纱的存在,三维五向编织复合材料的抗裂性和裂纹扩展性优于三维四向编织复合材料。     

基于碳纳米线传感器的三维六向编织复合材料内部损伤定位

为研究三维编织复合材料的实时结构健康状态监控,针对三维六向编织复合材料编织结构,采用三维四步六向编织方法将碳纳米线传感器以轴向纱和六向纱形式嵌入复合材料中,提出了一种构建智能三维复合材料的方法,建立了基于碳纳米线的三维编织复合材料试件内部损伤监测系统。基于碳纳米线测量的电阻值矩阵,采用四分矩阵奇异值分解方法分析信号矩阵的主要特征,计算试件内部的损伤准确位置。实验采用5种不同类型损伤试件进行分析,结果表明,该方法计算的试件内部损伤位置与实际损伤一致,测量的损伤位置坐标误差小于1。该研究可为智能三维编织复合材料的健康监测发展提供理论基础。     

体外降解过程中周围神经再生导管径向压缩性能的研究

介绍了几种用于修复周围神经缺损的编织结构聚乙丙交酯(PGLA)神经再生导管及其在体外降解过程中的径向压缩性能.讨论了编织结构、原料配比和涂层等工艺参数对导管径向压缩力、压缩力保持率和弹性回复率等径向压缩学性能的影响.结果表明,三向结构导管总体上优于规则结构导管,用PGLA90/10编织而成的导管其性能优于用PGLA99/01编织而成的导管,经过涂层处理的导管其性能优于未经涂层处理的导管.     

编织工艺参数对周围神经再生导管径向压缩性能的影响

叙述了编织型人体周围神经再生导管的生产工艺，通过改变导管制作的编织结构、编织角和轴纱线密度等工艺参数，探讨了编织工艺参数对神经再生导管径向压缩性能的影响。