层板复合材料疲劳性能的实验研究

对层板复合材料在拉伸－拉伸疲劳载荷作用下的初始静刚度、初始静强度、剩余刚度、剩余强度、疲劳寿命进行了实验研究,取得了大量的有意义的实验数据,分析了层板复合材料的初始静刚度、初始静强度和疲劳寿命的概率分布,讨论了层板复合材料在不同应力水平下剩余刚度随疲劳循环周次的衰减变化及损伤破坏的形式,得到了一些有意义的结论。     

三维正交机织复合材料低周弯曲疲劳力学性能有限元模拟

为了深入理解三维正交机织复合材料（3DOWC）疲劳性能,改进材料抗疲劳设计,结合三维正交机织复合材料试样经纱方向准静态三点弯曲及60%应力水平下的三点弯曲疲劳实验与ABAQUS有限元软件,构建了全尺寸三维实体模型,研究了三维正交机织复合材料在低周循环载荷下的弯曲疲劳性能,经分析得到循环加载下模型应力分布情况和疲劳损伤形态。结果表明：经纱为材料最重要的承载部件,中间加载区域为材料应力集中区,损伤主要位于应力集中区的Z纱通道处的经纱上,随着循环增加,逐渐在中心加载区域的上部和下部形成三角形损伤区域,该研究在复合材料设计与优化中具有指导意义。     

三维机织复合材料预制体经密与弯曲性能的有限元分析

借助绘图软件PRO/E构建出不同经密的三维浅交弯联机织复合材料结构模型。使用有限元分析软件ANSYS对构建出的复合材料三维模型在位移为1mm的弯曲载荷作用下复合材料的弯曲力学性能进行模拟,并分别对纤维、树脂的应力、应变分布进行模拟,分析其弯曲破坏机理。并通过定性实验,得到了与模拟结果相同的结论,验证了模拟结果的准确性。结果表明:在1mm的弯曲载荷作用下经密为4根/cm的复合材料弯曲性能优于经密为3根/cm的复合材料;复合材料与弯曲试样接触的位置更容易发生破坏;该复合材料模型在1mm的弯曲载荷作用下破坏模式主要为树脂的破碎、纤维与树脂间的脱粘。     

三维机织复合材料力学性能的各向异性

通过一系列的实验、分析, 客观地评价了4 种不同结构碳/ 环氧3D 层-层正交角联锁机织复合材料沿0°、30°、45°、60°、90°方向的拉伸、压缩、弯曲强度和模量。实验结果表明: 三维机织角联锁复合材料属正交各向异性材料, 各个方向的拉伸、压缩、弯曲强度和模量曲线呈枫叶形, 具有明显的双主轴特性; 4 种不同结构复合材料的各向异性力学性能有差异, 经向力学性能以带衬经的角联锁结构为最佳, 而纬向力学性能以纬密大的角联锁结构为最佳; 三维机织角联锁复合材料具有很强的性能可设计性, 正确选择纤维原料、纤维细度、三维预制件的组织结构和各个纱线组分的排列密度, 即可达到预期的性能指标要求。      

多层多向层联三维机织复合材料的拉伸性能

设计制备了3种不同结构的多层多向层联三维机织复合材料(M3DAWC),利用非接触式全场应变测量系统和SEM对其拉伸性能进行了研究。研究表明,织物结构对M3DAWC的宏观力学行为有重要的影响,沿0°方向拉伸,破坏模式随着斜向纱体积分数的增加,从齐口破坏演变为斜向纱的抽拔失效,沿90°方向拉伸,破坏模式基本一致,表现为斜向纱的抽拔和滑脱。同时,斜向纱体积分数对M3DAWC的拉伸强度和拉伸模量也有显著影响,沿0°方向拉伸,随着斜向纱体积分数的增加,拉伸强度和拉伸模量逐渐减小,沿90°方向拉伸则表现出相反的变化规律。      

三维机织C/C-SiC复合材料弹性性能预测

试验研究了三维机织C/C-SiC复合材料的弹性性能, 基于复合材料的扫描电镜(SEM)照片, 分析了材料的细观结构的特点, 并提出了一系列的假设, 建立了三维机织C/C-SiC复合材料的细观力学模型, 利用均匀化方法预测了复合材料的弹性常数, 分析了材料的弹性性能随经纱倾斜角的变化规律。结果表明: 预测结果与试验结果吻合较好, 表明该预测模型和方法的正确性; 随着经纱倾斜角的增加, 经纱方向的弹性模量降低, 其它方向的弹性模量均增大, 但面内剪切模量和厚度方向的弹性模量增幅很小。      

三维编织复合材料的疲劳性能

研究了三维编织复合材料的疲劳性能和编织结构对疲劳性能的影响。进行了应力比为011 、实验频率为10 Hz 的拉2拉疲劳性能测试。结果表明, 三维编织复合材料的疲劳强度约为其抗拉强度的60 %～80 % , 比金属材料的疲劳强度的相对值高。编织角是影响三维编织结构复合材料疲劳性能的一个主要因素。随着编织角的增大, 疲劳过程中易出现各种损伤, 而且伴随明显的升温现象。编织角大的试件在疲劳实验过程中模量变化明显, 并且呈现逐渐升高的趋势, 这与金属材料的双模量变化规律不同。在疲劳次数为100 万次后, 试件的剩余强度高于静载拉伸强度, 这主要是由于在疲劳测试过程中, 试件内编织纱线的取向更接近受力方向所致。      

间隙率对三轴向机织复合材料弹性性能的影响

采用有限元分析方法研究了间隙率对三轴向机织复合材料弹性性能的影响。首先,根据三轴向机织复合材料几何构型和基本参数,建立了三轴向机织复合材料的面密度和单胞特征边长与间隙率之间的关系;然后,建立了三轴向机织复合材料的有限元模型,利用该模型预测了拉伸、压缩和剪切刚度并与文献的实验结果进行了对比,证明了模型的有效性;最后,分析了间隙率对弹性性能的影响。研究发现,拉伸、压缩和剪切刚度随间隙率的增加而显著下降,而比刚度和泊松比随间隙率的增加变化较小。     

损伤形式对三维编织复合材料拉压性能的影响

通过对损伤前后三维编织复合材料试件进行纵向拉伸和压缩实验, 分析了材料的拉、压刚度和强度的变化规律和失效形式。主要讨论了4 种损伤加工方案, 包括沿宽度方向单边切割、沿宽度方向双边切割、沿厚度方向单边切割及沿宽度和厚度方向同时切割。实验结果表明, 宽度方向损伤对拉伸强度、模量和压缩强度影响不大, 压缩模量下降了20 %左右; 厚度方向损伤对纵向拉伸、压缩强度和模量影响较大。编织角20°时, 拉伸、压缩应力-应变曲线接近于线性, 试件的失效方式趋向于脆性破坏; 编织角35°时, 压缩应力-应变曲线表现出一定的非线性。      

Simulating in-plane fatigue damage in woven glass fibre-reinforced composites subject to fully reversed cyclic loading

The interest in using fibre‐reinforced composites in structural components is increasing. Some of these structural composites, such as wind turbine blades, aircraft components and torsion shafts are subject to fatigue loadings. It is widely accepted that fully reversed cyclic loading is the most adverse loading for fibre‐reinforced composites, but the modelling of the material behaviour under this loading condition is very difficult. In this paper, a damage model is presented for woven glass fibre‐reinforced composites subject to fully reversed cyclic loading. First fatigue experiments have been conducted in displacement‐controlled fully reversed bending and the stiffness degradation and damage patterns have been observed. Based on these experimental data, a damage model has been developed, which includes the in‐plane stress components and the degradation of the in‐plane elastic properties. The model has been implemented in a commercial finite‐element code and simulation of the successive stages in the fatigue life has been performed. The model has been validated for a plain woven glass fabric reinforced composite and simulated stiffness degradation, damage growth and damage distribution have been compared with experimental data.     

3D机织复合材料多向接头有限元分析

为了探究3D机织复合材料桁架接头的机械性能,采用有限元软件ANSYS对3D机织复合材料多向接头所在桁架总体进行有限元模拟,模拟中根据纤维走向对多向接头不同轴向圆管建立相应坐标系,并赋予材料属性,使用MPC多点约束法施加载荷.求解分析后结果表明:模拟结果与实测结果中最大应变的位置与数值基本吻合,确定了模拟的有效性;将最大应力与破坏应力对比发现接头在当前载荷下可能发生轻微破坏,破坏位置应位于副管顶部;通过模拟判断了实测中发生轻微响声的原因;将4种角联锁结构的多向接头模拟结果对比发现,带有衬经结构的复合材料为多向接头最佳材料.此次模拟补充了实测中无法得到的数据,为接头的优化设计和实际使用提供一定的帮助.     

Modeling strategies of 3D woven composites: A review

Due to advancements made in 3D weaving process, 3D woven composites have evolved as an attractive structural material for multi-directional load bearing and impact applications, due to their unique transverse properties such as stiffness, strength, fracture toughness and damage resistance. Substantial progress has been made in recent years for the development of new modeling techniques in design and analysis to understand the unique mechanical behavior of 3D woven composites. This paper systematically reviews the modeling techniques along with their capabilities and limitations for characterization of the micro-geometry, mechanical/thermo-mechanical behavior and impact behavior of 3D woven composites. Advantages, disadvantages and applications of 3D woven composites have also been delineated. In addition, this reference list provides a good database for future research on 3D woven composites.     

三维正交机织玄武岩/环氧树脂复合材料高温老化后低速冲击性质

研究了三维正交机织玄武岩/环氧树脂复合材料在180℃高温环境下老化不同时间后的低速冲击力学性能,测试得到了不同老化时间的试样在低速冲击过程中的载荷-位移曲线。研究发现:随着老化时间增加,三维正交机织玄武岩/环氧树脂复合材料能承受的最大载荷下降,位移逐渐增加,载荷-位移曲线斜率逐渐下降;随着冲击能量增加,老化条件相同的三维正交机织玄武岩/环氧树脂复合材料试样最大承受载荷增大,位移和曲线斜率增加。对高温老化后三维正交机织玄武岩/环氧树脂复合材料试样进行SEM观察,发现纤维与树脂基体脱粘有裂纹产生,且裂纹数目和面积随着老化时间延长而增加。      

Analytical elastic stiffness model for 3D woven orthogonal interlock composites

This research presents the development of an analytical model to predict the elastic stiffness performance of orthogonal interlock bound 3D woven composites as a consequence of altering the weaving parameters and constituent material types.     

三维正交机织玻璃纤维/环氧树脂复合材料动态力学性能的实验和理论研究

通过实验系统研究了三维正交机织玻璃纤维/环氧树脂复合材料厚度方向和面内方向的动、 静态压缩力学性能。结果表明, 动、 静态压缩载荷作用下该材料响应表现出明显的各向异性、 非线性和应变率敏感性。针对三维正交机织玻璃纤维/环氧树脂复合材料高速变形过程中不同形式的内部缺陷和微损伤的演化, 提出了一个依赖应变、 应变率的宏观损伤量, 建立了一种含损伤的非线性黏弹性本构模型。采用数据处理方法拟合了其本构方程材料参数, 在加载过程中, 模型计算值与实验结果吻合较好。     

Mesh generation and geometrical modelling of 3D woven composites with variable tow cross-sections

The modelling of 3D woven composites represents a key part in both material and component design. Current modelling techniques can struggle to mesh correctly accurate unit cell models and apply the complex but necessary periodic boundary conditions required, often with sacrifices made in idealisation of the weave architecture. An automated voxel meshing technique suitable for modelling failure in 3D woven composite unit cells has been developed, which is generic in nature and allows incorporation of architectural deformities within weaves, including tow rotations and misalignments. The model requires node points with only five independent variables to define the unit cell geometry. Application of a smoothing algorithm to the tow/matrix interface voxels produces a suitable surface for modelling tow/matrix debonding, leading to a more accurate representation of the stress field.     

Fatigue strength of woven fabric composites with drilled and moulded-in holes

The fatigue strength of glass-fiber woven-roving composites with a circular hole has been examined. Circular holes of two types, drilled and moulded-in, were considered. Experiments on the fatigue life and damage processes in (0, 90)_s and (45, −45)_s woven-roving composites with hole diameters of 5, 10, 14 and 19 mm were conducted. Experimental results show that laminates with moulded-in circular holes exhibit higher fatigue strength than those with drilled holes as a consequence of the altered mode of failure. Photographs of fatigue failure processes and specimen elongation with life are presented. The failure phenomena of laminates with drilled and moulded-in holes are compared and discussed.