正交各向异性易碎复合材料层合板的设计与试验研究

提出一种新型正交各向异性易碎复合材料结构,利用单向连续纤维板具有纵向拉伸强度高而横向易于被撕裂的特点,在制备好的单向板上垂直于纤维方向预制刻槽,然后将单向板正交复合而制备成正交各向异性易碎复合材料层合板,并对这种层合板作了承压试验与冲击试验.结果表明,所设计并制备的正交各向异性易碎复合材料层合板试样可承受一定的均布载荷...     

光纤缠绕用正交各向异性碳纤维复合材料线轴的研究

本文以四官能团氨基环氧树脂为基体,碳纤维T700为增强材料,缠绕制备了光纤缠绕用正交各向异性碳纤维复合材料线轴。结果表明：正交各向异性碳纤维复合材料线轴的径向热膨胀系数为0.4×10-6/℃,轴向热膨胀系数主要取决于树脂基体,灌注层越厚,线轴的热膨胀系数越大。     

重整反应器扇形管正交各向异性板模型的建立及有限元分析

为了研究重整反应器扇形管的变形机理,采用有限元理论,用正交各向异性板模型简化其结构。为验证模型的合理性,从试验、理论计算及有限元模拟3方面对扇形管材料进行了分析,得出了材料的抗拉、抗弯刚度。结果显示用正交各向异性板简化扇形管是可行的,所得数据也是后续计算的重要参数。     

积分方程求解复合材料开口板的应力分布

开口结构在各种结构中所占比例非常大,因此对其强度分析具有重要的意义。复合材料开口结构的应力集中系数要明显高于均质材料,应力状态取决于材料的非均质度、孔口几何形状及荷载大小。本文根据非均质各向异性弹性理论,对含椭圆孔的正交各向异性板的孔边进行应力分析,提出了积分方程法求解方案。这里,平面的应力场是借助于保角映射的方法通过复变应力函数得到的。按所建立的数学模型对含有椭圆孔型的复合材料板进行应力分析,针对不同荷载状况和它们对孔边应力集中系数的影响进行探讨。     

局部损伤正交各向异性矩形薄板的屈曲

本文利用伽辽金法对局部损伤正交各向异性矩形薄板的屈曲问题进行了分析,得到了损伤薄板屈曲临界载荷的近似计算方法,数值分析结果表明,局部损伤对正交各向异性矩形薄板的屈曲临界载荷有较为明显的影响,在进行玻璃钢／复合材料薄板结构稳定性设计与核校时,必须予以考虑。     

玻璃纤维一铝合金复合板的研究进展

玻璃纤维增强复合材料--铝合金复合板（GLARE）是利用胶接、铆接等技术将各向同性的铝合金板和各向异性的玻璃纤维/环氧树脂复合材料与巧妙地结合起来的一种新型结构材料,广泛应用于航空、航天、汽车等工业上。本文介绍了这种新型结构材料--GLEARE的性能、研究现状,提出了今后进一步研究方向及工作重点。     

玻璃纤维—铝合金复合板的研究进展

玻璃纤维增强复合材料──铝合金复合板（ＧＬＡＲＥ）是利用胶接、铆接等技术将各向同性的铝合金板和各向异性的玻璃纤维／环氧树脂复合材料巧妙地结合起来的一种新型结构材料，广泛应用于航空、航天、汽车等工业上。本文介绍了这种新型结构材料──ＧＬＥＡＲＥ的性能、研究现状，提出了今后进一步研究方向及工作重点。     

纤维增强光弹性复合材料应变-光学定律的探讨

本文根据无弹性复合材料的等倾线更接近于主应变方向而并不表征主应力方向的设想,讨论了纤维增强复合材料的应变-光学定律。利用应变-光学定律的概念,在进行正交各向异性材料平面应力的光弹性分析时,只需要测定光弹性材料的四个独立的弹性常数和任一正轴方向的材料条纹值。本文对Pipes等人提出的应变-光学定律进行了实验验证,发现模型材料所提供的数据与应变-光学定律相当吻合,等倾线参数与计算所得的主应变方向也相当接近。     

纤维增强复合材料钻削加工技术研究现状

纤维增强复合材料具有力学性能各向异性、导热能力差等特点,在钻削加工时,容易产生分层、撕裂等加工缺陷。综述了钻削轴向力、切削参数、刀具几何结构等对纤维增强复合材料钻削缺陷的影响,进一步分析了钻削加工技术的研究现状,提出合理的加工参数、刀具结构及新的钻削加工技术,对于提高钻削加工质量具有重要的意义。     

热塑性复合材料本构方程及应用

近年来,许多新型复合材料不断涌现,如热固性复合材料和热塑性复合材料等。这些材料在航空、航天、建筑等领域得到日益广泛的应用。因此,对这些材料力学性能的研究已引起国内外高度重视。本文根据弹性理论,考虑到流体不可压缩的条件,分析热塑性复合材料的力学性能,得出粘性各向异性、横观各向同性材料本构关系;通过细观力学研究,导出材料的粘性参数η11,η12,η22,η23;通过对层合板力学变形的研究,导出粘性各向异性层合板的膜应力和应变速率之间的关系及其实际粘性参数η-ij′,并对所得结果进行讨论。     

平面正交各向异性体材料参数识别算法及软件设计

基于边界元法,本文提出了平面正交各向异性体材料参数识别算法.通过构造以测量位移与边界元计算的相应位移之差的平方和作为目标函数,采用Levenberg-Marquardt方法迭代极小化目标函数,从而把参数识别问题转化为极小化目标函数的问题.同时在识别过程中考虑了测量位移含正态分布的误差,研究测量误差对参数识别结果的影响.算例表明本文提出的参数识别方法是有效的.     

Three‐Dimensional Simulation of Moisture Diffusion in Polymer Composite Materials

Abstract

This article presents a three‐dimensional Galerkin finite element methodology (GFEM) for simulating Fickian diffusion with temperature‐dependent diffusion coefficients, with particular application to moisture diffusion in composite materials. The coupled thermal and moisture diffusion problems are solved by using three‐dimensional finite element method with orthotropic diffusion coefficients and an implicit time‐stepping procedure. Both Frontal and Jacobi conjugate gradient (JCG) solution techniques are used. Numerical examples are presented to illustrate the methodology and include orthotropic diffusivities and multiple material regions. Moisture diffusion within a periodic unit cell of a typical composite material is also considered. The results show that the iterative JCG method is effective and computationally inexpensive to analyze diffusion three‐dimensional diffusion problems with multiple materials.     

纤维缠绕复合材料压力容器CAD/CAE/CAM一体化研究

本文用APDL参数设计语言编制的程序可同时进行压力容器缠绕过程的动态仿真模拟及应力分析,可将实际缠绕参数直接用于应力分析,分析后得到的仿真数据可直接用于数控缠绕机进行生产,实现了纤维缠绕复合材料压力容器CAD/CAE/CAM一体化.本文用微分几何理论推导出纤维缠绕复合材料压力容器的非测地线缠绕轨迹、包角方程及绕丝头运动方程.在应力分析过程中考虑了几何非线性和物理非线性.采用叠层的增量本构关系,以分段线性表示单层非线性应力-应变曲线,对损伤后引起的刚度降低进行了实验研究,实验特别研究了面内剪切破坏和层间剪切破坏对纵向弯曲刚度的影响.结果表明纤维缠绕复合材料压力容器损伤后,弯曲刚度的降低是影响轴向变形的重要因素.     

直升机旋翼复合材料桨叶结构设计与选材分析

介绍了直升机旋翼复合材料桨叶的结构特点和设计要求,分析了国内外复合材料桨叶结构设计的选材情况,总结了我国直升机复合材料桨叶结构选材现状与现存问题,并对无轴承旋翼柔性梁和主动控制智能旋翼国际新型桨叶复合材料结构设计与选材进行了讨论。综述研究表明,直升机旋翼桨叶工作环境复杂,在动力学设计方面有较高要求,复合材料桨叶结构设计及其成本与选材存在相互依赖和相互制约的矛盾关系,指出桨叶用复合材料与其结构设计技术的发展,对提高我国直升机旋翼桨叶性能、可靠性、寿命和安全性具有重要意义。     

复合材料缠绕法的对比研究

复合材料缠绕成型技术已成为复合材料加工的重要工艺.详细研究了2种复合材料缠绕加工方法:参数化缠绕法(parameter winding method,PWM)和网格缠绕法(mesh winding method,MWM),并分别用2种方法对叶片进行了缠绕成型实验.依据叶片缠绕实验的效果,从缠绕的设计、线型规划以及最终效果等方面对比分析2种缠绕法.结果表明:MWM比传统PWM在异型构件的缠绕成型方面更具灵活、方便、高效的优点.     

Quality assurance concepts for adhesive bonding of composite aircraft structures – characterisation of adherent surfaces by extended NDT

In order to ensure the performance of adhesively joined load-critical composite structures, suitable technologies are needed to steadily monitor adherent surfaces prior to bonding and to detect adhesion properties of bonded components. A novel class of non-destructive testing (NDT) techniques, classified as extended non-destructive testing (ENDT), is required to ascertain selected physicochemical properties which are important for the performance of adhesive bonds in place of detecting material defects like conventional NDT methods do. The European FP7 project, ‘ENCOMB – Extended non-destructive testing of composite bonds’ aims in the identification, development, adaptation and validation of ENDT methods for characterisation of adherent surfaces and adhesive bond quality. Here, recent NDT techniques such as optically stimulated electron emission (OSEE) and aerosol wetting test (AWT) as well as laser-induced breakdown spectroscopy (LIBS) were advanced and applied in field, and without contacting carbon fibre-reinforced polymer (CFRP) surfaces for detecting different contamination layers such as release agent, moisture or hydraulic oil as well as thermal degradation of CFRP adherent surfaces before performing an adhesive bonding process. Sensitivity and accuracy of these techniques allow distinguishing surface states which are suitable for bonding of CFRP adherents from surface states which are unfavourable for bonding. ENDT using OSEE, AWT and LIBS facilitated the detection of layers of release agent as thin as one nanometre and thin layers resulting from hydraulic oil. OSEE investigations of adherent surfaces before adhesive bonding allowed the indication of all surface states of potential CFRP adherents, which according to previous studies, were related to application scenarios reducing the joint strength of resulting adhesive joints by 20–70%.     

Smart composite materials for self-sensing and self-healing

Abstract

The various methods of self-sensing and self-healing developed within the Composite Systems Innovation Centre, University of Sheffield, are reviewed. Damage sensing using electrical resistance in carbon fibre reinforced composite or using the fibres as optical sensing elements in glass fibre reinforced composite is demonstrated. Amelioration of low level damage is demonstrated in both monolithic composite materials and sandwich structures using direct chemical reactions within the matrix without the use of encapsulants. These reactions can be activated by resistive heating of the material itself. The use of a combination of these techniques could create a truly smart structure able to both sense and repair damage and degradation.     

芳纶表面改性技术进展(三)——表面改性分析表征方法

对芳纶表面改性的分析表征方法进行了概述。主要介绍了傅里叶变换红外光谱(FTIR)、拉曼光谱(Raman)、X-射线光电子能谱(XPS)、扫描电子显微镜(SEM)、原子力显微镜(AFM)5种定性分析方法,以及测量比表面积、接触角、浸润速率、界面剪切强度(IFSS)、层间剪切强度(ILSS)、浸胶丝强度等6种定量分析方法。同时介绍了复合材料宏观试验方法、微复合材料试验方法、复合材料原位试验方法3种分析技术。最后指出,综合运用各种分析技术是目前解决问题的现实方法。     

Prediction of orthotropic mechanical properties of plain‐weave composites with matrix voids using unit cells at multi‐scales

A numerical procedure for predicting the orthotropic mechanical properties of plain‐weave composites with matrix voids through a combined approach of the representative volume element method and finite element analyses is presented. The representative volume element method was implemented using two unit cells established at different length scales with equation boundary conditions. By considering the presence of randomly scattered voids throughout the matrix induced during the manufacturing process, it was assumed in the simulation that the spatial distribution of matrix voids is completely random. The procedure was exemplified with a glass fiber‐reinforced (plain‐weave fabric) epoxy composite with matrix voids. Sensitivity studies were conducted to quantify the influence of fiber volume fraction and mechanical properties of the constituent phases on the orthotropic mechanical properties of the composite. The numerical procedure, which can be implemented in ABAQUS, is an efficient tool for guiding the design of plain‐weave composites at materials level and also provides effective properties of such composites for the design optimization of engineering structures made of such composite materials. © 2012 Society of Chemical Industry