纤维缠绕复合材料压力容器封头厚度预测

本研究的目的是建立一种用来预测纤维缠绕复合材料压力容器封头厚度的方法。针对固化成型的复合材料压力容器封头型面, 基于封头段所有缠绕纱带总体积保持不变条件, 提出了一种采用三次样条函数来预测复合材料压力容器封头厚度的方法。采用该方法对具有不同几何尺寸、 不同缠绕工艺参数的复合材料压力容器进行了封头厚度预测, 并与传统预测方法及实际厚度测量值作了对比分析。算例结果表明, 该方法能够比传统方法更准确地预测纤维缠绕复合材料压力容器的封头厚度, 从而为有限元建模分析提供精确的厚度参数。      

不等开口纤维增强树脂复合材料缠绕壳体非测地线线型设计

线型设计是纤维增强树脂（FRP）复合材料缠绕壳体设计的一项重要研究内容,它对壳体FRP复合材料缠绕制品的质量起关键作用。本文针对不等开口极孔或不同形状封头的FRP复合材料压力容器壳体,基于非测地线缠绕方程,提出了一套非测地线缠绕线型设计方法,建立了根据已知缠绕线型和芯模转角来确定相应的切点数和纱片宽度的计算模型,开发出了一套FRP复合材料缠绕壳体仿真软件系统,对非测地线缠绕线型进行了计算机图像仿真与检验。结果表明:各个设计区间的仿真结果满足设计要求,没有出现缠绕角突变、纤维分布不规律和纤维在局部严重重叠等异常现象。该仿真软件系统可以为工程人员在实际壳体缠绕之前提供参考,缩短缠绕线型迭代试错周期,同时也为后续缠绕角及缠绕顺序等缠绕参数的优化奠定了基础。      

配橡胶内衬复合材料板壳的敲击法无损检测

配橡胶内衬的复合材料板壳可以模拟真实纤维缠绕压力容器。本文通过比较复合材料被撞击的时间历程和频域曲线,检测了复合材料缠绕层与内衬之间、内衬与内衬之间的损伤区,并对某型火箭发动机壳体的缩小比例试件进行了实际检测。     

纤维缠绕固体火箭发动机壳体的应力及强度分析

纤维增强复合材料在许多领域得到广泛应用,固体火箭发动机壳体就是一例。因此,分析其不同内压下的应力及预报爆破压力是十分重要的。复合材料结构承载过程的应力分析,需进行单元失效判断,许引入失效单元的刚度衰退,这种方法是最合理的。本文采用该方法并结合大变形有限元分析理论,计算了某一纤维缠绕固体火箭发动机壳体的应力和爆破压力,数值计算结果与实测数据吻合,证明该方法可用于纤维缠绕复合材料结构的应力及强度分析,值得重视。     

复合材料气瓶的有限元建模与屈曲分析

复合材料气瓶在空间系统中逐渐取代全金属气瓶而得到越来越广泛的应用.利用ANSYS大型有限元程序建立复合材料气瓶及其内衬的有限元模型,建模中将纤维缠绕层作为复合材料层合板处理,考虑了封头处缠绕层厚度及缠绕角沿子午线不断变化的情况.建立了气瓶整体结构的特征值屈曲分析与非线性屈曲分析有限元方程,并分别进行了气瓶整体结构和内衬的外压失稳(屈曲)分析计算,得出了气瓶整体结构及内衬的屈曲模态形状和临界外压.     

复合材料缠绕压力容器缠绕过程模拟

为了提高复合材料缠绕压力容器缠绕工艺效率及优化缠绕过程,研究并设计了复合材料缠绕压力容器缠绕过程的模拟软件.模拟软件主要包括两个模块:缠绕设计模块和模拟模块.模拟模块中,通过在几何空间和色彩空间,描述纤维缠绕压力容器成型工艺的芯模、落纱点、悬纱、丝头的运动规律和运动轨迹,形成动态画面,直观地反映出缠绕过程中落纱、纱线排布、悬纱、芯模和丝头运动以及线形变化,显示出纤维缠绕成型的全部过程.该模拟软件的建立,有利于加深对复合材料缠绕压力容器缠绕工艺过程的理解.     

用应力波技术对配橡胶内衬的复合材料板壳进行无损检测

配橡胶内衬的复合材料板壳可以模拟宇航飞行器的纤维缠绕压力容器。本文提出用应力波技术(Stress wave)对复合材料构件的损伤进行无损检测,并实际检测了配橡胶内衬的复合材料板壳内衬与复合材料缠绕层之间、内衬与内衬之间的损伤.绘出了损伤区的幅频特性曲线,确定出损伤区在橡胶内衬的分布情况。最后,作者对某型火箭发动机的缩小比例圆柱壳体进行了实际检测,并获得了满意结果。     

一种无焊缝连接金属内衬复合材料压力容器的制备工艺及其液压实验

纤维缠绕复合材料压力容器(COPV)由于其轻质高强及先漏后爆等特性在航空航天、路面交通和石油化工等领域得到广泛应用。基于纤维缠绕工艺的特点,提出了一种新型无焊缝连接金属内衬COPV结构及其制备工艺。并通过缠绕工艺及在封头直边设置密封槽,解决了内衬的封头与筒体之间的连续性和密封性问题。基于该结构的特点,一种辅助成型工装被发明,成功实现了这种新型内衬结构的缠绕成型问题。之后,通过液压试验验证了该结构的可行性,该新型容器能够承受110 MPa的爆破设计压力。进一步对容器剖面进行宏观分析,获得了该结构的三种损伤模式。最后,基于Chang-Chang失效准则及层间内聚力失效模型,通过编写用户子程序VUMAT建立了该新型结构的有限元计算模型,确定了分层损伤为该结构的主要损伤模式及位于封头与筒身过渡区的纤维拉伸断裂为该结构的主要失效模式。      

纤维缠绕环形压力容器线型设计与仿真

纤维缠绕环形容器要求满足线型稳定和结构优化两个条件.基于微分几何理论,提出了用于复合材料环形压力容器成型的纤维缠绕线型,分析了芯模和吐丝嘴的缠绕速比,给出了缠绕参数优化设计方法.在对优化线型进行分析的基础上,模拟环形容器的纤维缠绕过程,实现了环形容器成型的计算机优化与图形仿真.通过应用缠绕仿真系统,可以检验线型模式的正确性和可行性.结果表明,优化设计的线型模式精确可靠,满足纤维缠绕的基本要求,为微机控制环形容器缠绕奠定了理论基础.     

固体火箭发动机复合材料壳体承载力分析

为了提高固体火箭发动机(SRM)的外载荷承载能力,研究了其复合材料壳体的失效机制,提出了复合材料壳体的增强改进结构形式。通过提高复合材料外缠绕层的轴向刚度和横向弯曲刚度,使得连接区域内的内、外缠绕层的轴向变形相协调,改善了内、外缠绕层的轴向承载分配,使增强改进后的复合材料壳体结构的承载能力提高了124%,而结构质量增加低于10%。研究结果表明: SRM复合材料壳体承载能力的关键因素是连接区域内复合材料内、外缠绕层的刚度匹配设计,只有保证连接区域内的刚度匹配和位移变形相协调,才能充分发挥复合材料壳体的承载能力。     

An engineering approach for predicting residual strength of carbon/epoxy laminates after impact and hygrothermal cycling

A semi-empirical analysis on residual compressive strength (RCS) of carbon/epoxy woven composite laminate was developed which included the damage effects caused by impact and hygrothermal cycling. Impact damage is modelled as a soft inclusion with an exponentially reduced stiffness and the stiffness is further reduced due to hygrothermal cycling. A complex variable method was used to determine the in-plane stress distribution near the impact-induced damage and point stress failure criterion is then used to predict the failure load. Based on the semi-empirical model, the RCS can be related to damage width, damage intensity, undamaged strength and a degradation factor due to hygrothermal cycling. The results from the analysis coincide reasonably well with the experimental data for the plain-woven fabric laminates.     

Modelling of fatigue damage progression and life of CFRP laminates

A progressive fatigue damage model has been developed for predicting damage accumulation and life of carbon fibre‐reinforced plastics (CFRP) laminates with arbitrary geometry and stacking sequence subjected to constant amplitude cyclic loading. The model comprises the components of stress analysis, fatigue failure analysis and fatigue material property degradation. Stress analysis of the composite laminate was performed by creating a three‐dimensional finite element model in the ANSYS FE code. Fatigue failure analysis was performed by using a set of Hashin‐type failure criteria and the Ye‐delamination criterion. Two types of material property degradations on the basis of element stiffness and strength were applied: a sudden degradation because of sudden failure detected by the fatigue failure criteria and a gradual degradation because of the nature of cyclic loading, which is driven by the increased number of cycles. The gradual degradation of the composite material was modelled by using functions relating the residual stiffness and residual strength of the laminate to the number of cycles. All model components have been programmed in the ANSYS FE code in order to create a user‐friendly macro‐routine. The model has been applied in two different quasi‐isotropic CFRP laminates subjected to tension–compression (T–C) fatigue and the predictions of fatigue life and damage accumulation as a function of the number of cycles were compared with experimental data available in the literature. A very good agreement was obtained.     

含雷击热-力耦合损伤复合材料层压板拉伸剩余强度预测

为了对含雷击热-力耦合损伤复合材料层压板的剩余强度进行预测,基于连续介质损伤力学法(CDM)和唯象分析法,建立了表征复合材料雷击热-力耦合损伤的刚度矩阵渐进损伤退化模型。基于该模型,通过ABAQUS有限元仿真软件,建立了含雷击热-力耦合损伤的复合材料层压板结构三维模型。结合UMAT子程序,完成了拉伸载荷下的剩余强度预测。结果表明:通过与试验对比,仿真结果与试验结果取得了良好的一致性。本文所建立模型,能够有效进行含雷击热-力耦合损伤复合材料层压板结构拉伸剩余强度预测。     

A parametric study of residual strength and stiffness for impact damaged composites

A parametric study of residual strength and stiffness for low-velocity impact damaged composites was performed. Possible compression after impact failure mechanisms, which may be caused by stiffness and strength degradation inside the damage region, were discussed. In order to understand the scaling effects on impact damage residual strength, finite element analysis was performed. With stiffness degradation inside the damaged area, the stress fields of small coupon and larger stiffened panels with the same damage were calculated numerically. The stress redistributions were found to be almost identical between the coupon and panels. This indicates that the stress redistribution is a local phenomenon, and will not be affected much by the existence of the stiffeners. It is believed that the residual strength of impact damaged composite structures is related more to the damage severity than to the load redistribution. The dependency of the stress concentration factor on the anisotropic engineering elastic constants of a laminate was extended from an analytical study by Lekhnitskii (Anisotropic Plates, Gordon and Breach Science Publishers, New York, USA, 1968).     

低速冲击作用下碳纤维复合材料铺层板的损伤分析

建立了一个有效计算模型, 以分析碳纤维复合材料层合板在低速冲击作用下的层内和层间失效行为。针对铺层板的层内损伤, 在基于应变描述的Hashin 失效准则的基础上, 建立了单层板的逐渐累积损伤分析模型;针对铺层板的脱层损伤, 建立了各向同性脱层损伤模型, 通过结合传统的应力失效准则和断裂力学中的能量释放率准则定义了界面损伤演化规律, 并在潜在产生脱层的区域模拟为粘结接触, 并将脱层损伤模型作为界面的接触行为。该计算模型通过商用有限元软件ABAQUS/ Explicit 的用户子程序实现。使用该计算模型对碳纤维增强环氧树脂复合材料层合板在横向低速冲击作用下的损伤和变形行为进行预测分析。数值仿真的结果与试验结果进行了比较, 取得了满意的结果, 验证了该模型的正确性。      

变刚度复合材料开孔板拉伸行为数值模拟及试验验证

纤维曲线铺放是提高复合材料构件力学性能的有效方法之一。本文针对复合材料开孔板铺放轨迹进行了研究,利用B样条曲线插值拟合获取了开孔板最大主应力铺放轨迹,并通过离散网格法建立了变刚度开孔板模型,通过引入Tsai-Wu损伤失效判据以及常刚度退化准则,进行了拉伸失效数值模拟及损伤失效分析,并分别铺放了两组常刚度和变刚度开孔板试验样件,进行了拉伸对比试验。结果表明：数值模拟与实验数据吻合较好,变刚度开孔板相比常刚度开孔板,拉伸强度提升了26.92%,且两者损伤失效演化过程显著不同。     

缝合复合材料层板低速冲击损伤数值模拟

建立了缝合复合材料层板在低速冲击载荷下的渐进损伤分析模型。模型中采用空间杆单元模拟缝线的作用;采用三维实体单元模拟缝合层板,通过基于应变描述的Hashin准则,结合相应的材料性能退化方案模拟层板的损伤和演化;采用界面单元模拟层间界面,结合传统的应力失效判据和断裂力学中的应变能释放率准则判断分层的起始和扩展规律。通过对碳800环氧树脂复合材料（T800/5228）层板的数值仿真结果和试验结果相比较,验证了模型的正确性,同时讨论了不同冲击能量下缝合层板的损伤规律。研究结果表明：缝线能够有效地抑制层板的分层损伤扩展;相同冲击能量下缝合与未缝合层板的基体损伤和纤维损伤在厚度分布上相似,缝合层板的损伤都要小于未缝合层板。     

复合材料层板损伤过程的刚度分析

本文对典型铺设的[0₂/±45₂/90₂]_s碳/环氧复合材料层板中的典型损伤状态进行了实验观察,测定出损伤对层板刚度引起的下降率.建立了横向裂纹扩展、分层伴以横向裂纹扩展的三维有限元分析模型,计算出对层板刚度引起的下降率,并与实验值进行了比较.结果表明,横向裂纹和分层是层板的主要损伤型式,分层损伤扩展是一个主导性的稳定的损伤扩展过程,是导致刚度下降的主要因素.     

Intralaminar Damage Model for Laminates Subjected to Membrane and Flexural Deformations

Prediction of transverse damage initiation and evolution for not necessarily symmetric laminates under membrane and/or bending loads is the subject of this work. The laminate stiffness reduction is computed via crack opening displacement (COD) methods and the generalization to multiple cracking laminas is made via continuum damage mechanics (CDM) concepts. Using available COD solutions combined with homogenization techniques leads to an analytical constitutive model capable of predicting the initiation and evolution of crack density versus applied strain, as well as laminate modulus degradation, not only for symmetric laminates subjected to membrane deformation but also for general laminates subjected to flexural deformations as well. To adjust the model parameters, experimental data is required in the form of crack density, or modulus reduction, versus strain for two laminates of the same material system. Then, the model is capable of predicting crack density and modulus degradation for other laminate stacking sequences. The model takes into account crack closure, which is important under flexure, as well as the case of the center lamina straddling the neutral axis. The effect of thermal stresses is incorporated in the formulation.     

Strength prediction of bolted joints in graphite/epoxy composite laminates

A parametric finite element analysis was conducted to investigate the effect of failure criteria and material property degradation rules on the tensile behaviour and strength of bolted joints in graphite/epoxy composite laminates. The analysis was based on a three-dimensional progressive damage model (PDM) developed earlier by the authors. The PDM comprises the components of stress analysis, failure analysis and material property degradation. The predicted load–displacement curves and failure loads of a single-lap single-bolt joint were compared with experimental data for different joint geometries and laminate stacking sequences. The stiffness of the joint was predicted with satisfactory accuracy for all configurations. The predicted failure load was significantly influenced by the combination of failure criteria and degradation rules used. A combination of failure criteria and material property degradation rules that leads to accurate strength prediction is proposed. For all the analyses performed, the macroscopic failure mechanism of the joint and the damage progression were also predicted.