复合材料球形气瓶非测地线缠绕线型设计和强度分析

碳纤维复合材料球形气瓶因其较高的比强度、比刚度和抗疲劳性,被广泛应用于航空航天及民用工业领域。基于微分几何理论,推导出满足球形气瓶缠绕基本原理的落纱点轨迹方程,给出缠绕线型轨迹和缠绕角应该满足的稳定缠绕条件,并对缠绕轨迹进行仿真。考虑球壳的变曲率特点,针对球形气瓶缠绕层进行变厚度、变角度的精细化有限元建模,对工作压力下的气瓶内衬和缠绕层各向应力分布进行数值模拟和分析,并预测了气瓶的爆破压强。结果表明,优化设计得到的缠绕线型参数既能满足缠绕工艺的基本要求,又有效提高了球形气瓶的结构力学性能。研究成果对复合材料球形压力容器的设计制造具有重要的意义。     

CNG-2环向缠绕气瓶纤维缠绕残余预应力的优化设计

复合材料气瓶压力容器的纤维缠绕预应力对容器的性能有很大的影响,合理设计纤维预应力可提高复合材料容器的综合性能。借助ANSYS有限元软件,建立了带有纤维缠绕残余预应力的环向缠绕气瓶的有限元参数化模型。在模型中,将纤维缠绕层视为复合材料层合板。按照GB 24160—2009《车用压缩天然气钢质内胆环向缠绕气瓶》的规定,并结合各工况下应力水平的要求建立数学模型,对环向缠绕气瓶的纤维缠绕残余预应力进行优化,得到纤维缠绕残余预应力的最优值,使内胆在工作压力下有较低的应力水平,提高了气瓶的可靠性。     

纤维缠绕压力容器几何非线性分析

本文使用有限元软件ANSYS对纤维缠绕压力容器进行了几何非线性分析，并对容器进行了强度以及失效研究。本文压力容器几何非线性分析的结果表明铺层方向是影响纤维缠绕壳体强度的最大因素。     

铝内衬碳纤维复合材料压力容器非测地线缠绕与强度分析

本文对碳纤维缠绕复合材料压力容器进行了非测地线缠绕线型设计、有限元仿真和纤维缠绕与水压爆破实验。根据非测地轨迹确定了复合材料压力容器的最佳缠绕参数;采用有限元软件ABAQUS对其受压状态下的应力应变值进行分析,研究内压为35 MPa时压力容器的应力状态,并预测其爆破强度为92.2 MPa;缠绕实验在五轴数控缠绕机上进行,使用T800碳纤维制备了铝合金内衬复合材料压力容器,其纤维缠绕层共26层,缠绕完成后纤维排列整齐均匀,无滑纱现象。固化后其爆破压强为87.5 MPa,与仿真结果相对误差为5.1%,验证了仿真分析的可行性。     

纤维缠绕压力容器扩极孔工艺研究

复合材料缠绕压力容器封头部位在进行多次螺旋缠绕时,纤维在极孔处堆积严重,造成封头部位厚度的极不均衡,降低了封头部位性能的有效发挥。本文主要对复合材料缠绕压力容器在封头部位的扩极孔缠绕设计进行了一些探索研究。     

FWRP压力容器的可靠性设计研究

纤维缠绕聚合物基复合材料(FWRP)压力容器在航空航天及民用领域的应用是当前研究热点。减轻结构重量对于性能和成本都具有非常重要意义。为实现FWRP压力容器结构设计和安全评定的高目标,引入可靠性理论,应用统计学原理,基于应力-强度干涉模型,以同一失效概率为标准进行FWRP压力容器结构设计,以取代现应用的传统安全系数法设计。采用无碱无捻玻璃纤维-环氧树脂材料体系,应用同一缠绕工艺制备8个压力容器。试验得到纤维强度、缠绕角、几何尺寸、爆破压力等随机变量特征值。其结构可靠性设计值(纤维缠绕壁厚)与试验结果基本吻合,并显著小于常规设计值。将各设计变量随机分布特征值与压力容器结构设计相结合,实现安全与经济的有效统一,为可靠性设计在FWRP压力容器上的应用与发展提供了依据。     

纤维缠绕压力容器表面损伤试验研究

通过制作纤维缠绕标准容器试样,并对部分试样表面纤维制作人工损伤,与标准容器试样比较爆破压力,并进行有限元分析、研究其破坏机理,对强度影响程度进行评估。结果表明：表面纤维损伤会造成压力容器在应力水平较低情况下局部发生层间剪切破坏,损伤容器爆破强度平均值降低22．4％,损伤修复后的容器爆破强度降低12．2％。     

单向纤维增强复合材料的基体微裂纹及其影响

本文根据单向纤维增强复合材料的破坏机理,提出了一个基体损伤微观力学模型,利用修正的剪切滞止方法和有限元法研究了复合材料基体损伤后的应力分布和应力集中情况,分析了纤维阻裂和刚度下降机理。结论与实验结果相一致。     

复合材料拐角的抗冲击性能实验研究

由于树脂基复合材料层合板对冲击作用比较敏感,因此,在使用过程中受到低能冲击时,极易产生不可见损伤,造成复合材料在强度和刚度上的损失,严重威胁结构的安全使用性。本文借助四点弯曲实验分别对五种不同铺层的乙烯基树脂/玻纤复合材料拐角在不同能量冲击后的弯曲刚度衰减进行了测试,讨论了不同铺层和冲击能量对复合材料拐角抗冲性能的影响。研究结果表明,随着冲击能量的增加,冲击损伤越明显,剩余弯曲刚度越低,各种铺层冲击破坏面积与刚度下降呈现基本一致的趋势;相邻铺层的铺层角相差越小,复合材料拐角的弯曲刚度越大,冲击后弯曲刚度损耗越小,[45°/0°/-45°/90°]铺层的冲击后刚度损失率最低,正交铺层的试样组抗冲击性能最差。     

2维C/SiC复合材料的拉伸损伤演变过程和微观结构特征

通过单向拉伸和分段式加载-卸载实验,研究了二维编织C/SiC复合材料的宏观力学特性和损伤的变化过程.用扫描电镜对样品进行微观结构分析,并监测了载荷作用下复合材料的声发射行为.结果表明:在拉伸应力低于50MPa时,复合材料的应力-应变为线弹性;随着应力的增加,材料模量减小,非弹性应变变大,复合材料的应力-应变行为表现为非线性直至断裂.复合材料的平均断裂强度和断裂应变分别为23426MPa和0.6%.拉伸破坏损伤表现为:基体开裂,横向纤维束开裂,界面层脱粘,纤维断裂,层间剥离和纤维束断裂.损伤累积后最终导致复合材料交叉编织节点处纤维束逐层断裂和拔出,形成斜口断裂和平口断裂.     

碳纤维复合材料迫击炮身管结构设计与缠绕工艺研究

纤维增强复合材料具有比刚度高、比强度大的轻量化优势,以及可设计性强、耐腐蚀性优、抗疲劳性好等显著特点,可作为武器装备轻量化设计的绝佳选材。在对迫击炮身管进行受力分析的基础上,提出了采用金属内衬外加碳纤维复合材料增强层的迫击炮复合身管双层结构,介绍了用于迫击炮复合身管加工的缠绕设备和缠绕工艺,基于实验结果,综合分析了碳纤维材料的选择、铺层顺序、纤维缠绕张力等工艺对迫击炮复合身管承压性能的影响,可为火炮复合材料身管以及复合材料承载圆筒的结构设计与加工提供参考。     

Processing and properties of solution impregnated carbon fiber reinforced polyethersulfone composites

Carbon fiber reinforced polymer composites are attractive because of their high stiffness and strength‐to‐weight ratios. In order to fully utilize the stiffness and strength of the reinforcement fiber, it is necessary to bring the polymer matrix and the reinforcement fiber together with homogeneous wetting. In this paper, a solution processing technique and the mechanical properties of carbon fiber reinforced polyethersulfone composites were investigated. The polymer was dissolved in cyclopentanone and fed onto a continuous carbon fiber tow using a drum winder. The solution‐processed composite prepregs were then layed up and compression molded into unidirectional composite panels for evaluation. The composite samples showed uniform fiber distribution and reasonably good wetting. The longitudinal flexural modulus was as high as 137 GPa, and longitudinal flexural strength 1400 MPa. In addition, the effects of polymer grade and processing conditions on the mechanical properties of the composites were discussed. It is suggested that the transverse properties and interlaminar fracture toughness could benefit from higher polymer matrix molecular weight. A careful design in the spatial distribution of the molecular weight would be necessary for practical applications.     

High-temperature properties and interface evolution of silicon nitride fiber reinforced silica matrix wave-transparent composite materials

In order to improve the high-temperature performance of wave-transparent materials especially for the high-speed aircrafts application, filament winding combined with sol-gel method was adopted to the fabrication of unidirectional silicon nitride fiber reinforced silica matrix composites. The mechanical properties and the interface evolution at high temperatures were investigated. The results show that the composite sintered in N₂ maintains a flexural strength of 210MPa at up to 1200°C, while its counterpart prepared in air experiences a dramatic reduction to about 73MPa. The degradation is due to the partial oxidation of silicon nitride fibers at the fiber matrix interface. Besides, it is also notable that the bending strength of these two composites undergoes a similar growth from about 160 to 210MPa when tested under 900°C, which can be explained by the release of thermal stress on the silicon nitride fibers.     

基于热芯缠绕工艺的缠绕张力研究

本文提出了一种适用于热芯缠绕工艺的缠绕张力制度设计方法.与传统缠绕工艺不同的是,热芯缠绕工艺使复合材料在缠绕同时加热固化.该方法在考虑外部纤维张力对内部环向应力影响的基础上,考虑了缠绕过程中温度引起的热应力、固化收缩应力以及各参数变化,通过对各缠绕层环向应力的分析,推导出考虑温度影响的缠绕张力制度,使各缠绕层纤维受力均匀,从而提高复合材料壳体的强度和抗疲劳性能.     

固体发动机纤维缠绕壳体的成型工艺设计及试验

采用网格理论对缠绕壳体进行了工艺参数的设计计算,计算出缠绕工艺参数,结合微机控制缠绕软件编制程序,提出了强度设计、线型控制、变形校核三位一体的设计思想,确定了缠绕工艺设计的内容、计算方法及所需和所应产生的参数结构,对包络线轨迹进行平滑处理,控制缠绕线型,用实验进行壳体筒身段的强度设计和变形(强度)校核,结果表明理论分析与实验结果能够较好地相互吻合,壳体的爆破压强误差较小,其值小于5%.     

格构腹板增强轻木夹芯复合材料桥面板的制备与受弯分析

提出了一种新型格构腹板增强轻木夹芯复合材料桥面板,这种面板具有轻质高强、耐腐蚀、易拼装等特点,可用于军事舟桥等组合结构桥梁领域。该新型桥面板的复合材料面层、格构腹板与芯材在模具内通过真空导入工艺整体一次成型,利用格构腹板提高面层与芯材的整体性,可更大程度地发挥新型桥面板的受力性能。基于复合材料夹层结构经典理论,对该桥面板在典型轮式车辆和履带式车辆荷载作用下的性能进行了受力分析。结果表明:该桥面板的刚度满足设计要求;纤维面层正应力和轻木芯材剪应力均满足强度要求;与原同尺寸军用桥面板相比,减重57%。     

接触热阻对复合材料身管热性能影响分析

采用金属内衬外部缠绕纤维增强复合材料,可减轻纯金属身管重量,提高身管刚度.为了详细分析复合材料身管分界面接触热阻对身管热性能影响,本文建立考虑复合材料身管分界面接触热阻效应的瞬态传热模型,运用有限差分法编制通用程序对接触热阻效应对复合材料身管热性能影响进行数值定量分析.结果表明,接触热阻对于复合材料身管的传热性能有较大影响,必须采取措施来减小接触热阻,这在复合材料身管的热性能设计中必须重点考虑.     

Influence of fiber slippage coefficient distributions on the geometry and performance of composite pressure vessels

In this article, the effects of several slippage coefficient distributions on the geometry, fiber trajectories, and the structural efficiency of non‐geodesic domes are evaluated for composite pressure vessels. Several functions, which ensure C¹ continuity of the winding trajectories, are respectively used to describe the slippage coefficient distributions along the fiber paths. With the aid of the fiber slippage law and the optimality condition of equal shell strains, the differential equations that govern the non‐geodesics–based dome shapes and related fiber trajectories are formulated. The meridian profiles and winding angle developments of the carbon–epoxy domes are obtained based on the given slippage coefficient distributions; their structural performances are then determined and compared with each other. The results conclude that the non‐geodesic dome designed using the maximum constant slippage coefficient exhibits better performance than those using other slippage coefficient distributions; this is mainly triggered by maximum utilization of the longitudinal strength of the laminate. It is also revealed that the structural efficiency of domed pressure vessels can be improved using non‐geodesics that provide higher degrees of freedom in the design of filament wound structures. POLYM. COMPOS., 315–321, 2016. © 2014 Society of Plastics Engineers     

Fatigue damage in composite cylinders

In this study, optimal angle‐ply orientation of symmetric composite cylinders under fatigue loading is investigated. The fiber‐reinforced plastic cylinders were manufactured from E‐glass/epoxy. The layers were manufactured symmetrically in [±75°]₂, [±60°]₂, [±55°]₂, and [±45°]₂ orientations. Burst pressure of filament‐wound composite cylinders under alternating pure internal pressure was measured experimentally. Internal fatigue pressure testing method was applied to the composite cylinders in close‐ended condition. For this study, a PLC controlled hydraulic pressure testing machine has been employed. The static burst pressure values of specimens were measured; subsequently, fatigue test pressure was applied in 70, 60, and 50% stress levels of burst pressure for each orientation. Damage propagations of the composite cylinders on these stress levels were observed as whitening, leakage, and final failure for [±60°]₂, [±55°]₂, and orientations. When the damage propagation of [±75°]₂ angle‐ply cylinder was observed, whitening and leakage did not occur and final failure occurred suddenly. Stress‐cycle curves obtained from the tests are given in graphics. Experimental results reveal that variation in stress levels and the winding angles have considerable effects on final failure cycles, which is also presented graphically. The optimum winding angle for the composite pressure cylinders or vessels under internal fatigue pressure load was obtained as [±45°]₂ orientation. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers