基于非测地线纤维缠绕压力容器线型设计与优化

为较好地满足纤维轨迹路径的稳定与均布,与传统测地线缠绕模式不同,提出了非测地线纤维缠绕压力容器的纤维线型方程,给出了非测地线型模式和缠绕参数的最优化设计方法,分析了环形缠绕机芯模和丝嘴的相对缠绕速比,结合均匀布满条件对优化线型进行了调整。将计算机仿真技术应用到环形容器的缠绕线型设计与验证中,研究了CAD系统各组成模块的功能及实现方法,对非测地线缠绕成型进行了计算机图形仿真与检验。结果表明:设计得到的非测地线满足缠绕工艺的基本要求;采用最优化的非测地线模式进行缠绕,可使非测地线缠绕角集中在筒形压力容器的最佳缠绕角55°附近,有效提高了压力容器的结构承载性能。      

Fiber Trajectories Design of Ellipsoid Component Based on Topological Mapping Methodology

This paper presents a topological mapping algorithm for ellipsoid component winding trajectory. The sphere with double opposite holes was used as initial winding trajectory design model. The double opposite holes ellipsoid winding trajectory was obtained form that of the double-holes-sphere based on topological mapping algorithm. The basic equation of equilibrium for ellipsoidal mapping trajectory was given and its slippage coefficients were calculated using the non-geodesic law and differential geometry. The variation of slippage coefficients with holes-radius and ellipsoid rate were analyzed. The results show that, when ellipsoidal rate get close to 1 gradually, the better stability of fiber trajectories was obtained by topological mapping function. The ellipsoid component with lager holes-radius requires lower coefficient of friction between the fiber bundle and the ellipsoid surface. This fiber trajectory mapping function in the paper presents a useful tool for designing the double opposite holes ellipsoid filament-wound component trajectory.     

基于圆环和等强度截面的纤维缠绕环形容器设计与分析

复合材料环形压力容器以其特有的结构形状得到了日益广泛的应用.目前关于纤维缠绕环形容器的研究主要局限于测地线缠绕圆环截面容器.由于环形容器的结构效率取决于它的管截面形状,所以使用圆环截面的环形容器无法实现等强度结构.本文提出了分别使用圆环截面和等强度截面的环形压力容器设计方法,并对二者进行了比较.基于最小应变能准则,得到了缠绕层铺设角和环壳内力间的最优化关系.根据网格理论,考虑截面缠绕层的厚度变化,导出了圆环容器缠绕的最优线型.引入应力比,分析了环壳上纤维的应力分布.描述了等强度经线曲线的一般形状,分析了轴向截荷对等强度曲线形状的影响.计算结果表明当轴向载荷达到一定数值时,等强度曲线能够实现闭合形成环形容器.进一步计算和比较了两种截面形状的环形压力容器在不同相对弯曲半径下的结构质量.研究表明,使用等强度截面设计的环形容器比使用圆环截面的环形容器要轻的多.通过等强度截面设计,环形压力容器的结构性能得到了明显的提高.     

纤维缠绕复合材料环形容器设计优化(英文)

纤维缠绕环形容器可充分利用空间,节省结构质量和消除系统质心漂移,目前在很多工业领域中发挥着日益重要的作用。本文基于复合材料层合理论和测地线缠绕原理,提出了纤维缠绕环形压力容器的线型优化设计方法。应用微分几何,导出了圆环面上测地缠绕轨迹和纤维不架空判据。以初始缠绕角和缠绕层厚度为变量,对结构重量进行最小化设计,得到了对应于不同管径比的优化缠绕线型。对优化线型进行了计算机缠绕仿真,并给出了缠绕铺层的各向正轴应力分布。结果表明,优化设计的缠绕线型模式精确可靠,满足纤维缠绕的基本要求。纤维缠绕角度大小更趋于合理,从而能充分发挥缠绕结构的力学性能,减经系统重量,使优化得到的环形容器结构性能比传统测地线缠绕环形容器有很大提高。本文的设计计算方法可直接用于复合材料环形气瓶的初步设计。     

Design of filament–wound domes based on continuum theory and non-geodesic roving trajectories

In this paper the optimal shapes and fiber architectures of non-geodesics-based domes for pressure vessels are determined upon the condition of equal shell strains. Based on the continuum theory and the non-geodesic law, the system of differential equations governing the optimal meridian profiles is derived. A specific function is chosen to describe the slippage coefficient distribution for the desired non-geodesic path, in order to ensure C¹ continuity of the roving paths when passing the dome–cylinder conjunction. Next, the meridian profiles are determined for various material anisotropies; the related winding angle developments of non-geodesic trajectories are also presented. The performance factors of non-geodesics-based optimal domes are obtained using various slippage coefficients and polar opening radii. The results show that the structural efficiency of the dome improves with increasing slippage coefficient. It is concluded that the non-geodesics-based dome designed using the present method gains better performance than the one relying on geodesics.     

纤维缠绕复合材料壳体刚度衰减模型数值模拟

应用微分几何理论,推导出纤维缠绕复合材料壳体的非测地线缠绕轨迹、包角方程及绕丝头运动方程,得到缠绕过程的动态仿真模拟数据。将封头处变化的缠绕角、厚度等实际工艺参数直接用于壳体结构的理论分析。采用叠层的增量本构关系,模拟层合板壳结构的损伤过程,建立了损伤后刚度衰减模型及刚度退化准则,并通过实验确定了刚度衰减系数。应用此模型对纤维缠绕复合材料压力容器进行了数值分析。结果表明:纤维缠绕复合材料压力容器封头处损伤会导致其弯曲刚度降低,这是影响轴向变形的重要因素。      

Design of filament-wound isotensoid pressure vessels with unequal polar openings

Previous studies on filament-wound isotensoids are mostly based on geodesic winding. However, the geometry of geodesics is certainly limiting the available design space. A typical restriction is the inability to create isotensoids with unequal openings at both ends. In this paper, a simplified method for designing isotensoid pressure vessels with unequal polar opening is outlined, using non-geodesic trajectories. Firstly we present the non-geodesic equations on general shells of revolution. Next, a direct relation among the shell curvatures, roving force, internal pressure and slippage coefficient, as a basis for determining non-geodesics-based isotensoid shapes, is provided. The governing equations for specifying meridian profiles are derived in terms of the slippage coefficient. The meridian profiles of non-geodesics-based isotensoids corresponding to various opening radii and slippage coefficients are determined, and the performance factors of the obtaining domes are calculated to demonstrate the effect the application of non-geodesics has on the structural efficiency. A stable and easily accessible solution procedure is proposed to determine the slippage coefficients fulfilling the winding requirements. Results show that the present method is suitable for the design of isotensoid structures with unequal polar openings. Results also indicate that the non-geodesics-based isotensoid domes show better performance than the geodesic–isotensoid.     

T700碳纤维增强树脂复合材料气瓶封头非测地线缠绕强度

利用微分几何理论和四阶龙格库塔法求解气瓶封头上T700碳纤维增强树脂复合材料（CFRP）非测地线缠绕角微分方程,得到稳定的非测地线缠绕轨迹;利用有限元仿真软件建立T700 CFRP缠绕气瓶有限元模型,分析不同非测地线轨迹对工作压力（30 MPa）下T700 CFRP缠绕气瓶强度的影响,并采用渐进损伤模型分析爆破压力的变化规律。对于封头高h=50 mm的T700 CFRP缠绕气瓶,滑线系数为0.2时承载能力最强,比T700 CFRP测地线缠绕气瓶提高了7 MPa,约为6.4%;对于封头高h=160 mm的T700 CFRP气瓶,滑线系数为0.2时承载能力最强,比T700 CFRP测地线缠绕气瓶提高了6 MPa,约为11.5%。结果表明,优化设计得到的缠绕线型既能满足缠绕工艺的基本要求,又提高了T700 CFRP缠绕气瓶的结构力学性能,可为实际缠绕工艺提供参考。      

Shape optimization of filament wound articulated pressure vessels based on non-geodesic trajectories

The most important issue for the design of articulated pressure structures reflects on the determination of the optimal meridian profile. In this paper, the optimal design for determining non-geodesics-based meridian profiles is outlined, subjected to geometrical limitations, stability-ensuring winding conditions and the Tsai–Wu failure criterion. The stress field is modeled using classical lamination theory, and the non-geodesic trajectories are employed to enlarge the design space and improve the structural performance. The searched optimal meridian profile is here approximated by cubic splines, which are based on equidistant knots. The objective is to maximize the performance factor using nonlinear optimization techniques. Two design problems are solved: firstly the optimal meridian profile determined using the present method is compared with the geodesic-isotensoid under the given opening radius. Secondly, the different optimal profiles with various slippage coefficients are obtained to demonstrate the effect non-geodesic trajectories have on the geometry and performance of articulated vessels. Results indicate that the articulated structure designed using the present method shows better performance, mainly triggered by increased internal volume as compared to that of the geodesic–isotensoid. Results also show that the structural performance of the articulated pressure vessel can further be improved with increasing slippage coefficients.     

缠绕纤维与芯模表面间滑线系数的测量表征

提出了一种新的滑线系数测量方法, 并基于一般曲面稳定缠绕条件, 设计了一种能够简便快捷测量滑线系数的新型芯模。该芯模在固定缠绕角情况下, 沿母线方向任意点处的纬度圆半径与该点的滑线系数之间满足线性关系。利用该方法及其装置对碳纤维和玻璃纤维在不同缠绕速度、缠绕张力和胶液黏度等条件下与铝质芯模间的滑线系数进行了测量表征。研究结果表明, 该方法可为缠绕纤维与芯模表面间滑线系数的测量及非测地线缠绕轨迹规划设计提供依据。     

带蒙皮复合材料圆柱网格结构的轴压稳定性分析

为获得高承载效率的带蒙皮纤维缠绕复合材料圆柱网格结构,利用有限元法对其轴压稳定性进行了分析.同时,结合ANSYS的二次开发语言APDL编写了圆柱网格结构参数化设计程序,并运用该程序研究了带蒙皮圆柱网格结构载荷质量比随纵筋缠绕角度、筋横截面积、筋高宽比、纵筋对数以及环筋条数的变化规律.对于一定尺寸的网格结构在INSTRO...     

复合材料干纤维增强回转体结构缠绕线型设计

复合材料干纤维缠绕增强结构可解决纤维缠绕树脂基复合材料结构耐冲击性差、低温环境树脂易失效等问题。干纤维增强结构缠绕过程中,纤维束重叠、压缩导致干纤维缠绕增强层各处厚度不一,会对缠绕线型稳定性产生影响。为满足缠绕线型稳定,研究了测地线干纤维缠绕增强层厚度变化及分布规律,分析了纱带宽度、极孔尺寸及芯模结构等参数对增强层厚度的影响,考虑芯模厚度的变化,逐层更新干纤维缠绕增强结构数学模型,进行了缠绕轨迹计算,获得测地线缠绕线型。缠绕实验表明：理论仿真获得的复合材料干纤维缠绕增强容器增强层厚度准确,缠绕线型稳定,无滑纱现象,验证了纤维厚度与缠绕轨迹计算方法的可行性和干纤维增强层厚度仿真的正确性。     

Evaluation of fiber material properties in filament-wound composite pressure vessels

Fiber material properties are the most important factors from among various material properties for the design of composite pressure vessels because of their dominant effect on the performance of composite pressure vessels. However, the fiber material properties of filament-wound pressure vessels are very sensitive to various processing variables and the size effect so that it is not possible accurately to measure fiber material properties using existing test methods. The hydro-burst test with full-scale pressure vessels is the best method to obtain fiber material properties, but it entails exorbitant costs. Consequently, the present paper proposes the hoop ring test, a newly developed test that is capable of pressure testing with ring specimens extracted from full-scale composite pressure vessels. The fiber material properties from the hoop ring test method showed good agreement with the results of the hydro-burst test with full-scale composite pressure vessels.     

Development of fast fabrication method for cylindrical-shaped grids and mechanical properties of CFRP pressure vessel reinforced with cylindrical-shaped grids

In order to reduce carbon dioxide and air pollution emissions, fuel cell vehicles (FCVs) are being developed, and CFRP pressure vessels have been used as the hydrogen storage systems for the FCVs. Since the FCVs are expected to increase driving distances of at least over 500 km, which is similar to those of conventional gasoline-fueled vehicles, the storage pressure of hydrogen must be raised from 35 to 70 MPa. It is important to decrease the amount of carbon fibers in order to reduce the cost and weight of the CFRP pressure vessels. In this study, a fast fabrication method for the cylindrical-shaped grids (CSG) composed of hoop stiffeners and helical stiffeners was developed with a particular mandrel and a 3-axis filament winding apparatus. Then, the CFRP pressure vessel was inserted into the CSG, and burst tests of the CFRP pressure vessels reinforced with and without the CSG were conducted. Moreover, their experimental results were compared with numerical ones obtained by a FEM analysis, and the mechanical properties and the reinforcement effects of the CFRP pressure vessels reinforced with the CSG were investigated.     

Influence of filament winding parameters on composite vessel quality and strength

An experimental design investigation of manufacturing and design variables that affect composite vessel quality, strength, and stiffness was conducted. Eight 20-in. cylinders (with one additional cylinder as a replicate) were manufactured and tested for hoop strength, hoop stiffness, fiber and void volume fraction distribution through thickness, residual stress, and interlaminar shear strength. Material and processing variables were divided into five categories: (a) resin, (b) fiber, (c) fabrication process, (d) design, and (e) equipment. Five variables were selected (from a list of 12) for study using a 1/4 fractional factorial design of experiment setup. The five variables were: (a) winding tension, (b) stacking sequence, (c) winding-tension gradient, (d) winding time, and (e) cut-versus-uncut helicals.

Statistical analysis of the data shows that the composite vessel strength was affected by the manufacturing and design variables. In general, it was found that composite strength was significantly affected by the laminate stacking sequence, winding tension, winding-tension gradient, winding time, and the interaction between winding-tension gradient and winding time. The mechanism that increased composite strength was related to the strong correlation between fiber volume in the composite and vessel strength. Cylinders with high fiber volume in the hoop layers tended to deliver high fiber strength.     

The effect of fiber volume fraction on filament wound composite pressure vessel strength

This paper is a continuation of previous research reported in Ref. [1]. The previous paper discussed the relationship between fiber volume fraction in filament wound composite vessels and failure pressure. This research included a design of experiment investigation of manufacturing and design variables that affect composite vessel quality and strength. Statistical analysis of the data shows that composite vessel strength was affected by the manufacturing and design variables. In general, it was found that the laminate stacking sequence, winding tension, winding-tension gradient, winding time, and the interaction between winding-tension gradient and winding time significantly affected composite strength. The mechanism responsible for increases in composite strength was related to the strong correlation between fiber volume fraction in the composite and vessel strength. Cylinders with high-fiber volume in the hoop layers tended to deliver high-fiber strength. This paper further examines the relationship between fiber volume fraction and fiber strain to failure. Data from unidirectional strand tests and additional vessel tests are presented. A computer program that is based on the thermokinetics of the resin and processing conditions is used to calculate the fiber volume fraction distribution in the filament wound vessel. The strand's strength-versus-fiber volume data together with the computer program are used to predict composite vessel burst pressure. In general, good agreement with experimental data is observed.     

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.     

玻璃钢管的长期刚度测量及预测

为建立玻璃钢管长期刚度理论模型并对其长期刚度进行预测。首先通过自主设计的恒位移加载试验装置,在不同初始挠度的恒位移条件下对纯环向缠绕和纯交叉缠绕铺层的玻璃钢管开展了长期刚度试验研究;然后,在试验基础上建立了不同初始挠度下玻璃钢管刚度与时间的折线双对数回归模型、50年后刚度降幅与初始挠度的线性回归模型,进而提出了玻璃钢管刚度降幅关于时间与初始挠度的二次曲面预测模型;最后,预测了玻璃钢管50年后的剩余刚度,研究了时间和初始挠度对玻璃钢管刚度的影响。结果表明:纯环向缠绕铺层的玻璃钢管抵抗刚度衰减的能力明显优于纯交叉缠绕铺层的玻璃钢管,纯环向缠绕铺层能有效提高玻璃钢管的刚度及其抵抗径向变形的能力,纯环向缠绕铺层的玻璃钢管有较好的长期力学性能。时间为8 313.2 h的测试数据表明提出的玻璃钢管刚度降幅预测模型具有较高的精度和较强的实用性。      

Head Shape and Winding Angle Optimization of Composite Pressure Vessels Based on a Multi-level Strategy

This paper presents a multi-level strategy for the optimization of composite pressure vessels with nonmetallic liners. The design variables for composite vessels include the head shape, the winding angle, the layer thickness, the number of layers, and the stacking sequence. A parameter called “modified shape factor” is introduced as an objective function. This parameter takes into account the effects of the internal pressure and volume, the vessel weight, and the composite material properties. The proposed algorithm uses genetic algorithm and finite element analysis to optimize the design parameters. As a few examples, this procedure is implemented on geodesic and ellipsoidal heads. The results show that for the given vessel conditions, the geodesic head shape with helical winding angle of nine degrees has the better performance.     

Mathematical curls and toroidal coils

The author discusses magnetic vector potential giving an alternative view of whether a magnetic field exists outside a toroidal winding. The author discusses circulation in circular fields, the magnetic vector potential of a toroidal winding, the current transformer worked 'backwards', and short solenoids. An appendix discusses the rate of decline with radius on a circular field on its circulation