粘弹性复合材料网格结构软模工艺数值仿真

复合材料网格结构软模成型共固化工艺具有低成本,高效率和高质量的特点.首先建立了网格结构软模成型共固化工艺过程有限元分析的数值仿真模型,然后通过典型算例,模拟了成型工艺中温度场,固化度场的相互影响及对粘弹性复合材料网格结构应力场的影响.论文工作对复合材料网格结构软模成型共固化工艺参数优化具有一定的参考价值.     

复合材料网格结构软模共固化成型工艺数值仿真

基于平面应变有限元分析模型与策略, 研究了软模共固化成型工艺中工艺间隙、固化周期和残余应力对复合网格结构性能的影响。通过模拟一典型复合材料网格结构的共固化工艺过程, 得出了合适工艺间隙的确定方法, 建立了降低耦合场梯度策略, 并且解释了产生残余应力的原因。这对复合网格结构的软模共固化工艺的工艺参数合理选择具有一定的参考价值。      

先进格栅增强复合材料结构在软模共固化成型过程中工艺参数研究

先进格栅增强复合材料结构(AGS)软模共固化工艺成型过程是一个包括固化度、温度和应力场等相互耦合作用的复杂历程,工艺参数的选择将直接影响AGS产品的性能.该文以一简单正交AGS板为例,采用有限元分析方法对其软模共固化成型工艺过程进行数值仿真,讨论了工艺间隙、工艺环境和固化制度等对成型工艺过程中预浸料内部固化度,温度和应...     

基于树脂流动的变截面复合材料结构固化过程热-流-固多场强耦合数值仿真

在考虑树脂流动对固化温度场影响的基础上,将树脂流动引入经典热-化学模型,并在考虑了固化过程材料性能时变特性条件下,建立了复合材料热-流-固多场强耦合有限元模型。通过对比文献中未考虑树脂流动对温度场的影响,本文所建模型温度场较实际结果的最大温差更低,厚度密实精度更高,模型可靠性更好。基于所建热-流-固强耦合有限元模型,对变截面复合材料结构固化过程进行数值仿真。研究发现,变截面复合材料结构较厚区域存在明显温度场、固化度场及树脂流场分布梯度,纤维体积分数分布不均性较大,这与结构不同区域的厚度、固化过程温度传递滞后及局部树脂流动受固化效应不同步产生的影响有关。变截面复合材料结构厚度由3.52 mm增加至42.24 mm,截面最大温差由0.3℃增加到34.3℃,纤维体积分数分布不均匀性由0.1%增加到1.3%。     

基于材料性能时变特性的复合材料固化过程多场耦合数值模拟

针对热固性树脂基复合材料固化过程中各种复杂的物理化学变化之间的相互影响,建立了基于材料性能时变特性的复合材料固化过程的二维多场耦合计算模型。该模型由已知的3个经典复合材料固化过程子模型构成,包括热-化学模型、树脂黏度模型和树脂流动模型。在此基础上,将固化过程中材料性能的时变特性引入多场耦合计算模型中。通过与文献中实验结果的比较,证明了所建立的模型具有较高的可靠性。对AS4/3501-6复合材料层合平板的固化过程进行了数值模拟,重点研究了固化过程中纤维体积分数变化及材料参数的时变特性对固化过程中温度、固化度和树脂压力等参量的影响。分析结果表明:考虑纤维体积分数变化和材料性能的时变特性后,固化过程中复合材料层合板中心温度峰值明显减小,树脂压力随时间的变化将有所滞后。     

复合材料网格结构软模成型工艺参数匹配分析

作为一种低成本的先进工艺,软模工艺因其膨胀压力的可控性受到了工程界的重视.在满足不同结构要求的前提下,工艺参数选择的合理性是降低复合材料网格结构残余应力,提高网格结构性能的关键.本文对软模工艺过程进行了数值仿真,并通过分析复合材料网格软模成型工艺中温度和压力的变化规律,旨在研究不同工艺参数对复合材料网格结构中肋骨固化压力的影响,为复合材料网格结构的低成本生产提供依据.     

复合材料网格结构软模成型工艺参数匹配分析EI

作为一种低成本的先进工艺,软模工艺因其膨胀压力的可控性受到了工程界的重视.在满足不同结构要求的前提下,工艺参数选择的合理性是降低复合材料网格结构残余应力,提高网格结构性能的关键.本文对软模工艺过程进行了数值仿真,并通过分析复合材料网格软模成型工艺中温度和压力的变化规律,旨在研究不同工艺参数对复合材料网格结构中肋骨固化压力的影响,为复合材料网格结构的低成本生产提供依据.     

热固性复合材料固化过程三维有限元模拟和变形预测

分析了复合材料热固化过程中各种复杂的物理化学变化之间的相互影响,在此基础上建立了复合材料固化过程数值模拟和固化变形预测的三维有限元分析模型。采用整体-子模块方法将固化过程分为热-化学、流动-压实和应力-变形三个相对独立的子模块。热-化学模块的控制方程基于Fourier 热传导方程和树脂固化动力学方程建立,解决了温度和固化度之间的强耦合问题。流动-压实模块的控制方程基于Darcy定律和有效应力原理建立,反映了树脂流动和纤维网络紧密压实之间的流固耦合关系。应力-变形模块建立了考虑热载荷和固化收缩载荷时复合材料层合板的有限元方程。各模块之间的相互作用通过它们之间的数据交换来实现,以树脂在固化过程中的凝胶点和玻璃化转化点为判断依据确定是否运行各模块及其子程序。典型结构的计算结果与实验对比验证了本文三维有限元模型的有效性。     

热压工艺热-化学-应力三维数值模型及有限元分析

建立了复合材料热压工艺的三维热-化学-应力耦合数学模型。该模型考虑了整个工艺周期过程中的热-化学应变、材料的黏弹性效应、各向异性及玻璃化转变温度与固化度的关系。其中热-化学模型可采用完全耦合的形式求解,而应力模型则可采用单向耦合的形式求解。对AS4/3501-6层合平板的热压工艺过程用有限元方法进行了数值模拟,得到的层合板翘曲度与实验结果相符。计算结果表明,层合板厚度减小或长度增大,都会使翘曲变形增大,而工艺压强对翘曲变形影响很小。层合板的翘曲变形随着模具与层合板热膨胀系数差距的变小而减小。       

热固性树脂基复合材料固化过程的三维数值模拟

针对热固性树脂基复合材料成型工艺的固化过程建立了数学模型,并采用有限单元法进行了三维瞬态数值分析。编制了有限元模拟程序CURESIM,通过具体数值模拟算例,表明本文中所建立的分析模型及算法具有较高的可靠性。模拟的固化过程并不特指某一成型工艺,因而模拟的数值方法具有一定的普遍性。模拟程序可以计算得到任意时刻复合材料内温度及固化度分布,通过数值模拟可以有效地优化固化加热工艺参数,提高产品质量。      

Resin Flow of an Advanced Grid-Stiffened Composite Structure in the Co-Curing Process

The soft-mold aided co-curing process which cures the skin part and ribs part simultaneously was introduced for reducing the cost of advanced grid-stiffened composite structure (AGS). The co-curing process for a typical AGS, preformed by the prepreg AS4/3501-6, was simulated by a finite element program incorporated with the user-subroutines ‘thermo-chemical’ module and the ‘chemical-flow’ module. The variations of temperature, cure degree, resin pressure and fiber volume fraction of the AGS were predicted. It shows that the uniform distributions of temperature, cure degree and viscosity in the AGS would be disturbed by the unique geometrical pattern of AGS. There is an alternation in distribution of resin pressure at the interface between ribs and skin, and the duration time of resin flow is sensitive to the thickness of the AGS. To obtain a desired AGS, the process parameters of the co-curing process should be determined by the geometry of an AGS and the kinds of resin.     

Study of filament wound grid-stiffened composite cylindrical structures

Grid-stiffened composite structures are known for their very high efficiency under compressive loading environment. The grid of stiffening ribs is the primary feature in these structures and filament winding is employed as the most convenient manufacturing technique. Three different types of circular cylindrical structures – unstiffened shell (with skin only), lattice cylinder (with ribs only) and grid-stiffened shell (with skin and ribs) – are considered for experimental study and a series of these structures have been manufactured adopting a simplified and cheap manufacturing process. Different aspects of manufacturing that include tooling and other processing aspects are presented in this paper. Axial compression tests have been carried out and the results are compared with finite element analysis. Based on the test results and comparison with finite element analysis, conclusions are drawn on the efficacies of this relatively new class of structures.     

复合材料夹芯结构非线性热传导分析

针对复合材料夹芯结构温度场分布的特点, 提出一种用于复合材料夹芯结构热传导精细分析的有限单元模型。这种单元模型为三维六面体模型, 单元模型厚度方向的插值函数在芯层和面板交界节点处温度值是连续的, 但温度变化率是不连续的, 而芯层内部节点处沿厚度方向温度值和温度变化率都是连续的。在考虑材料热传导参数随温度变化的情况下, 基于这种有限单元模型建立的复合材料夹芯结构瞬态温度场分析有限元方程为非线性方程。在求解此瞬态热传导非线性有限元方程时, 改进了常用的动力学平衡方程的解法, 改进后的动力学平衡方程解法避免了迭代运算, 提高了求解非线性动态平衡方程的效率。数值算例结果显示了该分析模型的有效性和可靠性。      

Thermal fatigue analysis of solar panel structure for micro-satellite applications

Thermal fatigue analysis based on 2D finite difference and 3D finite element methods is carried out to study the performance of solar panel structure during micro-satellite life time. Solar panel primary structure consists of honeycomb structure and composite laminates. The 2D finite difference (I-DEAS) model yields predictions of the temperature profile during one orbit. Then, 3D finite element analysis (ANSYS) is applied to predict thermal fatigue damage of solar panel structure. Meshing the whole structure with 2D multi-layer shell elements with sandwich option is not efficient, as it misses thermal response of the honeycomb structure. So we applied a mixed approach between 3D solid and 2D shell elements to model the solar panel structure without the sandwich option.     

用于AGS结构分析的混合法

结合均匀化模型和加筋单元模型构造了一种混合模型用来分析复合材料格栅加筋板/壳结构（AGS）。所构造的加筋单元模型是一种高性能协调转角独立加筋板壳单元,保持了肋骨和蒙皮位移场的协调性,同时还满足肋骨和蒙皮具有独立转动条件,该单元中肋骨的方向和位置任意。混合法具有精度高、速度快等特点。通过典型算例讨论了肋骨间距和高度对均匀化模型计算结果精度的影响,通过对带孔复合材料AGS板孔边特殊点应力值的分析证明了混合法的有效性。      

High performance 3D-analysis of thermo-mechanically loaded composite structures

This paper considers the analysis of composite structures, simultaneously loaded by mechanical and thermal loads, as often found in aerospace applications. Typically a thermal analysis providing the temperature field must precede the stress analysis, which has to account for thermal as well as for additional mechanical loads. Presently, thermal analyses are mostly carried out by finite difference methods or by 3D finite elements, whereas the stress analysis is usually performed by the use of shell elements. Thus, the temperature field has to be transferred from a finite difference or 3D finite element model to a shell finite element model. This process often requires lots of manual user interaction and can get very time consuming. The paper suggests an integrated analysis process which uses a shell finite element model throughout. Thermal lamination theories and related finite elements developed by the first author are used for the 3D thermal analysis. This leads to a reduction of the computing time by two orders of magnitude as compared to 3D finite elements whereas the accuracy of the results is nearly unaffected. The stress analysis is carried out using the same geometry model but with different mesh density. Interpolation between the different meshes can be accomplished automatically since both discretizations are defined on the same geometry. Standard shell elements based on the First order shear deformation theory (FSDT) provide the three in-plane stress components. A novel postprocessing scheme is adopted for determining all transverse stress components from the in-plane stresses and the temperature field. The postprocessing methodology is based on the extended 2D-method which utilizes the material law for transverse shear and the 3D equilibrium conditions. It is computationally very efficient and can be applied in conjunction with any standard finite element package. The interaction of thermal and stress analysis is demonstrated by the example of a composite wing box for a future large airliner.     

三维机织复合材料残余应力/应变多尺度分析及工艺参数优化

为预测三维机织复合材料工艺引入的残余应力/应变,提出工艺制度优化方案,建立了一种工艺过程分析的多尺度模型.通过建立纤维尺度及纱线尺度代表体元(RVE),计算了成型过程中纤维纱线及三维机织复合材料的模量演化历程.考虑固化过程中树脂的化学收缩效应,在纱线尺度上开展热-化学-力学耦合分析,预测了细观残余应力-应变及其演化规律...