航天器薄膜结构折叠展开过程的几何精确建模方法研究

Ultra-light ultra-flexible membrane structures are widely used in various space applications. In space missions, the membrane structures with large size in space are required to be foldable and deployable; the simulation and analysis of its folding-deployment process have to be of high accuracy to ensure successful on-orbit deployments. However, large geometric nonlinearity of the membrane structures in the folding-deployment process makes it very challenging to obtain an accurate model. This project aims to accurately model the folding-deployment process of the membrane structures based on Geometrically Exact Modeling Theory. It develops a geometrically exact modeling method for the membrane structures with large displacements and large strains. Based on Jaumann strain, it establishes the analytical model of the membrane structures, applies the energy momentum method to build the finite elements, and conducts simulations and analysis by integrating the finite elements into the commercial finite element software. By considering membrane crease, thermal distortion and anisotropic viscoelasticity, the geometrically exact model is enhanced to be adaptive to space applications. A large-displacement experiment and a folding-deployment experiment are carried out with comprehensive deformation data measured, the geometrically exact modeling approach proposed in this work is validated, and the accurate simulation of the folding-deployment process for the membrane structures is achieved. The accomplishment of this project would provide theoretical and technical supports for the design of large deployable membrane structures.

薄膜结构因其超轻质量、超高柔度被广泛应用于各类航天器产品中。航天任务不仅需要薄膜结构折叠展开以满足对大结构尺寸的需求，更要求对薄膜折叠展开过程实现高精度的仿真分析从而确保薄膜结构在轨展开的成功。然而薄膜结构在折叠展开过程中的高度几何非线性响应使现阶段对其展开过程的精确建模研究极具挑战。本项目以薄膜折叠展开过程的精确建模为目标，应用具有高精度建模特点的几何精确建模理论，研究航天器薄膜结构大位移、大应变下几何精确建模方法。基于Jaumann应变构建薄膜结构的几何精确解析模型，应用能量动量法建立有限单元，利用集成有限元环境进行仿真分析；引入薄膜折痕、结构热变形和黏弹各向异性等要素，增强模型的航天应用适应性；进行薄膜大变形实验和薄膜折叠展开实验，全面测量变形信息，完善并验证几何精确建模方法，实现航天器薄膜折叠展开过程的精确仿真分析。本项目的研究成果将为大型薄膜类可展结构设计提供理论储备和技术支撑。

项目通过理论建模与实验测定相结合的方式，形成了一套经过一系列标准实验验证的、准确可靠的薄膜结构几何精确建模方法，实现了考虑航天应用适应性的薄膜结构大位移、大应变下的高精度非线性仿真，为以星载薄膜天线、薄膜电池翼、太阳帆等为代表的大尺寸空间薄膜结构提供了准确的非线性动力学分析技术和可靠的仿真验证评估手段。.针对传统薄膜大变形非线性建模方法使用Green应变进而应力应变描述存在理论误差的问题，本项目利用基于几何定义的Jaumann应变描述大变形下的几何非线性，提出了考虑褶皱特性的薄膜结构几何精确建模方法，并通过子程序技术实现了几何精确模型与有限元软件环境的集成，为该建模方法的工程应用做好了准备。.针对航天应用中薄膜结构预设折痕、经历空间热环境、出现大应变变形等三项变形特征，本项目一方面利用待定系数法综合三项特征的理论模型，提出了融合折痕、热变形、大应变等非线性特性的薄膜理论模型，一方面利用应力应变试验曲线测定模型待定系数，获得了考虑航天应用适应性的几何精确模型，为解决航天薄膜结构复杂工况下的非线性变形问题提供了理论基础。.针对现有薄膜非线性仿真分析缺乏多方面精度评估的问题，本项目以流程合理、陈述完备、数据可靠等为依据，筛选出了一系列包含静动态多种载荷工况的薄膜变形实验作为评估精度的标准实验组，为后续薄膜非线性建模研究提供了统一的精度分析参照；同时本项目的几何精确模型对照标准实验组实现了良好的仿真精度，证明了该建模方法为薄膜结构大变形下的非线性仿真分析提供了准确、可靠的技术手段。