A Study on an Intelligent Optimum Material Design System for Utilization of the Anisotropy of Composite Materials

为了充分利用复合材料的各向异性，需要从以下几个方面进行研究：1)结构力学各向异性结构设计方法的建立；2)材料各向异性设计的理论方法的发展；3)为结构设计人员提供实际帮助的专家系统的开发。(1)功能变形：建立了负泊松比材料和具有一定弯曲-扭转耦合变形的结构的设计方法。分析结果与实验结果吻合较好。该方法的一个应用是在扭转载荷作用下，端部扭转角为零的悬臂管。(2)基于应变能的材料优化设计：使板材的应变能最小，从而使其抗弯刚度最大化。该方法在任意载荷条件下均可得到板的最佳取向角。(3)基于可靠性的材料优化设计：发现确定性加载条件下的纤维最佳取向角与概率加载条件下的不同。在概率加载条件下，采用先进的一阶二阶矩法（AFOSM）获得了最优定向。此外，还提出了一种基于可修复性确定最佳角度的分析方法。该方法在评估可靠性相对值方面是非常有效的。(4)人工智能材料设计系统：对材料优化设计的知识进行分析和分类，构建其层次结构。利用面向对象语言Smalltalk实现了知识的表示，并成功开发了复合材料设计专家系统。

For the complete utilization of the anisotropy of composite materials, the following aspects are necessary to study: 1) the construction of the design method for structures with the anisotropy in structural mechanics, 2) the development of the theoretical method for designing anisotropy in the material, and 3) the development of an expert system which yields practical aid for structural designers. From these points of view, the research has been conducted as follows:(1) Functional Deformation : The methods for designing a material with negative Poisson's ratio and a structure which has a specified bending-torsion coupling deformation were constructed. Good agreement was found between the analytical and the experimental results. An application of the methods a cantilevered pipe which yields torsional angle of zero at the tip under torsional loading.(2) Optimum Material Design Based on Strain Energy : The bending stiffness of plates are maximized by making its strain energy minimum. Optimum orientation angle of a plate was obtained using this approach for any loading conditions.(3) Optimum Material Design Based on Reliability : It was found that optimum fiber orientation angles under deterministic loading conditions are different from those under probabilistic loading conditions. For probabilistic loading conditions, optimum orientations were obtained using the AFOSM ( advanced first-order second-moment method. Additionally an analytical method for determining optimum angles based on rehability has been proposed. The method is very effective in evaluating the relative value of the reliability.(4) Material Design System with Artificial Intelligence : The knowledges for optimum material design were analyzed and classified, and their hierarchical structures were constructed. The representation of the knowledge was performed by using object-oriented language, Smalltalk, and a trial expert system for composites design has been successfully developed.