摘 要

当今社会现代工业的高速发展，给人们带来许多便利的同时也所带来了环境的污染、能源的短缺和资源的枯竭等方面的问题。为了保护人类所居住的环境，保障能源的供给，各国的政府不惜投入大量的人力、物力和财力去寻求解决这些问题的办法。而汽车作为现代工业文明的代表,对社会的影响十分巨大。因此对汽车排放的控制以及新能源的开发与利用已经成为了备受各国的政府以及各大汽车制造公司瞩目的焦点之一。汽车轻量化在众多的汽车行业的节能减排途径中一直是最有效的方式之一，而通过对新型材料的应用来推动汽车轻量化设计是各大汽车制造公司一直着重研究的目标。

碳纤维复合材料（CFRP）是由作为增强材料的碳纤维和作为基体材料的树脂组合而成的一种先进微晶石墨材料。由于其具有低密度和优越的力学性能，碳纤维复合材料已经成为了汽车轻量化研究中被赋予重要意义的一种最具潜力的材料。翼子板为汽车车身覆盖件中重要部件之一，因其结构较为简单，而且所受的载荷工况，所需要的生产加工工艺和其功能特点等都非常具有广泛的代表性，常作为研究时的首选对象。本文采用翼子板这一车身覆盖件作为载体，为探究碳纤维复合材料这一最具潜力的材料对于汽车轻量化工作的意义，主要开展了以下研究工作：

（1）本文首先对复合材料进行了简介。然后阐述了复合材料的力学特性及其相关的理论基础，包括单向复合材料的力学性能和层合板复合材料的力学性能，为后续的建模、分析以及优化等一系列过程奠定了基础。最终决定以碳纤维复合材料层合板形式应用于汽车翼子板结构上。

（2）本文介绍了有限元方法及其相关分析软件。通过获得的汽车翼子板有限元模型，根据这一汽车覆盖件实际应用中所受载荷等设计了相应的工况，通过Altair公司的HyperWorks软件组对高强度钢汽车翼子板结构进行了包括应力-应变分析以及模态分析的力学性能分析模型。通过分析高强度钢翼子板结构的有限元结果，运用等代法确定了T300/5208碳纤维复合材料的最初铺层方案，完成相关建模及分析后将高强度钢翼子板与碳纤维翼子板两组分析结果进行对比，得出了碳纤维复合材料在汽车轻量化设计中的优越性与潜力。

（3）本文在优化方面，对比分析了采用不同铺层厚度和不同中间层厚度的汽车翼子板模型的静态和动态特性，得到了汽车翼子板的力学性能参数随不同铺层厚度和中间层厚度的变化规律。在所得到的对比分析规律的基础上，对碳纤维复合材料翼子板进行基于Optistruct的优化设计后得到的最佳的碳纤维汽车翼子板的模型，并且对比分析优化后的碳纤维汽车翼子板轻量化效果。

本文通过一系列的理论介绍、模型建立、工况分析以及优化设计，阐明了碳纤维复合材料相对于传统金属材料的优越性，得到了不同材料以及不同设计方案的翼子板的力学性能，最终通过对比发现碳纤维复合材料的合理利用可以在完全保证汽车性能的情况下极大程度的减少重量从而达到汽车轻量化的目的。通过上述的分析与优化设计，我们可知这些结果在汽车轻量化的设计和制造中起到了非常重要的借鉴和引导作用。本文作为工程应用性的课题，对碳纤维材料在汽车轻量化进程中的应用与发展有着一定的现实意义与推进作用。

关键词：有限元方法；碳纤维复合材料；高强度钢；汽车翼子板；优化设计。

Abstract

The rapid development of industry brings convenience to people at the same time, it also brings problems such as environmental pollution, energy shortage, resource depletion and so on. In order to protect human's living environment and ensure the energy supply, governments at various countries are willing to invest a lot of manpower and material resources to find ways to solve these problems. As a representative of the modern industrial civilization, the car has a great influence on the society. Therefore, the development and utilization of new energy sources and control of vehicle emissions has become one of the focus of attention of governments and automobile manufacturing companies in the world. Lightweight of automobile in a large number of car industry means of energy saving and emission reduction has been one of the most effective way, and through the application of new materials to promote the design of lightweight vehicle is the automobile manufacturing company has been focusing on the goal.

Carbon fiber composite (CFRP) is a kind of advanced microcrystalline graphite material, which is formed by the combination of carbon fiber and resin as matrix material. Due to its low density and excellent mechanical properties, carbon fiber composites have become one of the most promising materials in the lightweight research of automobile. The wing is one of the most important parts of automobile body covering parts, because of its simple structure and by the loading conditions, needed for the production and processing technology and its functional characteristics is very broadly representative, often as a study of the preferred target. The wing of the body panel as a carrier, to explore carbon fiber composite material the most potential material for automobile lightweight, The following research work has been carried out:

（1）In this paper, the composite materials are briefly introduced. And then expounds the theoretical foundation of the mechanical properties of composite materials and its related, including the mechanical properties of the mechanical properties of unidirectional composites and laminates composite materials, for subsequent modeling, analysis and optimization of a series of process laid the foundation. The final decision to use plywood form of carbon fiber composite layer on the fender structure.

（2）In this paper, the finite element method and its correlation analysis software are introduced. Through the fender finite element model, according to the automobile cover parts in practical application by loading in the design of the corresponding condition, through Altair HyperWorks software group of high strength steel fender structure of should include stress strain analysis and modal analysis of mechanical performance analysis model. Through the analysis of

the finite element results of high strength steel fender structure, the use of generation method is used to determine the carbon fiber T300 / 5208 composite initially shop layer scheme, the comparison of the results of the analysis of the two groups after the completion of the modeling and analysis of high strength steel fender and carbon fiber wing, carbon fiber composite materials in the design of lightweight vehicle superiority and potential are obtained.

（3）The optimization, comparative analysis of the the shop is different from the static and dynamic characteristics of layer thickness and different intermediate layer thickness of the fender model, the mechanical parameters of automobile fender with different shop layer thickness and middle layer thickness variation. On the basis of the comparative analysis of the rules, the carbon fiber composite wing were based on Optistruct optimization design, through the free size optimization, size optimization, the stacking sequence optimization has been the ultimate carbon fiber composite wing model and to score and analyzed before and after optimization of wing lightweight effect.

Through a series of theoretical introduction, model establishment, condition analysis and optimization design of clarify the carbon fiber composite material with respect to the superiority of the traditional metal materials, different materials and different design schemes of the wing of mechanical properties and finally by comparing hair rational utilization of carbon fiber composite materials can fully guarantee the vehicle performance greatly reduce weight so as to achieve the purpose of lightweight of automobile. The results of the above analysis and optimization design are of great importance for the design and manufacture of automobile lightweight. As a subject of engineering application, the application and development of carbon fiber materials in the lightweight process of automobile has a certain practical significance.

Keywords: finite element method; carbon fiber composites; high strength steel; fender; optimization design.