【作者】 岳广全；

【导师】 杜善义； 张博明；

【作者基本信息】 哈尔滨工业大学 ， 工程力学， 2010， 博士

【摘要】 复合材料整体成型技术在满足结构总体性能的要求下,通过减少零件和紧固件的数量减轻结构重量,降低成本,特别是降低制造成本,是目前世界上在该技术领域大力提倡和发展的重要技术之一。而对于大尺寸、结构复杂的整体化成型的结构件,固化变形是影响其成型质量的重要因素。为减小复合材料的固化变形,传统的方法是在经验和工艺试验的基础上对构件的固化工艺制度和模具型面进行反复的调整和补偿性修正加工,这种方法费时费料,增加了制造成本。因此,针对复合材料整体化成型构件建立完整的固化变形分析和预测方法,就成为保障制造质量、降低制造成本的核心关键问题之一。本文建立了整体化成型复合材料结构固化过程的分析模型及其相应的三维有限元模拟方法,考虑了固化过程中树脂基体固化收缩以及升降温阶段热变形导致的残余应力,分析固化阶段以及固化后降温阶段构件残余应力的发展。预报结果与构件固化温度发展历程及固化翘曲变形量的实验测量结果基本吻合,从而验证了固化过程三维有限元模拟方法的有效性。热压罐整体化成型工艺中,金属模具与复合材料构件之间的热不匹配、柔性模具的使用、框架式模具变形及温度分布是影响构件固化变形的重要的模具因素,是目前解决构件固化变形问题的难点。本文使用光纤光栅监测了固化过程中单向板不同厚度位置的应力发展,得到了单向板沿厚度方向的应力梯度,据此分析了模具与构件之间热不匹配导致的相互作用。引入剪切层模型模拟分析了由模具与构件之间热不匹配导致的构件固化变形,并建立了剪切层参数与构件尺寸及固化压力之间的关联模型,通过层板固化变形的模拟结果与实验结果的对比验证了剪切层模型的有效性。整体化成型工艺中柔性模具传递到构件表面不均匀的压力会影响构件的固化变形,同时柔性模具的使用还会影响到构件固化温度场的分布。本文根据柔性模具传压特性的实验研究和模拟分析结果,得到了由L型橡胶柔性模具传递到构件表面不均匀的压力分布。将柔性模具传递的不均匀压力作为残余应力及变形分析模块的边界条件,而在热化学分析模块中同时模拟柔性模具与复合材料构件整体的固化温度场。通过算例分析发现柔性模具的使用增大了L型构件的固化变形。框架式模具在工艺过程中的变形及温度分布同样是影响整体化成型构件固化变形的重要的模具因素之一,本文模拟分析了固化过程中的模具变形场及温度分布,并进行了实验验证。研究了平板型框架式模具变形随模具结构参数的变化规律。将模拟得到的模具型面的变形情况及温度分布作为构件固化残余应力及变形分析的边界条件。通过算例分析发现固化过程中框架式模具变形及型面温度的不均匀分布导致单向板出现了翘曲变形。分析了共固化和胶接共固化工艺下碳纤维/双马5428整体化成型T型加筋壁板结构的固化温度场及固化变形,其中考虑了包括金属模具与复合材料构件之间的热不匹配、柔性模具的使用、框架式模具变形及温度分布在内的模具因素的影响。模拟结果表明金属模具与复合材料之间的热不匹配对T型加筋壁板的固化变形影响最大,框架式模具温度及变形次之,而柔性模具的影响作用较小。胶接共固化工艺下T型加筋壁板的温度场分布比共固化工艺下的温度场分布均匀,同时胶接共固化时T型加筋壁板的固化变形量也小于共固化时的固化变形量。最后本文从成型工艺选择和模具设计的角度提出了减小T型加筋壁板固化变形的四个控制因素,得到了各自的影响规律,为变形控制提供指导和依据。更多还原

【Abstract】 Integrated process is an important technique of cure process for composites to reduce parts and fasteners and meet the needs of structure performance. Fabrication cost can be reduced in integrated process. Cure-induced deformation is key problem to improve process quality of large-scale and complex structural composite integrated structure. For reducing cure-induced deformation, conventional method is that adjust and correct the skin of mold and cure system again and again according as experiences and process tests. But the conventional method increases fabricate cost. So it is important to guarantee a product and reduce fabrication cost that the method of analyzing and predicting deformation is developed for integrated composite structure.In this paper, analysis models and three-dimensional finite element method (FEM) for cure process of composite integrated structure were developed. Thermal deformation and cure shrink were considered in analysis models and the evolution of residual stresses in the entire cure process was studied. Numerical predictions compared quite well with experimental measurements for the development of cure temperature and cure-induced deformations.During autoclave integrated process, the mismatch between coefficients of thermal expansion of metal mold and composite part, flexible auxiliary mold, temperature distribution and deformation of framed-mold are important mold influencing factors for cure-induced deformation of composite structures. In this paper, fiber Bragg grating sensor was used to monitor residual stresses development in the unidirectional laminate. According as stress gradient in the direction of thickness obtained by experimental measurement mold/part interaction was studied. Shear-layer model was introduced and an associated model between shear-layer parameters, the dimension and cure pressure of composite structure was developed. Simulated results for laminate by shear-layer model could accurately predict cure-induced deformation compared with experimental measurements. Non-uniform pressure distribution on the surface of part transferred by flexible mold will influence cure-induced deformation, and flexible mold also has an effect on cure temperature distribution of composite part. In this paper, the performance of transferring cure pressure of flexible mold was studied with experiment and simulation. Non-uniform pressure distribution transferred by L-Shape flexible mold was obtained. The pressure from flexible mold on the part was as boundary condition to predict residual stresses and cure-induced deformation. And in thermal-chemistry model cure temperature of flexible mold and composite part are simulated together. Then cure-induced deformation of L-shape part was predicted and using flexible mold increased deformation. Framed-mold deformation and temperature distribution are important factors of cure-induced deformation for integrated structures. In this paper, framed-mold deformation and temperature distribution was obtained with FEM and numerical predictions compared quite well with experimental measurements. Structural parameters of flat-plate framed-mold have an effect on framed-mold deformation and the regularity was studied. Then deformation and temperature distribution of framed-mold were as boundary condition of cure-induced deformation simulation. Cure-induced deformation of unidirectional laminate induced by framed-mold was obtained.In this paper, cure temperature and cure-induced deformation for Carbon/BMI5428 T-Shape stiffened panel were investigated with considering mold factors during co-curing process and glue joint co-curing process. The results showed that tool/part interaction was the major mold factor to induce deformation for T-Shape stiffened panel, framed-mold temperature distribution and deformation was the secondary mold factor, and flexible mold was the third mold factor. And cure temperature distribution in glue joint co-curing was more uniform than in the co-curing. Cure-induced deformation in glue joint co-curing was less than in the co-curing.Lastly, in this paper, four control factors were presented to reduce cure-induced deformation by selecting processes and mold design. And the regularities of four factors were obtained to direct deformation control.更多还原