摘要
复合材料构件的装配是整个复合材料产品生产制造过程中的重要环节,而装配尺寸质量是反映装配过程甚至复合材料产品整体生产水平的关键要素。特别是对航空航天用复合材料产品,装配尺寸精度将直接影响到产品的外观及气动特性。因此,分析并预测产品的装配偏差,对提高复合材料产品的装配精度具有重要意义。
目前,复合材料产品的装配工艺和装配制造仍然采用与传统金属结构装配相同的方法,其装配质量还有待提高。另外,复合材料构件的偏差对装配偏差有显著影响,建立构件偏差与装配体偏差之间的关系非常重要。热固性树脂基复合材料构件在热压罐固化成型过程中产生的变形是造成其偏差的主要原因,现有的解决方法是在大量实验的基础上,对固化工艺进行反复调整和对模具型面进行反复试凑或修正完成的,由此导致了产品制造周期长、效率低、成本高的状况。
为此,本文围绕如何进行复合材料构件的装配偏差预测展开研究。采用有限元数值分析方法,研究复合材料构件在热压罐成型过程中的温度场分布,通过对复合材料构件变形的有限元仿真,建立典型复合材料构件的固化变形回归模型,在此基础上进行复合材料产品的装配偏差分析。本文的主要研究工作如下:
(1)热固性复合材料构件固化温度场的有限元模拟
研究复合材料构件固化成型过程中的传热规律,考虑模具型面、辅助封装材料等对复合材料构件内部温度场分布的影响;在一定固化工艺条件下,基于有限元分析方法,将固化动力学方程以内热源的方式加入到Fourier热传导控制方程中,根据不同固化状态下的材料模型建立复合材料构件固化成型过程中温度场分布的三维有限元模拟模型。最后通过ABAQUS软件及其用户子程序实现固化温度场模拟,为研究复合材料构件的变形预测提供依据。
(2)典型复合材料结构固化变形仿真及回归模型的建立
基于热变形的有限元分析理论和ABAQUS软件和由温度场模拟模型所获得节点瞬态温度数据,考虑了成型模具在热压罐成型过程中对复合材料构件固化变形的影响,实现了对复合材料构件固化成型过程的固化变形的有限元仿真。在此基础上建立了L型和C型两种典型复合材料结构的固化变形回归模型,研究了不同的几何和工艺参数对典型结构单元固化变形的影响规律。
(3)薄壁复合材料构件装配偏差分析
在复合材料典型结构偏差回归模型的基础上,通过基于坐标转换理论的结构树法分析和预测复合材料构件及部件的偏差,并通过复合材料构件和装配体的偏差分析实例验证了该方法的有效性。综上所述,本文薄壁复合材料构件的装配偏差分析包括三个关键技术——热固性复合材料构件固化温度场模拟、典型结构薄壁复合材料构件的固化变形分析和复合材料部件装配偏差分析。采用Abaqus及其子程序对复合材料典型结构的固化变形进行有限元仿真,根据复合材料典型结构固化内回弹变形的回归模型采用结构树法对复合材料部件装配偏差进行分析,为薄壁复合材料产品面向装配的尺寸设计提供的一种快速、有效的设计方法,也为产品的装配偏差控制提供了一种分析方法。
The assembly of composite components is a very important part of the manufacturing process for the composite production, and the dimensional quality of assembly is a key element to reflect the production level of the assembly process or even the composite products. Especially for aerospace composite products, assembly dimensional accuracy will directly affect the appearance and aerodynamic characteristics of the products. Therefore, control the assembly variation and improve the assembly accuracy is of great significane for the composite product.
Currently, the assembly of composite products usually adopt the traditional assembly methods of metal structures, which is not suitable for the anisotropic composite structures. For the composite structures, part variations have significant impact on the assembly variation, and it is important to establish their relationship. The cure-induced deformation is the main factor affecting the shape accuracy for the thermosetting resin matrix composite structures in the autoclave molding process. In engineering practices, the deformation is usually eliminated by optimizing the cure parameters and modifying the mold surface in an expensive trial-and-error effort based on a large number of experiments, which will inevitably lower the production efficiency, improve the manufacturing cost.
To this end, this paper carried out systematic research on how to analysis and forecast the assembly variation of the composite produts. On the basis of the Finite Element Analysis method, this thesis focuses on the simulation of the temperature field distribution of the composite component during the curing process, the prediction of the cure-induced dimensional deformation and developing a regression-based dimension variation model for the typical composite strutures such as L-shaped and C-shaped components, aiming to conduct the assembly variation analysis and optimization for composite products.The following are the main researching work in this paper.
(1) the FEM simulation of the temperature field distribution of the thermosetting resin matrix composite
Based on analyzing the heat transfer route and rule of composite components in the curing process, the cure kinetics equation is introduced into the Fourier’s heat conductive governing equation through the internal heat generation pattern, and according to the composite material properties in different curing conditions, a three-dimensional finite element analysis model is developed for simulating the temperature field distribution of the composite component during the curing process. The curing temperature field of the composite components are simulated by ABAQUS and its user subroutines, which is the basis for prediction the deformation of composite components.
(2) the cure-induced deformation and a regression-based dimension variation model for the thermosetting resin matrix composite
Based on the research of the thermal deformation FEM model and the transient temperature data of the nodes obtained from the curing temperature field, the cure-induced deformations are implemented by ABAQUS and the regression-based dimension variation models are developed for the L-shaped and C-shaped typical compostie components.
(3) assembly variation analysis of thin-wall composite aerostructures
Based on the the regression-based dimension variation models of the typical compostie components, an approach called the structural tree method (STM) was developed to analysis the deformation of the components and assembly. The method is verified to be effective through an example of variation analysis for a composite assembly.
In summary, this paper presents solving solutions on three key technologies: the simulation of curing temperature field, the forecast of the cure-induced deformation and the assembly variation analysis for thin-wall composite components. The FEM simulation of the cure-induced deformation is conducted by using the Abaqus secondary development. The methods developed in this paper provide an effective tools for design for assembly (DFA) of composite products.
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