A Study of Friction in Composite Materials Forming

复合材料行业正在迅速发展，以满足通过减轻重量来节约能源和减少排放的需求-特别是在汽车和航空航天等运输部门。许多复合材料零件是使用成形工艺生产的（特别是那些具有不规则形状的零件）。在这些过程中，最终部件必须符合设计规格，并且没有褶皱、空隙和不必要的厚度变化。然而，目前确保成功的唯一方法是提前进行昂贵的试错式测试。由于零件的几何形状可能会定期变化，因此成形行业希望拥有一种预测工具，可以预测结果，从而可以用于最佳地设置工艺以生产所需零件。任何预测模型的一个关键工作是预测形成力。在成形过程中起作用的重要力之一是摩擦力。为了正确预测成型过程中的摩擦力，必须对摩擦行为有一个基本的物理理解，并且必须对使用相关织物和树脂类型的摩擦响应进行表征。以前已经进行了一些摩擦测试，但这些测试通常是理想化的或在不具有代表性的小接触面积上进行的。该项目将设计实验，在各种边界条件下对不同的织物和树脂系统进行有代表性的摩擦力测量。将建立一个数据库的结果，给出摩擦响应的变化，在各种变量影响摩擦，如树脂类型，织物类型，温度，法向载荷和剪切速率等工具层和非工具层摩擦将进行调查。然后，将开发基于实验数据库的ABAQUS用户子程序，以模拟接触行为。然后，将这种成形过程中摩擦的预测能力添加到我们小组目前可用的成形模型中，以改善其成形预测。最后，该模型将通过比较预测与测试结果的一些案例研究类型形成的例子。该项目将产生成形中摩擦的有价值的物理描述，相关结果的数据库和可添加到现有模型中以提高其准确性的预测子程序。其结果将是朝着精确预测成形模型方向迈出的重要一步，该模型有可能大幅降低成本并优化产品。该项目的最后一个方面将是寻找可行的方法来减少成型过程中的摩擦。

The composite materials industry is rapidly growing in response to the need to conserve energy and reduce emissions by reducing weight - particularly in transport sectors such as automotive and aerospace. Many composite parts are produced using a forming process (especially those with irregular shapes). In such processes, it is essential that the final component meets the design specifications and is free from wrinkles, voids and unwanted thickness variations. At present, however, the only way to ensure success is to carry out costly trial and error type testing in advance. Since the component geometries can change on a regular basis, the forming industry would like to have a predictive tool which can predict outcomes and can therefore be used to set up the process optimally to produce the required part. A crucial job of any predictive model is to predict the forming forces. One of the important forces acting during the forming process is friction. To correctly predict friction forces in forming, an underlying physical understanding of the frictional behaviour must be developed and the frictional response using relevant fabric and resin types must be characterised. Some friction tests have been carried out previously, but these have often been idealised or on small contact areas which are not representative. This project will design experiments to give representative friction force measurements for different fabric and resin systems under a wide range of boundary conditions. A database of results will be established giving the friction response to changes in the various variables affecting friction such as resin type, fabric type, temperature, normal load and shear rate etc. Both tool-ply and ply-ply friction will be investigated. An ABAQUS user subroutine based on the experimental database will then be developed to model the contact behaviour. This predictive capability for friction in the forming process will then be added to presently available forming models within our group to improve their forming predictions. Finally, the model will be validated by comparing predictions with test results for some case-study type forming examples. The project will produce a valuable physical description of friction in forming, a database of relevant results and a predictive subroutine which can be added to existing models to increase their accuracy. The result will be a significant step in the direction of accurate predictive forming models which have the potential to reduce costs considerably and to optimise products. A final aspect of the project will be to look at viable approaches to reducing friction during the forming process.