Study On Trajectory Planning And Layup Suitability Of Carbon Fiber Prepreg For Automated Placement

ACM (Advanced Composites Material) has a lot of advantages compared to the traditional material, such as light weight, high specific strength and modulus, function and structure integration, design and manufacture integration, easy forming as large component, and now is playing a very important role in aerospace industry. As the dominant material of 21st century, ACM has been widely adopted in various types of civil aircraft, military aircraft, and its amount has become one of the important indicators of advanced aerospace vehicle. High cost of composite material is still a major obstacle to the large application of composite material in aircraft structure. A survey reveals more than 70% of the cost of composite components comes form manufacturing process. Thus, reducing the manufacturing cost of composite components is still the key problem to be tackled in the development of composite material. ATP (Automated tape placement) is an important way to deal with this problem, and is gaining more and more attention in fabrication of aerospace high performance composite structures.Currently, a few large aircraft manufacturers have introduced the automated tape laying machine. However, due to the blockade in western countries, automated tape placement technology has become one of the bottlenecks restricting the application of a large number of composite materials for aerospace vehicle in china. Thus, it is urgent to study this technology intensively. This paper researches on the path planning and placement suitability in ATP, and aims to ensure the product quality and placement efficiency.The influence of layup path on the distortion of composite tape is investigated in order to reveal the optimal layup path. With the assumptions for ideal mapping and by applying some principles and theorems of differential geometry, the mapping rule of prepreg on the mold surface is obtained. Based on this mapping rule, a mathematical model which characterizes the relationship between distortion and layup path is established. Moreover, the optimal layup path under the constraint condition of minimum distortion is acquired. Another mathematical model reflects the relationship between distortion and wrinkling is proposed, and we examine this model on three types of non-developable mold surfaces. A group of placement criteria is built to find out the adequate width of prepreg for a specific placement process. The criteria take care of the placement quality and the placement efficiency at the same time, and are verified by an engineering case.The relationship between adjacent composite tapes is examined, and a mathematical model of gap is established. We compare the geodesic strategy and the parallel strategy, and find out that the superiority of the former strategy is controlling the distortion while the other one is controlling the gap. A modified geodesic strategy is addressed so as to control the gap between adjacent composite tapes, and we study on this strategy in Matlab.A geometric method for computation of geodesic on smooth surface is presented. The geometric method is based on a simple theory that the principle normal of a geodesic is parallel to the normal of the underlying surface. The advantage of this method is simple and efficient. Meanwhile, we do not need to solve the geodesic equations which are quite complex. Through derivation process, the calculation error of this algorithm is obtained. Based on this, a step adjustment strategy is proposed. The presented geometric method is compared with Beck's method and Ravi Kumar's discrete method on accuracy and efficiency. Experimental results indicate that our method is accurate and efficient on surfaces which are relative flat, so it is well suitable for the ATP. In this process, the composite tapes generally follow geodesic path on a mould surface which is nearly flat or nearly conventional cylindrical.The bonding mechanism of ply is analyzed and and the bonding process is modeled as squeezing flow of resin patch under parallel plate. It is pointed that when the viscosity of resin is constant, the bonding capability will become stronger when infiltration effect of the interface becomes better. The calculation formula of the infiltration effect is deduced by using fluid mechanics theory. Influence of main processing parameters (layup pressure, layup velocity, mould temperature, etc) on infiltration effect and bonding capability is analyzed. The peel force is used to quantify the bonding capability of the ply. A series of experiments are carried out on the automated tape laying platform. It is shown that the bonding capability will become weaker as the layup velocity increases and become stronger as the layup pressure increases. This law conforms to the calculation formula of the infiltration effect.The layup suitability of 5228/T700 prepreg for ATP is examined. A mathematical model for the drape of carbon fiber prepreg is established. The influence of processing parameters (layup pressure, layup velocity, temperature, etc) on the layup suitability of this type of prepreg is obtained through a series of tack and drape test.This dissertation researches on the trajectory planning and layup suitability of carbon fiber prepreg for automated placement. The formed key technologies (placement suitability criteria, modified geodesic strategy, etc) will help to ensure the placement quality and improve the placement efficiency, and can be extended to the dual-phase directly.