Study of the influence of mould release agents and surface treatments on the welding properties of thermoplastic composites (Praktikumsbericht).

Kurzfassung

The aerospace industry is currently experiencing a growing demand for light, strong materials capable of meeting the performance and safety requirements of aeronautical structures. In this context, thermoplastic composites are emerging as the materials of choice, offering a unique combination of lightness, mechanical strength and ease of forming. Welding thermoplastic composites is thus becoming a major challenge in the manufacturing process for aeronautical components. Indeed, making aircraft lighter is a crucial objective for reducing fuel consumption and CO2 emissions. In this respect, the subject of welding becomes all the more crucial. This technology could eventually make it possible to eliminate fastening systems, which account for a significant proportion of aircraft weight. By replacing mechanical fasteners with welded joints, we not only reduce the weight of the structure, but also increase its mechanical strength and durability. The development of efficient welding techniques for thermoplastic composites is therefore of particular importance in the manufacture of light, strong structures, thereby contributing to the performance and energy efficiency of aircraft. This internship report presents an in-depth study of the welding process for thermoplastic composites, focusing on the different techniques used, the influencing parameters, as well as the challenges encountered in their application in the field of aeronautics. As part of this internship, we will be studying the impact of various parameters on the mechanical strength of the weld (more specifically resistance welding), in particular the release agents used during processing and the surface treatment. These parameters play a crucial role in the final weld quality of thermoplastic composites. For this study, three configurations of release agents will be used during processing: a film of Upilex alone, a film of Upilex with Mikon 205, and a film of Upilex with TakeOff. Two plates of each configuration will be made: one will receive a plasma surface treatment, while the other will not. This approach will enable us to assess the effect of these parameters on the quality and strength of thermoplastic composite welds in the aerospace industry. We will be focusing in particular on the mechanical strength of welds, by carrying out SLS-type tensile (Single Lap Shear) tests and analyses of welded joints using micro-cutting and ultrasonic inspection. In addition to these analyses, we will be carrying out surface energy analyses in order to seek a correlation between surface energy and the weldability of materials. These analyses will enable us to gain a better understanding of the impact of release agents and surface treatment onTitle: Version: 1.0 Page: 6 the quality of welds, and thus to optimise welding parameters in order to obtain high-quality, highperformance joints. This internship report will detail our methods, observations and conclusions on this subject, highlighting the implications of our results for the field of thermoplastic welding and suggesting avenues for future research in this area. This study will follow the following plan : Firstly, we will carry out a state-of-the-art review of the various techniques that we will be using during all our test phases, in particular vacuum consolidation, surface energy measurement, resistive welding and tensile tests. This state of the art will enable us to situate our work in relation to advances already made in the field of thermoplastic composite welding. We will then describe the methods used for each stage of this project and the different parameters used. We will detail our experimental protocols in order to guarantee the reproducibility of our results and ensure the reliability of our study. Following this, we will present the results and observations obtained during each of the tests and implementation stages. We will analyse the data obtained in detail, highlighting trends and correlations between the various parameters studied. Finally, we will present our analysis and the conclusion of our study, opening up potential followup and questions raised by this report. We will discuss the implications of our results for the field of thermoplastic welding in the aerospace industry and suggest avenues for future research.