In the aviation industry, a major market for carbon fibre reinforced plastics (CFRP), <40.000 drilling operations are performed throughout the assembly process of a small aircraft. Additionally, the drive to minimize costs and time are prevalent in the manufacturing process. The quality requirements in the aviation industry are set to a high level and drilling tools have to be changed frequently, causing considerable costs in terms of tooling and time losses. Laser processing offers benefits such as flexible, and wear free cutting, which contributes to the optimization of processing costs. In this investigation a laser machine, process control, processing strategies and handling equipment adapted to high precision macro drilling and low cycle times were presented. The setup included a novel short pulsed high power laser source by TRUMPF Laser GmbH emitting at λ = 1030 nm integrated in a 5-axis machine. The lab-state laser source provides pulses at tp = 20 ns, at a maximum pulse energy of Ep = 100 mJ and a maximum average power of Pavg = 1.5 kW, while maintaining a very good beam quality, allowing small focus diameters. Due to a large variety of parameters that have an influence on the process, a test plan based on design of experiments was applied to identify ideal parameter fields. Parameters optimized towards high ablation rates and orthogonal kerf angles were identified. The results revealed a promising industrial processing option for high quality macro boreholes.
An adequate use of finite resources is one of the greatest challenges of our times. To address this, lightweight concepts based on continuously fiber reinforced composites (FRC) are already being adapted for the transportation industry, especially within the automotive and the aerospace sectors. In order to broaden the use of lightweight composite structures and components, suitable processing, monitoring and control techniques are required for a variety of materials, constituting a prerequisite for economic, flexible and automated high volume production. In this regard, photonic technologies can provide valuable solutions. In this presentation, the latest developments within the field of FRC laser machining are summarized. For the processing of large structures such as resin transfer molding parts, combinations of galvo scanners with robots or axis systems are of particular interest. For this purpose, both high brightness cw fiber lasers and pulsed systems are used. Within the repair chain for valuable FRC parts, pulsed UV and NIR lasers are used for the precise removal of fiber layers in order to generate a defined scarfing. For both applications, disintegration of the fiber matrix interconnection due to thermal impact has to be avoided. Thermoplastic composites are becoming increasingly important for many industrial applications. In contrast to thermoset systems, welding techniques are particularly applicable. In this context, laser welding is not limited to the joining of transparent-absorbing-combinations, as it is required for conventional laser transmission welding processes but can be extended to the welding of structural parts consisting of high-performance carbon fiber reinforcements.
Due to their outstanding mechanical properties, in particular their high specific strength parallel to the carbon fibers, carbon fiber reinforced plastics (CFRP) have a high potential regarding resource-efficient lightweight construction. Consequently, these composite materials are increasingly finding application in important industrial branches such as aircraft, automotive and wind energy industry. However, the processing of these materials is highly demanding. On the one hand, mechanical processing methods such as milling or drilling are sometimes rather slow, and they are connected with notable tool wear. On the other hand, thermal processing methods are critical as the two components matrix and reinforcement have widely differing thermophysical properties, possibly leading to damages of the composite structure in terms of pores or delamination. An emerging innovative method for processing of CFRP materials is the laser technology. As principally thermal method, laser processing is connected with the release of potentially hazardous, gaseous and particulate substances. Detailed knowledge of these process emissions is the basis to ensure the protection of man and the environment, according to the existing legal regulations. This knowledge will help to realize adequate protective measures and thus strengthen the development of CFRP laser processing. In this work, selected measurement methods and results of the analysis of the exhaust air and the air at the workplace during different laser processes with CFRP materials are presented. The investigations have been performed in the course of different cooperative projects, funded by the German Federal Ministry of Education and Research (BMBF) in the course of the funding initiative “Photonic Processes and Tools for Resource-Efficient Lightweight Structures”.