Project: Laser transmission welding of thermoplastic composite structures

Endless carbon and glass fiber reinforced composite structures (CFRP, GFRP) are recognized as having the greatest lightweight construction potential of all materials. Hence, CFRP and GFRP are representing significant materials for all branches of the industry where large masses have to be moved or weight has to be saved. Besides the field of mobility, including the aircraft, the automotive, the marine and the railway sector, the need of components based on fiber reinforced composites is particularly increasing within the field of energy, e.g. wind turbines, heavy-duty pipeline elements for off-shore applications and electronics, as well as within the field of sports and leisure._x000D_In particular CFRP is characterized by high stiffness and strength, excellent corrosion resistance as well as high static and dynamic loading. An outstanding property of CFRP can be found within the potential of significant weight reduction compared to metallic materials, e.g. up to 30% for aluminium [CFK09]. Thus, in order to contribute significantly to energy and CO2 savings by use of intelligent light weight constructions within the mobility sector as well as to supply optimized manufacturing processes, the use of CFRP will play an increasing role._x000D_Although thermoset polymers COly based on epoxy resins are representing the predominant kind of CFRP matrix materials, reinforced composites on the basis of thermoplastic polymers (TPC) are of rising interest due to their superior producibility and formability. The potential of TPC parts inside the forming process is the ability of in-situ consolidation in just one process step. Thermoplastics offer several benefits such as uncritical and unlimited storage time, a better impact tolerance compared to thermoset matrices, a good ultimate strain performance, reduced crack propagation, excellent chemical resistance and quick forming process availability. They are recyclable and customized laminates and matrices are available within a wide range. The most significant advantage over thermoset based composites is their weldability. _x000D_A today‘s barrier for a comprehensive dissemination of TPC structures is the lack of economic, quick and reliable component manufacture processes. To overcome this deficit, fully-automated process chains for the manufacturing and assembly of thermoplastic composites have to be developed in order to achieve production rates and cycle times required by automotive and aircraft industry as well as the civil engineering sector [PUR07, PET08]. Integrated process cells can be adapted to specific material requirements and to new process elements including laser based techniques for cutting and in particular joining applications [HER08, JAE09]. Today, different techniques like resistance welding, ultrasonic welding, vibration welding or induction welding are used, revealing respective advantages and disadvantages [OFF06, KEL04]. _x000D_It is the aim of this project to develop a novel joining technique for TPC parts based on the laser transmission welding technology (LTW). Today, LTW is an industrially established welding technique for unreinforced and partially reinforced thermoplastics [KAG03, MCG07, CHE02], offering the possibility of flexible, controllable and contact-free processing with a high automation potential._x000D_Within the frame of the project this technology shall be transferred to the specific requirements of TPC materials. Besides the manufacturing of pure TPC components, combinations of reinforced and unreinforced or partially reinforced materials are of interest._x000D_In order to achieve these goals, a project working plan has been arranged consisting of the following CO activities:_x000D_- Development of adapted TPC base materials and manufacturing of real components_x000D_- Development of laser welding process for TPC materials and welding of real parts_x000D_- Testing of novel TPC structures and real parts according to industrial specifications_x000D_- Exploitation of project results._x000D_Correspondingly, a powerful consortium has been composed, covering all subject areas to be essential for the fulfilment of these objectives. The consortium comprises five R&D-performing SMEs, all operating within the field of thermoplastic composites, working on the manufacturing of TPC base materials for specific applications, injection moulding, forming of TPC components, induction welding and testing of composites. The SMEs are supported by one large company, representing the global market leader in manufacturing of TPC materials as well as two non-university research institutes, specialized within the fields of fiber technology and laser technology._x000D_Besides the aerospace sector, the products and services of the SMEs are established on further markets, e.g. wind turbines, pipelines and electronics. The availability of this new welding technique will represent a unique feature, which will strengthen the position of the SMEs and open new markets, e.g. automotive, shipbuilding and sports & leisure._x000D_

Acronym	LaWocs (Reference Number: 5252)
Duration	01/12/2010 - 30/11/2013
Project Topic	A novel joining technique for thermoplastic composites will be established. The development of optimized material properties in conjunction with adapted laser transmission welding strategies will facilitate enhanced manufacturing processes for todays most sought lightweight construction material
Project Results (after finalisation)	Within the project LaWocs, DEVA adapted and enhanced thermoplastics as well as the injection molding processes, with the goal of optimizing the laser weldabiltiy of the parts in their portfolio. Therefore, the basic weldability of their materials were determined. Based on the first welding results, the matrix materials were selected for the components produced by DEVA. These materials were unreinforced or contained short glass fiber reinforcements as well as short carbon fibers. For all of the injection molded demonstrator parts, suitable molding parameters were determined. Furthermore, DEVA developed a new molding process to generate parts with new optical characteristics, especially for the laser wavelength. For example, in this process DEVA used additives to make the matrix black for the human eye but transparent for the laser wavelength. For these studies, different additives were tested from various manufacturers. Since suitable injection molding parameters for the additive masterbatches were not yet available, the parameters had to be determined first. These parameters were varied in order to determine optimal processing conditions as previously described. This allows DEVA to respond to their customer’s needs. In addition, the close cooperation with the project Ps has provided in-depth insights into the areas of material testing, the use of fiber composites and different joining methods. This newly acquired knowledge will enable DEVA to respond quickly and flexibly to future requirements in use of injection molding components in fiber composites DEVA.
Network	Eurostars
Call	Eurostars Cut-Off 3

Project partner

Number	Name	Role	Country
8	DEVA Kunststoff-Technik GmbH	Partner	Germany
8	EPL Composite Solutions Ltd	Partner	United Kingdom
8	Faserinstitut Bremen e.V. (FIBRE)	Partner	Germany
8	Kok & Van Engelen Composite Structures BV	Partner	Netherlands
8	Laser Zentrum Hannover e. V.	Partner	Germany
8	Materials Engineering Research Laboratory Ltd	Coordinator	United Kingdom
8	TEN CATE ADVANCED COMPOSITES BV	Partner	Netherlands
8	Tods Aerospace Limited	Partner	United Kingdom