The Federal Ministry of Education and Research of Germany provided project funding for HyBriLight. A group of 9 companies formed a business alliance, which was responsible for the development of innovative composite roof bows and verified the laser connection process Feasibility in new lightweight products. It is worth mentioning that all the basic information such as the dimensions and mechanical requirements of the demonstration products are based on the original parts of the BMW 7 Series models.
The top beam uses a fiber-reinforced plastic bar and two steel plates connected to it. Spot welding can be used to mount the component to the body. Instead of using traditional adhesives and riveting methods, the composite material and metal parts are replaced by innovative laser bonding methods. Therefore, metal connection plates need to be pre-treated with ultrafast lasers to create spongy surface topography.
This connection process is also used in the compression molding process of plastic strips. Molten polymer is first pressed into the resulting structural part, and after it is hardened, a strong and stable joint is formed, which mainly uses mechanical interlocking between the two materials. Composite material contacts based on laser technology can withstand shear stress of nearly 50 MPa. This connection process can only be achieved by special variable temperature thermoplastic technology, and the metal connection plate needs to be preheated. During process operation, integrated sensors are used for process control.
In order to save costs, the carbon fiber reinforced thermoset material in original parts is replaced with PA6 Matrix and long glass fiber reinforcement. In order to maintain the hardness and strength of this part, the top beam needs to be partially reinforced with carbon fiber UD tape. The production cycle of this type of compression molding process is about 75 seconds.
Then, using a new high-speed scanning system, the demonstration product was trimmed with a single mode fiber laser. In addition, multi-pass cutting can be used to cut multiple material mixtures in a single process to minimize heat input. This demo part successfully integrates a new laser machining process into the process chain。