Robust Integration of Electronics into Lightweight Structures
Continuous Fiber-Reinforced Moldings with Electronic Functions
In a research project named Temag, scientists of TU University Dresden, Germany, developed a process to produce continuous fiber-reinforced injection molded components with integrated electronic functional elements. The new process is said to provide for unprecedented robust and inexpensive integration of electronic functions into lightweight structures.
By using injection molding processes, operators are able to produce lightweight structures with a complex geometry, at an affordable price. Reinforcing these structures with continuous fibers will enhance their mechanical properties. Integrated sensors, LEDs, plug contacts or other functional elements further extend the range of properties for these components. However, to position functional elements and their cables necessary for signal or energy transmission, as well as plug contacts, inside the injection mold is a severe challenge because of the high pressure and temperature prevailing during injection molding.
Within the framework of the Temag research project to investigate thermoplastic continuous fiber-reinforced multi-axial grid structures, scientists of the Institute of Lightweight Engineering and Polymer Technology (ILK) and of the Institute of Textile Machinery and High Performance Material Technology (ITM) at TU Dresden worked together. They developed a new production process for continuous fiber-reinforced injection molded components with integrated electronic functional elements. The Dresden scientists say that they used a novel type of approach: they applied textile high-performance grids to mechanically reinforce the moldings, enhancing the grids to make them serviceable as carriers for the electronic components.
Textile High-Performance Grids as Carriers of Electronic Components
Hybrid yarns of glass and thermoplastic material serve as starting materials for the high-performance grids. They were designed by ITM scientist according to the requirements, and produced on a warp knitting machine with a yarn manipulation unit. During production, the scientists added the wires required for energy and signal transmission. The semi-finished product was thermally consolidated in a previous step, followed by conditioning and forming – corresponding to the geometry of the final component.
The scientists designed functional elements they placed on the carriers in a way to make sure they withstand process conditions during injection molding and can be connected to the wires inside the high-performance grid. For this particular purpose they developed a special supersonic welding technique.
The new joining technique is said to be very robust, enabling even wires that are covered inside the roving of the grid to be connected safely and with low transition resistance. In addition, spacers and locators were placed on the grid in a generative process, in order to determine the later position in the injection mold cavity.
The partners to the project use a trunk lid as an example to demonstrate the production process developed. The component’s grid reinforcement was designed to withstand applied loads. It was also equipped with a touch sensor that serves to open the trunk lid with its signal. Moreover, a brake light was integrated.