Yibo Su, a PhD student at the University of Twente, has brought the development of lighter aircraft a step closer. He developed a strong joining method for lightweight structures with thermoplastic composites.
Thermoplastic composites are new, strong and above all lightweight, fuel-saving materials consisting of fibres and thermoplastics. It is increasingly used in the automotive and aircraft industries, among others. The latest aircraft types from Boeing and Airbus, for example, already consist of 50% of the weight of composite materials, a growing proportion of which is thermoplastic composite. But the application also faces challenges, especially when it comes to connections between different materials. Su's research focuses specifically on the connection between metals and thermoplastic composites, something that is certainly important for aviation.
Research
The university's website explains Su's research: "Thermoplastic composite parts are usually made by so-called prepreg. These are fibres already impregnated with a plastic, which are consolidated, reinforced, in a press or an autoclave. Su developed a way to place a metal insert already in the mould, and consolidate it along with the prepreg at the same time. This has not been done before and provides significant gains in production time and cost. The student investigated which mechanisms contribute to the insert adhering well to the thermoplastic composite and then which factors influence adhesion.
One of Su's sponsors for the research is the Thermoplastics Composites Recearch Centre (TPRC), a research centre in the field of thermoplastic composites. Among other things, Su used TPRC's state-of-the-art equipment to process and test thermoplastic composites. "Su's work fits the current trend of lightweight construction; the right material in the right place," said Wouter Grouve of TPRC. "In these multi-material solutions, the connection between different materials is crucial. This is currently the subject of quite a lot of research around the world, think for example of the gluing in the BMW i3 and i8. Su specifically looked at joining thermoplastic composites and metals. By having the joining take place during the processing process of the thermoplastic composite (called co-consolidation), you don't need to use a line. That gives an advantage in terms of costs and process times."
Scaling up production
According to Grouve, Su's research is a building block in the bigger picture of multi-material structures. "Thermoplastic composites play an important role in scaling up production. The processing time of these materials has the potential to be very low. This is because, unlike thermoset composites, no curing reaction is required. Thermoplastic composites can be heated, deformed and cooled again. This makes it possible to use press forming processes, for example, with cycle times on the order of minutes. This is very interesting for larger series. In addition, you can weld thermoplastic composites. This makes it possible to assemble parts quickly and relatively cheaply. With the required scale-up in mind, it seems necessary to make more and more parts from thermoplastic composites. In addition to these advantages, thermoplastic composites offer higher toughness than thermoset composites, allowing potentially lighter construction, and thermoplastic composites can be more easily recycled."
Follow-up research is still needed for a truly widely applicable technology. Grouve: "We still need a better understanding of the underlying physics. If we better understand which physical and chemical processes play a role, we can better match materials and pretreatment methods. Furthermore, technological developments are needed. For instance, how do you make thermoplastic composite parts with metal inserts? Which processes do you use for this and how do you ensure that these processes are robust. Questions that are essential before this technology can be used in structural parts."
By: Kelly Bakker
Photo source: Pixabay
