Daher now has the initial results of the “Carac TP” R&D project. The aim of the project is to identify and characterize those thermoplastic composites best suited to aerospace applications and compare them with thermoset materials.
Thermoplastics now play central role in aerospace engineering, and provide a key lever for creating lighter structures, and promoting recyclability, production process automation and component assembly. Although a large proportion of the industry recognizes this fact, the use of long fiber reinforced thermoplastics remains an area for further and more detailed research. That was the ambition of Daher when it initiated the Carac TP project in 2019.
“Our goal is to learn more about thermoplastic composite materials, their properties and their implementation,” explains Daher Composite R&D Project Manager Martin Denize. “The data generated by this project will give a clearer understanding of the process windows of these materials – by which I mean the temperature, pressure and time ranges acceptable within the production processes – and identify which are the most appropriate for each type of aircraft component: fuselage and wing, engine environment, interior components, exterior components, etc. We can also use the same data to build predictive models that will simplify our testing campaigns and provide rules for the process teams.”
Putting materials to the test
“We work with composite panels created using a range of different configurations prepared for each of the materials we’re studying,” explains Daher Composite Materials Expert and Materials Department Manager Stéphanie Patel. “The materials used are thermoplastic and thermoset composites, some of which have already been qualified by our aircraft manufacturer customers and used in their programs. Other materials included in the project are still under development with materials suppliers.”
The samples then underwent a series of tests to establish their fire resistance, environmental aging (exposure to ozone, UV, fluids, etc.), impact resistance, static mechanical strength and fatigue resistance characteristics (including tests above their glass transition temperature). The impact of production processes on material physical chemistry properties and performance is also studied. The results obtained for each material are then compared with those of a reference material supplied by Victrex. This material is being used because it offers the best processability window for all the fabrication modes targeted by Daher. Have agreed with Victrex that no reverse engineering of the material would be undertaken, the Carac TP project team was supplied with sufficient single batches of material for the entire project.
Tests on one of the reference thermoplastics are now virtually complete. And the remaining thermoplastic and thermoset materials to be tested are ready.
“The knowledge we gain from this project will give us the information we need to act as a specifier for our aircraft manufacturer customers, and provide proactive input to the process of recommending which thermoplastic and thermoset materials should be used for which application”, emphasizes Daher Mechanical Engineering Expert and Head of Structural Calculation Charles Naejus.
In parallel, Daher has begun work on a certification process for weld-assembled thermoplastic components using a process that eliminates the need for the metal fasteners (rivets, bolts, etc.) that add weight to the aircraft and make components more fragile. “This is a strategically important space within which industry players are currently in the process of developing their skills, and where Carac TP could well give us a head start,” concludes Martin Denize.
The Carac TP project is expected to run until the end of 2023.