Thermoplastic Composites, Future of Aviation

With the rapid development of the civil aviation industry—especially driven by novel manufacturing methods—the application of thermoplastic materials has achieved significant progress. Additive manufacturing (AM), commonly known as 3D printing technology, has opened up new application possibilities in the aerospace sector. Currently, multiple aerospace enterprises are testing and deploying 3D-printed thermoplastic components, fully leveraging the technology’s advantages of speed and precision. For example, Boeing has incorporated 3D-printed parts into its 737, 747, 777, and 787 Dreamliner aircraft series; specifically, the 787 program alone has generated $3 million in cost savings [2]. This technology is particularly suited to rapidly and accurately manufacturing parts with complex geometries. The Airbus A350 XWB aircraft utilizes over one thousand PEI-based 3D-printed components [3], paving the way for broader adoption of 3D printing in large commercial aircraft and future aviation programs—thanks to its speed, lightweight nature, durability, and high precision—gradually replacing conventional materials and manufacturing processes.

Moreover, several ongoing projects are dedicated to extending TPC technology to space applications. Multiple aerospace companies employ various thermoplastic processing techniques to manufacture both large and small rocket components. For instance, the German Aerospace Center (DLR), under the ATEK project [4], replaced aluminum-based primary structures with in-situ manufactured carbon-fiber-reinforced polyetheretherketone (CF-PEEK) composite materials for sounding rocket test components. This project aims to develop reusable and recyclable spacecraft components to reduce manufacturing costs. Relevant research is illustrated in the figure.

Figure: Rockets used in the ATEK program and original aluminum components replaced by CF-PEEK thermoplastic composites

Weldability is a significant advantage of thermoplastic composites and one of the main reasons for their increasing share in aerospace applications. By welding multiple individually manufactured components into a single integrated structure, the need for additional fastening materials is eliminated, thereby reducing weight and minimizing damage caused by assembly. In one study, an induction welding process was used to fabricate a CF-PPS thermoplastic composite demonstrator for the leading edge of the Airbus A330-200.

Figure: Thermoplastic Composite Fuselage Section

In the field of aviation, the polyaryletherketone (PAEK) family materials, including PEEK, PEKK, and LMPAEK, are the most widely used and versatile. For example, in the TAPAS2 project, GKN Fokker introduced the "Orthogonal Grid Joining Technology," achieving economically efficient manufacturing of thermoplastic composite fuselages.

Another key application involves using online ultrasonic spot welding to join CF/PEEK hinges, CF/PEKK clips, and CF/PEEK C-shaped frames into a demonstrator component, which is part of the “Clean Sky” eco-design project [9]. Research shows that different materials can be selected according to actual requirements and integrated into the same product.

PEKK is not only suitable for aerospace applications but also holds broad prospects for space structures. Lockheed Martin Space is developing next-generation 3D-printed thermoplastic components for NASA’s Orion spacecraft and conducting related R&D projects.

To improve production efficiency and aircraft manufacturing speed, the aerospace industry is continuously innovating aircraft structural design and manufacturing processes. Among these innovations, PEEK overmolding is a representative technology. For example, the PEEK lattice-reinforced demonstration panel shown in the figure combines compression molding with injection molding, integrating the high performance of continuous-fiber composites with the geometric stiffness of injection-molded lattices; the entire molding cycle takes less than two minutes, significantly reducing production time.

Figure: CF/PEEK grid reinforced demonstrator manufactured by encapsulation molding technology

LMPAEK was used as a uni-directional (UD) prepreg tape in the Clean Sky 2 large passenger aircraft demonstration project and was one of the first laminates manufactured in this 30-month project. LMPAEK was first introduced in the TAPAS1 project, and at the 2013 Paris Air Show, Airbus Nantes presented a fuselage panel with integrated stringers, which was made using CF/LMPAEK tape supplied by TenCate and had Omega and T-stringers welded to the skin using the Automated Fiber Placement (AFP) process. AFP, stamping, and welding processes are particularly suitable for processing LMPAEK, which performs excellently in automated production, such as Automated Tape Laying (ATL). Figure 11 shows a laminate manufactured using ATL and compression molding processes.

Polyphenylene sulfide (PPS) composites are widely used in the aerospace and defense industries, and are approved for use in circuit boards, sockets, connectors, electronic components, and anti-aircraft aircraft [15].

ABS is typically used as a lightweight alternative to traditional aerospace materials in applications where strength and high-temperature resistance are not critical. By modification or blending with other materials, ABS can also be used to manufacture critical components to achieve the desired performance. Due to their good chemical resistance and flame retardancy, ABS and its hybrid materials are often used in the interior of commercial aircraft cabins. In components where extremely high structural strength is not required but lightness, economy, durability, and ease of maintenance are desired, ABS is an ideal choice. For example, CF/ABS thermoplastic composite sandwich structures have been used to manufacture dual-tilt clamps for quadcopters, and tests have shown that their performance is superior to that of traditional monolithic structures [19].