Composights Blog

Thermoplastic Composites Taking-off into a Clearer Future

Composites have had an incredible story from being just 4% in 1970s to having more than 50% share in aircraft structural weight now. Known for its demanding requirements, the aerospace industry has driven significant advancements in material science. In recent years, the spotlight has turned to thermoplastic composites (TPCs). During 2024-2030, the A&D industry is projected to generate a cumulative demand of ~27 million lbs. for thermoplastic composites.

In early 2024, production of the world’s largest thermoplastic composite aircraft fuselage segment was successfully completed by welding two 8-meter-long CFRP (Carbon fiber reinforced plastics) half-shelf. This feat was achieved under the aegis of EU-funded Clean Sky 2/Clean Aviation project ‘Large Passenger Aircraft’ (LPA) by the Fraunhofer- Gesellschaft in Stade, Germany, together with international project partners, which joined together a true-to-scale upper and lower shell of the ‘Multi-Functional Fuselage Demonstrator’ (‘MFFD’) using automated positioning and joining processes.The almost rivet-less structure and the automated pre-integration resulted in 10% savings on each, weight, and cost.Another interesting EU-funded project is the DOMMINIO project (Digital Method for Improved Manufacturing of Next-generation MultIfuNctIOnal airframe parts) which aims to demonstrate technologies enabling multifunctional, intelligent airframe parts that would also have benefits in repair and recycling at the end of life (EOL). The project bets on thermoplastic composites using Toray Advanced Composites TC 1225 unidirectional (UD) tape comprising carbon fiber and LM PAEK polymer by Victrex.There are more such projects where prominent companies in the aerospace and composites industries have joined forces to promote thermoplastic composites and bring them into the mainstream.Known for its demanding requirements, the aerospace industry has driven significant advancements in material science. In recent years, the spotlight has turned to thermoplastic composites (TPCs), a material class that has the potential to revolutionize the way we approach aircraft system design. The Impressive Story of Composites in Aerospace & Defense (A&D)Composites have had an incredible story from being just 4% in 1970s to having more than 50% share in structural weight now. From A300 to A350XWB for Airbus, and from 757/767 to 787 for Boeing, the composites usage has taken a big leap, now accounting for 53% of the material mix of A350XWB and 50% of 787. (Check Figure.1. for composites usage trends in different aircraft programs)The usage of composites in aircraft, however, can be traced back to the World War I & II eras with notable examples like ‘the flying boat’ and ‘the Mistel (mistletoe)’. However, specific details on the type and quantity of composites used in these aircraft are limited.It was also noted that Glass fiber reinforced plastic (GFRP) was the composite structural material used in a wide range of aircraft and missile applications between the 1940s and 1960s. According to the Defense Technical Information Center (DTIC), the A-1E was the first production aircraft to incorporate composite GFRP. Grumman Aircraft produced fiberglass vertical tail structures for this military aircraft. This occurred during the mid-1960s when another breakthrough - ‘Boron fiber reinforcement’ was introduced to the A & D industry.During the 1970s, metals like aluminum, steel, and titanium dominated the aerospace manufacturing industry, comprising ~70% of the average aircraft’s structure. In contrast, the share of composites was infinitesimal, accounting for just 4% of materials used in aircraft manufacturing.The benefits of composites were numerous, and impressive, but there wasn’t any rush in adapting composites in this industry. Gradually, after a lot of research and analyzing the long-term benefits of composites, the industry embarked upon the usage of composite materials.In the early 2000s, the Boeing 787 Dreamliner broke new ground as the world’s first major commercial airliner to feature a primary airframe constructed from composite material. The aircraft is notable for its extensive use of composite materials, comprising ~80% of its volume and 50% (that is approximately 32,000 kgs of carbon fiber reinforced composite) of its total weight. Each Boeing 787 aircraft then used composites for wings, tails, doors, fuselage, and interior.Not just Boeing, but other aviation giants like Bombardier, BAE systems, Raytheon, Lockheed Martin, and GE Aviation gradually jumped on the bandwagon of using composites in their aircraft. Figure1: Composites Usage Penetration Trend in Different Aircraft Programs  Evolution of Thermoplastic CompositesThroughout this transition, thermoset composites and autoclave processing have been the predominant choices for manufacturing aircraft components. Since the outset of this century, out of autoclave (OOA) processing techniques have begun attracting interest owing to the possibilities of faster production and lower fabrication costs, which is the industry’s priority. Owing to their properties, the surge in interest in OOA paved the way for the adoption of new materials - thermoplastic composites - which are well-suited to these processing methods.Applications of thermoplastic composites date back to the US military’s F-22 jet fighter’s landing-gear and weapons-bay doors in the 1980s, and the outer wing trailing edge skin panel or shroud for the Fokker 50 passenger aircraft in the 1990s. (Check the evolution of TPCs in Figure.2.)Figure 2: Evolution of TPCsToday, most of the modern aircraft feature thermoplastic composites in several applications, such as clips, cleats, fixed-wing leading edges, J-nose leading edges, panels for fuselage, profiles & brackets, ribs & angle brackets, control surface parts, seat backs, window panels, and cockpit floor.Clips and cleats are considered to be the largest applications of thermoplastic composites in the industry and are made from carbon fibers with either PPS or PEEK resins. There are about 8,000 clips and cleats used in each A350XWB and about 10,000-15,000 clips and cleats in a B787 aircraft.  Figure 3: Key Applications of Thermoplastic Composites in an Aircraft  Thermoplastics Vs ThermosetsCurrently, thermoset composites dominate the A&D composites market; however, thermoplastic composites are successful in marking their presence in the structural sections of an aircraft by replacing both thermoset composites as well as traditional metals.Unlike their thermoset counterparts, thermoplastics are capable of being reheated and reshaped repeatedly without losing their structural integrity. Known as thermoplasticity, this unique property enhances thermoplastic composites’ recyclability.Here’s a quick rundown of the differences between ‘thermosets’ and ‘thermoplastics’ - Properties Thermosets Thermoplastics Viscosity Low High Chemical Resistance High Moderate Toughness Moderate High Age (Shelf life) Moderate Infinite Reusability (Thermoformable) Low High Cost Medium High Melting Point High Low Molecular Weight High Low Overall Cost Savings Low High Table 1: Property Comparison of Thermosets & Thermoplastics Owing to their many benefits, thermoplastic composite materials in the A&D industry are witnessing an illustrious journey. Valued at US$ 330 million in 2023, the global aerospace thermoplastic composites industry is expected to reach US$ 870 million in 2030, growing at a skyrocketing annual growth of >14%.It is important to note that the above figure represents only a fraction of the overall composite usage in the A&D industry. Despite the impressive growth, thermoplastic composites (TPCs) still account for merely 2% of total composites usage in the A&D industry which is around 34.5 million pounds.Once considered unsafe for even structural components, TPCs are now being applied to critical control surfaces too. Figure 4: Thermoplastic Composites Contribution in the A&D Composites Market in 2023 (Volume)