CW Blog

Qualification of composite materials — particularly prepregs for aerospace applications — traditionally has been so time-consuming and expensive that its funding usually comes from one of the aerospace primes (Boeing or Airbus) or an independent laboratory, such as the National Institute for Aviation Research (NIAR) at Wichita State University (Wichita, Kan., U.S.).

When a prime funds a material qualification, allowables are usually developed for a specific application, but this can restrict or hinder the utility of the data beyond the application for which it was developed. A lab, such as NIAR, using the NCAMP process, can build an approved test plan followed by the appropriate specifications and test reports to deliver material allowables that are useful and helpful to the aviation industry. However, lacking infinite resources, NIAR cannot qualify every prepreg brought to market. This causes the industry to pick and choose the most significant material systems for NCAMP inclusion, though these may not always cover all needs of the aviation industry partners, which range from large OEMs to smaller suppliers.

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SAMPE 2019: The highlights

 

SAMPE 2019 was held in Charlotte, N.C., U.S., which represented the event’s first foray to that city. CompositesWorld was there and offers this summary of highlights from the show and conference.

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When resin transfer molding (RTM) began transitioning into high-pressure RTM (HP-RTM) roughly a decade ago, it was mostly lauded for automotive applications, reducing composite part cycle times from hours to less than 2 minutes. Less has been said about applying this technology to aerospace parts. The aircraft industry has a long history with conventional RTM, including its use to produce thousands of carbon fiber-reinforced plastic (CFRP) fan blades and containment cases for commercial aircraft engines. Airbus has even prototyped a 7-meter-long, one-piece composite multispar flap for the Airbus A320 using RTM. But is it possible to transition this experience with hours-long processes into fully automated molding of composite aircraft parts in minutes? Several key players say it is possible.

Traditional RTM, referred to here as LP-RTM for clarity, typically uses injection pressures of 10-20 bars. HP-RTM, on the other hand, uses injection pressures of 30-120 bars. 

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When Boeing and Airbus decided 15 years ago to fabricate major structures of, respectively, the 787 and A350 twin-aisle aircraft from carbon fiber composites, myriad choices were made by both companies about resin type, fiber format and manufacturing process. Much of this decision-making was driven by material trade studies, technologies available at the time, material and capital equipment costs, and internal and supplier manufacturing capacity, as well as the expected build rate of the aircraft.

When it came to wing structures — wing box, spars, ribs and skins — the decision was a simple one, at least compared to decisions regarding fuselage structure fabrication. The long, moderately contoured surfaces of wing structures were a good fit for automated tape laying (ATL) and automated fiber placement (AFP). These systems are adept at accurately and consistently laying large amounts of prepreg over large areas quickly. And, the fact that the epoxy resin matrix used in these prepregs required curing in very large autoclaves was just part of the state of the art at the time — the cost of the process. Further, the autoclave has a long history of very effectively consolidating composite laminates and achieving the critical sub-1 percent porosity levels that the aerospace industry demands.

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With 7,000 employees worldwide and 2018 revenues of €2.2 billion, STELIA Aerospace (Toulouse, France) plainly states its primary products and industry position: No. 1 in Europe/No. 3 in the world for aerostructures, No. 1 worldwide for pilot and crew seats and No. 3 worldwide for first- and business-class passenger seats.

STELIA Aerospace’s use of composites extends to Airbus A350 forward fuselage sections, wings for ATR turboprop aircraft, various helicopter structures and in some seat products, including its newest OPAL seat. Composites production facilities include French sites Méaulte (large fuselage sections) and Salaunes (smaller composite parts), detailed parts and assembly in Morocco and Tunisia and a wide range of composite parts for aircraft, defense and space at the previous Composites Atlantic site in Lunenburg, Nova Scotia, Canada.

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