An alternative to thermoset aramid fiber-reinforced honeycomb composites for semi-structural aircraft interior parts was recently announced by Sabic Innovative Plastics.
Featuring the company’s Ultem polyetherimide (PEI) resin, new composite aerospace board (CAB) sheets were co-developed and manufactured with Crane & Co., a global leader in specialty paper. In a nutshell, the CAB sheets—an Ultem resin and glass fiber-reinforced composite panel—can be quickly thermoformed, are recyclable, and offer potential to be refurbished with a newly developed decorative film layer while still meeting FAA requirements to extend useful life.
The sheets are currently being trialed by a major airline.
“While years of Ultem and Ultem fiber technology contributed to the final product, the current Ultem CAB sheets have been in development for approximately 24 months,” said Kim Choate, Global Ultem Product Market Leader, Sabic Innovative Plastics. “They will be flying in commercial aircraft in Q4 2010.”
There were many challenges in the development of the sheets, Choate shared with Aerospace Engineering & Manufacturing. Optimizing the performance of the composite matrix and developing a manufacturing process that ensures a very consistent product were two of the larger ones, he noted.
“With Ultem CAB sheet, Sabic Innovative Plastics and Crane have achieved dramatic advantages over traditional honeycomb composites across the board, from slashing cycle time to doubling part life,” he said. “The fact that CAB sheets are made with a thermoplastic resin matrix that is not susceptible to long-term moisture and UV degradation, combined with the ability to ‘reskin’ an existing panel, results in the improvement over traditional aramid and phenolic systems.”
The use of advanced thermoplastics to replace traditional thermosets in aircraft interiors offers multiple benefits, according to Choate, the most noteworthy being system cost reduction. Because aramid honeycomb composites are highly sensitive to moisture and UV light, the porous edges of a part must be filled and sealed.
CAB sheet parts can be thermoformed in minutes and require minimal secondary operations before applying decorative coverings. “The low moisture absorption characteristics of the material also eliminate the need for edge sealing/potting, which enables significant part manufacturing cycle time and labor cost savings advantages,” said Choate. “Finished part cycle times can be reduced from multiple hours to less than 10 minutes.”
Ultem CAB sheet also cuts system costs through its ability to be reskinned while still meeting required flame-smoke-toxicity (FST) properties to lengthen its useful life, an option previously not available to customers with aramid honeycomb composite, the company claims.
The material exceeds the Ohio State University (OSU) 55/55 standard.
“The robust flame, smoke, toxicity, and heat release properties of the composite sheet allow for the addition of up to two layers of some adhesive/decorative systems while keeping the total system in compliance with the OSU 65/65 requirement,” Choate said.
Light weight is yet another stated benefit of the new product. An Ultem CAB sheet weighs an average of 1350 g/m2 and can be customized to meet a range of part weight requirements.
The weight savings varies by each unique part design and composite stack system employed, Choate said, noting that one current example delivers equivalent mechanical, acoustic, and FST performance as incumbent systems at 25% less weight.
“Parts can be molded at various thicknesses using the same basis weight blank,” Choate explained. “The highlighted 1350-g/m2 product can have a flexural modulus as high as 7700 MPa with a corresponding flexural strength of 135 MPa.”
Target applications for the new composite include sidewalls, cockpit panels, ceiling panels, door liners, and dividers.
“We saw an opportunity to apply our expertise in specialty paper technology in a totally new way and chose to collaborate with Sabic Innovative Plastics because of its leadership in high-performance materials for aircraft interior applications,” said Dennis Lockyer, Vice President of Nonwovens and Technical Materials, Crane & Co. “Ultem resin was the solution we needed to create a technologically advanced paper composite [that presents] a new market opportunity.”