Apr 08 2014

Surfx In The News: Plasma used for consistent surface preparation while increasing chemical bond.

Certification of bonded composite primary structures.

OEMs develop technology to quantify uncertainty in pursuit of the no-bolt bondline.

Composites have flown on commercial aircraft primary structures — those critical to flight — for more than 30 years, but only recently have they conquered the fuselage, wingbox and wings, most notably on the Boeing Co.’s (Chicago, Ill.) 787 Dreamliner and the A350 XWB from Airbus (Toulouse, France). These carbon fiber-reinforced plastic (CFRP) structures, however, still require assembly with thousands of mechanical fasteners. Why? Because it is the easiest and least expensive way to meet current certification requirements, which mandate proof that each and every adhesively bonded joint will not separate and cause structural failure should it reach its critical design load. But many in the industry argue that the full cost and weight savings of composites cannot be realized until bonded joints can be certified without fasteners.

The development of technologies to address this need has steadily progressed, from programs in the late 1990s such as the U.S. Department of Defense (DoD) Composites Affordability Initiative (CAI) to more recent initiatives, including the European Union (EU)-funded Boltless assembling Of Primary Aerospace Composite Structures (BOPACS) project. Here, HPC looks at current efforts to build a certification regime for bonded primary structures on aircraft. Boeing, Airbus and Lockheed Martin Aeronautics (Palmdale, Calif.) have mounted independent efforts toward that end. Their research offers the hope of building reliability into the bonding process, and of gauging final bond strength via a coordinated certification system that includes design, process control and quality assurance (QA).

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