2014 Issue

54 Bomber. Reducing weight was a major driver in the research and development of these new materials, alongside the need for improved mechanical properties and greater design flexibility. Hexcel’s first commercial prepregs - a composite material made from combining high performance reinforcement fibers or fabrics with a thermoset resin matrix- of the late 1960’s and early 70’s were reinforced with glass fiber and supplied for submarines, aircraft, helicopters and racing boats. Prior to prepregs, composite structures were manufactured by wet lay-up, combining resins and fibers in a process that made it difficult to accurately control and reproduce the fiber content throughout a structure. The development of prepreg, in which the resin is pre-impregnated into the reinforcements in very precise quanti- ties, partially cured (b-staged) and supplied on ready to cut rolls, ultimately revolutionized the composites industry. But it wasn’t until the development of carbon fiber in the late 1960’s that prepreg became a serious contender for manufacturing even more efficient and lighter structures, with greater strength, stiffness and durability. The “advanced composites” era had begun. Performance andweight-savings have historically been the key driv- ers behind the increasing penetration of composites into aircraft structures at the expense of aluminum, however there are many other major advantages: • Density. The lower density of carbon fiber composites makes composite structuresmore than 20% lighter than even the latest aluminium alloys. Weight savings mean greater fuel efficiency, reduced emissions, and lower operating costs. • Durability. Composites are not subject to corrosion and exhibit excellent fatigue properties, for a longer service life. Aluminium fatigues and is subject to crack propagation. Most metal parts are subject to ALI (Airworthiness Limitation Items) whichmeans mandatory inspections in service. • Design optimization. Thewide choice of resin systems available enables special features to be designed into the composite, such as meeting fire, smoke and toxicity requirements, high temperature performance or higher impact resistance. In addition, the fiber-reinforcement can be uniquely tailored to meet the stiffness/strength design requirements, by orienting the fibers in a particular direction to achieve maximum perfor- mance where it is most needed, without any weight penalty. • Reduced part count. With composites, several components can be combined into one single composite part, saving manufacturing and assembly costs. • Better buy-to-fly ratio. With aluminium, the finished part may weigh as little as 10% of the raw material from which it was cut – the remaining 90%being scrapmaterial (that can be recycled, but with lower value). Composites have a buy-to-fly ratio that is 50% lower than aluminium – and even less with automated processes like Automated Fiber Placement where thematerial is placed directly where needed so there is very little scrap. As the most vertically integrated supplier in the industry, Hexcel manufactures the full spectrum of advanced material solutions. From carbon fibers and reinforcement fabrics, to RTM resins, prepregs, tooling materials and structural parts, Hexcel is pres- ent at every stage. Our fiber reinforced composite materials are complemented by our honeycomb technologies which extend from lightweight core materials to aircraft flooring panels, engineered core and Acousti-Cap® noise dampening systems. Hexcel is the only composites supplier that supplies this wide range of fiber reinforced matrix technologies together with an extensive range of honeycomb, adhesives and engineered products. Hexcel’s Utahmanufacturing site is located in Salt Lake City and has had a presence here since 1913. Carbon fiber production began in 1970, with prepreg tape following in 1971. The Salt Lake City site manufactures carbon fibers and hot melt prepregs with both woven and unidirectional reinforcements. The plant also produces epoxy resins, adhesive films and solvated fabric prepregs. HexTow® carbon fiber from Hexcel’s Salt Lake City facility is pro- duced in a continuous operation in which polyacrylonitrile (or PAN) undergoes a series of precisely controlled processes. Exposure to extremely high temperature changes the precursor, yielding high strength-to-weight and high stiffness-to-weight properties through oxidization and carbonization. The successive surface treatment and sizing steps improve bonding and handling of the fiber. The resulting carbon fiber is stronger than steel, lighter than aluminum, and as stiff as titanium. The end result of this process is bobbins of carbon fiber in different tensile strengths for different applica- tions. These fibers may be woven into an engineered fabric or go straight to the prepregging process, also done in Utah. Hexcel’s customers will cure the thermoset resin at elevated temperatures, undergoing a chemical reaction that transforms the prepreg into a solid structural material that is highly durable, temperature resistant, exceptionally stiff and extremely lightweight. The location here in Salt Lake City, Utah has seen tremendous growth over the years. In addition to the consolidation of several prepreg facilities into Salt Lake City, our facility has been expand- ing to help accommodate the growth of composites and support customers that are located in Utah, as well as other customers throughout the United States. This expansion allows Hexcel to have a highly effective supply chain for prepreg production, which results in shorter lead times, greater responsiveness, reduced transportation of materials, point of use delivery, less packaging, reduced inventory and less requirement for cold storage space. Stephanie Dunning is Product Manager - Space and Defense, Salt Lake City Matrix at Hexcel Corporation and is responsible for the Space and Defense Market customers for forecast, pricing, LTAs as well as helping review customer specifications. Rachel Owen is Corporate Communications Manager at Hexcel Corporation. HEXCEL | continued from page 53