At JEC Europe 2015, Hexcel (Stamford, CT, US) showcased its latest composite innovations for aerospace, automotive and wind energy applications.
For aerospace customers, Hexcel launched a new RTM resin, HexFlow RTM230 ST, that it says performs at high temperatures with superior toughness and has excellent high rate impact resistance. The resin is said to be particularly suitable for jet engine components, such as fan blades and fan cases, spacers and outlet guide vanes. Matching the current market leader in terms of high in-plane and impact performance with good long term thermal stability, HexFlow RTM230 ST is reportedly easier to process, having a 45-minute injection window. In addition, the system, Hexcel says, demonstrates outstanding resistance to aggressive fluids, including commonly used solvents and aviation fuel.
Hexcel also launched pre-cured, thick-ply carbon fiber elements for structural reinforcement applications based on its advanced and tradmarked Polyspeed material. Carbon fiber tows are impregnated, shaped and cured in a continuous process that creates "perfect" fiber alignment and a uniform surfaced product. Polyspeed laminates have very high structural properties and are available with epoxy and polyurethane resins. The laminates form production-ready components for structural applications in marine, wind and automotive. They are reportedly fully compatible with Hexcel’s epoxy thermoset resin matrices and can be used in combination with Hexcel prepregs for wind blades, including HexPly M79. They also are compatible with many commercial thermoset infusion resins.
For the automotive market, Hexcel promoted products and manufacturing technologies for the large volume production of structural parts. Hexcel’s M77 resin cures in 2 minutes at 150°C, or 1.5 minutes at 160°C, and is available as HexPly M77 prepreg or as HexMC molding compound, which is reportedly ideal for complex shapes. The gel time of M77 allows the resin to quickly flow into mold contours to achieve precise geometries and its high Tg of 130°C enables cured parts to be demolded while warm for faster production cycles.
Building on the attributes of HexPly M77, Hexcel has now installed a fully automated production line in Austria that converts UD prepreg into 2D preforms in seconds. The process allows prepreg plies of different weights and orientation to be combined in the same ply-book and includes automated cutting, camera-assisted ply positioning, integration of adhesive and automated packing.
Also on Hexcel's stand: Carbon fiber-reinforced polymer Body in White (BIW) parts made with HexPly® M77 preforms from Hexcel’s automated process. The preforms’ low tack, sys Hexcel, allows for automated handling by the customer. The preforms require no surface preparation and are designed for one-step bonding and curing in a press, requiring no finishing operations. Common BIW part joining technologies, such as welding can be used, and the parts are compatible with e-coating processes.
Also on hand was a Lamborghini Aventador monocoque, with a roof made from Hexcel’s XF3 surface film and HexPly M47 prepreg for a Class A painted surfaces. The tub structure was made by resin transfer molding (RTM) using Formax UK Ltd. (Leicester, UK) multiaxial structures specifically designed for preform applications. Multiaxial fabrics combine drapeability with good structural properties and allow carbon fiber to be processed at speeds and efficiencies conducive with high volume automotive manufacturing processes. (Hexcel acquired 50% of Formax UK in December 2014.)
In Hexcel’s wind energy display, a wind blade section manufactured by SSP Technology featured Hexcel’s HexPly M79 prepreg, developed to meet industry requirements for a faster and lower-temperature curing prepreg for thick laminates in the wind energy and marine industries. The system cures in 8-10 hours at 70°C or in just 4-6 hours at 80°C. The very low exotherm of HexPly M79 allows the temperature to be increased more quickly in the mold, resulting in a shorter cure cycle.
Hexcel also promoted HexPly M92, its latest-generation 125°C-cure prepreg, which combines superior hot/wet performance up to 115°C, self-adhesion, high toughness, fire-resistance, low exotherm and a long out/tack life. On display: A wing fuselage fairing door demonstrator, manufactured by Embraer using HexPly M92 carbon fiber prepreg. This honeycomb sandwich structure requires no adhesive, thanks to the self-adhesive properties of HexPly M92.
Hexcel says it was the first company to manufacture honeycomb on a commercial scale more than 60 years ago. At JEC Europe 2015, Hexcel is launching HexSHIELD, a technology product providing high-temperature resistance in aircraft engine nacelles. By inserting a thermally resistant material into honeycomb cells, Hexcel provides a core product with unique heat-shielding capabilities, that allows for the potential re-use of material after a fire at 1093°C/2000°F. The product builds on Hexcel’s long history of heat resistant honeycombs, including HexWeb HRH-327, with temperature resistance up to 260°C. HexSHIELD combines the structural and formable benefits of honeycomb with thermal resistance performance and can be combined with various facing materials, making it tailorable to customer needs.
Advancements to Hexcel’s Acousti-CAP broadband noise-reducing honeycomb have resulted in Multi-Degree of Freedom (MDOF) liners that bring significant improvements in acoustic absorption capabilities in aircraft engine nacelles. The acoustic treatment may be positioned at a consistent depth and resistance within the core, or it can be placed at a pattern of varying depths and/or resistances, offering an acoustic liner that is precisely tuned to the engine operating conditions. Acousti-CAP has been tested at NASA on a full engine test rig and meets all 16 design conditions without trade-offs.
Hexcel reports that since it launched HexTow HM63 carbon fiber at JEC 2014, this high-modulus fiber has been quickly adopted by customers and is already in multi-lot qualification with major space and aerospace OEMs. HexTow HM63, says the company, has the highest tensile strength of any high-modulus fiber and provides outstanding translation of fiber properties in a composite, including superior interlaminar shear and compression shear strength.