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Building on its motor sport success, ACG now provides the global composites industry with a unique combination of materials, design and manufacturing expertise, as well as custom-formulated, innovative materials and manufacturing solutions for complex applications.
(Published on March - April 2008 – JEC Magazine #39)
STEVEMILNER, TECHNICAL AUTHOR,
DR. JOHN NIXON, TECHNICAL MARKETING MANAGER, ADVANCED COMPOSITES GROUP
he Advanced Composites Group (ACG), which is part of the Composites Division of Umeco plc, has been operating in the advanced composites industry for over 30 years. In its early days, the Group manufactured composite parts for race cars, i.e. skirts, body panels, etc., but it soon realised that if the full potential of these exciting new materials could be acknowledged, a new generation of safer, faster, composite race cars would become reality. This would also initiate an era of boundless design freedom. Many recipients, including major race car, sports car and yacht building manufacturers/competitors, have – for many years - benefited from the application of ACG's advanced composites materials. ACG's perpetual product evolution programme has led to the development of customized resin matrix systems that have been used by leading names to manufacture functional, aerodynamic and aesthetically pleasing structures. Recent press articles, reporting successes and trophies held aloft, bear witness to these accomplishments and the realisation of many dreams.
Today’s design engineers now have access to a range of products that offer:
A truly international group
ACG is now a truly international group that operates through four divisions: two in the UK, one in North America and one in South Africa. Currently employing over 560 professionals, including specialist design engineers and formulation chemists, ACG is underpinned by a network of dedicated market sector development managers and a host of independent agents and distributors. This experienced team is supported by a UK-based Technology Centre, a central research and development facility that has been focusing on advanced fibre reinforced composites technology for many years. Over the years, the Group has been engaged in a range of major development programmes in the aerospace, motor sport, automotive, marine, space, sports & leisure, wind energy, and construction industries. Its determination to push the boundaries ever further and develop innovative solutions has led to significant involvement in a range of programmes that have paved the way for the successful application of new technologies for tomorrow’s ground-breaking products. What you get from ACG is advanced, fully-compounded reactive systems ready to laminate. While off-theshelf products are available, the Group is profoundly motivated to provide products designed for application, thus ensuring that optimum suitability for purpose is achieved at all levels of functionality, performance and environment.
ACG’s products evolved rapidly over a period of ten years. It all started with the LTM® (Low Temperature Moulding) series of resins. A key aspect of LTM technology is its ability to “step ahead” cure. These resins are formulated to cure at low temperatures and can be transformed into highly robust structures by further heat treatment. From a performance viewpoint, these resins have better mechanical and thermal characteristics than those expected from a particular curing condition. This enhanced stability allows initial curing to take place at 50 to 60°C, thereby utilising relatively lowcost tooling. The cure can then continue to a much higher level, with stability still running ahead of the cure temperature, but with the part now out of the mould and without risk of distortion. This concept was first exploited in the LTM tooling systems, which have formed a solid foundation upon which the Group has grown.
ACG initially developed innovative, robust tooling systems for a range of applications. The LTM resins developed for these systems were extremely resistant to high temperatures, but their inherent brittleness made them totally unsuitable for structural applications. A prepreg laminate requires a combination of pressure and heat to consolidate the layers and initiate the resin curing reaction, which, in the early days, usually meant resorting to high-temperature autoclave processing. While the use of an autoclave remained the ultimate route to high-performance components, it was seen as a barrier to the wider adoption and application of high-performance composite materials and prepregs in many industries. Simplified processing and a degree of toughness were required to make LTM prepregs more attractive to a wider market. This was achieved, but the reactive nature of the LTM systems still meant a relatively short working life, which delayed the wider acceptance of these materials. However, they experienced considerable success with one-off projects such as SpaceShipOne and GlobalFlyer. ACG has always produced a range of “standard” 120°C curing prepregs. Again, these materials are generally aimed at autoclave processing, but many were capable of low pressure, vacuum-only processing, offering more realistic work lives, albeit not possessing the original lowtemperature curing capabilities of LTM systems.
ACG’s VTM® (Variable Temperature Moulding) system is derived from both the LTM and MTM cure chemistries and offers optimised low temperature, low-pressure processing, and flexible cure temperatures between a modest 65°C and 120°C, with “step ahead” cure. Moreover, autoclave curing is no longer needed, while the extended working life of one month provides a wider window of operation in which to complete the laminating process. Resin rheology is controlled to optimise fibre wet-out, but not at the expense of excessive resin bleed. As stated earlier, the autoclave is the ultimate route to general laminate and surface quality. Low-pressure prepreg processing has always suffered from poor surface quality and a high level of subsequent surface re-work.
A parallel development of the VTM system, which originally targeted the automotive industry, has also been embraced by the marine and exclusive sports car industries. The development in question is the ZPREG® rapid laminating system, in particular, the associated Body Panel System (BPS). The qualities and features of this product finally addressed the issues of achieving high-quality surface finish without high-pressure processing. The VTM range has now grown into a family of structural, tooling, and surfacing systems that offer high performance and excellent surface quality products via lowcost processing routes. While being firmly established in the marine industry, the VTM system has also proved to be a worthy and valuable entry level product for many component manufacturers. Many builders go on to install autoclaves and use other higher-temperature cure systems.
One of the most recent applications of ZPREG® is on the Farbio GTS super car, which has a space-frame chassis completely clad in the BPS240 carbon fibre body panel system (ACG’s ZPREG® rapid deposition system). With its integrated surface film, BPS240 is a stable, high-temperature system that is capable of producing and maintaining in-service Class A surfaces. The system offers enhanced moulding capabilities, excellent and stable surface quality, effective processing benefits and a significant cost saving over traditional prepreg technologies. When compared to traditional advanced composite materials, BPS240 panels can be moulded from highquality, low-cost composite tooling, thereby reducing manufacturing times by as much as 50%.
Many of the lessons learnt from past experience are now being integrated into the next generation of out-of-autoclave MTM prepregs and film infusion systems. With simplified processing and further developments in toughening mechanisms, these systems offer the performance levels demanded by the aerospace industry.
Products such as MTM®44-1, MTM®45-1, MTM®46 and MVR444 form ACG’s new generation of out-of-autoclave processing systems currently in use or under qualification for a variety of civil and military applications. With the recent launch of Virgin Galactic, which is the Virgin Group’s new commercial spaceline, commercial spaceflight will take a further step forward by offering the first commercial sub-orbital passenger space service. Virgin Galactic will operate five spaceship systems manufactured from ACG’s MTM®45-1 prepreg resin system by The Spaceship Company, a joint Venture between Sir Richard Branson’s Virgin Group and Burt Rutan’s Scaled Composites. Taking advantage of the characteristics of the out-of-autoclave processing systems, ACG has now travelled full circle by developing a new series of out-of-autoclave LTM tooling systems that address the evergrowing need for larger tools, especially those required to satisfy the present developments in the commercial aircraft market. Having installed additional state-of-the-art prepreg processing equipment for new production lines at its UK facility, ACG has its sights set on its future. These new production lines, which are part of a multimillion pound investment from its parent company, Umeco plc, set the scene for further success in the aerospace market.