The NCC is a prime commercialisation agent and manufacturing accelerator for composites of all types, from regional to international markets. This conference is a fine example of what it is attempting to accomplish – being a clearinghouse for the latest in plastic composite information. What's old, what's new, what's reapplied to new uses – all ideas and applications were on the table and open to discussion.
Charles Kazmerski of Lucintel, a market research company in the global composites industry, presented an update on aerospace composite usage, indicating there are 50 major original equipment manufacturers (OEMs) in the global aerospace market, and eight major composite material suppliers. With its weight sensitivity – 25 gallon fuel savings/year/lb weight saving in the Boeing 747 – composites are rapidly getting more market usage.
The driving forces for composite usage in aerospace are:
- high specific strength;
- weight reduction, toughness and stiffness; and
- improved resistance to fatigue and corrosion.
Composites allow more design flexibility, sometimes accompanied by a great reduction in parts, eg. 6000 rivets and 300 parts with metals reduced to 100 composite parts in the Airbus A340 fin; and 2 tons (25%) weight savings in the central wind box on the Airbus A380. Adam Aircraft, Boeing (B787) and Bell Augusta (BA 609) also have composite success stories. Longer times between maintenance checks, better cabin pressure, and more cabin room, are other advances that are allowed by the use of composites.
Market research indicates the aerospace industry will be following the automotive manufacturers' model, where OEMs reserve integration and final assembly unto themselves and suppliers do larger sub-assemblies, including design and supply chain management.
Chris McClure of McClure Consulting suggested uses for composites that are presently dominated by more conventional materials. Fibre reinforced plastic (FRP), used for over 20 years in the residential door market, has recently experienced substantial double-digit growth in this market. As the housing market is cooling off, McClure suggests other areas of the home building market should be considered – garage doors for example – especially with the advancements in material technology and equipment. Machinery advancements now allow for bigger doors, better adhesion for the insulating foam and surface coatings such as stain and paint with a variety of designs. They can now produce matching front and garage doors, having the identical wood grain and accenting and may even offer higher insulative value, as well as being dent, rust and rot proof regardless of the ambient temperatures.
Composite Products adapted its Advantage In-Line Compounding process to produce an agricultural tractor cab roof using polypropylene (PP) with 30% fibreglass. Previously, the moulded roof had been manufactured using either a sheet moulding compound (SMC) process or a metal weld and assembly, compiling the many sub-assemblies one at a time. Now, all holes and features in the part are moulded-in with no secondary finishing operations. The designs incorporate carefully designated gate locations with some rib design replacing thick parts.
Many more composite materials are being used in construction (bridges, buildings etc), primarily for structure, repair and reinforcement. However, since composite materials have not been used as long as conventional materials and composites composition can be tailored much more than conventional materials, there is far less long term in-use data available, and while there are many viable analytical models, there is not agreement on when and where to use them. Kristin Jugenheimer of Metis Design suggests a formal framework be put in place to organise the testing. ASTM tests should be used wherever possible. The software Service Life Assessment Methodology for Composites (SLAM-C) would be common to all users. Menu options would include testing by type of structure (bridge, building etc) then application (standard, desert, etc). Data entry could accept all of the physical properties and strength and durability information. The final report would be given with certification for a product in an application. SLAM-C would be maintained by certified testing houses and Service Life Certificates could be issued.
Jugenheimer suggested possible implementations of the software using two examples of how it might work (desert and rain forest with E-glass/vinyl ester). She concluded the SLAM-C program was a simple way to standardise the certification of service life for composites materials exposed to the environment.
Charlie Kazmierski, Lucintel, keynoted on the opportunities in the global wind energy market. Presently, there are 12 global suppliers with four representing 72% of the market. Germany and Spain lead Europe, which leads the rest of the world in the use of wind energy, with China and India growing the fastest (50% a year to 2012), and the US also growing. Technology is changing quickly with most technology now being used developed in the last two years. Many wind turbine blades are made of carbon fibre composite materials using lay-up with resin infusion process.
The development direction is for larger capacity wind turbines with rotor weights up to 41 tons, especially in offshore platforms applications.
Ara Asadorian introduced attendees to Schibley Chemical's Film Transfer's Hard Coating (FTHC), a unique film that has a specialised hard coating on one side. The coating's unsaturated sites make it available to crosslink to a polymer. As an unsaturated polymer goes through the curing process, coming in contact with FTHC, the film will crosslink to the polymer. FTHC coats parts during the manufacturing process, having immediate in-plant coating capability with low start up cost, zero volatile organic compounds (VOCs), increased durability and weatherability, and the ability to imprint an image, like wood grain, upon the material. It's widely applicable to SMC, BMC, infusion, and open mould manufacturing processes.
While autoclave parts are of high quality and well characterised materials, they have the disadvantages of expense, labour intensity, high capital investment, large factory requirement, high cost of nitrogen, poor energy efficiency, and long turn-around times. With Quickstep, presenter Ben Leudtke said the material is placed between a rigid or semi rigid mould and a flexible bladder. The mould and bladder, which sandwich the laminate, are placed in a container which can circulate high temperature fluid. A vacuum is drawn on the laminate inside the bladder while a balanced pressure is applied to the high temperature fluid. The liquid can be quickly and precisely controlled to produce fully cured product much faster. Since the entire operation involves low pressures, economical construction is possible.
Citing a carbon fibre reinforced thermoplastic (CFRTP) hood cost study, Leudtke reported 20% material savings, 62% tooling/capital investment savings, 25% lay-up bagging and curing labour savings, and 80% energy cost reduction.
Meanwhile, Ticona evaluated Quickstep, hoping to extend the range commercially available to include most significant resins, fibres and additives to create a process suitable for large area components and structures and accommodate curvature, cored structures, and thick sections.
CompForm, presented by AGFM's Dan Buckley, is a high volume preforming process for engineering fabrics. It uses a very fast and efficient high intensity visible light cure targeting high volume applications. Fibreglass, engineering fabrics and continuous as well as chopped strand mats, can be utilised, with virtually no heating of materials, low energy use, and flexible cell designs. Further, the binders are compatible with all common matrix resins and can be used behind and onto skins and films. Advantages are that it makes extremely fast cycles possible, allows the user to determine the binder amount and location and is even compatible with other binders and any reinforcing material. Disadvantages are: limited to single step thickness; requires a liquid binder application (requires preform); high costs of high intensity lighting and binder; high material scrap rate depending on the application; unusable on opaque applications, etc.
In the 2006 SPE Automotive Composites Conference and Exhibition (ACCE) conference it was reported that the statistics-based methodology to tie product quality output to manufacturing process and raw material criteria were part of the SMC consistency programme. Two case studies showed excellent product improvements using the Continental Structural Plastics (CSP) methods. Customers requested that they do a similar project to address viscosity since customers cited ‘viscosity variations’ lead to: non-fills, porosity, cracks, and higher handling cost. CSP undertook this study with Probur Guha reporting on it.
Analysis indicated better control of the viscosity could eliminate much of the scrap and rework associated with SMC products. Some of the problem areas were examined and the initial analysis showed a lot of variability, with some of it seemingly seasonal. But closer analysis indicated that 30% of the variability came from only 3 of the 20 variables. Testing is underway to better understand these variables and possible changes to decrease them.
Emabond's Steve Chookazian purports to have many types of plastic bonding solutions. The Emabond resin is designed to melt when exposed to the carefully controlled induction heating which then causes the adjacent surfaces to melt and bond, producing a high strength joint with low energy and pressure input. He said the company designs and supplies solutions to vendors' bonding problems and they have experience with a wide range of materials, bonding similar and dissimilar materials, in many difficult applications, in products from appliances, automotive, medical, semi-permeable membranes, etc.
Some of the advances in closed moulding, focusing particularly on the use of light resin transfer moulding (LRTM) and sandwich structures used in LRTM and RTM were reported by Tim Johnson, Nida-Core. Two sandwich materials were introduced. Process technology improvements now permit closed moulding for increasingly large objects and smaller series part runs, with economical tooling. LRTM utilises a vacuum on the interior of the mould and thus atmospheric pressure on the exterior of the mould to supply the mould pressure, thus allowing for light weight, low priced moulds. Injection pressures must be closely controlled to just below atmospheric pressure to insure maximum cycle speed and mould integrity respectively. Resins, reinforcement material and speciality core materials have been developed for use with LRTM. New built-in pressure sensors and automatic injection valves allow for flow pressures to be sensed and controlled to near 1 mb (0.0147 psi) of target pressure.
The presenter indicated that RTM is replacing spray-up and hand lay-up as the preferred method of producing many parts. In 1996 spray-up and hand lay-up represented 80% of the production of this type of part. Now it is reduced to 39% spray/hand lay-up and 38% RTM.
Two closed cell foam cores for RTM were introduced. They have fibreglass reinforced sides and a triangulated truss network for strength. One product is a rigid foam for one-sided moulds and the other is a flexible foam that can conform to shape in a two-sided mould, eliminating the need for moulded or machined-to-fit cores. These foams can be designed to meet strength and weight requirements.
Vinicius Mardegan of Ticona outlined the advantages of the Celstran LFT (long fibre thermoplastic) process for making thermoplastic and also introduced a new polyacetal copolymer thermoplastic. He indicates that in Celstran LFT all fibres are evenly spaced and completely surrounded by polymer. This technology generates a complete ‘fibre skeleton’ inside the part after injection moulding. Good adhesion between the fibre and the polymer is the result of the proper coupling agents which bond the sizing on the glass fibre with the polymer. Products made with this polyacetal copolymer are reported to have high strength and stiffness, and resistance to creep, warp, moisture and chemicals. Potential applications include rear hatch backs, large appliance functional parts and high performance gears.
Cyclics reported CBT resin is a mixture of four cyclic precursors to the thermoplastic polymer polybutylene terephthalate (PBT). When heated CBT resin melts at lower temperatures than PBT with a water-like viscosity, CBT resin can polymerise (with the appropriate catalyst) below the melt temperature of PBT, and CBT resin can be processed isothermally. Products have all of the well known properties of PBT. Essentially, all thermoset and all thermoplastic processing methods are possible using CBT resins. Processing advantages of CBT resin are reported to include: low viscosity; adjustable reaction times; no heat released in reaction; no VOCs; long shelf life; and it is a thermoformable material.
Refined core materials
Brian Hynes, ADZEL, featured two product technologies. The first, Superlite Reinforced TP Sheet, is a thermoformable, formable at low pressure, composite matrix, comprised of thermoplastic resin and long chopped fibres produced in natural state or combined with outer layers tailored to application. The second, Glass Mat Thermoplastic (GMT) Laminate Sheet, is a compression moulded or thermoformed composite laminate that consists of five or three layers of glass fibre and thermoplastic resin, formed using standard industry methods or used as flat sheet. Both products can be made with a wide range of resins and can be tailored to the customer's needs.
Christopher Edwards of Fulcrum Composites Inc introduced a high performance foam which bridges the gap between high-end marine/aerospace foams and cheap ‘beadfoam’ materials. It utilises a highly oriented structure to create shear and compressive properties much higher than would be expected based on its density. The company also has techniques for the manufacture of highly shaped sandwich panels. The bubbles that make up the foam are elongated, making it much stiffer and stronger for a given density/cost. This structure looks like a mini-honeycomb and allows the properties of the foam to be aligned in the beneficial through-thickness direction. This new core offers cost effective sandwich panels for new markets like trailer bodies and even furniture. Work is proceeding to develop a procedure to produce curved panels without the need for thermoforming or kerfing of the core.
GrafTech has recently developed a carbon foam core material for composite structural panels that can be tailored to the customer's application. Using a proprietary high temperature processing method, it can manufacture large, cost-effective carbon foam blocks of excellent uniformity and quality in a wide range of densities. The paper presented various test results to prove these statements. A series of computer models and engineering curves are being developed to allow them to predict performance. Special attributes include fire resistance, corrosion and rot resistance, impact resistance, electromagnetic shielding, sound dampening, and thermal insulation.
Basalt fibre was tried as a substitute reinforcement for high performance composite applications. The manufacturing process and economics basics were explained by Allan Murray, Allied Composite Technologies, who offered comparisons with other composite reinforcements to help identify application areas. Since basalt is naturally occurring from lava, it is abundant but of different characteristics depending on the location of its particular lava flow. Basalt fibre use was worked on by the Soviets and recently became declassified. Basalt's high temperature stability, chemical resistance, high strength, relatively low cost, excellent combination of properties, and positive environmental factors are the plusses which may offset its greater expense to produce than E-glass. There were many suggested uses, e.g. asbestos replacement in composite brake pads, and replacing steel and fibreglass plastic rod in road and building reinforcement since it won't interact during the curing of concrete. Basalt's high temperature combustion zones won't clog the incinerators like E-glass might. Costs must decrease before many of these avenues become viable, however.
Polymers for improved properties
Michael Favaborn of Ticona described Fortron PPS (polyphenylene sulphide) as a semi-crystalline thermoplastic polymer with high melting point which is inherently flame resistant; chemical and oil resistant; has good hardness, stiffness and creep resistance; and is easy to injection mould and machine. It promises weight reduction with good dimensional stability. Favaborn made the case for thermoplastics, including PPS, over thermoset plastics citing melt processability; reformability; no shelf life expiration; and good properties.
Department of Science and Engineering personnel from the University of Illinois believe in the potential superiority of aromatic thermosetting copolyester (ATSP) matrix compared to conventional epoxy matrix for carbon fibre reinforced composites. They changed the matrix not the fibre mat and used relatively low cost monomers. The ATSP is processed as two components (oligomers) that can be melt-processed at 100-250°C, depending on the molecular weight of the oligomers.
Edward Zenk, International Truck and Engine Corp, did a tutorial on composites, where he observed there was a lull in the 1980-1990s in plastics technology improvements. During that period the major problems were due to porosity, particularly in SMC, resulting in appearance and other deficiencies. Many of these problems have been addressed. Presently, the biggest obstacle faced by all the transportation industry, is the issue of recyclability. Mandates have come down for more recyclable content which may deter the use of SMC and other composites unless they can be reformulated. Research is underway at many levels.
Anthony Camarota, AMCRG, suggested a way to expand market share using flame retardant (FR) solutions. His talk on polymers focused on flame retardancy. After outlining the various test procedures for flammability, toxicity, etc., he indicated the present use of brominated compounds combined with antimony synergists have a variety of well known problems, such as lack of recyclablilty, toxic fumes, etc. Government leaders are demanding new chemistries to achieve fire retardancy in polymers. Systems based on organic phosphates and other chemistries should be utilised in a wide range of applications since they will form a char coating that will prevent more air and heat from getting to the plastic, thereby suppressing the flame. The char layer has to be sufficiently strong so that it remains intact during the combustion process.
Alexis Abramson, Case Western Reserve University, spoke on the nanotechnology landscape in Ohio, where it is a strong player with general strengths in research funding and publications, and concentration of small companies.
The challenge of introducing new applications for composites can be seen by the wide array and flavour of the papers and presentations. They ran the gamut from a call to change our thinking on flame retardants, building entry doors, agricultural tractor roofs, to traditional improvements in SMC, better foams, etc. It was a call to think of the future of plastic composites in a very positive manner.