By Anthony J. Berejka, Radiation Processing & Polymer Technology Consultant
Abstract: The New York State Vehicle Composites Program will produce multiple structural and nonstructural carbon fiber composites for vehicles using the facilities at the Composite Prototyping Center (CPC) to assess the time and energy use factors involved in the manufacture of these components, including fast ambient temperature X-ray curing in inexpensive molds at IBA Industrial, Inc. Guidance on component design and molds for these composites is being provided by Nordan Composite Technologies. X-ray curable matrix materials are being supplied by Rapid Cure Technologies (RCT). Laboratory facilities at the State University of New York College of Environmental Science and Forestry (SUNY-ESF) are being used to perform tests and component analyses. This program is co-funded by the New York State Energy Research and Development Authority (NYSERDA).
Background: General Motors’ Corvette introduced the use of composites for automotive use in 1953 with the production of all-fiberglass bodies. Since then, every Corvette has featured a composite material body. Likewise, military aircraft have been built using composites. This has led to most of the research and development efforts in composites technology being oriented toward aerospace use. New commercial aircraft for passenger transport are being built using carbon fiber composites, such as the Boeing 787 Dreamliner and the Airbus 350. Carbon fiber composites are preferred because of their excellent strength-to-weight ratios; wherein, the lighter weight translates into greater fuel efficiency.
Table I compares the specific strength, the strength-to-weight ratios, for steel – the historic material used in vehicles – with aluminum and carbon fiber composites. When carbon fiber composites are compared to steel, there is a substantial reduction in weight and a more than three-fold gain in specific strength.
Indy and Formula 1 racing cars and performance vehicles, such as Aston-Martin, Porsche, Lotus, BMW, Tesla and others, all have carbon fiber models that take advantage of the high specific strength of carbon fiber composites. These vehicles can bear the costs of using composite materials and the changes in methods of manufacture. Look for the following videos online: “An Inside Look at BMWs Carbon Fiber Manufacturing Process” and “From a Single Fiber to a BMWi3 – The Journey of Carbon.”
To demonstrate the fuel economy of a carbon fiber composite vehicle, Nordan Composite Technologies took part, in 2010, in a Shell-sponsored Eco-Marathon in collaboration with the engineering department of the Polytechnic Institute of New York University. This team developed a 227-pound carbon fiber full body prototype car, Concept Zero, powered by a 1.1 horsepower engine that achieved greater than 140 miles per gallon in this endurance test. Figure 1 shows this vehicle.
In auto racing, carbon fiber composites have demonstrated the ability to absorb impact during crashes, as shown in Figure 2. The impact energy is absorbed by disintegrating and breaking up the composite in order to protect the driver. There is no mass of bent metal coming toward the driver.
In addition, crash tests performed by Automotive Composites Consortium (ACC) showed the impact resistance of an experimental Ford car with a front end section made with composite materials. The consortium concluded that the vehicle provided as much passenger protection as a typical all-metal car.
In April 2005, Ionicorp+ responded to a New York State Energy Research and Development Authority Program Opportunity Notice (PON-917) by submitting a proposal to study the feasibility of using X-rays to cure carbon fiber composites. This concept goes back into the mid-1970s when Frank Campbell at the Naval Research Laboratory and Walter Brenner of New York University and a consultant to the accelerator manufacturer, Radiation Dynamics, Inc., proposed using radiographic equipment to cure graphite (carbon) composites. Such equipment is far too low in power to be commercially viable, however, Brenner and Campbell pioneered the use of ionizing radiation from electron beams to cure the matrices of composites by using EB-curable coating binders as matrix materials. EB-curable materials are cured with X-rays, but at a lower dose rate.
The conversion from accelerated electrons to X-rays is dependent upon the accelerator voltage and its beam current. With the development of high-current, high-voltage accelerators, X-ray conversion has become an industrial reality. Figure 3 shows how the interposition of a tantalum target is used to convert scanned accelerated electrons to X-rays. X-rays effectively penetrate >20 centimeters down from the target, in contrast to only a few centimeters of penetration of electrons from the highest energy, 10 MeV, industrial accelerators. Figure 4 shows the X-ray conversion system at a SteriGenics facility in New Jersey, which has been doing X-ray treatment of parcels for the US Postal Service since 2002. Totes containing materials to be treated by X-ray are positioned so they can traverse in front of two X-ray targets that are each 2 m in length. The accelerated electrons were delivered from a 130 kW, 7.0 MeV Rhodotron™ accelerator and converted to X-rays.
The NYSERDA co-funded X-ray feasibility study showed that four-ply carbon fiber twill composites with X-ray cured matrices could withstand heat distortion under a 1.82 MPa load (as per ASTM D-648), showing no deflection up to the maximum temperature of the heating oil, 180°C. The temperature was increased at 2°C per minute with a 13 mm wide test bar supported across a 100 mm gap within the bath, as shown in Figure 5, and a gauge sensitive to 0.01 mm used to determine any deflection of the test specimen.
This feasibility study also demonstrated that carbon fiber composites could be cured by X-ray while being constrained against a mold using vacuum bagging de-aeration and pressure. Wide-wheel Honda motorcycle fenders were made using four-ply hand lay-ups of a 2×2 3k carbon fiber twill and an X-ray curable matrix material. Since these high dose X-rays – six orders of magnitude greater in dose than as received in a chest X-ray – can penetrate materials (400 mm), metal pieces were embedded within the plies that then could be used in mechanical fastening. Figure 6 shows metal pieces placed between the carbon fiber plies. Figure 7 shows the vacuum-bagged fender molds under an X-ray target, and Figure 8 shows the metal pieces when cured into the back side of the fender. The results were a Class A finish on the wide wheel motorcycle fender, Figure 9. A sports car fender (Lotus) was also produced, Figure 10.
At the conclusion of the “X-ray Curing of Fiber Composites Feasibility Study” (NYSERDA report Contract No. 9079 of 9 November 2007), estimates were made as to the power consumption needed for X-ray curing and in contrast for thermal curing, for which almost no data exists.
In spring 2014, Ionicorp+ responded to another NYSERDA Program Opportunity Notice (PON-2858) and proposed a “Comparison of EB and X-ray Curing of Fiber Composites with Thermal Autoclave Processing for Vehicle Applications.” This would be an extension of the X-ray-curing feasibility study, but combining that with the facilities available at the Composite Prototyping Center in Plainview, New York, which opened in September 2014. X-ray curing still would be conducted at IBA Industrial, Inc. (formerly Radiation Dynamics, Inc.) in Edgewood, New York, using its 3.0 MeV, 90 kW electron beam to generate X-rays. Since the launch of the feasibility study, IBA Industrial has installed a 7.0 MeV, 700 kW accelerator at Synergy Health in Daiken, Switzerland, which only operates in X-ray mode and is being used to sterilize medical devices. The higher energy and higher power of this accelerator enhances the X-ray conversion efficiency and significantly increases dose rates.
The Composite Prototyping Center opened in spring 2014 and has in its 25,000-square-foot facility a full array of state-of-the-art processing equipment. It provides rapid use, full-scale composite prototyping capabilities for use with various components, including those intended for the automotive industry.
The CPC has:
- 3D design and modeling software/hardware with composite Design and Analysis suites (CATIA, NX etc.)
- Advanced Analysis capabilities with FEMAP/NASTRAN & classical analysis suites
- 3D Printing up to 16 x 14 x 16 inch components, with an array of material capabilities, such as ABS, PC-ABS, Polycarbonate, PPSF, ULTEM and other materials
- Automated ply cutting system by Gerber (Figure 11)
- Laser projection system – for facilitating precision laminate lay up – that uses CAD data to guide and control the process
- Automated fiber placement (AFP) machine for winding thermoset and thermoplastic materials – including in-situ laser consolidation/curing – up to 800°F, by Automated Dynamics
- 5 axis composite machining, routing & trimming/drilling unit by Thermwood
- Two Autoclaves
- 8-foot diameter x 20 foot long, 450°F, 165 psi autoclave (Figure 12)
- 5-foot diameter x 8 foot long, 800°F, 300 psi autoclave
- Heated platen presses
- 250 ton, 800°F, with a 48″ x 48″ platen and a 36″ stroke
- 100 ton, 800°F, with an 18″ x 18″ platen and a 36″ stroke
- Coordinate Measurement Machine (CMM), portable Faro machine with laser scanning, ideal for reverse engineering and depot repair process development
- Nondestructive Inspection System (NDI) – Ultrasonic systems by Olympus
- Bond Master – Bond line and sandwich structure inspection/evaluation
- Hall affect through thickness measurements
- Digital ultrasonic through thickness measurements
- OMNI Scan Phase Array MX2
- OMNI Scan Phase Array SX
- EPOCH-600 Digital Ultrasonic Flaw Detector (A-Scan)
- Opto-Digital Microscope 69X to 9014X magnification capability, by Olympus, for photo-micrographic evaluations
- Plurality of test equipment for evaluating and validating composite structures, including:
- 56,000-pound capacity universal testing machine with an environmental chamber for hot-wet and cold temperature testing, by INSTRON, testing and validation in tension, compression, shear, bending and bond-lines
- 300 foot-pound impact testing machine, by INSTRON
- Testing equipment for physical properties of material
- Muffle furnace (up 2000°F) for material validation
The program to conduct a “Comparison of EB and X-ray Curing of Fiber Composites with Thermal Autoclave Processing for Vehicle Applications,” the New York State Vehicle Composites Program, was awarded $185,000 in NYSERDA co-funding for its overall budget of $376,200 – $191,200 of which is in-kind contributions by the program participants. This program is expected to run for 22 months. It will determine how each composite fabrication step contributes to the overall time and energy demand needed for vehicle composite component manufacture. Thermoset pre-preg materials have been obtained for use in autoclave curing from commercial sources. Rapid Cure Technologies is providing X-ray-curable matrix materials that will be converted into pre-pregs. The program has drawn together a multidisciplined, experienced team to complete its objectives. Carbon fiber components for automotive use will be made using autoclave and X-ray curing.
The program team:
- Leonard Poveromo, executive director of CPC, a composites expert at the Northrup Grumman Corporation for 44 years.
- Max Gross, director of engineering and technology for CPC, principal of SciMax Technologies, dealing with innovations in composite structures.
- Dan Montoney, with Rapid Cure Technologies, a specialty materials formulator and supplier dealing with matrix systems.
- Dan Dispenza, president/owner of Nordan Composite Technologies, a specialist in manufacturing carbon fiber components for performance vehicles, including race cars.
- Rick Galloway, vice president at IBA Industrial, Inc., experienced in the installation and operation of electron beam accelerators and their use for X-ray conversion.
- Marshall Cleland, scientific advisor to IBA Industrial, Inc., an accelerator developer who more than 50 years ago formed Radiation Dynamics, Inc. (now IBA Industrial, Inc.), which has over 200 accelerators in industrial operation around the world.
- Mark Driscoll, director of the UV/EB Tech Center at the State University of New York College of Environmental Science and Forestry.
- Tony Berejka, Ionicorp+, the NYSERDA contractor, a consultant with more than 45 years of experience in specialty polymer development and processing, including interaction with the automotive industry, notably while employed at Exxon Chemical Research.
This team formed and met in November 2014 to outline its program. Using the CPC and the IBA Industrial, Inc. facilities, multiple units of carbon fiber vehicle components will be made to assess key factors, such as time and energy use in composite manufacture. A vehicle hood will be cured using commercial thermoset carbon fiber pre-pregs and pre-pregs made with X-ray-curable matrix materials. The hood from an Aston-Martin will be produced using the CPC autoclaves to thermoset pre-pregs, and the X-ray curing will be completed at IBA Industrial, Inc. An Aston-Martin is pictured on page 40 and Figure 13 is its hood made of carbon fiber.
Berejka, A.J. “Electron Beam Cured Composites: Opportunities and Challenges,” RadTech Report, (March/April 2002) 33-39.
Berejka, Anthony J. “X-ray Curing of Fiber Composites Feasibility Study,” NYSERDA final report, Contract No. 9097, November 9, 2007, Albany, NY.
Berejka, A.J., Montoney, D., Cleland, M.R. and Loiseau, L. “Radiation Curing: Coatings and Composites,” at Polyray 2009, Universite de Reims, Reims, France, March 2009, and in NUKLEONIKA 2010; 55 (1): 97-106.
Berejka, A.J. “Rays of Hope,” Medical Device Developments, March 26, 2014, 65-67.
Campbell, F.J., Brenner, W., Johnson L.M., and White, M.E. “Radiation curable resins” (part of a larger report circa 1979) 79-92.
Campbell, F.J., Brenner, W., Johnson L.M., and White, M.E. “Radiation Curing” (Task D of a Naval Research Laboratory report circa 1979).
Cleland, M.R., Galloway, R.A., Montoney, D., Dispenza, D., Berejka, A.J. “Radiation Curing of Composites for Vehicle Components and Vehicle Manufacture,” IAEA/ANS AccApp 09, Vienna, Austria, 4-8 May 2009 at www.pub.iaea.org/MTCD/publications/PDF/P1433_CD/datasets/papers/ap_ia-04.pdf.
Herer, A., Galloway, R.A., Cleland, M.R., Berejka, A.J., Montoney, D., Dispenza, D., Driscoll, M. “X-ray-cured carbon-fiber composites for vehicle use,” Radiation Physics and Chemistry, Vol. 78, Issues 7-8, July-August 2009, Pages 531-534.
Anthony J. “Tony” Berejka is an industry consultant specializing in radiation processing and polymer technology. He has worked with corporations such as Exxon Chemical, Raychem Corporation, Bristol-Myers Squibb and IBA Industrial, Inc.; with agencies such as the International Atomic Energy Agency and the National Academies and its National Research Council; as well as many other firms and industrial start-ups. Berejka is co-founder and past president of RadTech International North America and the Council on Ionizing Radiation Measurements and Standards, both of which have honored him for his lifetime achievements. The Ionizing Radiation and Polymers Symposium has honored him as well. Contact Tony Berejka at firstname.lastname@example.org.