At the European Pultrusion Technology Assn.’s (EPTA) 9th World Pultrusion Conference, held March 26-28, 2008 in Rome, Italy, there were abundant signs that this composite process — once a trial-and-error art form — is undergoing a transformation to a computer-driven production manufacturing science.
After a welcome from Dr. Luigi Giamundo, president of EPTA, and Prof. Luigi Nicolais, minister for Public Administration Reform and Innovation in Italy, the conference opened with keynoter William Hayden’s (Atlas Hovercraft, Green Cove Springs, Fla.) presentation on “Designing for Pultrusion — The First Pultruded FRP Hovercraft Ferry.” The largest hovercraft built to date, scheduled for launch summer 2008, the Atlas hovercraft was developed with the aid of both finite element analysis (FEA) and CAD software, then built with 80 percent composite panels and beams pultruded over about three weeks’ time by Creative Pultrusions Inc. (Alum Bank, Pa.). Compared with a fiberglass/foam sandwich construction, the cost of materials was reduced by about 30 percent and the cost of labor by about 25 percent (see “Learn More,” p. 27).
Finite element analysis programs were the subject of four technical papers presented in the first session. The papers were the work of the University of Architecture in Venice, Italy; the STTC ApATeCh-Dubna University, Mathematics Simulation Dept., in Moscow, Russia; Ashland Composite Polymers (Kehl, Germany) and Huntsman Polyurethanes (Auburn Hills, Mich.). Each was well received by an attentive audience of 110 delegates from 22 countries.
A presentation on “Continuous Production of Curved Composite Profiles for Aircraft Applications,” by Holger Purol from the University of Bremen Faserinstitute (Bremen, Germany), was the favorite of attendees, according to a poll conducted by organizer Brisk Events (Leusden, The Netherlands). Purol pointed out that because of the roughly cylindrical shape of most aircraft fuselages, nearly all airframe profiles are curved, with radii ranging from 2m to 12m (6.6 ft to 39.4 ft) — a shape easily produced in metal. Future monolithic carbon composite fuselage designs, he explained, will require hundreds of kilometers of curved stiffeners and frames per year. Unfortunately, the composite processes currently used to make such profiles, i.e., resin transfer molding (RTM) and hand layup, are not competitive with metal fabrication. Purol reported that the university has tackled this challenge by setting up a pultrusion machine manufactured by Thomas Technik + Innovation (Bremervörde, Germany and Portland, Ore.) to examine manufacture of curved profiles using glass or carbon fibers in an epoxy matrix. Following extensive research, the pultrusion line was set up using a sloped die (as shown in the top photo, opposite). Purol reports that, using this setup, curved rectangular and T-profiles have been made with repeatable quality control. While the desired curvature was consistently achieved, he reported that the parts exhibit considerable out-of-plane waviness outside of acceptable tolerances. A mathematical study of the waviness is underway to determine if this disarrangement could be accounted for in the part stress and design calculations. Curved pultrusion has long been the pultruders Holy Grail, so the progress of this research will be closely watched.
EPTA’s annual Innovation Award for 2008 went to an industry-first prefabricated sunroom that is 90 percent composites. All structural members and fenestration products are manufactured entirely from pultruded fiberglass profiles. The sunroom, which bested nine other product entries from six countries, is a product of manufacturer Comfort Line Ltd. (Toledo, Ohio). According to company president Jeffrey Miller, the profiles are pultruded from Type 30 unidirectional roving (OCV Reinforcements, from Owens Corning Composite Solutions LLC, Toledo, Ohio) along with a variety of special mats, chosen both to add lateral strength and enhance the surface finish, in an isopolyester resin matrix. Produced to order in a pre-engineered and prefabricated post-and-beam construction method, the sunroom parts are shipped to the customer in kit form. The kits come with fully assembled windows and doors that feature similarly pultruded frames. The sunrooms are assembled on site by trained Owens Corning (OC) franchisees who also market them under the OC trademark SunSuites. Miller says the sunroom’s structural members fit together using a patented corner key system wherein a male injection molded “key” mates to integrally pultruded openings in the structural parts; the molded key and the parts are then fastened with self-drilling, self-tapping screws that are not visible from the exterior or interior of the structure. After window installation, the joints are sealed with a silicone sealant. The roof panels are conventional sandwich construction with an expanded polystyrene (EPS) core and aluminum skins. An oriented strand board (OSB) installed under the roof panel exterior aluminum skin allows for attachment of shingles. (OSB is manufactured from waterproof, heat-cured adhesives and wood strands in cross-oriented layers.) The company started out as a manufacturer of storm windows in the 1950s, pioneered PVC windows in the 1970s, switched to fiberglass in the 1990s and now solely manufactures fiberglass pultruded profiles for windows, doors and sunrooms. Comfort Line now maintains five pultrusion lines, comprising its first machine, built in-house; two pultruders from Strongwell (Bristol, Va.), custom modified for its fenestration products; and two new pultruders from Pultrex Ltd. (Colchester, Essex, U.K.).
The presentation “Pultrusion of Large Structural Sandwich Panels with Integrated Edge Detail and Injected Core” discussed technology developments underway at KaZaK Composites Inc. (Woburn, Mass.) to reduce the total installed cost of panel systems. According to Jerome Fanucci, KaZaK’s president, pultrusion of very wide structures reduces the number of costly joints needed in a structure, and the incorporation of highly engineered joints that are integrally pultruded into the edges of wide panels enables cost-effective connections. The joints are designed to carry the full panel-bending load and also serve as self-fixturing assembly aids that provide additional cost reduction. A recent innovation is KaZaKore, a proprietary phenolic syntactic foam core. KaZaK has demonstrated co-extrusion and cocuring of KaZaKore with glass/phenolic facesheets and projects that the cost per board foot will approach one-half the cost of the balsa core it aims to replace. KaZaK specializes in large, special purpose pultrusion, including high performance military and commercial applications — notably a 200-ft/61m structural boom for the Shuttle Radar Topography Mission (SRTM), which Fanucci contended is “the largest item ever deployed from the Space Shuttle.”
John Ilkka, closed mold business development manager for Reichhold Inc. (Research Triangle Park, N.C.), reported on the increasing opportunities in high-performance pultruded composite markets. He cited as key trends that are driving this growth the increasing demand on energy resources, concerns over global warming, commodity price increases in raw material costs, and the outsourcing of work to countries with low-cost labor. Noting that wind energy is the fastest growing market, Ilkka projected that in 15 years a wind turbine blade will be turned out every 15 minutes compared to the current rate of every four hours (see “Learn More”). One win/win opportunity for pultrusion has been identified in engineered rotor blade stiffeners, which have proven to be very effective in managing stresses in the blades, permitting their construction at lower overall weight, a result that increases wind turbine operating efficiency.
John Hartley, technical director of Exel Composites UK (Runcorn, Cheshire, U.K.), presented a unique Deep Ocean Environmental Long Term Observatory System (DELOS). Comprising two ocean floor platforms, each 8m by 8m by 4.5m tall (26 ft by 26 ft by 14.8 ft), constructed from structural pultruded profiles and Super Deluxe steel, DELOS will be fitted with underwater data collection systems and installed at a depth of 1400m/1493 ft at BP Plc (London, U.K.) operations in Angola for observation and monitoring of the deep ocean environment.
Also announced at the EPTA Conference: Load Resistance Factor Design (LRFD) standards for pultruded composites are scheduled for publication in September 2010. Jointly developed by the America Composites Manufacturers Assn. (ACMA), Pultrusion Industry Council and the American Society of Civil Engineers (ASCE, Reston, Va.), the standards will provide engineers with substantial data on the structural soundness of specific pultruded parts.