Published 09/12/2017

Pultrusions growing in construction: new EPTA report

There’s a new report out from EPTA (European Pultrusion Technology Assn., Frankfurt am Main, Germany) that discusses new trends for pultrusion in building and construction.

Sara Black

Senior Technical Editor Emeritus

There’s a new report out from EPTA (European Pultrusion Technology Assn., Frankfurt am Main, Germany) that discusses new trends for pultrusion in building and construction. I’ve summarized the report here, including a helpful table of properties, and included a link to the entire report on EPTA’s Web site. And, the group’s next meeting is March 1-2, 2018 in Vienna, Austria (here’s a link to the event information page: https://pultruders.org/pdf_news/1_WPC_Save%20the%20date.pdf).

According to EPTA, more architects, engineers and builders are discovering the benefits of pultrusion and finding ways to incorporate pultrusions in construction projects. The properties of pultruded profiles make them well suited to numerous applications in the residential housing market, where they provide strong, durable solutions, outperforming traditional materials for many years. This is particularly true, says the report, for window and door systems, and now in a further range of applications such as exterior trim, decking, pergolas, columns and fencing. Composite profiles also present excellent potential for the building of affordable housing, a growing demand worldwide. Offering a combination of properties not available with traditional building materials, and attractive attributes for green builders, the prospects for pultruded profiles are bright.

If you don’t already know, pultrusion is a continuous process for producing linear fiber-reinforced plastic (FRP) composite profiles with a uniform cross-section (curved sections are also possible, as CW has reported, here: http://www.compositesworld.com/articles/curved-pultrusion-no-longer-an-oxymoron). In the pultrusion machine the reinforcing fibers are impregnated with resin and pulled through a heated die where curing takes place. The finished profiles are cut to length at the end of the line and can then be stored and used as structural units when required. The pultrusion operation can be readily automated, and represent a fast, efficient way of producing high performance composite parts, with significant design freedom. Both solid and hollow profiles can be manufactured, in simple and complex cross-sectional shapes, including tubes, rods, I-beams, T-, U- and Z-profiles. EPTA says pultrusion allows for extremely high fiber loading and accurately-controlled resin content, so parts have excellent structural properties. A range of reinforcing fibers, and formats, can be used, including glass and carbon fiber, and a variety of thermoset matrix resins, including polyester, epoxy and vinyl ester, as well as thermoplastic resins. In the residential housing market glass fiber reinforced polyester resin (GRP) is typical.

According to the report, almost any profile cross-section can be manufactured within the following parameters:

maximum length: 12m (determined by transportation limits);
maximum width: 1350 mm/900 mm (depending on the flammability rating);
wall thickness: at least 1.5 mm, to a maximum of 60 mm, and typically 3-3.5 mm;
undercuts and different wall thicknesses are possible;
radii between 0.5 mm and 2 mm are required.

Pultruded profiles are pigmented throughout the thickness of the part and can be made to virtually any color. Surfacing veils may be employed to create special appearances such as wood grain, marble and granite. Profiles can also be painted, cut and drilled using conventional hardened tools, and connected using bolts, screws, rivets or adhesives. A durable UV-resistant coating is typically applied to profiles intended for outdoor use.

EPTA points out that a number of standards have been developed covering the design, fabrication and installation of pultruded profiles. These include the Pre-Standard for Load & Resistance Factor Design (LRFD) of Pultruded Fiber Reinforced Polymer (FRP) Structures developed by the American Composites Manufacturers Association (ACMA) and the American Society of Civil Engineers (ASCE), and European Standard EN 13 706, which specifies minimum requirements for the quality, tolerances, strength, stiffness and surface of structural profiles. Other codes currently in use are the Eurocomp Design Guide and the CUR96 in the Netherlands. The report says work towards new European technical specifications for the design and verification of composite structures used in buildings, bridges and construction works is currently being conducted by Working Group WG4 “Fibre Reinforced Polymers” under the European Committee for Standardisation (CEN) Technical Committee 250 (CEN/TC250).

At the end of their service life pultruded profiles can be recycled. A grinding process results in a by-product that can be used as a filler in building materials such as concrete and asphalt, or reused in the pultrusion process as a filler in the matrix resin, says EPTA. An important advance in Europe involves the recycling of glass fiber-based composite regrind through co-processing in cement kilns. This route is becoming increasingly popular since it is highly cost effective, helps to improve the ecological footprint of cement manufacturing, and is compliant with the European Waste Framework Directive (WFD) 2008/98/EC. The composite regrind used for co-processing in cement kilns is both an alternative fuel and raw material (AFR). When combined with other feedstock materials into an input stream with consistent composition and caloric value, the inorganic fraction acts as valuable raw material, while the organic fraction acts as efficient fuel for the calcination process.

The report includes a table comparing pultruded composites with other materials:

A comparison of the properties of pultruded composite with alternative building materials. (*According to EN 13 706.)

Material	Specific weight (g/m3)	Tensile strength (MPa)	Elastic modulus (GPa)	Thermal expansion coefficient (K-1)	Thermal conductivity (W/mK)
Wood	0.7	80	12	14 x 10-6	0.1
PVC	1.4	70	3	85 x 10-6	0.1
Pultruded glass fiber composite*	1.8	240 (axial) 50 (transverse)	23 (axial) 7 (transverse)	11 x 10-6	0.3
Aluminum	2.7	250	70	23 x 10-6	170
Steel	7.8	400	210	12 x 10-6	40

EPTA says pultruded composites are viewed as a new material option that can meet the most stringent demands and offers manufacturers, dealers and distributors the ability to differentiate themselves in a highly competitive marketplace. The low maintenance, durability and high strength characteristics of pultruded composites are attractive to both home owners, who want to reduce maintenance time and expense, and contractors wanting to reduce service recalls. Pultruded profiles in window systems have earned a maintenance-free reputation over the last 20 years and are recognized for superior performance in dimensional stability and thermal performance. This has led to opportunities for pultruded composite to replace wood, PVC and aluminum in a variety of other applications including exterior trim, decking, columns, pergolas and arbors, as well as railings, fencing and decking. Projects have also demonstrated the application of pultruded profiles to low cost modular housing systems.

One potential application for pultrusions, says the report, is to prevent thermal bridging through steel and concrete framing, which impacts a building’s energy performance. Reducing thermal bridging reduces conduction of heat and energy consumption, and prevents surface condensation from forming inside the building. Because of its superior thermal performance, glass fiber composite is a good option to provide thermal breaks. Various projects and applications are being developed in this area.

The corrosion resistant properties of composite materials make them ideal for products exposed to the weather. Pultruded roof trim, fascia and soffit are extremely tough and durable and provide a low maintenance solution while maintaining the appearance of wood. The lightweight profiles are easy to transport, handle and install.

Pultruded profiles are also being used in roof rain gutters. In some cases, the gutter system and fascia are combined in a single pultruded piece, reducing the labor required for installation. Pultruded gutters have a smooth inner finish to prevent deposits. The report details many more potential apps.

Although still relatively new to the residential housing market, EPTA says the properties of pultruded composite profiles have earned them a position of awareness and respect among architects, engineers and building owners. The potential for further growth is high. Design flexibility and the ability to customize the mechanical performance of pultruded profiles according to the application are recognized advantages. The development of further standards covering the design, fabrication and installation of pultruded profiles will continue to make it easier for designers and builders to specify pultruded products. Pultruded glass fiber composites offer a high performance, cost-effective alternative to more familiar building materials, and are suited to a large number of applications in the residential construction market. A heightened global emphasis on green building and sustainable building practices will only bring increased interest in the potential for pultruded profiles to create energy efficient and sustainable solutions for the future.

Here’s the link to the complete paper: https://pultruders.org/pdf_news/1_EPTA%20Construction%20Briefing.pdf. The European Pultrusion Technology Association was created in 1989 by a group of leading European pultruders with the mission of supporting the growth of the pultrusion industry by maximizing external communication efforts and encouraging knowledge sharing between members. Since 2006, the association has existed under the umbrella of the AVK – Industrievereinigung Verstärkte Kunststoffe e.V., in Frankfurt, Germany. Membership of EPTA is open to all companies and individuals worldwide wishing to further the application of pultruded profiles.