Advanced Engineered Wood Composites Show Promise

Whoever said ‘You can’t improve on Mother Nature’ obviously never visited the Advanced Engineered Wood Composite (AEWC) Center in Maine. Researchers at the AEWC Center are finding new ways to combine wood and plastic to develop composites that are stronger, more durable and better than the base materials. Although the forest products industry is generally thought of as a fairly low-tech industry, advancements in composites are taking wood boldly into the future.

            Founded in 2000, the AEWC Center has become the leading research facility in the country focusing on the next generation of Wood Plastic Composites (WPC). A 48,000 sq. foot research facility, the AEWC Center has been involved in developing composites for bridges, skateboards, decking, advanced engineered lumber, pallets and even popsicle sticks. With 20 full time staff members, the center can help companies all the way from the concept stage through developing pilot projects and full-scale prototypes to subsequent comprehensive testing and evaluation.

            While the AEWC industry is very much in its infancy, one study projected it to grow 750% by 2010. Pilot studies during the 1990s demonstrated the viability of AEWC. Research by the University of Maine indicated that engineered wood with minimal fiber reinforcement can increase the strength of the wood beam by over 50%. In 1995, the University of Maine developed the world’s first fiber-reinforced polymer timber ocean pier. This 124-foot long experimental pier used AEWC and was 25% less expensive than steel.

Not All Wood

Re-Created Equal

            AEWC shows promise in a variety of structural and exterior decorative applications, especially decking. “The extruded wood plastic technology is definitely up and coming,” said Dr. Habib J. Dagher, AEWC Center Director.

            One early success of the Center has been its work with CorrectDeck, a start-up company manufacturing a decking material made of Maine hardwood sawdust and UV-stabilized polypropylene. CorrectDeck has sold more than 10,000 decking systems throughout the United States, mostly through home centers and building material supply retailers.

            CorrectDeck combines the advantages of wood and plastic into one product. With CorrectDeck, no special stains or treatments are needed for protection. It offers a consistent quality and appearance with no splinters. CorrectDeck is unaffected by wood-boring insects such as termites and beetles. CorrectDeck is stiffer, lighter and harder than solid wood decks. The big drawback for the composite deck is the sticker price. CorrectDeck claims its product is actually cost competitive over the lifetime of the deck when you consider that it requires very little maintenance.

            Habib said, “The power of composites is that you can engineer material to meet needs of its end use.”

            Habib believes that wood plastic composites for fencing and framing could reach 70-80 % market penetration in the next 10 years, especially for outdoor applications.

            While composite decking is still in its infancy, the market shows significant promise and could become a good market for wood fiber in some parts of the country. It likely will never be as prominent as something like mulch or animal bedding. But composites are going to become more common in the future. Martin Grohman, president of CorrectDeck, said, “We buy mixed hardwood, custom blend, tight specifications for color and particle size, 100% through 40-mesh. We are looking for more material meeting our specifications in New England and eastern Canada.”

            In order to be used in composites, wood fiber has to be ground down to very fine wood particles. Similar to a flower-type material, it must be milled to about 40-60 mesh product. Material should be fairly dry, typically 2-6%. Depending on demand and the amount of fine wood milling and grinding equipment in your area, there may be an opportunity in the future for companies to setup plants to mill wood fiber for use in composites.

            Extruded boards are typically 60-70% wood by weight. Two main key advantages of AEWC are durability and weatherability. Plastic covers wood and keeps air from getting to it, which improves durability. Major disadvantages are strength and stiffness. WPC tends to have the strength of #2 grade material and stiffness less than #2 grade material. Currently, most WPC lumber costs twice the initial purchase price of pressure treated wood.

            WPC offers tremendous variety when it comes to colors and appearance. Habib said, “You can make it look like whatever you want it to look like.” A very viable market for the future of WPC is door and window frames. WPC are durable and would work well instead of vinyl according to the AEWC Center.

            Habib said, “WPC will exceed life of preserved and treated wood. All WPC are not created equal. Different fillers, resins and processing methods affect product durability and quality.”

            WPC does not work well in all applications. For example, WPC is very dense and not suited for things that move. Since many products using WPC are just beginning to enter the market, you may not have seen many of them being used. In a few years, the situation likely will be very different.

            By adding a small percentage of synthetic fibers to a WPC, the strength properties of the material can be significantly strengthened. The AEWC Center has done research with WPC using reinforced polymers. Adding Kevlar, fiberglass or carbon fiber can make a big difference. Synthetic reinforced WPC is ideal for construction including bridges, buildings, peers and even skateboards. These products use low grade material combined with reinforced polymers and are somewhat similar to glulam type products.

            Composites can help remove or reduce the impact of defects on lumber. The AEWC has been doing research on Advanced Engineered Lumber (AEL), which improves the strength of wood by taking defect areas apart and putting them back together so that the defect is not in just one location. Knots make wood week. AEL randomizes a defect so that its impact is spread about the entire piece. AEL are being targeted for building applications and are most cost effective for 20-40ft long beams whereas WPC with reinforced fibers are better for larger beams 50-100 ft. in length.

            Another area where WPC show significant promise is Oriented Strand Lumber (OSL). OSL is similar to conventional Oriented Strand Boards (OSB) except that all the strands line up in one direction, allowing the processor to make a solid piece of lumber. OSL primarily will be used for construction applications. This technology produces straight lumber that doesn’t swell, warp or twist. OSL can come in whatever length you want.

            Habib said, “The higher end markets are starting to use OSL for stud applications and general framing. Who would have thought five years ago that OSL would replace stud lumber?”

            OSL needs to come down in price because it costs $1,200-1,300 per cubic foot. The properties can be changed per the customer’s requirement. OSL will hold a nail well because it can change the density of the material. It tends to have more resin than typical OSB. With various amounts of pressure and heat applied, producers can change the properties of OSL. Habib said that you can make OSL that you can’t shoot a bullet through.

Technology Advances

            It has taken a number of years for the AEWC Center to work out processing problems involved in producing WPC. Wood and plastic combination problems were largely resolved when researchers started using uniform, smaller fiber. Habib said that the problems in the past were essentially cost effective processing problems that have been overcome. The cost issue really comes down to how fast can you run material through an extruder.

            Wood and plastic material complement each other very well. Wood fiber is significantly stronger than plastic. Wood is a lot cheaper than plastic and acts as a great filler material, which reduces the amount of plastic needed to make a product. Wood is a good re-enforcer of plastic fiber.

            Wood has excellent thermal properties. For example, if you walk on all plastic lumber deck in the heat of summer, you will burn your foot. But if walk on WPC deck barefoot, you will not burn your foot due to wood’s thermal properties.

            Habib said, “It’s like taking two materials and by mixing them make a product that is superior to either of the components.”

            The AEWC Center is primarily looking for niche applications. It has even done some research on WPC for pallets. The big drawbacks of WPC are the weight and the cost. A pallet made out of WPC would weight 60-70% more than wood. The big advantage would be durability.

The AEWC Center

            Pilot studies in the 1990s showed the viability of AEWC. Responding to the need, the University of Maine conducted research on fiber reinforcement of wood composites. This lead to the founding of the AEWC Center, which is part of the University of Maine. It receives extensive support from both government and private sector sources. The AEWC Center was developed in Main primarily because the forest products industry is so integral to the state’s overall economy. The AEWC Center houses laboratories for composite materials manufacturing science, polymer/interface science, environmental-durability testing, mechanical testing, nondestructive evaluation (NDE), advanced microscopy, and large-scale multidegree-of-freedom static and dynamic structural testing.

            Currently, product research and development at the AEWC Center includes structural beams, building panels, furniture, skateboards, marine piling, composite aircraft, decay-resistant decking, highway guardrails, utility pole crossarms, and bridge decks and girders.

            Many new markets for AEWC likely will develop over the next 5-10 years. This will obviously impact the lumber industry as a whole and create new markets for wood fiber. The next generation of wood technology will help the industry adapt to a changing world. The ability to scientifically change and enhance the properties of wood will open new doors for forest products. What can the ‘new’ wood do for you?