The Amazing Adventures of 'Superwood'
Composite Research Is Adding Muscle to Maine's Mild-Mannered Timbers
Technology at The University of Maine
is transforming the state's lower-grade wood species into "super wood" —
new value-added building materials.
Engineers and wood scientists at UMaine's Advanced Engineered Wood
Composites Center (AEWC) are developing new materials by combining wood
with space-age plastics, such as fiber-reinforced polymers (FRPs). The
goals: stronger, cost-efficient construction materials to build
structures that withstand natural disasters, such as earthquakes and
hurricanes; marine piers that resist decay and pest infestation, such as
shipworms; and strong bridges that last longer, offering an alternative
to traditional spans of steel and concrete.
Wood composites will help the country address a variety of problems,
according to Habib Dagher, AEWC director and a professor in the
Department of Civil and Environmental Engineering, whose confidence in
wood composite technology stems from years of testing in both the
laboratory, and in existing bridges and piers.
"Our research has already demonstrated the potential for wood composites
to lower costs, increase efficiency and improve the performance of
structures. Our goal is to demonstrate the reliability of new
applications and move as quickly as possible to the marketplace," says
Insurance industry figures put the annual average cost of natural
disasters in the United States (in damages to property and loss of life)
at about $50 billion, he says. Meanwhile, according to the National
Partnership for Highway Quality, 25 percent of the nation's bridges are
deficient, and wooden poles and pilings need to be replaced because of
rot and insect infestations.
Habib Dagher, AEWC director and professor in the Department of Civil
and Environmental Engineering, has long stressed the importance of
using technology to transform Maine's abundant timber resources into
new, value-added products.
Wood composites products under study:
• Structural beams
• Building panels
• Marine pilings
• Rot-resistant decking
• Highway guardrails
• Utility pole crossbeams
• Bridge decks and girders
In pursuit of its goal, AEWC opened a
33,000-square-foot laboratory for building and testing wood composite
materials in 2000. Formal partnerships have been created with industry,
government research labs and other universities. Research by AEWC
scientists has already led to three patents, and two more applications
"In the last five years, we have focused on building a world-class
laboratory. Now that we have achieved that, we are turning our attention
to research and economic development," Dagher says.
At its core, the laboratory is a teaching facility where students work
with faculty to develop new technology. They use sophisticated computer
models to determine what happens to wood as it breaks or as adhesives
permeate pores and bind the wood to other materials. They build
structures that they shake, bend and twist to simulate years of wear and
Working directly with the business community is John Fiutak of UMaine's
Department of Industrial Cooperation. Before coming to UMaine, Fiutak
ran a manufacturing facility for Willamette Industries in Albany, Ore.,
a major producer of engineered wood building materials. He has been
meeting with landowners and managers in Maine's forest products industry
to lay the groundwork for a facility in the state to make laminated wood
beams, known as glulams.
One focus of Fiutak's efforts has been a product that could be Maine's
first step into the engineered wood products industry. It takes
advantage of low-grade red maple, hard maple, birch and beech already
being produced as a residual in some mills. AEWC research has shown that
when these materials are glued together into beams, they can out-perform
industry standards for strength upward of 30 percent. Red maple is
Maine's most abundant hardwood, but it has little commercial value.
AEWC is working on revisions to building codes to include this product,
More than 75 million board feet of glulams were sold in the Northeast
and Canadian Maritimes for the residential construction market in 2000,
he points out, but the closest manufacturing facility is in New York
state. Moreover, that facility specializes in high-end softwood
products. Fiutak's vision is for a plant to turn out hardwood beams that
will be custom cut to almost any length and delivered to a contractor's
specifications, reducing labor costs at the building site.
While hardwood laminated beams are close to reality, the future lies in
products that take advantage of the low cost and flexibility of wood and
the high strength of FRPs. "Wood is one of the best materials available
from the perspective of strength to cost," says Robert Lindyberg, AEWC
research engineer, "but it suffers from a perception as a low-tech
material. We are working to change that. Wood composites are very much
AEWC engineers and scientists are attacking that problem on several
fronts. In the laboratory, they are subjecting wood composite materials
to stresses and strains that are more severe than what they might
actually encounter in a structure. Samples of composites are repeatedly
drowned in water and dried out. They are run through freeze-thaw cycles,
bombarded with ultra-violet light and subjected to constant pounding and
At issue is not only the integrity of the wood and FRP. The glue line
between the two is critical. Failure there could drastically reduce
performance and cause a structure to become dangerously weak.
Researchers now are taking a microscopic look at how well different
adhesives keep wood and FRP together.
In addition to laboratory studies, AEWC has created a network of
demonstration projects to monitor the performance of bridges and piers
in actual use. Most of the projects are located in Maine, but others
exist in Pennsylvania and Ohio, and more are planned across the country
as part of collaboration with state departments of transportation and
the Federal Highway Administration.
One of those projects, a commercial marine pier in Milbridge, Maine, met
performance requirements with a composite structure weighing a third as
much as a conventional one made of reinforced concrete. Today, trucks
drive over a deck made with laminated wood and sheets of FRP applied at
Also in Milbridge is a two-lane road bridge built with timbers that are
strapped together with half-inch thick FRP cables, a technology known as
post-tensioning. The bridge has proven its worth by requiring less
maintenance than a similar AEWC-built structure in Gray, Maine, that
uses standard steel rods in place of the FRP. Whereas the steel rods
have to be retightened frequently, the FRP cables do not.
During the first two-and-a-half years of service, the FRP cables lost 14
percent of their tension strength compared to a 67 percent loss in the
steel rods. Both bridges were built to be safe even without the
tensioning. UMaine has received a patent on the FRP cable technology.
An AEWC project in Pennsylvania shows that futuristic wood composite
products can even have a role in historic preservation. A timber
structure partially built with composite beams now carries the Delaware
Canal, originally constructed in the 1830s, over Tohickon Creek.
Lindyberg worked with the aqueduct's owner, the Pennsylvania Department
of Conservation and Natural Resources, and the U.S. Forest Products
Laboratory to design the structure.
Another AEWC project, a road bridge scheduled for construction in
Crenshaw County, Ala., uses the same approach as a smaller AEWC bridge
in Medway, Maine. The large load-bearing beams that support the
structure will be made of laminated planks with an FRP layer on the
bottom of each beam. Repeated tests at AEWC show that an FRP layer
nearly doubles beam strength, even when lower-quality woods are used.
The AEWC's FRP technology also has been applied to the concrete pillar
of a highway overpass in Bangor, Maine. The goal is to determine if the
material can extend the life of the pillar by protecting it from road
At all of the demonstration sites, AEWC engineers monitor structural
performance under a variety of operating conditions. Much of the work is
simple and straightforward. Researchers load dump trucks with sand,
drive the trucks onto bridges and measure how far the structures sag.
They also visually inspect beams and decks, and in some cases, use
strain gauges to make precise measurements.
Their data show how wood-FRP hybrids perform under a range of
temperatures, humidity levels and loading stresses. With more composite
bridges planned in the next few years, AEWC is working with the Federal
Highway Administration to develop national engineering standards for the
use of wood composites in highway infrastructure.
While these structures provide a foundation for AEWC research, new
ventures are giving students and faculty other opportunities. For
example, in the last year, stress tests have been run on building panels
strengthened with FRP. The goal is to create a product that will
effectively withstand the stresses of hurricanes, earthquakes and other
disasters, saving money and lives. That work is supported by a grant
from the National Institute of Standards and Technology.
Repair or strengthening of existing wooden structures is another avenue
that AEWC researchers have explored. In one experiment, solid beams were
cut nearly in half, then patched with FRP. Tests showed that the patches
restored the beams to full strength.
Through contracts with private companies, AEWC technicians now are
evaluating wood composite designs for skateboards, furniture, decking,
home construction materials and shelving. In each case, they are testing
the ability of wood-FRP technology to add value to products used in
daily life — and to meet the nation's building needs in the 21st
by Nick Houtman
for more stories from this issue of UMaine Today Magazine.