Cranking up composite trailers

IT LOOKS LIKE no other trailer plant in the United States because it produces a trailer that is different from any built in America.

Look around the new 185,000-sq-ft plant and try to find welding machines, rivet guns, press brakes, and shears.

They aren't there because they aren't needed. This trailer-manufacturer, formerly related corporately to a subsidiary of an aerospace contractor, uses space-age materials that are bonded together — without a lot of bolts, bends, or weld beads.

Martin Marietta Composites is brand-new in the trailer business. In a special ceremony December 18, the company commemorated the first trailer produced at its plant in Sparta, North Carolina. The initial product, a 48-ft live-floor transfer trailer, is constructed of glass fiber-reinforced polymer materials. The only metal is the kingpin, landing gear, axles, wheel and brake components, and miscellaneous fasteners.

The trailer is so lacking in metal content that the electrical system cannot rely on the trailer itself to provide a ground. Separate wires have to be run to power such components as the lights and the Haldex 4S/2M antilock brake system.

Although the plant is new and the company is just now establishing itself in trailer manufacturing, the product has been widely acclaimed in Europe. The design has been produced for several years by Composittrailer n v of Lokeren, Belgium. It has received several awards, including the European Road Transport Innovation Award in 2002; the Trailer Award at the 2001 International Trailer Show in Kortrijk, Belgium; and the Most Innovative Application award at the Fifth World Pultrusion Conference held April 2000 in Berlin. The trailer also was runner-up for the Best New Product Award at the 2002 International Composites Exposition in Paris, France.

Composittrailer is a wholly owned subsidiary of Groep Stevens International. Founded in 2000, the company was created to design, produce, and market composite truck trailers for the world market. The company is a spin-off of Stevens Carrosserie n v, which claims to be the oldest continuously operated producer of commercial truck trailers in the world. It, too, is wholly owned by Groep Stevens.

Martin Marietta signed an agreement with Composittrailer in 2002 that gives the Raleigh, North Carolina, company a license to manufacture and market the trailer in North America. The agreement authorizes Martin Marietta to produce trailers using Composittrailer's patented, all-composite chassis technology. However, Martin Marietta also will draw from its own composite fabrication expertise.

Worst-case scenario

In selecting transfer trailers as its initial entry into the trailer business, Martin Marietta is putting its product into a particularly abusive environment.

“We need to prove to customers that this type of technology is durable,” says Grant Godwin, vice-president and general manager of Martin Marietta Composites. “When we do, it will be easy to branch out into other applications.”

The company plans to do just that, eventually offering trailers such as platforms and refrigerated models.

“Our company is looking forward to introducing composite commercial truck trailers to the North American market,” says Stephen Zelnak Jr, chairman and chief executive officer of Martin Marietta. “This agreement with Composittrailer is an extension of our company's expertise in structural composite materials and represents a significant stepping stone to broader commercial applications. The American transportation industry is just beginning to consider the use of composites to reduce costs and increase the serviceable life of trailers.

“Our initial focus will be in the live-floor trailer market with $300 million in annual sales. However, we estimate the potential size of the composite truck trailer market in the United States to be $2.5 billion to $3 billion in annual sales, with the total truck trailer market at approximately $5 billion annually.”

What's the difference?

The sides of the Martin Marietta transfer trailers utilize panels of fiber-reinforced composites made of continuous glass or carbon fabrics in a polymer resin. The composite material forms the skin of the panels, completely encapsulating blocks of polyurethane foam.

While other companies have offered composite panels of comparable design, the Martin Marietta technology addresses one of the primary concerns regarding composite panels — delamination.

The composite skin is bonded to the block of foam. However, the skins are further joined with strands of glass fiber that are inserted through the panel and become an integral part of both skins. The density of the insertions throughout the panel — or in specific areas within the panel — are computer-controlled. The density of the insertions can be controlled by engineering.

Producing composite panels

Martin Marietta produces its own composite panels at its Sparta plant. A wall running the length of the plant divides the building almost in half. Trailers are assembled on one side of the wall, with panel production, paint booth, bridge deck production, and storage area occupying the remainder.

Panels are produced in continuous lengths and in variety of thicknesses. Bridge decks are pultruded as profiles that are then bonded together to create sections that will be installed in a single operation. Martin Marietta has been producing bridge decks for eight years.

The composite bridge decks offer many of the same advantages: high strength, low weight, and no corrosion.

“Highway departments are constantly having to fight corrosion on bridges, especially with the new chemicals used for ice control,” says Brady Jones, plant manager.

According to the company, the bridge decks weigh one-fifth as much as a comparable concrete deck, they are more resistant to corrosion and freeze/thaw cycles, easier to fabricate and transport, and more rapidly installed.

Closer look

So just what does a composite transfer trailer look like?

The first one off the Martin Marietta assembly line was a 48-ft trailer, but the company offers lengths of 40 to 57 feet.

Sidewalls are only 13/16" thick, which provides 99¾" inside width. As such, a 50-foot trailer will provide 132 cubic yards of capacity, approximately 5% greater volume than a comparable aluminum or steel trailer, the company says.

The understructure of the trailer, including the subframe rails, cross sills, and suspension hangers are made of glass fiber-reinforced polymer. Furthermore, the upper coupler and axle supports also are made from the same material.

The slats of the live floor are composite pultrusions.

Add it all up, and the first trailer off the line weighed only 13,140 pounds.

One of the most unusual features of the understructure are trumpet-shaped lower crossmembers. The flared ends provide strength and dimensional stability while at the same time absorbing stress.

“Composite material absorbs vibration and shock so well,” says Larry Dickinson, manager of engineering and technology. “It will result in less wear and tear on furnished components such as brakes.”

Blank sheet of paper

The plant is housed in a nearly new building that, from the perspective of the company's industrial engineers, was almost a blank sheet of paper.

Located in the mountains of western North Carolina, the building had been home to a manufacturing company that had expanded by opening a second plant. After a brief period operating its Sparta plant, a major change in the market led the company to close the facility and move production back to its headquarters.

With no intermediate support columns to design around, engineers were free to lay out the plant as they saw fit.

“It was an empty plant with few restrictions,” Jones says. “Engineers dream to have that.”

The building matched the needs of the company so closely that Martin Marietta was willing to locate manufacturing in a remote area of North Carolina, well removed from the urban confines of Martin Marietta Composites headquarters in Raleigh and its parent company, Martin Marietta Materials.

“We are proud to become part of the community of Sparta and pleased to have the chance to benefit the community economically” says Phil Sipling, executive vice-president of Martin Marietta Materials. “We believe our composite products represent the building materials of the future, with applications in several industries.”

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