Marine foam technology lowers refrigerated trailer weights

Features - Materials

Wabash National’s next-generation reefer trailers increase their thermal efficiency without sacrificing interior space, thanks to foam technology developed for boats by Structural Composites.

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December 6, 2018
Robert Schoenberger
Photo courtesy of Wabash National

Usually, when innovative materials technologies work their way from one transportation sector into the motor vehicle world, the approach focuses on how an automaker adapted a low-volume, finicky aerospace process to mass-production scale. But when trailer maker Wabash National wanted to completely reimagine the structure of its refrigerated trailers (reefers), inspiration came from the water.

“About five years ago, my boss at the time who’s now our CEO Brent Yeagy, told us to go out and really build some breakthrough customer value,” says Robert Lane, vice president, engineering for commercial trailer products at Wabash. “Everybody in the refrigerated trailer market basically makes the same product with the same materials, using the same manufacturing processes. It’s hard to really differentiate yourself.”

Given a Moon Shot-like mandate, Lane and his team initially looked to the skies, envisioning a carbon fiber reinforced plastic (CFRP) trailer body that would weigh a fraction of the wooden, steel, and aluminum structures in use by Wabash and its competitors. But the value proposition just didn’t work. CFRP material costs were 10x to 20x higher than metals and wood, so the finished trailer wouldn’t appeal to anyone, despite thousands of pounds in weight savings.

“The payback on it, in our industry, is just not there. If you look at how often a trailer weighs out before it cubes out [hits its weight max. before it runs out of cubic feet of available space], it’s very small, somewhere between 2% and 10% of the time,” Lane says. “If I give you back 2,000 lb in weight, the only thing you’re saving is fuel, and that’s only about a 1% fuel savings.”

Foam boat construction

Lane invited several materials companies to discuss options with Wabash engineers, hoping to find a way to lower CFRP costs or find other materials that could drastically lower trailer weights. One of those companies was Structural Composites, a technology company that had developed a composite preform material for boats.

Structural Composites President Scott Lewit says he thought his company’s Prisma Preforms, reinforcing fabrics cast into shape with expanding foam, could be a starting point for materials for trailers. However, the technology had been developed for low-volume marine production, and he knew little about the challenges the reefer market was facing.

Prisma uses a pultrusion-like manufacturing process – layers of fabric are formed into a shape then filled with expanding foam – creating a low-cost, lightweight building block for composites. Once laminated to a structure, it offers the design freedom of plastics with the strength of aluminum, at a lower weight.

“Most commercial pultrusion operations run at 6"-to-12" per minute. We’re making some pre-formed elements at 16ft per minute,” Lewit says. “With what Robert [Lane] has done, they’ve scaled it much faster. That was a really important development – the technology had to be able to scale to their market.”

Getting production speeds higher, however, was just the start of the multi-year engineering challenge to develop the materials and processes for what Wabash calls molded structural composite (MSC).

Abusive environments

With boats, composites withstand odd bending stresses coming at hulls from various sizes of waves, corrosion from salt, and infiltration from water. With trailers, the challenges are much more dynamic.

“There will be times that a trailer has 48,000 lb in it, and it will be going over roads that aren’t always in the best shape, so it takes a beating when it’s going down the road,” Lane explains. “Then, when it’s loading or unloading, that’s where a trailer takes a lot of abuse. They get dinged into each other. When you load a trailer using a fork truck, you’re really beating the walls of the trailer up. That’s what our unknown was. How do you design for that with a material that’s not steel or aluminum?”

He adds trailers suffer a lot of damage from fork trucks. Fleet managers fear drivers taking a bad angle with loaders, sending forks through the side of insulated trailers.

“Drivers often use the trailer as a guard rail,” Lane says. “You have to load that trailer 100% full, so when they bring the fork truck in, they’ll put it up against the side wall, and they’ll run it all the way down the side. That’s intense abuse.”

Lewit says the breakthrough to providing the strength needed to withstand that treatment came from advanced coatings for the composite material. Working with Interplastic Corp. and BASF, researchers discovered ways of reinforcing the material’s strength and increasing toughness.

“CoCure technology was a discovery we made. Taking inexpensive polyester resins, we can inject a urethane component into it and upgrade the performance characteristics of the resin,” Lewit says.

The updated CoCure coatings replace traditional gel coats, improving crack resistance and weathering performance, allowing engineers to tune performance characteristics for the MSC material.

Results

The first fleet of Wabash Cold Chain reefers with MSC bodies are being tested now by fleet owners. Lane says he wants those companies to abuse their trailers to figure out ways to improve the models once full production begins. The company bought a former boat plant in Little Falls, Minnesota (along the Mississippi River, north of St. Cloud) to build the trailers.

“The amount of insulation we use, and how we use it, is pretty close to the same. The composites give us the ability to design the trailer to maximize space for insulation,” Lane says. “We’ve seen up to 30% improvement in thermal efficiency on a trailer that provides the same amount of usable cargo space.”

In the future, Wabash will be able to offer customers options – maintain existing thermal performance with more interior space or maximize thermal performance without reducing space.

“For some customers, that will be very important, if you tell them they can have 2" more height,” Lane says. “Most carriers are going to respond to the thermal performance and expected longevity. We’re going to be able to design a trailer that will last longer and hold its insulative properties better.”

Lewit says the trailer’s release is already having a massive impact on the composites market.

“The marine market is about 68% penetrated with composites. So, there’s a 32% opportunity,” Lewit explains. “When you look at the transportation market, it’s at 4% composites penetration. And, that 4% is 5x the size of the marine market.”

Lane adds that once Wabash is more comfortable with the material in the reefer market, he hopes to apply lessons learned to dry vans, a much larger portion of the trailer market.

“Most of the people in the industry, Wabash included, have a tremendous amount of capital invested in the way we do things today. So, to say we’re going to develop something that doesn’t use the equipment that we have in our manufacturing facilities, that takes a lot,” Lane says. “It takes vision from our executive team and our board of directors to give us this flexibility.”

Structural Composites Inc.
http://www.structuralcomposites.com

Wabash National Corp.
http://www.wabashnational.com

About the author: Robert Schoenberger is the editor of TMV and can be reached at 216.393.0271 or rschoenberger@gie.net .