As automakers look for ways to reduce vehicle weight, often through the use of fiber-reinforced composite materials, Michigan State University researchers are developing ways to join composite and traditional materials without compromising the materials.
“If you drill a hole with mechanical means (in the composite), damage is introduced at the edges of the hole, and the layers that make up the composite separate,” says Mahmood Haq, assistant professor of civil and environmental engineering at Michigan State. “You lose up to 60 percent of the capacity of the composite to carry load.”
He also says using an adhesive to bond the two materials together has limitations.
“That, unfortunately, is a one-time cure,” Haq says. “Once the adhesive cures, the joint can’t easily be undone.”
Haq and his team are developing an advanced adhesive with special properties that allow them to be taken apart, repaired, or healed. The special properties are obtained by adding electrically conductive nanoparticles to the adhesives.
“Millions of these nanoparticles are embedded in the adhesive,” he says. “By using what we call targeted heating we can bond them and reverse the bond and take them apart.”
Haq says one key to making the joining technique practical is to be sure it can be integrated into today’s auto assembly line practices.
“We want joints that are easily and quickly produced,” he says. “We don’t want to have to totally re-tool the assembly lines. We don’t want to have to invent a new technology which disrupts current manufacturing practices.”
Haq says composite materials are lighter, stronger, and stiffer than most traditional materials, such as steel or aluminum. However, he says manufacturing vehicles completely out of composites is an expensive alternative.