Industry professionals must work together to tackle the challenges of mixed-material joining.

Even the best designed composite component doesn’t usually operate solo. In many applications, composites are attached to another part made from materials as varied as high-strength steel (HSS), aluminum, magnesium, another thermoset composite or thermoplastics. And that can create challenges.

“Composites are this incredible material platform,” says Dustin Davis, director of business development for Norplex-Micarta, a producer of thermoset prepregs, sheets and shapes. “We go out and tell OEMs how we can integrate parts, provide design flexibility and solve a lot of problems. You sell the OEMs and then they say, ‘Wait a second: How do I get this attached to my other parts?’”

Composite joining technologies have been around for decades, including an array of mechanical fastening, adhesive bonding and welding processes and products. But each method has some limitations, and none of them present a one-size-fits-all solution for composite applications. In addition, some industries are hesitant to fully embrace composites, in part because of concerns over the performance and predictability of joining techniques.

Automotive is one of those industries. “The automotive industry has talked about, investigated and done some upfront testing with composite bonding, but they have not fully accepted and adopted it,” says Tim Uebbing, an application engineering specialist in 3M’s automotive division. “There are a few OEMs who have been integrating composite materials in higher production models. But the industry as a whole is a bit slow in full adoption of composites.”

There are admittedly several reasons why the automotive industry and others are cautious when it comes to composites. But joining makes the short list. “It’s a key enabling technology, no doubt about it,” says Davis. “We know there are future applications at a high-volume scale that are going to rely heavily – if not entirely – on joining technologies.”

Evaluating Mixed-Material Joining

Last spring, Lightweight Innovations For Tomorrow (LIFT), a public-private partnership committed to the development and deployment of advanced lightweight material manufacturing technologies, launched a project with the Center for Automotive Research (CAR) to test and evaluate mixed-material joining technology. As automakers consider a wider range of materials to save on weight, joining those dissimilar materials will be paramount to solutions they adopt.

“Even though a particular part may have the proper stiffness, if you can’t transfer the stresses to other components or transfer the stress through the joints, then having a stiffer part doesn’t help at all in terms of a better structural component,” says Abhay Vadhavkar, director of materials and manufacturing technology for CAR. “So joining is absolutely the key to being able to use lighter weight materials.”