Scientist at the United States Department of Energy’s Oak Ridge National Laboratory in Tennessee have developed a new, more cost-effective method for joining carbon fiber composites and aluminium. This new process could make it even easier to utilize these materials in the process of lightweighting consumer cars and trucks.
The technique for bonding aluminium and carbon fiber today is laborious, as it involves manually applying abrasives, grit blasting, or applying toxic solvents in order to prepare the surface of the materials to be joined. The scientists in question have developed a method of preparing the surface using lasers, which improves bonding and allows for automation of the process.
“Our technique is vastly superior to the conventional surface preparation methods,” said Oak Ridge’s Adrian Sabau. “Combined with the potentially dramatic reduction in the cost of carbon fiber polymer composites, this represents an important step toward increasing the use of this lightweight high-strength material in automobiles, which could reduce the weight of cars and trucks by 750 pounds.”
Surface preparation is an important step in the joining process, and directly impacts the quality of the adhesion to be done. Aluminium surfaces contain artifacts from production including oils and other contaminants, while the surface of carbon fiber frequently have mold.
“These surface contaminants affect surface energies and the quality of adhesion, so it is critical that they are removed,” said Sabau. He went on to point out that the laser penetrates the top layer of resin, exposing the carbon fibers themselves, which improves adhesion as well.
Tests of joints made by using the new process showed significant improvements in strength and energy absorption over joints made using the traditional process. Energy absorption, which doubled using the new process, means that the process has promise for increasing impact safety in vehicles, as well as having the potential to find use in vehicle and personal armor.
“The results are most encouraging, enabling the automated processing of a multi-material carbon fiber-aluminum joint,” said Tim Skszek of Magna International, a project partner. “With this work, we were able to focus on addressing the gaps in technology and commercial use, and we look forward to applying these findings to products.”