In order to save costs, the automotive and aerospace industries often need to design lightweight materials. Lightweight materials often need to combine different types of materials (such as metals and polymers), which will greatly increase manufacturing costs. Recent work has shown that the use of laser technology can increase the bonding strength of metal and plastic mixed materials. Engineers have used infrared laser to pretreat aluminum plate technology to bond plastic and aluminum together. They elaborated on their work in the Journal of Laser Applications. The above are two scanned images. (A) is the aluminum chip at the edge of the CW laser structure, and (b) is the aluminum remaining in the grooves on the surface of the molded polymer after the tensile shear test.
As developers in the automotive and aerospace industries continue to push for more efficient vehicles, people are currently working to design rugged, lightweight machines. However, designing lightweight materials requires combining different types of materials such as metals and polymers, and these extra steps increase manufacturing costs. Recent work has shown that the use of laser technology can increase the bond strength of metal and plastic hybrid materials.
An engineer from a German research group recently invented a technique for bonding plastic to aluminum by pretreating the aluminum plate with an infrared laser. Their results are published in the Journal of Laser Applications. Researchers have found that roughening the aluminum surface with a continuous laser beam produces mechanical interlocking with thermoplastic polyamides, which results in significant strong adhesion.
One of the authors, Jana Gebauer, said: "In other connection methods, generally we need a plastic part that we want to mate with the metal part. In the injection molding process, we create the plastic part directly on top of the metal part in the machine cavity. This is very difficult compared to hot pressing or other joining technologies due to specific thermal conditions. "
To solve these problems, Gebauer and her colleagues applied a continuous laser and a pulse of 20 picoseconds to the aluminum plate surface each time, which can make the aluminum plate surface more sticky, so that a polyamide layer can be molded thereon. They then placed the sheet into an injection mold and overmolded it with a thermoplastic polyamide, a nylon-related polymer commonly used in mechanical parts such as power tool housings, machine screws, and gears.
"Then we analyzed the surface morphology of the aluminum sheet and mechanically tested the bonding behavior to find out which parameters can achieve the maximum bonding strength," Gebauer said.
Tests performed using an optical 3D confocal microscope and a scanning electron microscope show that the aluminum plate grooves treated with a pulsed laser have a smoother line pattern than the topography in the aluminum plate grooves treated by continuous laser. Aluminum plates treated with infrared lasers also show stronger adhesion, but these properties decrease with increasing moisture content.
Despite the team's success, Gebauer believes that there is still much work to do to understand how to optimize the pretreatment of metal surfaces to make the manufacturing process more economical. Now, she and her colleagues are studying how molded thermoplastics shrink when they cool.
Gebauer said: "Thermal shrinkage causes mechanical stress, which separates the two components. The current challenge is to find a structure that compensates for the stresses generated during the shrinkage process. It also requires that the structure does not cause aluminum due to laser processing. Softening. At the moment we hope to use the ultra-short pulse laser to produce a reliable bond to reduce thermal damage to metal parts. "
The Fraunhofer Institute for Materials and Beam Technology of the Leibniz Institute for Polymer Research at the Technical University of Dresden participated in the study.