How Lasers Could Increase Composites Adoption by Auto Makers
A number of factors have prevented the automotive industry from going all-in on composite parts for as many applications as possible. One of the hindrances is cost, but another is the physical problem of joining metal and composite parts in a way that is mechanically sound, efficient, and automated. Lasers may be the thing that overcomes this barrier.
For many years, there were only two ways to fasten carbon fiber and glass fiber parts to metal parts. Each method has its pros and cons. Neither is highly automated – which is a problem for an industry that automates a substantial portion of its assembly process. If laser technology currently being developed proves to be everything engineers hope it will be, it could replace the other two methods entirely.
According to Industrial Laser Solutions, the first method for joining metal and composite parts is mechanical joining. Think of it as similar to joining two pieces of wood with some sort of fastener. Mechanical joining is fast and cheap. It has a long history of reliability. However, there are some downsides.
First and foremost, adding fasteners only adds to weight. One of the reasons for adopting composite materials is to reduce weight. Second, drilling holes in composite parts can compromise the strength of individual fibers and the parts as a whole.
Adhesive joining is the second method. This is essentially gluing parts together. The upside for the automotive industry is that there are plenty of adhesives to work with, adhesives that can be adapted to meet the needs of a particular application. The downsides are longer processing times, the need for additional materials, and an excessive amount of surface prep before parts can be joined.
Joining glass or carbon fiber parts with metal using lasers is a better and more efficient way to do things. It is fast, repeatable, and creates high joint strength with no additional materials required. The two downsides are the limited use of lasers with thermoplastics and the need to have joints fully accessible in order to treat them.
Laser joining is a highly technical two-step process. The first step prepares the metal surface with one of two specialized lasers that essentially create a texture at the site of the joint. For all intents and purposes, the laser is used to scuff the metal in order to give the composite something to adhere to.
The second step involves melting the plastic component of the composite, pressing the material against the metal to create the joint, then allowing everything to cool and cure. Done correctly, this process creates an extraordinarily strong joint.
Reinforced Plastic Materials
At this point, something might seem off to the uninitiated. It may be due to a lack of understanding about composites like glass and carbon fiber. What we normally call carbon fiber really is a carbon fiber reinforced plastic (CFRP). A part made of fiberglass is actually glass fiber reinforced plastic (GFRP).
Rock West Composites out of Salt Lake City, Utah says that your typical CFRP is created by combining a carbon fiber fabric with an epoxy resin. When the two are combined and cured in a high heat autoclave, they meld into a single piece of plastic. The plastic is reinforced by the carbon fiber material within.
Thus, you can melt the plastic component of a CFRP in order to join it with metal. You can do it with lasers, and you can do it efficiently and automatically. Laser joining could be a big part of composites’ future in the automotive industry.