Adhesive bonding has always been an alternative to traditional fastening systems. It sounds like you need a structural high-strength adhesive. It is very important that you choose a system that will: give reliable bonding to the steel, cure quickly to give high strength for handling, and have the durability to maintain the weight of the panel during the lifetime of the panels.

You really need to know what loads the assemblies will carry. The necessity for high strength and load-bearing capability will preclude many adhesives. In your case, a high-performance, two-component epoxy adhesive will be an obvious candidate. These adhesives can be formulated to give highly crosslinked thermoset systems that will resist creep under load for long periods of time. In addition, their cure speed can be varied to suit your assembly process. For example, a system that may take 24-72 hrs. to cure fully at room temperature can often be spot-heated to fixture and hold the parts together in a minute or two.

The only negative of these epoxy adhesives is that they tend to be somewhat rigid and brittle, with low peel strengths. A few rivets are sometimes used to minimize the peel issues (e.g., in the assembly of school buses). In recent years, auto manufacturers have used so-called “crash-resistant” epoxies in panel and roof bonding.

Ensure that you work with your adhesive supplier to do some testing. Depending on your specific requirements, alternative adhesives would be reactive acrylics or polyurethanes. These two types of adhesives will give you toughness and impact resistance at the expense of the highest tensile shear strength.
 

Any views or opinions expressed in this column are those of the author and do not represent those of ASI, its staff, Editorial Advisory Board or BNP Media.