Adhesives are becoming a formidable competitor to mechanical fasteners in structural applications. The reason: recent improvements in peel strength, flexibility, and resistance to moisture, temperature, and chemicals.
The potential advantages of adhesives over mechanical fasteners have long been recognized; however, industrial acceptance of adhesives for structural applications has been slow. The main reason for this lack of use is that adequate information about the characteristics of adhesives was not available until recently. Development studies by the aerospace industry greatly improved the technical database on structural adhesives, and many industrial designers are now convinced that the adhesives can provide bonds that are both cost effective and durable.
Structural adhesive bonds have replaced both mechanical fasteners and assembly techniques such as soldering and welding in many industrial applications. The advantages of structural adhesive bonding over other joining techniques include:
The potential advantages of adhesives over mechanical fasteners have long been recognized; however, industrial acceptance of adhesives for structural applications has been slow. The main reason for this lack of use is that adequate information about the characteristics of adhesives was not available until recently. Development studies by the aerospace industry greatly improved the technical database on structural adhesives, and many industrial designers are now convinced that the adhesives can provide bonds that are both cost effective and durable.
Structural adhesive bonds have replaced both mechanical fasteners and assembly techniques such as soldering and welding in many industrial applications. The advantages of structural adhesive bonding over other joining techniques include:
- Cost savings, including lower labor costs.
- Weight reduction.
- Elimination of stress point concentrations by even distribution of stress over the entire bonded surface, plus improved load bearing capacity.
- Protective sealing against contamination by liquids or gases.
- Bonding of dissimilar materials. Often the adhesive bond line acts as an insulator against galvanic corrosion in metal assemblies.
- Improved fatigue resistance, and resistance to shock, vibration, and thermal cycling.
- Enhanced structural appearance because protrusions, punctures, and attachments are eliminated.
- Increased tolerances on machined parts because some structural adhesives can fill gaps left when parts mate poorly.
Few available adhesive materials meet the stringent requirements of structural bonding, such as durability, high strength, and dimensional stability over a wide range of environmental conditions. The main classes of adhesives meeting structural requirements are epoxies, cyanoacrylates, reactive acrylics, and polyurethanes. Also, recently developed materials that appear to be especially suited to high temperature use include polyimides and some silicones.
