The bonding capabilities and performance characteristics of adhesives like epoxy are better understood by studying the fundamentals of fracture mechanics.
Typically, composite pipe supports, such as FRP wear pads and pipe shoes, are attached to the pipe using an epoxy or some sort of adhesive. This is advantageous because epoxied pipe supports avoid the need for welding, which can become a complicated process. It goes without saying that adhesive joints need to have high bonding strengths to enable the pipe support to remain intact throughout the entire service life.
The fundamentals of fracture mechanics can be used to better understand the bonding capabilities of adhesives such as epoxy. Fracture mechanics predict material failures by applying stress and strain concepts to material cracks and defects. Understanding fracture mechanics is important to the design process of components to ensure that they will behave as expected in their respective applications.
In fracture mechanics, there are three basic modes which are used to describe various material failures.
- Mode 1 — Opening mode (think: crocodile opening its jaw)
- Mode 2 — Sliding mode
- Mode 3 — Tearing mode
Testing according to these three modes can be performed to simulate field conditions and predict performance of an epoxy. For example, to test based on mode one, you can initiate a crack by sticking a blade between the epoxy and composite part. From there, the energy required to separate the two (energy release rate) can be measured.
In addition to using a high strength epoxy, there are a couple of measures you can take to ensure optimal bonding strength between the pipe and its support.
- Rough Surface — The surface of the composite should be properly roughened to provide an anchor profile for the epoxy. Epoxy will not be able to stick well to a slick surface.
- Clean Surface — In addition to an ideal, roughened surface, it is important that the surface of the composite is clean and free of any dust, dirt, and debris, which can inhibit bonding capability.
Overall, the purpose of the epoxy is to hold the FRP wear pad or pipe shoe in place while providing a seal to prevent moisture from accumulating between the pipe support and the pipe. If moisture is able to get in, crevice corrosion could ensue.
Effective epoxy, like the APP Epoxy, will protect your expensive piping systems by holding the pipe support in place and preventing moisture build-up. The APP Epoxy was developed for aerospace applications and is specifically formulated to bond lightweight composites to metallic materials. Our reliable and robust epoxy is used with our ProTek Wear Pads, ProTek Flat Plates, and CryoTek Pipe Shoes.