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Eric Pieper


This research was performed to explore the possibility of using epoxy joint connections in place of welded connections in a tube frame structural design. Welded connections work very well when the frame is made of steel, aluminum or titanium. Carbon fiber tubes are available and have a higher strength-to-ratio than the metal tubes, but the connection<; cannot be welded. The long-term goal of this research is to be able to use carbon fiber tubing to construct the solar car chassis. A junction made using high strength epoxy to bond an insert into the adjoining tubes can be almost as strong as a tube that has not been cut. Using a 6061-T6 aluminum tube, an insert of the same material, and Araldite 2015 two-part epoxy the junction was almost as strong as a welded connection in two different types of tests. In a 3-point bending test a sample with the glued joint yielded at bending stresses of 10 to 20 ksi. In a torsion test the glue yielded at shear stresses of 4.5 to 10 ksi. A welded connection will typically yield at 16 ksi in bending and 8 ksi in shear. Since the results are so close to the strength of welded connections, this method may be examined as an alternative to welding in some instances.

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