Experimental Strength Characterization of Epoxy Double Lap Joint for Carbon-Fiber Reinforced Polymer Tube

Abstract

Composite materials are increasingly affordable and utilized across many industries as they become better characterized and manufactured at high volumes to stock dimensions. One major challenge in their utilization is designing predictable structural joints. This report focuses on predicting the critical load of an epoxy adhesive double lap joint through experimentation. Test samples were designed and fabricated from off-the-shelf spindle-wound tubes and machined forged carbon fiber. An assembly of aluminum parts was designed and fabricated to hold the samples in an Instron universal testing machine for gathering of force-extension measurements as the joints were tested to failure. The stiffness of the off-the-shelf tubes was also experimentally determined to allow for the calculation of the theoretical critical load to fail the joint, according to a flat-plate joint theory. The collected data did not clearly support or contradict the applicability of the existing theory for double lap joints. While a few issues in the test setup limited the quantity and reliability of data, the process of designing the experimental hardware and procedure demonstrated the feasibility of this type of research and yielded valuable insights that can aid in the design of future experiments.