Experimental investigation of 3-D printed bonded scarf joints failure response

• Main Author: Theng, Clarence Wen Jun
• Other Authors: Sridhar Idapalapati
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2021
• Subjects: Engineering::Aeronautical engineering; Engineering::Mechanical engineering
• Online Access: https://hdl.handle.net/10356/150574
• Institution: Nanyang Technological University

The use of traditional manufacturing methods for the repair of composite in the aerospace industry has been prevalent. However, as the world revolves and moves towards additive manufacturing, additive manufacturing has been explored for the use of repairs. A frequently used repair technique is adhesive bonding joint repair. In the repair of adhesive bonding joint, commonly used joints include scarf joints, butt joints and lap joints. However, these joints have trade-offs. The repair requires large amount of materials to be removed and thus in return might damage the material further. Butt joint and lap joint does not give a flushed aerodynamic finishing. Extensive research has shown that scarf joint has the best mechanical properties all repairs however it has a large repair signature. Therefore, new novel joints figuration was developed to attempt to reduce the repair signature while having similar or better mechanical properties of a scarf joint. A combination of interlocking joint, scarf joint and step joints were used in the designing process. Four different joint configurations were 3D printed. Namely scarf joint as a control, step joint, stagger joint and stager joint with pins. These joints was printed using Carbon Fiber Reinforced Polymer with Onyx as the polymer. Tensile test was then conducted on these four joints using scarf joint as the benchmark. Strain and load were recorded with a strain gauge and plotted on a graph to be observed. The experimental results of the three novel joints in comparison with a scarf joint showed promising results. The results obtained have shown that the novel mechanical joint designs were stronger than the adherend. However, further research must be done to fulfil the criteria of reducing repair signature while keeping the mechanical properties similar to a scarf joint.