Testing of mechanical butt joints in composite structures

As the main contribution of the present study, an I-shaped joining element, which allows the plates used in large composite structures to be joined butt-to-butt, has been improved in terms of load capabilities. It is desirable that the joining zones of composite plates not be visible according to the design of composite structures and the requirements for the desired use in particular. In other words, it is not desirable to create any surfaces that would cause protrusions in the joining zones. The only joining technique that fulfils this condition is the butt joint. Generally, butt joints are performed by bonding. With this technique, it is possible to make a more durable mechanical butt joint using an I-shaped joining element. In this way, instead of bonding butt joints, stronger non-bonding or bonding mechanical butt joints can also be achieved. In this study, the geometric changes in the shape of an I-shaped joining element used in mechanical butt joints and the changes in load-carrying capabilities have been studied experimentally and numerically. Experiments were carried out with tensile, three-point bending and four-point bending tests. The experimental specimens and I-shaped joining elements were cut using a water jet machine. Abaqus finite element analysis software was used for numerical analysis. The numerical data obtained in the study were found to be consistent with the experimental data. The load-carrying capabilities of the joining elements of different geometric shapes were studied numerically and experimentally, and it was found that the ideal element was the joining element with a 60 degrees angle.