Comparison of the response of different configurations of aircraft repair patches under static and dynamic loading
- Autores: Siddharth Pitta
- Directores de la Tesis: José Ignacio Rojas Gregorio (dir. tes.), Daniel Crespo Artiaga (codir. tes.)
- Lectura: En la Universitat Politècnica de Catalunya (UPC) ( España ) en 2020
- Idioma: español
- Materias:
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- Resumen
In the modern era of transportation, air travel has gained a huge pace and still kept increasing. The global demand for air transport is increasing at a rate of 6%, because of population growth and ticket price reductions. Airlines aim at minimizing their operational costs and maximizing aircraft use factor (i.e., make the maximum possible trips with the least turn-around time). Operational costs can be reduced by, for instance, improving the fuel efficiency, reducing the drag acting on aircraft and lowering the maintenance cost.
As Aviation structural engineer, better understanding of repair technologies plays an important role in minimizing the operational costs. Namely, a major time consuming process is the maintenance of the aircraft in between flights, to detect early formation of cracks, monitoring crack growth, and fixing the corresponding parts with joints, when necessary. This project is focused on repair technologies of the structural parts in aircraft to regain their strength. In the modern aviation more than 50% of the structure is made of Composites. Composites have many advantages over conventional Aluminium alloys, which have been extensively used since the 1950s. Composites have very high specific strength compared to aluminium alloys, but when they are riveted about 60% of the material strength is lost (the plies of composite are damaged due to the holes made in the structure for riveting, which may fail without any early detection before the scheduled maintenance checks). Riveting of Composite parts is still practiced in the aviation as a quick and temporary fix. To overcome this far-from-optimum, it is necessary to study the methods of repair technologies and compare their behavior under various failure modes especially fatigue. Majority of structural parts fail due to fatigue, which is well known phenomenon in engineering.
In this PhD thesis, we present the static and fatigue behavior of repair joints and their response to in-service loading conditions. Static and Fatigue experiments were conducted on metal-metal, metal-composite, composite-composite and composite-metal joint configurations under riveted, adhesive bonded and hybrid joining. Aluminum rivets and araldite adhesive was used in the preparation of specimens. Static and fatigue tests were conducted using a universal testing machine. Later, numerical analysis is performed on the experimentally studied joints using finite element tool ABAQUS. Experimental and numerical results agreed with a maximum margin of 5%. Open source software such as FRANC 2D and FRANC3D were used for fatigue lite prediction and analysis of riveted and adhesive bonded joints. Finally, Autodesk Helius composites tool was used to analyze ply-load distribution, first ply failure with progressive failure analysis and failure envelopes of composite substrate in longitudinal, lateral and through-thickness directions.
