Comparison of the response of different rivet layout patterns in aircraft repair patches
The skin structure of modern aircraft is composed of frames, which are complex structures assembled by joining several sub-assemblies. One of the most used methods for joining aircraft structural parts, as well as repair patches, is through rivets. These fasteners are extensively used in the aircraf...
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| Tipo de recurso: | tesis de maestría |
| Fecha de publicación: | 2021 |
| País: | España |
| Institución: | Universitat Politècnica de Catalunya (UPC) |
| Repositorio: | UPCommons. Portal del coneixement obert de la UPC |
| Idioma: | inglés |
| OAI Identifier: | oai:upcommons.upc.edu:2117/350279 |
| Acceso en línea: | https://hdl.handle.net/2117/350279 |
| Access Level: | acceso abierto |
| Palabra clave: | Airplanes--Design and construction Materials composites carbon glass fibre fiber epoxy mechanical properties yield stress tensile stress elastic modulus Young's modulus hands-on experiments numerical analysis FEA Avions -- Disseny i construcció Àrees temàtiques de la UPC::Aeronàutica i espai::Aeronaus::Avions |
| Sumario: | The skin structure of modern aircraft is composed of frames, which are complex structures assembled by joining several sub-assemblies. One of the most used methods for joining aircraft structural parts, as well as repair patches, is through rivets. These fasteners are extensively used in the aircraft industry due to many competitive advantages. For the load distribution, the classical method assumes that the force is distributed equally among all the rivets, but this simplification of the problem does not match reality. The riveting process has a nonlinear behaviour. This non-linearity appears from the interaction of geometry, riveting process, inelastic materials, and contact, boundary, and thermal conditions. Several previous works focused on rivet modelling have studied the impact of different factors on the riveted joint life, fatigue life, residual stress and material deformation, crack initiation and propagation, fretting fatigue, load distribution, etc. But some limited research has been carried out on the rivet distribution pattern. In this thesis, we studied lap patches riveted to the skin structure. The analysis was done with finite element methods using the commercial software packages Patran and Nastran. Different rivet pattern distributions were tested in order to check the rivet load distribution and the stress concentration in the plates and rivet holes. Particularly, two types of rivet patterns were used: Staggered pattern (Zig-Zag distribution of rivets) and Chain pattern (Equally distribution of rivets). The rivets and plates used in this work are made of the same material: aluminium alloy 2024-T3. The results obtained show that the classical assumption is not appropriate. The load distribution is not uniformly distributed. The typical tendency of the load distribution among the rivets is that the loading tends to be higher in the rivets in the corners. To reduce this load concentration, it is better to use a greater number of rows. The direction of the applied load affects the stress distribution depending on the rivet pattern design. In the staggered configuration, if we apply a longitudinal load, the rivets suffer from a higher net stress. However, if we apply a transversal load, the net stress is nearly the same as for the non-staggered design, but the first row of rivets must sustain more stress than the subsequent rivets before they begin to share the load in this loading direction. In that design, the pattern is more important, and the distance from the rivets to the edges and the distance between the rivets must be carefully considered. |
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