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Projecte llegit

Títol: Comparison of the response of different rivet layout patterns in aircraft repair patches

Estudiants que han llegit aquest projecte:

Director/a: ROJAS GREGORIO, JOSEP IGNASI

Departament: FIS

Títol: Comparison of the response of different rivet layout patterns in aircraft repair patches

Data inici oferta: 21-11-2019     Data finalització oferta: 21-06-2020


Estudis d'assignació del projecte:
    MU AEROSPACE S&T 15
Tipus: Individual
 
Lloc de realització: EETAC
 
Segon director/a (UPC): PITTA, SIDDHARTH
 
Paraules clau:
materials; composites; carbon; glass; fibre; fiber; epoxy; mechanical properties; yield stress; tensile stress; elastic modulus; Young's modulus; hands-on; experiments; numerical analysis, FEA
 
Descripció del contingut i pla d'activitats:
Main goal: In this project, the static and fatigue behavior of
various joint and repair configurations used commonly in the
aviation industry, as well as other innovative configurations,
is analyzed. In particular, combinations involving
aluminum/composite material as substrate/doubler, with
different joining techniques (i.e., mechanical fastening with
rivets, adhesive bonding and hybrid bonding) are studied. The
main focus is places in analyzing the effect of the following
factors on the performance of the repair patches and/or
joints: layout patterns of the rivets, repair patch lay-out
shapes and step lap joints, thicknesses and bond lenghts of
the adhesive layer, etc.

The research is performed by means of Finite Element Analysis
(FEA) using NASTRAN/PATRAN and experiments.

The procedure and methodology will be as follows:

1. Literature search and review of relevant bibliography
2. Formation on appropriate software packages (e.g.,
SolidWorks, Abaqus, Helius Composite Tools, FRANC2D, FRANC3D,
NASTRAN/PATRAN, etc.)
3. Numerical analysis/Finite Element Analysis (FEA) of
the problem:
a. design of the CAD geometry or geometries
b. meshing of the geometry or geometries
c. definition of the physics of the problems and the
boundary conditions
d. definition of the solver settings and solving of the
fluid problems with suitable solver
e. post-processing and analysis of the obtained results
4. Preparation of samples for experiments
5. Realization of experiments
6. Processing of experimental results and FEA results:
calibration of numerical results from FEA with experimental
results, comparison of results, etc.
7. Draw conclusions from the study
8. Write thesis and prepare final presentation

More info can be found in:
https://www.researchgate.net/project/Comparison-of-the-
response-of-different-configurations-of-aircraft-repair-
patches-under-static-and-dynamic-loading
 
Overview (resum en anglès):
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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