Buckling Analysis of Laminated Stiffened Plates with Material Anisotropy Using the Rayleigh–Ritz Approach

An energy-based solution for calculating the buckling loads of partially anisotropic stiffened plates is presented, such as antisymmetric cross-ply and angle-ply laminations. A discrete approach, for the mathematical modelling and formulations of the stiffened plates, is followed. The developed formulations extend the Rayleigh–Ritz method and explore the available anisotropic unstiffened plate buckling solutions to the interesting cases of stiffened plates with some degree of material anisotropy. The examined cases consider simply supported unstiffened and stiffened plates under uniform and linearly varying compressive loading. Additionally, a reference finite element (FE) model is developed to compare the calculated buckling loads and validate the modelling approach for its accuracy. The results of the developed method are also compared with the respective experimental results for the cases where they were available in the literature. Finally, an extended discussion regarding the assumptions and restrictions of the applied Rayleigh–Ritz method is made, so that the limitations of the developed method are identified and documented

Bird strike simulation on a novel composite leading edge design

A methodology for the numerical simulation of bird strike on a novel Leading Edge (LE) structure of a Horizontal Tail Plane is presented. The innovative LE design is based on the ‘tensor skin’ concept, comprising one or more folded composite sub-laminates, which unfold during the bird impact providing high-energy absorption characteristics. The simulation technique is based on a non-linear dynamic Finite Element (FE) analysis and is performed in three steps. The first step deals with the development of suitable material damage models capable to represent the high strain rate behaviour of the composite systems used in the LE structure. The second step deals with the development of a FE modelling procedure for simulating the complex failure modes and unfolding mechanisms of quasi-static penetration of simple ‘tensor skin’ strips, representative of the complete LE composite structure. The third step deals with the numerical simulation of bird strike experiments on two novel aircraft LE designs. The influence on the numerical results of the critical modelling issues, such as, the mesh density of the highly impacted areas, the substitute bird flexibility, as well as, the material damage and contact interfaces parameters are discussed in detail. The numerical results are in good qualitative and quantitative agreement to the results of the experimental tests

Microstructure modifications induced by a laser surface treatment in an AA7449 aluminium alloy

International audienceThis work investigates the modification of the precipitate microstructure induced by laser surface treatments in an AA7449 aluminium alloy in T7651 temper. Microhardness maps in the cross-section below the laser lines, as well as maps of the precipitate size and volume fraction obtained by Small-Angle X-ray Scattering, show that a significant precipitate dissolution and coarsening has been induced by the laser treatment. Integrated modelling is carried out to quantify this effect, including a thermal finite element model, a size class precipitation model and a precipitation hardening model. The precipitation model is calibrated using separate reversion experiments, and then coupled to the thermal and mechanical models, allowing a quantitative description of the modification of the microstructure. (C) 2010 Elsevier B.V. All rights reserved