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Applied Composite Materials: An International Journal for the Science and Application of Composite Materials (v.11, #5)
Fatigue of Woven Composite Laminates in Off-Axis Loading I. The Mastercurves by V. Tamuzs; K. Dzelzitis; K. Reifsnider (pp. 259-279).
The behaviour of woven orthotropic composite laminates in static and fatigue off-axis loading is described. It is shown that all phenomena: linear and nonlinear deformation; accumulation of damage, measured as change of cyclic modulus or hysteresis loop; and the static and cyclic strength can be described by single master curves using the generalized stress and strain functions. These functions always contain the quadratic expressions of invariants of orthotropy, but coefficients of the invariants depend on the severity of nonlinearity in the described processes or phenomena.
Keywords: woven composite laminates; fatigue; off-axis loading; mastercurves
Fatigue of Woven Composite Laminates in Off-Axis Loading II. Prediction of the Cyclic Durability by V. Tamuzs; K. Dzelzitis; K. Reifsnider (pp. 281-293).
Fatigue data of glass epoxy woven laminate specimens cut at different angles to principial axes are reported. The monitoring of changes in the cyclic modulus and hysteresis loop was carried out in all tests. It was found that the final critical damage level before failure, measured as a reduction in the cyclic modulus, did not depend on the durability and was invariant with respect to the loading direction too. Such an invariance of reduction in the final modulus allows one to predict the cyclic durability of investigated material with a reasonable accuracy for any testing angle.
Keywords: woven composite laminates; fatigue off-axis loading; damage accumulation; durability prediction
Modelling of Bird Strike on an Aircraft Wing Leading Edge Made from Fibre Metal Laminates – Part 1: Material Modelling by M. A. McCarthy; J. R. Xiao; N. Petrinic; A. Kamoulakos; V. Melito (pp. 295-315).
Fibre Metal Laminates with layers of aluminium alloy and high strength glass fibre composite have been reported to possess excellent impact properties and be suitable for aircraft parts likely to be subjected to impacts from objects such as runway debris or birds. In a collaborative research project, aircraft wing leading edge structures with a glass-based FML skin have been designed, built, and subjected to bird strike tests that have been modelled with finite element analysis. In this first part of a two-part paper, a material model developed for FML suitable for use in impact modelling with explicit finite element analysis is presented. The material model is based on a recent implementation in the commercial finite element code PAM-CRASH/SHOCK of a Continuum Damage Mechanics (CDM) model for composites, incorporating anisotropic strain rate effects. Results from the model are compared with experimental results on FML at variable strain rates and the model is shown to be capable of capturing most of the complex strain rate dependent behaviour exhibited by these materials.
Keywords: bird strike; fibre metal laminate; finite element analysis; continuum damage mechanics; strain rate effects; aircraft leading edge
Modelling of Bird Strike on an Aircraft Wing Leading Edge Made from Fibre Metal Laminates – Part 2: Modelling of Impact with SPH Bird Model by M. A. McCarthy; J. R. Xiao; C. T. McCarthy; A. Kamoulakos; J. Ramos; J. P. Gallard; V. Melito (pp. 317-340).
Fibre Metal Laminates with layers of aluminium alloy and high strength glass fibre composite have been reported to possess excellent impact properties and be suitable for aircraft parts likely to be subjected to impacts such as runway debris or bird strikes. In a collaborative research project, aircraft wing leading edge structures with a glass-based FML skin have been designed, built, and subjected to bird strike tests that have been modelled with finite element analysis. In this second part of a two-part paper, a finite element model is developed for simulating the bird strike tests, using Smooth Particle Hydrodynamics (SPH) for modelling the bird and the material model developed in Part 1 of the paper for modelling the leading edge skin. The bird parameters are obtained from a system identification analysis of strikes on flat plates. Pre-test simulations correctly predicted that the bird did not penetrate the leading edge skin, and correctly forecast that one FML lay-up would deform more than the other. Post test simulations included a model of the structure supporting the test article, and the predicted loads transferred to the supporting structure were in good agreement with the experimental values. The SPH bird model showed no signs of instability and correctly modelled the break-up of the bird into particles. The rivets connecting the skin to the ribs were found to have a profound effect on the performance of the structure.
Keywords: bird strike; fibre metal laminate; finite element analysis; smooth particle hydrodynamics; aircraft wing leading edge