The development of more powerful and efficient aero-engines requires ways of increasing the torque transmitted by shafts, whilst also restricting their dimensions and weight. Thin-walled designs can assist this objective, but their use is limited by their torsional collapse behaviour. Of particular interest are conditions leading to buckling instability. The paper investigates the factors influencing this behaviour in order to provide the basis for an improved analysis method applicable to typical gas turbine aero-engine components.

The Riks finite element algorithm has been successfully applied to both plain shafts and shafts with holes. In the former case, it is shown that the perfect cylindrical geometry must be given an initial perturbation in order to give accurate predictions. The perturbation imposed is obtained by scaling the mode shape from an eigenvalue solution so that the maximum radial deformation is a percentage of the wall thickness. The predictions for both plain and holed shafts have been validated experimentally.

The Millennium now being upon us, it is perhaps appropriate to pause a while and take stock before leaping into an ever more problematic future. But why pause? Indeed, why bother with the past? Surely our newest, ever more sophisticated computer packages provide all the necessary paths to that next commercial edge, that future, unassailable military superiority? To this the German polymath, Gottfried Wilhelm von Leibniz, provides an apt, timely and, indeed, timeless corrective:

A two step procedure is proposed for the design of nonlinear aircraft control systems. A classical design is first denned, based on a linearised aircraft model, and easily optimised by means of standard approaches. An outer-loop nonlinear controller is then used to enhance the whole control system. This latter controller is based on fuzzy logic rules and is of fixed structure. Its behaviour is based on the choice of a set of parameters that may be tuned by means a genetic algorithm based routine. The whole methodology is simple to handle and may be effectively used to give quick and efficient responses to the designer. The procedure has been verified with a couple of examples: the obtained results clearly show important improvements with respect to a classical methodology.

This paper considers defence and aerospace research in the UK from the perspective of a research worker. The distinction between research, technology demonstration and development, the particular characteristics of research and the qualities required in a research worker are discussed. The important influence of the research environment, both within an organisation and nationally, is highlighted. The contribution of the past environment to the research underlying the present strength of UK technology, and subsequent adverse changes in the environment, are noted. The decline of UK research funding and of the UK research base is contrasted with the situation of our main industrial competitors. Finally, the author lists the actions which he believes are needed to rebuild research to a level which will underwrite the long-term future of UK defence and aerospace.

Fibre reinforced metal laminates (FRMLs) are a new family of aerospace structural materials developed for fatigue critical applications. These materials are laminated sheets of thin and high strength metal layers, usually aluminium, and alternating plies of fibre reinforced polymer composite layers, viz, aramid/epoxy, carbon/epoxy, glass /epoxy, etc. Afaghi-Khatabi and Ye have considered the fracture data existing on various ARALL (aramid reinforced aluminium) laminates containing a circular hole for evaluation of notched tensile strength, using the effective crack growth model (ECGM), point stress criterion (PSC) of Whitney and Nuismer and damage zone criterion (DZC) of Eriksson and Aronsson. It is noted that ECGM overestimates, whereas PSC and DZC underestimate the notched tensile strength of FRMLs. This note highlights briefly the two different criteria of Whitney and Nuismer known as ‘point stress criterion (PSC)’ and ‘average stress criterion (ASC)’, and suggests a modification in the criteria for accurate evaluation of the notched tensile strength.