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Applied Composite Materials: An International Journal for the Science and Application of Composite Materials (v.12, #6)
Development and Validation of a Novel Bird Strike Resistant Composite Leading Edge Structure by Th. Kermanidis; G. Labeas; M. Sunaric; L. Ubels (pp. 327-353).
A novel design of a fibre-reinforced composite Leading Edge (LE) of a Horizontal Tail Plain (HTP) is proposed. The development and validation approach of the innovative composite LE structure are described. The main design goal is the satisfactory impact resistance of the novel composite LE in the case of bird strike. The design concept is based on the absorption of the major portion of the bird kinetic energy by the composite skins, in order to protect the ribs and the inner LE structure from damaging, thus preserving the tail plane functionality for safe landing. To this purpose, the LE skin is fabricated from specially designed composite panels, so called ‘tensor skin’ panels, comprising folded layers, which unfold under the impact load and increase the energy absorption capability of the LE. A numerical model simulating the bird strike process is developed and bird strike experimental testing is performed, in order to validate the proposed layout and prove the capability of the structure to successfully withstand the impact loading. The numerical modelling issues and the critical parameters of the simulation are discussed. The present work is part of the European Aeronautics Research Project, ‘Crashworthiness of aircraft for high velocity impact – CRAHVI’ [1].
Keywords: bird strike; tensor skin; material damage model; numerical simulation; bird strike test
A Method for Crash Tests on Laminated Composite Scaled-Down Models by Rémi Grenêche; Yves Ravalard; Daniel Coutellier (pp. 355-368).
Based on the experimental studies carried out at the University of Valenciennes in close collaboration with ONERA, a study of GFRP profile crashworthiness has been carried out in order to find out a method permitting to scale down this type of structures. The relations obtained from Cauchy's similarity law have been found not to be directly applicable because of distortions due to the type of material used or the type of loading applied. An empirical model has been developed using data originating from experimental static tests in order to bring to the fore these distortions. Changing scale relations have been determined from this model then applied on the experimental data curves. The results obtained display a significant improvement as compared to the ones obtained with Cauchy's similarity law. Taking into account the distortions can permit an optimisation of the experimental conditions as well as the stratified materials stacking sequence. The aim is to limit their influence on the results obtained from scaled-down structures.
Keywords: laminated composite; similarity law; distortion; crash; energy absorption
Effect of Short Fibre Reinforcement on the Friction and Wear Behaviour of Nylon 66 by G. Srinath; R. Gnanamoorthy (pp. 369-383).
Use of thermoplastic composite material for load bearing components is increasing due to economical processing of complicated shapes in large quantities. Addition of fibre improves the strength and modulus of composites. Although the tribo-behaviour of thermoplastic composites were investigated, the friction and wear mechanisms are not yet fully understood. Friction and wear behaviour of injection unfilled Nylon 66, glass fibre reinforced Nylon 66 and carbon fibre reinforced Nylon 66 is investigated under dry sliding conditions. Tests were conducted at different normal loads and sliding velocities at room temperature. Coefficient of friction, wear loss and heat generation during the wear tests were quantified. Presence of fibre affects coefficient of friction and wear resistance of Nylon 66 matrix composites. The formation and stability of the transfer films affects the wear resistance. The rise in temperature during sliding was also calculated and also measured. The contact temperature rise is influenced by the composition which in turn influences the fibre adhesion and thereby the wear resistance. Glass fibre reinforced Nylon exhibited the lowest wear rate among the materials investigated. Both adhesive and abrasive wear mechanisms were observed in polymer matrix composites.
Keywords: friction; wear; polymer matrix; glass and carbon fibre