G. Catalanotti

Concept of a Conducting Composite Material for Lightning Strike Protection

Abstract The paper focuses on development of a multifunctional material which allows conducting of electrical current and simultaneously holds mechanical properties of a polymeric composite. Such material could be applied for exterior fuselage elements of an aircraft in order to minimize damage occurring during lightning strikes. The concept introduced in this paper is presented from the points of view of various scientific disciplines including materials science, chemistry, structural physics and mechanical engineering with a discussion on results achieved to-date and further plans of research.

Three-dimensional invariant-based failure criteria for transversely isotropic fibre-reinforced composites

Abstract This chapter describes failure criteria for polymer composites reinforced by unidirectional fibres. The failure criteria are based on an invariant quadratic formulation based on structural tensors that accounts for the preferred directions of the transversely isotropic material. Failure in a single UD ply is predicted, requiring the analysis of strains and stresses ply-by-ply when analysing multidirectional laminates. Because the proposed failure criteria does not use geometrical information to predict failure (due to its invariant-based formulation), we propose a pragmatic approach to estimate the orientation of the fracture plane. To account for the effect of ply thickness when the laminae are embedded in a multidirectional laminate, the in situ properties are defined in the framework of the failure criterion for transverse damage mechanisms. When compared against experimental data available in the literature, good agreement for transverse failure modes, for failure under off-axis loading and for the effect of superposed hydrostatic pressure on failure behaviour of different fibre-reinforced composites is obtained. For more complex three-dimensional stress states, where the test data available shows large scatter or is not available at all, a computational micro-mechanics framework is used to validate the failure criteria. We obtain a good correlation between the predictions of the two modelling strategies.

Synthesis and testing of a conducting polymeric composite material for lightning strike protection applications

Lightning strike protection is one of the important issues in the modern maintenance problems of aircraft. This is due to a fact that the most of exterior elements of modern aircraft is manufactured from polymeric composites which are characterized by isolating electrical properties, and thus cannot carry the giant electrical charge when the lightning strikes. This causes serious damage of an aircraft structure and necessity of repairs and tests before returning a vehicle to operation. In order to overcome this problem, usually metallic meshes are immersed in the polymeric elements. This approach is quite effective, but increases a mass of an aircraft and significantly complicates the manufacturing process. The approach proposed by the authors is based on a mixture of conducting and dielectric polymers. Numerous modeling studies which are based on percolation clustering using kinetic Monte Carlo methods, finite element modeling of electrical and mechanical properties, and preliminary experimental studies,...

A Finite Fracture Mechanics Model for the Prediction of the Notched Response and Large Damage Capability of Composite Laminates

A new model based on Finite Fracture Mechanics (FFMs) has been proposed to predict the open-hole tensile strength of composite laminates [1]. Failure is predicted when bothstress-based and energy-based criteria are satisfied. This model is based on an analytical solution, and no empirical adjusting parameters are required, but only two material properties: the unnotched strength and the fracture toughness. In the present work, an extension of the proposed FFMs model to predict the notched response of composite laminates with notch geometries other than a circular opening [2] is presented and applied to the prediction of size effects on the tensile and compressive notched strength of composite laminates. The present model is also used to assess the notch sensitivity and brittleness of composite laminates by means of versatile design charts and by the identification of a dimensionless parameter designated as notch sensitivity factor. A further extension of the FFMs model is proposed, which takes into account the crack resistance curve of the laminate in the models formulation, and it is used to predict the large damage capability of a non-crimp fabric thin-ply laminate [3].