Composite Structures 

Abstract: In response to the marked increase in research activity and publications in multifunctional materials and structures in the last few years, this article is an attempt to identify the topics that are most relevant to multifunctional composite materials and structures and review representative journal publications that are related to those topics. Articles covering developments in both multiple structural functions and integrated structural and non-structural functions since 2000 are emphasized. Structural functions include mechanical properties like strength, stiffness, fracture toughness, and damping, while non-structural functions include electrical and/or thermal conductivity, sensing and actuation, energy harvesting/storage, self-healing capability, electromagnetic interference (EMI) shielding, recyclability and biodegradability. Many of these recent developments are associated with polymeric composite materials and corresponding advances in nanomaterials and nanostructures, as are many of the articles reviewed. The article concludes with a discussion of recent applications of multifunctional materials and structures, such as morphing aircraft wings, structurally integrated electronic components, biomedical nanoparticles for dispensing drugs and diagnostics, and optically transparent impact absorbing structures. Several suggestions regarding future research needs are also presented.

Abstract: This paper presents an investigation on the nonlinear bending of simply supported, functionally graded nanocomposite plates reinforced by single-walled carbon nanotubes (SWCNTs) subjected to a transverse uniform or sinusoidal load in thermal environments. The material properties of SWCNTs are assumed to be temperature-dependent and are obtained from molecular dynamics simulations. The material properties of functionally graded carbon nanotube-reinforced composites (FG-CNTCRs) are assumed to be graded in the thickness direction, and are estimated through a micromechanical model. The governing equations are based on a higher order shear deformation plate theory with a von Karman-type of kinematic nonlinearity and include thermal effects. A two step perturbation technique is employed to determine the load-deflection and load-bending moment curves. The numerical illustrations concern the nonlinear bending response of FG-CNTRC plates under different sets of thermal environmental conditions, from which results for uniformly distributed CNTRC plates are obtained as comparators. The results show that the load-bending moment curves of the plate can be significantly increased as a result of a functionally graded reinforcement. They also confirm that the characteristics of nonlinear bending are significantly influenced by temperature rise, the character of in-plane boundary conditions, the transverse shear deformation, the plate aspect ratio as well as the nanotube volume fraction.

Abstract: The recent applications of fibre-reinforced polymer composites to naval ships and submarines are reviewed Since the mid-1980s the use of composites has increased considerably as the military strive to reduce the acquisition and maintenance costs and improve the structural and operational performance of naval craft A wide range of new applications of composites to naval vessels are described, including their current and potential use in the superstructures, decks, bulkheads, advanced mast systems, propellers, propulsion shafts, rudders, pipes, pumps, valves, machinery and other equipment on large warships such as frigates, destroyers and aircraft carriers Potential applications of composites to submarines are also described, such as their possible use in propulsors, control surfaces, machinery and fittings The growing use of composites in the complete construction of fast patrol boats, minehunting ships and corvettes is discussed For each application the major benefits gained from using composites instead of conventional shipbuilding materials, such as steel and aluminium alloys, are identified The paper also outlines the main drawbacks of using composites in naval vessels

Abstract: A theoretical model has been developed for predicting the elastic constants of honeycombs based on the deformation of the honeycomb cells by flexure, stretching and hinging. This is an extension of earlier work based on flexure alone. The model has been used to derive expressions for the tensile moduli, shear moduli and Poisson's ratios. Examples are given of structures with a negative Poisson's ratio. It is shown how the properties can be tailored by varying the relative magnitudes of the force constants for the different deformation mechanisms. Off-axis elastic constants are also calculated and it is shown how the moduli and Poisson's ratios vary with applied loading direction. Depending on the geometry of the honeycomb the properties may be isotropie (for regular hexagons) or extremely anisotropic. Again, the degree of anisotropy is also affected by the relative magnitude of the force constants for the three deformation mechanisms.

Abstract: Fibres have been used since Biblical times to strengthen brittle matrices; for example straw and horse-hair was mixed with clay to form bricks and floors. In modern technology, steel fibres were for the first time proposed as dispersed reinforcement for concrete by Romualdi in his two papers in 1963 and 1964. Since that time, the concept of dispersed fibres in cement-based materials has developed considerably: hundreds of books and papers, many dissertations, and also applications in building and civil engineering structures all over the world. After over forty years, it is interesting to review the present state of knowledge and technology of FRC. The balance of achievements and shortcomings is certainly positive. Our knowledge, based on theoretical solutions and experimental findings, is rich and quite large. Test methods that are transferred from the so called high-strength composites are very effective. However, practical applications are not so numerous as it was initially expected with developments not exactly in the foreseen directions. In this paper the main fields of application of FRC composites are examined and future perspectives discussed. After a brief review of various kinds of fibres and applied techniques, some attention is paid to computation methods and composite materials’ design approaches. Large practical application of FRC in construction is mostly hampered by insufficient development of relevant standards, based on performance concepts. It should also be admitted that the cost of fibre reinforcement and related technological operations is certainly an obstacle for use of FRC in ordinary structures. On the other hand, in successful applications in demanding structures very special requirements are satisfied; probably future developments will go in this direction.