Design, characterisation and application of structural and multifunctional composites to large ship structures

Abstract

Composite materials have been widely used in the aerospace, automotive and ship (particularly naval military vessels) industries, primarily due to their outstanding specific strength and stiffness. Over the last few decades, a large amount of research has been carried out to improve their performance further by introducing other functionalities such as noise and vibration control, self-repair, thermal insulation and energy harvesting/storage. Although more than half-century has passed since the boatbuilding sectors accepted the use of composite materials, it is still difficult to find a significant application of composite materials in the large cargo shipbuilding sectors. However, recent guidance from international regulations for environment protection strongly demands lightweight and eco-friendly cargo ships to achieve considerable reductions in fuel consumption and toxic gas emissions. Based on the considerable structural, environmental and economical benefits achievable from the adoption of structural and multifunctional composites, the aim of the research presented in this PhD thesis is, therefore, to design, characterise and implement structural and multifunctional composites in cargo ship structures which are currently made of steel. Firstly, a patch-wise layup and damping treatment method has been proposed to improve the vibration performance of composite ship structures. The determined design reduced the vibration response level by over 50% compared to that of a benchmarked quasi-isotropic (QI) design. The patch-wise design approach provided a unique opportunity to conceptualise composite wave-breaker with a considerable reduction in vibration response level, mass savings and cost-effectiveness compared to conventional designs. Multifunctional composites offer the opportunity to take traditional composites beyond the typical structural role by embedding, for instance, energy storage. Thus, a novel design methodology was investigated to achieve optimised multifunctional microstructures. Numerical predictions on the multifunctionality were successfully validated by experiments using 3D printed specimens. As an extension of this study, the optimised multi-scale structures for multifunctional composites have been investigated and have demonstrated very promising multifunctionality (i.e. high stiffness and high ionic conductivity) with considerable savings in computation cost. The contributions of this research would provide great insights into their potential uses in industrial applications and the next steps in academic research.