After wind and solar energy, tidal energy presents the most prominent opportunity for generating energy from renewable sources. However, due to the harsh environment that tidal turbines are deployed in, a number of design and manufacture challenges are presented to engineers. As a consequence of the harsh environment, the loadings on the turbine blades are much greater than that on wind turbine blades and, therefore, require advanced solutions to be able to survive in this environment. In order to avoid issues with corrosion, tidal turbine blades are mainly manufactured from fibre reinforced polymer composite material. As a result, the main design and manufacture challenges are related to the main structural aspects of the blade, which are the spar and root, and the connection between the blade and the turbine hub. Therefore, in this paper, a range of advanced manufacturing technologies for producing a 1 MW tidal turbine blade are developed. The main novelty in this study comes with the challenges that are overcome due to the size of the blade, resulting in thickness composite sections (> 130 mm in places), the fast changes in geometry over a short length that isn't the case for wind blades and the required durability of the material in the marine environment. These advances aim to increase the likelihood of survival of tidal turbine blades in operation for a design life of 20 + years.

Structural adhesives characterized a turning point in the post-connection of structural elements due to their excellent performances and ability to transfer stress without losing their integrity. These materials are typically particle-reinforced composites made by a thermoset polymer matrix and fillers. During the in-situ application of this material, the thermal activation of the polymer is typically not possible, leading to an undefined degree of cure and therefore to a variation of the mechanical performance over time. This altering means that after applying a sustained load on a bonded anchor system installed at regular temperature, the adhesive changes material properties. Ample studies convince that the progressive increase of the degree of cure of the thermosetting polymer leads to higher strength and stiffness. However, limited studies have been dedicated to the post-curing effects on the long-term behavior. The main goal of this work is to investigate the tensile and shear creep behavior of two commercially available structural adhesives and the influence of curing conditions on their long-term performances. An extensive experimental campaign comprising short and long-term characterizations has been carried out on specimens subjected to three different curing and post-curing protocols, with the scope of imitating relevant in-situ conditions. The results demonstrate that structural adhesives cured at higher temperatures are less subjected to creep deformations. As a material equation, the generalized Kelvin model is utilized to fit the tensile and shear creep data, and two continuous creep spectra have been selected to represent the creep behavior and facilitate extrapolations to the long-term behavior.

Carbon fibres can be reclaimed and processed to different forms as feed material to make remanufactured carbon fibre composites. Use of semi-long (25-100 mm) and long (> 100 mm) reclaimed carbon fibres in composites has the potential to enhance the overall mechanical performance of composites made from reclaimed carbon fibres. However, the present processes of recycling of carbon fibres lead to shortening of fibre length, surface degradation, alignment, which in turn, decrease the load bearing capacity and matrix bonding in the composites. To increase the structural performance and mechanical characteristics of reclaimed carbon fibres-based composites, possible pre-treatment methods to semi-long/long reclaimed carbon fibres should be explored. This paper presents a detailed review of various preparation and remanufacturing processes for semi-long/long reclaimed carbon fibres and evaluation of their performance and potential applications. It is found that among all the recycling methods, the Electrically driven Heterocatalytic Decomposition method can produce semi-long/long reclaimed carbon fibres with minimal damages. After reclaiming the carbon fibres, they must be opened and separated from the fluffy form for further processing; long staple carding is one of the mostly used methods for opening and producing randomly aligned mats and tapes. To enhance the performance of composites made from semi-long/long reclaimed carbon fibres, it is essential that fibres are aligned unidirectionally as much as possible. Friction spinning is found to be an efficient method to achieve high alignment of semi-long/long fibres. Furthermore, this paper advocates the use of advanced manufacturing techniques for fibre alignment and customization, which could result in improved repeatability, reduced variability, reduced material waste, and increased suitability for specific applications.