The Nacra 17 is a foiling catamaran selected to compete in the 2024 Olympic Games. The Nacra 17 is a one-design class, which requires all equipment to be identical. The Dutch Olympic team found through testing the bending stiffness that there is a slight difference in how each of their hydrofoils performed. The question was asked: What are the manufacturing deviations in the Nacra 17 hydrofoils and how do they impact the performance? This research aims to answer the previously stated question. The 3D scanned hydrofoils validated that there is indeed a measurable difference in shape between the different hydrofoils of the Olympic team. A successful method was proposed that automatically extracts 2D profile section properties from the point-cloud data of a 3D scanned hydrofoil. This method used a rough orientation using the profile plotted in polar coordinates. The mean camber line could be extracted using the Voronoi vertex points and the offset of the profile surface. The resulting data set was fitted using non-periodic cubic B-spline curves. This produced a curve for the mean camber line and the thickness profile. Comparison of profile properties resulted in the conclusion that profile thickness (yt) could show that the two female mould halves were probably spaced differently for the different hydrofoils by a standard deviation of 0.0669 mm at a thickness of 22.6 mm. Differences are found in the maximum thickness location (xt), Leading edge radius (rle), maximum camber (yc) and its location (xc). However, the differences in lift over drag for the different hydrofoils are minimal. The size of the drag bucket did not differ more than 0.1 of the lift coefficient (cl) for the same drag coefficient. With the exception of in general one section that presented an early separation. The specific profile showing early separation changes along the span, not allowing for the generalisation for the complete hydrofoil. It shows that the curvature at the leading edge of the profile is critical for the performance of the Nacra hydrofoil. Knowing which part of the profile shape is critical. Companies can take this area into account when designing the production process for the next hydrofoil, and the Olympic team can focus on maintaining these areas of the hydrofoil. Allowing the best preparation to be competitive at the next Olympic games.

The aim of this study is to analyse the influence of ply drop-off regions and related parameters on the VARTM cure-induced residual stress generation and related distortions within thick thermoset composites. These parameters include the resin pocket material properties and geometry, ply orientations and cure cycle parameters. By means of a coupled thermal-mechanical cure model it is observed that during the initial part of the cure process, both the chemical shrinkage and thermal expansion of the resin pocket evolve in counteracting manner. The resin pocket geometry and orientation of the surrounding plies influence the out-of-plane direct tensile stress within these plies whenever either the aspect ratio of the resin pocket or the in-plane stiffness of these plies is increased. The orientation of the terminated ply proved to be of influence as well, where higher in-plane shrinkage and thermal contraction of this ply increases the out-of-plane stress around the drop-off region. Implementing multiple drop-off regions introduce stress interactions caused by the different ply orientations used. These regions influence the local out-of-plane stress levels around the drop-off regions, where the stagger distance between these drop-offs generally lowers this effect. As result of this study, existing drop-off design guidelines are reconsidered and new guidelines are proposed for implementing ply drop-off regions within composite laminates.

Carbon fibre reinforced polymer (CFRP) composites are well-known for their specific strength and stiffness properties. For the past two decades, various industries have increasingly used these materials to improve performance and reduce emissions. This increased use has caused a problematic growth in both production and end-of-life CFRP waste. Recent developments in recycling processes allow recycled carbon fibres (rCF) to have undamaged and clean surfaces with intact sizing, retaining the mechanical properties of non-recycled virgin carbon fibres (vCF) at a considerable cost reduction. Unfortunately, CF recyclate from these recycling procedures is highly diffuse making them useless for structural application. For making rCF material viable to be used in structural applications, further processing of the recyclate is necessary. To manufacture high-performance rCF materials which feature homogenously distributed, orientated and aligned fibres, considerable effort has to be spent in controlling the microstructure during processing. The presented thesis has focused on introducing an initial characterisation method that allows for quantitative analysis and comparison between rCF microstructures. Characterisation is performed by analysing elliptical CF footprints in perpendicular cross-section micrographs. Fibres in the micrograph are identified and segmented through a semi-supervised machine learning tool. The elliptical fibre shape is measured by the method of ellipses (MoE) in FIJI ImageJ. This MoE extracts the position and elliptical shape of every fibre footprint in the micrograph. Analysis of the microstructure is done in python to quantify the microstructural morphology by fibre diameter, fibre orientation distribution (FOD), global-local fibre volumes (Vf), fibre density distribution (FDD) and Fibre-to-Fibre (FtF) spacing. It was found that the method is accurate and reliable in identifying and measuring fibres present in the cross-section micrograph. Similarly, calculated values for Vf, FDD and FtF spacing can be used for characterising the quality of studied materials. Unfortunately, despite being frequently used in literature to characterise highly aligned and orientated CF materials, all fibre orientation measurements were flawed by the inherent susceptibility of the MoE to calculate fibre orientation with large biases. This orientation bias was caused by the error sensitivity of the arccosines function used for calculating the out-of-plane (OoP) angle. Minute elliptical shape differences in near perpendicular fibres with almost circular footprints resulted in large non-linear errors. Recommended is to study FODs in samples that are sectioned at a 45 or 60° angle, resulting in large elliptical fibre footprints which are less error sensitive when analysing with the MoE. The induced section angle can easily be transformed back to yield an unbiased FOD measurement.

Thermoplastic composite materials are increasingly used in aircraft construction due to their high-mechanical properties, toughness, rapid processing rates and reprocessing possibilities at their end-of-life. In the production thermoplastic composite parts, 10-40% of the material remains unused, so-called production waste. Despite being a high-performance material that can be re-processed, real-world applications of the material into structures or products are lacking. This research explores how the thermoplastic composite production waste material can be utilised by designers and engineers, by demonstrating its use in a design process of new applications. This exploration resulted in the design of a structural member, that can be tailored to a specific function, and a design of a pedestrian bridge, which aims to stimulate the creative use of the material. By evaluating the design process, a framework is proposed which engineers and designers can utilise to design new applications from composite waste material.

Recent findings have highlighted the potential of a 3D-printable high-strength Liquid Crystal Polymer, whose anisotropy can be fostered for topology optimization intents. The mesostructure of a 3D-printed liquid crystal polymer is studied: the observation of interlayer features under the form of regular notches or spiraling patterns swirls is reported on optical microscopy of cross-sections. A formation mechanism is proposed: interlayer features may be formed as a result of an offset in placement of material. Another question is raised by the observation of these crenelated shapes: by providing mechanical interlocking between layers, they are expected to enhance interlaminar shear strength of a part. Short-beam shear tests indicate that when interlayer features are tall with respect to the layer height, and oriented perpendicular to the shear loading direction, the interlaminar shear strength of the 3D-printed part is enhanced by up to 112%. Microscopic evidence further indicates the crack-arrest ability of these features.