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 offshore wind energy market is highly dynamic and one of the major challenges is to become more cost competitive against other sources of energy. The support structure of an offshore wind turbine shows a high potential for further cost reduction. Jules Dock is investigating in the replacement of a steel tower on a monopile foundation by a Glass Fiber Reinforced Plastic (GFRP) tower, which has a higher specific strength and better corrosion resistance compared to steel. This would enable lower transportation and installation costs and a potentially longer lifetime. Currently Jules Dock assesses the feasibility of a GFRP tower versus a steel tower using an aero-elastic simulation tool. However, such a tool is computationally demanding and requires detailed turbine data, which are often not available in a preliminary design phase. For this reason, a research project has been set-up to develop a parametric design model which can effectively be used without detailed turbine data and aero-elastic simulations, to identify the design driving constraints for preliminary designs and mass optimization purposes. The parametric design model analyses the natural frequency constraint and Ultimate Limit State (ULS). The natural frequency of the support structure is intended to be in the soft-soft region, which will result in the lowest mass possible as has been found in previous research. The natural frequency of the support structure is analyzed with a finite beam element model, in which the Rotor Nacelle Assembly (RNA) is modelled as a point mass. The interaction with soil is also included using a three spring model. For the ULS, the yield and buckling capacity of the support structure are analyzed. For the steel monopile and transition piece, dedicated design standards have been used. For the composite tower, however, these design standards are not existing and therefore analytical solutions from composite tube applications have been used and verified for this purpose. FEM analysis showed that the yield capacity can be determined exactly. The buckling capacity approximation in the parametric design model showed conservative results compared to a dedicated buckling analysis tool. In the parametric design model the maximum loading for the ULS constraints has been analyzed using a quasi-static load analysis method which includes turbulence and dynamic wave loading effects. This method has been compared with the time-domain simulation tool Phatas, which is integrated in Focus6. This comparison showed that also the tower top bending moment should have been included. If this is taken into account, the integrated load analysis method appears to approach the maximum loading for a very stiff tower quite accurately compared with the time-domain simulations. For flexible towers, however, the loads are less accurately approached, since dynamic interactions between wind and wave loading have appeared to be relevant, especially for load cases with a wave excitation frequency close to the natural frequency of the support structure. In the quasi-static load analysis method these dynamic effects are only taken into account for the submerged part of the support structure, but the time-domain simulations have shown that these effects will increase the maximum loading on the support structure above water level as well. For mass optimization and identification of the design driving constraints of this support structure, a genetic algorithm has been developed. Several optimization runs have been made, resulting in multiple feasible solutions with only small differences in support structure mass. While the buckling constraint drives the design of the monopile, transition piece and top of the tower, the lower part of the tower is design driven by the yield constraint. It has been concluded that the loading analysis method in the developed parametric design model should include the tower top bending moment, since this leads to a mass increase of up to 20% of the support structure mass. Next to that, it has been observed that the optimization algorithm tends to converge to solutions with a natural frequency to be as low as possible, such that the dynamic amplification of the wave loading is minimized. For these solutions, the loading analysis method in the parametric design model may have underestimated the maximum loading on the flexible support structure. This needs to be further investigated.

Running Specific Prosthesis (RSP) allow amputee sprinters to compare to the best able-bodied sprinters in the world. In RSP research, the current state of the art mainly focusses on highly detailed analysis of discrete moments in the sprint, but more data of the entire sprint process in terms of RSP characteristics and sprinting technique are needed for further development of RSP-design and sprinting technique. In recent research Petrone et al. [4] and Galvão et al. [2] developed instrumented RSPs for collection of Ground Reaction Force (GRF)s suring sprinting, however both methods have disadvantages for implementation of instrumented RSPs in amputee sprinting training purposes. A different instrumented RSP approach was taken in this research by measuring surface strain in Fiber Bragg Grating (FBG) sensors attached to two RSPs; one Ottobock 1E90 and one Gyromotics ArcX Sport. From the collected data the internal moments and axial forces could be approximated, from which the GRF magnitude, direction and point of application were determined. The sensor system was calibrated in a 1-DOF load-cell compression bench and was conducted to a field test in which a participant performed load shifting, walking and running trails on the instrumented Gyromotics RSP. The compression tests showed that the measurement system complied to design requirements and that it was possible to estimate the point of application of the GRF. The field test indicated that loads applied in different directions than applied in the compression bench could lead to measurement errors. Additional calibration, predominantly in the x-direction, is therefore needed.

With a changing market for offshore crew transfer systems the current Ampelmann systems are vulnerable for competitors. One of the downsides of the current system is its influence on the ship due to the system mass. A lightweight re-design of the current steel gangway using composites could start an overall weight decrease. A composite gangway has been designed with the focus on producibility and certifiability. As there are no active regulations regarding the use of composites for this offshore application collaboration has taken place to define the critical points. The created composite design saves 65% weight compared to the current design while being 40% cheaper over a 20 year life time excluding initial investments. A prototype needs to be build and tested to get the required certification once the fire requirements are decided upon.

Guidelines dating back 50 years, NASA SP-8007, are employed today in the design of thin-walled launch vehicle structures. Due to advances in materials, structural designs, and manufacturing techniques since the publication of SP-8007, the development of new knockdown factors for contemporary launch vehicle structures is an ongoing subject of research. The work presented herein was performed in collaboration with the NASA Engineering and Safety Center on the Shell Buckling Knockdown Factor Project. A laboratory-scale composite cylindrical shell test article, which had previously been designed according to a novel scaling methodology, was the subject of simulation and testing. Its inner, outer, and boundary surface imperfection signatures were measured and implemented in finite element models for buckling test simulations. These were then used to provide prediction data for an experiment conducted at NASA Langley Research Center. Buckling loads from the two pre-test analyses were within 0.08% and 3.7% of the experimental buckling load. The concurrence of axial shell stiffness, localized strains, and buckling shape evolution was also established between the experiment and simulations. A slight loading imperfection was found during the test; however, it was demonstrated through post-test analyses that this did not affect the buckling load substantially. The test article's 0.91 normalized buckling load was much higher than the 0.59 knockdown factor specified by SP-8007. The correlation between the experimental and simulation results, as well as their contrast with SP-8007's prescription, suggests that directly measured imperfections are capable of playing a role in the development of modern and potentially less conservative knockdown factors for future launch vehicle structures.

Offshore wind turbines are used more and more for the production of our electricity. The wind turbines are located in a remote and harsh environment, and are subject to heavy cyclic loading, which may cause fatigue in the support structures. Periodic inspections are required to assess the structural health of the wind turbines. Acoustic Emission Monitoring is the technique of acquiring and processing of the high-frequency sound waves emitted during crack growth. Accurate processing of these signals can lead to detection and localization of fatigue cracks, and further reduction of the need for costly periodic inspections. The factors that determine the coverage area of acoustic emission sensor nodes are source signal strength, attenuation of signal in the medium, and onsite noise level. Together with a cost benefits analysis, this leads to insight into the feasibility of this technique for offshore wind turbines. Investigation of the attenuation is done using a higher-order Spectral Element Method with the input acquired from experiments. The signal that is detected at the sensor has to have sufficiently higher intensity than the surrounding noise. The most severe sources of noise are rain drops hitting the water surrounding the turbine, for which a setup is used in the laboratory, and noise from rotating equipment, for which a measurement has been performed at an on shore wind turbine. The localization accuracy of 5 – 10 percent was shown to be achievable in a laboratory setup. With the coverage area determined, a monitoring strategy for a single wind turbine is proposed, as well as how an acoustic emission monitoring system can be efficiently implemented at a larger scale for a wind farm. It is concluded that acoustic emission monitoring is generally feasible for this application, yet further testing is required in order to decrease the uncertainties and to demonstrate the capabilities to potential operators.

Is improvement of pole vaulting performance still possible, or has the theoretical peak level already been achieved? Looking ahead to the 2020 Tokyo Olympics, in 2016 the NOC*NSF asked the TU Delft Sports Engineering Institute to identify the possibilities of improving pole vaulting performance. Marco Reijne developed a mechanical model in which a vault can be simulated. During my thesis, as a follow up on the research of Reijne, several improvements have been made to the model. A method has been developed to include vaulting poles with a variable stiffness. A variable stiffness vaulting pole could influence the flight path of the vaulter. It also has an effect on the weight distribution of the pole. Furthermore, an axial spring was added to the pole at different locations. At pole-planting box impact, a significant amount of energy is dissipated. An axial spring reduces the amount of energy loss. The feasibility of this innovation has been reviewed. Among other factors, the technique of the vaulter determines if a vault is successful. The control strategy of the athlete has been optimized for various vaulting poles. To conclude, the results of this research show that there is still room for improvement in pole vaulting performance.

On board of High Speed marine Craft (HSC), the crew and the passengers are exposed to high levels of Whole Body Vibrations (WBV) and large magnitude Repeated mechanical Shocks (RS) caused by the motions of the craft. The HSCs are typically 10 meters long, capable of reaching a maximum speed up to 50 knots and widely used by various maritime organizations. However, the operators and crew suffer from fatigue and injuries, leading to a reduced effectiveness and operational capacity of the marine craft. In an attempt to reduce the physical loads, passive Shock Mitigating Seats (SMS) can be installed. Numerous research has shown that an improperly designed SMS may amplify the wave impacts forces through phenomena such as bottoming out and dynamic amplification. Therefore, it is necessary to ensure that a suspension design works properly by testing the performance during wave impact events, before the seat is manufactured and installed onboard the craft. The problem is that it is difficult to determine the performance of the seats in both the design and off-design conditions with either sea trials or laboratory tests. This research focuses on the prevention of injuries and adverse health effects due to repetitive wave impacts by incorporating an injury model in the analyses of various suspension principles in the design of SMS. In the current analyses of SMS either simplistic or specific models are used which restrict the application of these models to other suspension designs. Therefore, a computer program based on the finite element method is developed that allows realistic input accelerations in the surge, heave and pitch direction. The program incorporates highly non-linear elements, including the effect of bottoming. Additionally, the validity of the half-sine approximation for the wave impact excitation pulse was reviewed and concluded to be inappropriate for design purposes as it underestimates the probability of bottoming. Furthermore, the modified evaluation methods of ISO 2631 Part 5 using an optimized age-dependent coefficient based on gender in combination with a Weibull injury risk model were implemented to evaluate the resulting seat level accelerations. A case study was conducted on a Fast Raiding Interception and Special forces Craft (FRISC) of the Royal Netherlands Navy (RNLN). A design based on a parallelogram of pinned truss elements in combination with a coil spring element was altered by replacing the coil spring with a gas-spring element. The design was analysed with dynamic simulations of full-scale measurements of wave impacts on a lifeboat of the Royal Sea Rescue Institution (KNRM). For the most severe wave impact of the acceleration record, the seat level acceleration was reduced from 17.7 [g] to 2.8 [g]. An operator of the age of 24 years who is exposed to the accelerations for half an hour a day, 30 days a year for two consecutive years was assumed. The probability of spinal injury was reduced for a male operator from 99.5% to 16.3% and for a female operator from 100.0% to 42.0%. These results illustrate the high risk of injury to which the HSC operators are exposed. By incorporating highly non-linear elements and spinal injury models, the program and evaluation methods are capable of modelling various SMS suspension designs and analyse the performance. This can assist the seat designer, engineer or researcher with investigating suitable suspension designs before sea trials, experimental tests and prototype iterations. Therefore, the method offers the possibility to save time and reduce costs. Furthermore, the method can assist in defining new regulations in order to limit the exposure of the operators to physical loads and reduce the risk of spinal injury to an acceptable level.

The development of the pole vaulting record is only improved by 1 centimeter over the last 25 years. Multiple studies show signs of different control strategies in elite pole vaulters, without pointing out what the cause of the differences is The aim of this research is to explore pole vaulting strategies by a control torque optimization. The optimization is performed for a simplified biomechanical model. The vaulter contains three segments: arms, a trunk including the head and legs. The joints are represented by torque actuators, located at the hands, shoulder joint and hip joint. The torque profile of each actuator is optimized. The optimization starts just after the pole is planted. It ends when the vaulter releases the pole. The pole length, pole stiffness, the vaulter’s length, the vaulter’s mass and the take-off angle are varied to discover the influence of these parameters on the control strategy. Three control strategies are found, as well as two power management strategies. Global trends are found. An increased pole stiffness, a decrease in length and mass of the athlete and a decreased take-off angle improved the performance. A possible optimal pole length is found.

Running-specific prostheses enable amputee athletes to perform at the highest level. However, current prosthesis design still impairs sprinting performance in multiple ways. An example is the constant mechanical stiffness of the prosthetic devices. The dynamic behaviour of the blade is determined by this property, but it is static and cannot change according to the gait phase-specific sprinting dynamics. During acceleration a different stiffness might be required as opposed to steady state running. Therefore, it is hypothesised that amputee athletes can improve their performance with prostheses that have a gait phase-specific stiffness. In order to investigate the effect of stiffness on amputee sprinting performance a novel and unprecedented modelling approached is used. Modelling is economical and straightforward in comparison to other research methods such as laboratory experiments. In this thesis, an extension of the established Spring-Loaded Inverted Pendulum model is proposed that qualitatively describes amputee sprinting motion. The Actuated Spring-Loaded Inverted Pendulum (ASLIP) is capable of predicting stable forwardly integrated sprinting motion with the inclusion of the start and acceleration phase. Optimisation of the model predicts that phase-specific spring stiffness leads to a significant time reduction on the 100m sprint for given physiological parameters. In general it can be said that a stiffer spring results in better performance. More specifically, the model benefits from a stiff spring during acceleration and a more compliant one in steady state. Although it has its limitations, the ASLIP model additionally provides a valuable insight into the mechanics of amputee sprinting. For example, it seems that optimal phase-specific stiffness is strongly dependent on biomechanical parameters such as touchdown angle, force angle and CoM velocity. Future work in this direction can provide a better understanding of the underlying mechanisms that determine amputee sprinting performance. The outcomes of this study suggest that amputee sprinters might be able to achieve a reduction in finishing time with prosthetic devices that have a phase-specific stiffness. The modelling approach used in this thesis is promising and lends itself well to investigate this opportunity in more detail.

Having seen exponential growth in demand for air travel, the aviation industry has found itself trying to find a balance between economic growth, technological development, and environmental sustainability. This saw a shift in attention towards materials such as fiber reinforced composites, predominantly thermoset in the past with higher strength-to-weight fractions. Relatively recent was the introduction of high-performance fiber reinforced thermoplastic polymer composite materials possessing more promising prospects of circularity in addition to the lightweighting capabilities. But as is, these only form for qualitative claims with no indication on how the ecological effects would pan out over the life cycle phases objectively, as well as on a relative scale. Extending beyond the orthodox considerations and measures of aircraft performance, life cycle assessment studies encompass a comprehensive analysis of the environmental impact associated with aerospace products through the various phases of their life cycle including material extraction/production, manufacturing, operation, and the respective end-of-life treatment. The primary objective is to quantify the environmental impact of the system, offering a holistic view of the emissions, energy demand, and resource consumption. To this end, this study constructed a comparative environmental profile, modelling for five material/manufacturing systems, namely numerically machined aluminium alloy, autoclave cured and resin transfer molded carbon fiber reinforced epoxy, autoclave consolidated, and press consolidated carbon fiber reinforced Polyetherketoneketone (PEKK) over the cradle-to-gate and the cradle-to-end of service phases in an attempt to find the best variant from an environmental perspective, while also adding a novel, semi-quantitative, robust framework of data quality assessment to the state-of-the-art. The characterization results, under the assumption of each scenario yielding a product of the same mass and equal importance being given to each impact category (equal weighting), indicated the press consolidated carbon fiber reinforced PEKK product to be the scenario with the lowest impact over the cradle-to-gate (including only material production/extraction and product manufacturing). Over the cradle-to-end of service phases (including material production/extraction, product manufacturing, and the operational phase of the aircraft), the operational phase was observed to have an exponentially larger impact compared to the other life cycle phases causing the comparative profile to homogenize. This was reiterated by outcomes of the performed contribution analyses. Sensitivity analyses were conducted to explore the environmental benefits of lightweighting and processing waste optimization (buy-to-fly ratios quantifying the relative, quantitative benefits of lighter products and leaner manufacturing systems.

The subject of this thesis is the forming of sandwich panels on a reconfigurable mould. The field of research is composite sheet forming. This novel manufacturing process at Curve Works has problems with panel quality, especially out-of-plane wrinkles. Exploratory research on quality improvement is performed by analysing the underlying mechanisms of single curved resin infused sandwich panels where the tooling surface is reconfigured to a concave shape. This will be done under the influence of diaphragm reinforcement, infusion pressure, and forming speed. It has become clear that a reinforced diaphragm reduces out-of-plane wrinkle displacement at the cost of residual stress. The effect of forming speed and infusion pressure on out-of-plane wrinkles is considered to be insignificantly small under the testing conditions as described in this work. For future research it is suggested to look in to reducing frictional forces and the application of tensile stresses to improve formability and panel quality.

This report shows the intended process to automatically manufacture Carbon Fibre Reinforced Thermo Plastic (CFRTP) double bend frames. Bicycle rims were chosen as a scaled down representation for difficult to manufacture double bend products. Fuselage frames require a too large facility. The aim is to manufacture CFRTP products in an automated process, with lower cost compared to current methods. Local automated production minimizes transport costs, increases the control over the quality of the product and the production process compared to outsourcing to low income countries. This would increase the grip on quality, lower the necessary transport and create a more economical solution. The scope of this thesis was to tackle the automation and manufacturing difficulties of double bend products. Braids were evaluated as a solution, which proved to be usable for automatic manufacturing. In order to achieve full automation, the main manufacturing issues are correlated to design details of the product. These details need proper production equipment and optimized processes in order for quality to be consistent. Braids were tested for automation and were found to be very successful with respect to simplicity of forming. A rim was manufactured using braids only, together with a thermoset matrix. Applying a thermoplastic matrix would be a logical next step, and could mean further advancement in automation of carbon fibre products.

Spacecraft are under constant threat of structural damage from hypervelocity impacts by micrometeoroids and orbital debris. To bolster the shielding used for protection against these impacts, ballistic materials can be employed. Aramid-based materials are currently used aboard the International Space Station (ISS), but Ultra High Molecular Weight PolyEthylene (UHMWPE) fibres are a common alternative for ballistic protection on Earth. In this report, the suitability of UHMWPE-based composites for spacecraft impact shielding is investigated. Hypervelocity impact simulations using smoothed particle hydrodynamics discretisation form an essential part of the design and analysis of such protection systems. Two formulations of nonlinear orthotropic hydrocode models are proposed for this purpose, which are validated using footage from hypervelocity impact experiments on Dyneema® HB26 targets. One of the proposed models yields good prediction of residual impactor velocities, generally being within 10% of experimental data. The other reproduces both residual velocities and debris cloud shape well for the highest considered impact velocities, but suffers from decreased performance as the ballistic limit is approached. Numerical comparison between UHMWPE- and aramid-based composites shows comparable ballistic performance for the considered cases.

Frontal polymerization (FP) has emerged as a promising alternative to traditional bulk curing methods in recent years for manufacturing high-performance fibre-reinforced polymer (FRP) composites. The energy utilized in this self-propagating curing strategy is solely derived from the exothermic enthalpy of polymerization, making it potentially more efficient than traditional curing methods, which are extremely energy-intensive and therefore unsustainable. Research in the field of FP has been primarily focused on studying the effectiveness of the FP formulations, particularly the relationship between the monomer types and initiator concentrations on front properties. However, the research on the use of FP for manufacturing FRPs has been limited to flat rectangular plates. Therefore, this research aims to investigate the behaviour of the propagating fronts in composites with varying fibre volume fractions (Vf) within the sample and varying geometries to assess the feasibility of using FP in structures that more closely resemble real-life applications. Several test setups were explored to determine the best method for maintaining the heat balance required to sustain a propagating front. Through these trials, a stainless steel-based closed mould test setup with Teflon sheets was conceptualized and manufactured, consistently allowing for the manufacturing of composite samples with a Vf below 36%. The influence of changing Vfs on the behaviour of the front was studied, and the results were quantified using temperature data captured via thermocouples placed at strategic locations. Through a series of experiments, a critical length was established that allowed the propagation of the front from the low Vf region to the high Vf region. When the length of the low Vf region with respect to the high Vf region was smaller than the critical length, the front was seen to quench at the interface. This phenomenon was attributed to the physical reduction in the volume of the resin, which implied a reduction in the generated heat through polymerization. This led to fronts with lower peak temperatures, which upon reaching the interface would quickly fall below the threshold temperature required to sustain the front due to the higher rate of heat loss resulting from the higher fibre content. This study was followed by the manufacturing of L-shaped composite samples with uniform Vf, which showed the propagation of the front in complex geometry. Finally, the Vf was varied within the L-shaped samples, and the behaviour of the front showed similarities to the rectangular samples with varied Vf, leading to the conclusion of the presence of a critical length irrespective of geometry. These findings effectively contribute to the knowledge base necessary for implementing FP as a curing strategy for FRPs. The results obtained from this study can inform the design of manufacturing processes and setups tailored for the use of FP, potentially leading to more efficient and sustainable manufacturing practices.

This report comprises the research entitled 'Numerical and experimental investigation on the resistance of a human upper airway'. The objective of this research is: To investigate the effects of a swirl producing inlet on the pressure drop in a simplified human upper airway model at high ow rates, by means of numerical simulations and experiments. In the literature study done by the author Hak (2014b) it is found that during exercise up to 15% of the maximum oxygen uptake (V O2;max) is spent by the breathing muscles. The breathing muscles support the breathing process by moving the diaphragm, creating a low pressure in the thoracic region, thereby starting the inflow of air. Since the human upper airway is featured by a complex shape, associated with highly three-dimensional ow patterns, it has a relatively high ow resistance compared to the remainder of the airways. If the ow pattern would be influenced by passive ow control in the form of a breathing aid, the pressure drop could be reduced, thereby decreasing the demand on the breathing muscles. The result is that more O2 can be used in the skeletal muscles and thus the anaerobic-threshold is postponed. This lead to the following main research question: What kind of swirl generating mouthpiece device can influence the inhaled ow, such that a pressure drop reduction is achieved, during intensive exercise? The research started off with an identification and simulation of the the upper airway ow. Typical human upper airway ow behavior which cause losses in pressure are found to be jetlike ow, re-circulating ow, detached ow, secondary ows such as Dean ow. If the upper airway is highly idealized, it can be seen as 'elbow pipe', a pipe with a 90o bend. Dean vortices and boundary layer separation in bent pipe ow are responsible for pressure losses. For the setting up of the simulation, the process of breathing is translated into boundary conditions. Simpli_cations and assumptions are done to the usual periodic behavior of breathing: a stationary inhalation rate is assumed, and only inspiration is considered. The compliance of the airway is not taken into account for simplicity and the ow rate is based on that of an exercising male adult