The current concerns regarding global warming and climate change in Europe and other parts of the world also influence developments in the automotive sector. Not only are alternative energy and power sources making their advent, but greenhouse gas emission reduction has also become a major factor in the development of vehicles with combustion engines. As passenger vehicles with such engines will be sold for probably a few more decades, additional options for emission reduction are still welcome. Mass reduction results directly in less greenhouse gas emission per driven kilometer, both in practice as in the official carbon dioxide (CO2) emission determination procedures.
This thesis is part of a project that tries to develop an additional option for passenger vehicle mass reduction, more specifically by replacing steel in the exhaust system with fibrereinforced plastic. The principle behind this solution is that fibrereinforced plastic has better mechanical properties per kilogram of material than steel. Yet, no plastic could endure direct exposure to exhaust gas flows because of the maximum gas temperature of 800 1000 ∘C....

The aerospace industry is an ever-evolving field that has seen many technological advances over the past decades. The desire for aircraft to be not only efficient and reliable but also cheaper and safer has brought about many proposals across the industry. One of these advances is towards morphing aircraft wings to make wings lighter, more flexible, aerodynamically efficient and structurally stable. One of the key elements of a morphing wing is sensors that monitor the loads and shape of the wing throughout the flight. Within the framework of the SmartX project, the goal and contribution of this study is on the design and development of novel sensing methods for Structural Health Monitoring. This has been performed with a specific focus on shape sensing and load monitoring. This thesis is focussed towards the design and development of a Structural Health Monitoring tool for adaptive aerospace structures and at the same time to reduce the dependency on a high number of sensors. Within the already available fibre optic sensor techniques an identification was made for demonstrating the potential of a higher performing SHM tool involving the combination of FBG spectral sensing and FBG-Pair interferometric sensing. A proposal is made to have a reliable, robust and cost effective sensing methodology for real time monitoring of morphing structures with a simultaneous focus on the SmartX morphing wing demonstrator. The method developed and demonstrated in this thesis is not limited to aerospace (and morphing) structures and can be extended to other engineering structures. Load carrying structures that undergo deformations/deflections can be monitored provided they are properly calibrated. These include, but are not limited to, rotor blades, masts, beam structures and bridges.

In this thesis persistent problems with the shock isolating behaviour of the Jockey Seat are identified and analysed. These Jockey Seat are used on fast planning crafts like the FRISC which is in service with the Royal Netherlands Navy. Past research and existing technology were presented along with two redesign directions. Furthermore, several tools to further analyse the problem in both a static and dynamic setting have been developed.

The popularity of thermoplastic composites (TPCs) has been growing steadily in the last decades in the aircraft industry. This is not only because of their excellent material properties, but also owing to their fast and cost-effective manufacturing process. Fusion bonding, or welding, is a typical joining method for TPCs due to the intrinsic properties of thermoplastic polymers. Among different welding technologies, ultrasonic welding has been regarded as one of the most promising techniques for the assembly of TPC components. Ultrasonic welding is by nature a spot welding technique. As it is known that a series of problems result from using mechanical fasteners for joining composite structures, e.g. breaking fibres during drilling and extensive labour work, ultrasonic spot welding can be considered as a promising alternative from the perspective of fast manufacturing cycle. However, fundamental understanding is still lacking to achieve application of ultrasonic spot welding in composite structures to be achieved:

Fibre metal laminates (FMLs)were developed and refined for their superior crack growth resistance and critical damage size that complimented the damage tolerance design philosophy utilized in the aerospace sector. Robust damage tolerance tools have been developed for FMLs. However, they tend to focus on the evolution of an isolated crack. There is also a risk that they will be invalidated overtime as a result of the occurrence of multiple cracks within one structure (one form of widespread fatigue damage). To combat another failure due to widespread fatigue damage, the airworthiness regulations were revised to include the concept of a Limit of Validity (LOV) of the damage tolerance analyses. Consequently, it is crucial to examine fatigue crack growth (FCG) in FMLs containing Multiple-site Damage (MSD) cracks despite their superior damage tolerance merits. The focus of this thesis therefore is to analyse MSD crack growth in FML structures. Mechanically fastened FML joints are potentially weak structural designs that are susceptible to MSD due to the stress rising contributors such as secondary bending, pin loading and open holes subjected to bypass loading. In this thesis, predictive models were developed to address several key mechanisms that affect FCG in FML joints containing MSD, and validated with corresponding experimental work. Then the predictive models were systematically integrated and implemented for FML joints. It was identified that the nature of fatigue in FMLs led to the load redistribution mechanism as the key factor to be modelled in predicting MSD growth in FMLs. The structural stiffness reductions caused by the presence of multiple cracks resulted in load redistribution from the other cracks to the single crack to be analysed, exacerbating the total stress intensity factor (SIF) experienced at the tips of the single crack, increasing the crack growth rate (CGR). The load redistribution mechanism was first substantiated by investigating FCG in FMLs containing discretely notched layers. The prediction model fairly captured the load redistribution mechanism by idealizing the notches in the metal layers as removals of metal strips. The crack acceleration over a major portion of the crack propagation was well predicted with the model; however, the surge in CGR over roughly 3 mm crack length prior to the link-up was underestimated since the plasticity interaction was not accounted for. The capability of modelling the load redistribution mechanism allows the states of multiple cracks to be analysed one by one. It was found that the load redistribution could not be symmetric for every crack and non-symmetric crack configurations therefore developed in FMLs with finite width. Hence, non-symmetric crack growth in FMLs was also investigated in this work. It was also found that both crack tip non-symmetry and delamination shape non-symmetry affected the crack growth in the metal layers. The model for non-symmetric crack growth in FMLs was validated with experimental data. Good correlation was observed. The model for MSD growth in FML panels sequentially analyses each crack state. The other cracks are idealized as removals of metal strips when analyzing the state of a single crack. This non-physical idealization of the cracks led to consistently conservative prediction results in comparison with the test data. Nevertheless, the prediction model provided good predictions of the evolution of MSD configurations. Additionally, it was proven that a very non-conservative predicted fatigue life could be obtained if the load redistribution mechanism was not considered. The effects of pin loading on FCG in FMLs were also investigated. The test data showed very rapid growth of the crack in the vicinity of the pin loading. The CGR decreased with increasing crack length. The model applied the principle of superposition to split the non-symmetric tension-pin loading into simpler tensile loading and a pair of point loads acting on the crack flanks. The SIFs for the simpler loading cases were derived and superposed to obtain the total SIF as a result of the tension-pin loading. The predicted CGR and equivalent delamination shape correlated with the measurements very well, but the model failed to predict the crack path and the measured delamination shape which were trivial issues for this work. The relevance and applicability of the developed models in this thesis for predicting the MSD behaviour in mechanically fastened FML joints was examined. The predicted results captured the trends of the measured CGR in FML joints containing MSD cracks, although there were some discrepancies. The discrepancies are mainly due to the two major shortcomings of the model which are neglecting the load redistribution over multiple fastener rows and neglecting the effects of secondary bending stresses.

The scope of this thesis is to improve the production of tire Single Aisle (SA) aircraft family carbon fibre outboard flaps produced at Airbus Stade. Currently, the SA outboard flaps are in insufficient quality and many need to be repaired after manufacturing due to manufacturing defects In order to save time and money, a new tooling concept needs to be developed which can produce panels of good quality. The causes of manufacturing defects were previously unknown So as a first step, the causes have to be identified for the defects of the SA outboard flaps. Finding the causes and setting the requirements for the tooling topics of this thesis...

first investigation into identifying challenges for up-scaling, proposing and testing new ultrasonic welding concepts and utilization of the best concept in the design of a sequential welding procedure for a practical application.

The aerospace industry is looldng to reduce their enviromnental impact through projects like the Clean Sky Joint Technology Initiative. Two measures to help achieve this goal are to reduce the aircraft weight so the emissions during flight decrease and to increase the manufacturing efficiency. Composites often offer lighter solutions and new manufacturing possibilities. Especially thermoplastic composites, which have the ability to melt and fuse, offer many interesting possibihties in manufactming and structural integration. Ultrasonic welding (USW) is a fusion bonding process which utilizes the ability of thermoplastic composites to form a fusion bond. USW has extremely short process cycles, does not introduce any foreign materials regardless of
the composition of the samples to be welded, is energy efficient and has the ability to be on-line monitored, providing joint quality information during welding. With USW it is possible to create fast, clean and consistent welds in lap shear samples. However the step to up-scaling of the process has yet to be made. If found possible, USW might contribute to clean joints with strongly reduced processing times and therefore reduce the environmental impact...

The aim of this thesis is to investigate the feasibihty of manufacturing polyurethane glass fibre laminates with vacuum infusion. Thermoset resins classically used for infusion have been polyesters, vinyl esters and epoxies due to their long pot life. Polyurethanes have faster reaction kinetics and therefore the cycle time could be reduced. Additionally, it is expected that polyurethanes bring improved fatigue and impact resistance properties which would enable a re-design of the structures,
reducing its thickness. Therefore, the manufacturing costs of large structures, such as wind turbine blades, could be reduced...

The V-Cart project was a coUaboration between Donkervoort Automobielen B.V. and Delft technical university, with a common goal to design a composite chassis for the next generation of cars. This research originates from the need of a reusable adhesive bond for connecting large structural composite parts. Unfortunately, the collaboration ended during the research. This thesis focuses on the design of the reusable bond itself, with application in a small sportscar chassis in mind.

In the aircraft industry residual stresses have been utilized for long time to increase the fatigue performance of structural elements by cold hole expansion and shot peening. Next to these intentional stresses, residual stresses are also present in the structure as a result of the manufacturing process and aircraft assembly. It is well-known that tensile residual stresses decrease fatigue life, while on the other hand compressive residual stresses increase fatigue life. Despite of this, the aerospace industry still does not give credit to residual stress as a design parameter, mainly because of the poor correlation between experimental and predicted crack growth rates. It is believed that this is mainly due to confounding factors like heat affected
zones in welding, two-dimensional crack fronts, sub-surface inititation, multiple cracking and an inaccurate residual stress estimation in the experiments.