Twin matrix composites consists of fibre bundles impregnated by a hard matrix. These bundles are then embedded in a flexible polymer to increase the transverse failure strain of the laminae, but a tougher flexible matrix should also provide better impact resistance. In this thesis, a twin matrix composite is made using carbon pultrusions embedded in a vitrimer, and its behaviour under impact is tested using a quasi static indentation test and compared to a traditional unidirectional laminate. The twin matrix composite exhibits higher deflection, and a non destructive test using ultrasounds revealed lesser delamination area at the same energy and strain rate than the UD one. ... Read more

This thesis investigates designing and verifying a new frame for the HyperScout, a hyperspectral optical instrument used for earth observation. Due to changes in the instrument's size, the research aims to develop a frame that meets the thermal and structural requirements. The study explores six design concepts, focusing on innovative materials like titanium, PEEK, and wood and advanced manufacturing techniques such as 3D printing. Three promising designs were selected for further development and underwent structural, thermal, and optical testing to ensure their suitability for space conditions. Finite Element Modeling (FEM) and Thermal Vacuum Chamber (TVAC) tests were used to simulate the harsh environment of space and validate the designs. The findings highlight the strengths and limitations of each material and design approach, with recommendations for future research in optimizing spacecraft components. ... Read more

The European Commission’s roadmap aims to install 60 GW of offshore wind energy by 2030 and 300 GW by 2050, requiring substantial raw materials. Airborne wind energy (AWE) offers a promising alternative with lower material demand and environmental impact. This thesis assesses the environmental impact of a 100 kW soft-kite AWE system using life cycle assessment (LCA). The target market for these AWE systems includes off-grid remote areas. Thus, a comparative LCA of hybrid power plant (HPP) configurations was conducted using site data from a military base in Marseille, France. Results show the Falcon AWE system has a GWP of 8.6 kg CO2 eq/MWh and CED of 144.1 MJ/MWh, with the ground station being the most impactful component. For the HPP, including diesel generators and batteries reduces the oversizing of renewable components, enhancing sustainability. Future recommendations include developing AWE-specific databases and evaluating more impact indicators. ... Read more

Safety and reliability of aircraft structures are of main concern within the aerospace industry, preferably without influencing the availability of the aircraft and maintenance and operation costs. As damages in composites can be hard to detect, methods are being developed to detect damages which can potentially lead to a (catastrophic) failure of a (sub)system. Interest in structural health monitoring (SHM) has thus gained a strong interest within aerospace engineering, with the development of new systems or optimising existing ones to contribute to a safe and reliable aircraft. This research focuses on the development of an impact damage detection and quantification method for composite structures. The main research objective of this thesis is to investigate the capabilities of a PZT and a state-of-the-art FBG sensor system for passive impact damage detection and quantification on a simple composite panel and a complex stiffened composite structure. ... Read more

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.
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To reduce greenhouse gas emissions, electrification is the biggest trend in the current-day automotive industry. In this transition, important topics are efficiency and weight reduction. This study focuses on the application of composite materials for the undershield of an automotive rechargeable energy storage system (REESS). In this application, the undershield forms the structural floor of a battery enclosure. The goal of the research was to determine if the homologation and safety demands for the undershield can be met with a composite-dominant design. Additionally, the goal was to determine if such a design can result in mass, cost, and emissions improvements compared to current metallic designs. Based on European and Chinese homologation documents, SAE standards, and demands by Volvo Cars, a set of relevant requirements was constructed. Based on these requirements, a sandwich design proposal was done and potentially suitable materials were identified. Multiple material configurations for the design were then verified based on the driving requirements. Lastly, a performance comparison was done of the mass, cost, and CO¬2 emissions of each configuration. The results indicate that it is feasible to meet the homologations and safety demands for the undershield of an automotive REESS with a composite sandwich design. Using polyester or phenolic glass fiber SMC for the top face of the sandwich can provide a successful fire protection barrier. PET foam was identified as a low emissions core material for improved impact protection in combination with steel or PP GMT bottom plate. Additionally, lower costs and emissions can be offered with steel configurations compared to current metallic designs. Alternatively, PP GMT configurations offer mass and emissions reductions. All in all, the research has succeeded in demonstrating the potential of composite or hybrid designs for the application in an automotive REESS for the improvement of mass, cost, and/or greenhouse gas emissions. ... Read more

Current large-scale additive manufacturing extruders use short reinforcing fibre-filled thermoplastic pellets, which marginally improve the mechanical performance but are too short to exploit the strength of the fibres fully. Long fibre pellets have much higher potential strength, and the development of higher strength materials could create stronger parts and/or reduce the mass of products, lowering their energy consumption in the case of vehicular parts of heated tooling.

By developing long-fibre thermoplastic pellet processing, this thesis works toward improving the mechanical performance of fused granulate fabricated parts. Extreme die-swell was encountered when extruding long glass-fibre polypropylene pellets. This die-swell is theorised to be caused by energy storage in an entangled network of long fibres, which is released upon extrusion. This issue was solved by developing a mix of two different material pellets, which was used with the tactical use of temperature zones to create a hetero-phasic blend inside the extruder. This technique and material blend enable controlling the melting of the long fibre pellet resin, lubricating the pellets to promote macro-alignment, and reducing heating through shear friction. These effects delay the dispersion and entangling of fibres.

This method eliminated the problem encountered; reducing porosity by 82%, increasing strength by 960% over the original swollen material and achieving specific strength 16% higher than the short fibre compound currently being used. This research presents a new method to make previously un-processable long fibre thermoplastic pellets useable with a 25 mm diameter screw extruder. It contributes to the development of unprecedented high-performance parts 3D printed at a large scale. ... Read more

Disassembly of fusion bonded joints aided by induction heating was investigated. Single-lap shear experiments were performed while heating the joint with an induction coil to research the effect on force required and damage inflicted during disassembly. Co-consolidated CF/PEEK samples with and without a metal mesh susceptor and ultrasonically welded samples were tested and compared. An induction heating model was built to facilitate experimental design and to help analyse the effect of the susceptor on the heating process. Induction heating appeared successful in lowering the disassembly force. Large reductions were achieved, but this came at the cost of thermal damage in the disassembled adherends. For a reduction to 37% of the original strength, no thermal damage was inflicted during disassembly, except for one outlier. A susceptor facilitated disassembly for co-consolidated joints, while PEEK energy director remnants hindered heat development in ultrasonically welded joints. Further research is required to develop the method. ... Read more

The IsoTruss is an interesting continuous fibre reinforced polymer composite design which is closely related to open lattice composite structures, although it is currently aimed mostly at civil applications. While it currently lacks applicability to the aerospace sector, its production process is easier to automate (or change the shape input parameters on the fly) than open lattice structures, which rely on a fixed mandrel. Although automated compaction of these structures is a challenging problem, the structure can be optimised for any (static) load case if their production process could be automated, providing a range of applications where aerodynamic contour is not a requirement. To bridge the gap between the IsoTruss and other composite lattice structures, a conceptual design for an IsoTruss derivative, termed the "iso-truss", was envisioned. This raised the following research question: Can composite continuous fibre reinforced iso-truss structures be produced using a scalable and cost-effective automated manufacturing method? Through this thesis project, an affirmative answer to this question was sought. The focus of this thesis was on the investigation of all the aspects necessary for a production of this iso-truss structure, focusing on a process suited for later automation. Initial concepts using thermoset composites like the original IsoTruss could not solve the issue of automated compaction, as these would always rely on vacuum bagging to minimise the void content within the composite members. Automated vacuum bagging of the finished iso-truss structure was considered to be an infeasible solution due to the product's complexity. Through the use of thermoplastic composite materials however, the process steps could be split up and compaction could be moved to the very beginning of the process in the form of pultrusions. The shape of the resulting iso-truss was designed to make use of this process, providing a parameterised structure which could easily be optimised. The structure would make use of straight pultrusion rods, acting as the longitudinal members in the truss, and curved pultrusion rods, which would act as helical members. The iso-truss structure would be created by joining these members together at intersections by means of thermoplastic welding, forming a continuously produced open lattice tubular structure. With this, conceptual production of an iso-truss was based on three key steps: pultrusion, forming, and intersection welding. The pultrusion process was outsourced to an outside company, vDijk Pultrusion Products (DPP), due to its high required equipment cost. It was not the aim of this thesis to re-invent this process, as it has already reached a sufficient state of maturity. Nevertheless, the process has not yet been optimised for thermoplastic based composites, leaving room for improvement in this area. Materials for the concept were based on availability. Elium resin (a PMMA based thermoplastic polymer developed by Arkema) was chosen for its similarity to existing process materials and its direct availability from DPP. As reinforcement, a Toray T700SC type carbon fibre was used. By taking pultrusion out of the research scope, forming and welding were left as processes to demonstrate. A separate welding test was isolated to provide a way to perform standardisable tests. Simultaneously, a forming process demonstrator was designed, as well as a welding jig to demonstrate assembly of the iso-truss. For the execution of the welding and forming experiments, a single batch of material was ordered from DPP. The batch was the result of a first successful attempt to make rods of this diameter with this combination of materials. Upon arrival of the samples, several tests including SEM, TGA and DSC were performed to estimate important composite material parameters. From these tests, the fibre volume fraction could be estimated to be around 70%, while the onset of T_g was estimated to be 95degC by definition of maximum loss modulus. Additionally, several interesting phenomena were observed at elevated temperatures in the form of fibre kinking when bent and circumferential decompaction when twisted, indicative of a weak fibre-matrix interface. More indications of this limited fibre-matrix interface were obtained from SEM images, some of which showed small voids around fibres. DMA tests showed a steady decline of the material's (shear) stiffness over a large temperature range, including before the onset of glass transition. This could likely be attributed to the amorphous nature of the polymer. For the execution of joining experiments, a standard intersection layout was established, after which several joining techniques were considered to create these intersections. From these techniques, heated mould welding was selected as the best currently feasible option. After performing numerous experiments to fine-tune the method of heated mould welding, a standard setup could be designed around this technique. This setup addressed methods for heating, alignment of members to be welded, a compaction mechanism, physical test preparation and physical testing. Simultaneously, a detailed design of a helical winder demonstrator was made, which was prepared for production by DEMO. The design focused on the demonstration of the mechanical aspect, leaving heating as a secondary concern. Similarly, a more detailed concept of an assembly demonstrator was discussed and designed, although a production-ready design did not prove feasible within the time frame of this project. The main goal of the intersection welding experiments was to optimise the joint strength by optimising the processing conditions. Due to the limited resin volume content, PMMA foil and epoxy adhesive were used to locally increase resin volume, greatly improving the bond strength compared to initial samples. Using mould temperatures in between 180 to 200degC, a large degree of deformation could be achieved to maximise the joint area, creating mostly consistent intersection samples. Physical tests proved that the PMMA-based joints were very fragile, while epoxy based joints performed significantly better. Estimated shear strengths for the samples varied from 3MPa for some of the lower performing PMMA-based intersections which were believed to have sustained prior damage, to as high as 13MPa for the epoxy based intersections. For the buckling tests, maximum loads in between 2.1 to 3.2kN were observed. In the final buckling test setup, diagonal members did not increase the buckling load by forcing higher-mode buckling. Instead, they offered some support in post-buckling by resisting out-of-plane deformation. Failure modes in both shear and buckling tests were within the adherend, occurring as a combination of fibre break-out, member kinking and member splitting, more indications of a poor fibre-matrix interface. In summary, the experiments proved that the investigated welding method is feasible if the base material can be improved. As of writing, such improvements have already been reported by DPP through increased process stability and (likely) better fibre sizing. For the helical winding experiments, the main goal was to demonstrate the production process of heated forming of initially straight pultrusion samples into helices. The physical test setup was designed to offer continuous support of the members over their full length, realise a gradual increase in radius of curvature and allow torsional and axial forces to be introduced independently. For the resulting setup, heating of the central cylinder and introduction of heat through both contact and a heated air chamber proved most feasible within the time frame of this project. It did not prove feasible to produce carbon-Elium composite helices due to the current material limitations, that is the fibre kinking observed in previous tests. Instead, the process was demonstrated using pure PMMA rods at forming temperatures of around 90degC, which proved highly effective. The process showed the potential to create constant curvature helices with controllable helical angle, although more testing should be performed to achieve accurate and repeatable results. It is concluded that it is theoretically possible to produce continuous fibre reinforced iso-truss structures using a scalable and cost-effective automated manufacturing method. The process would rely on existing production capabilities which can easily be scaled up or down, without greatly affecting the cost of equipment. The pultrusion, helical shaping and intersection welding processes can all be easily automated using existing techniques to be able to produce an iso-truss tube of indefinite length. The only limitation of this manufacturing method would be the variation of process parameters within the same iso-truss sample. While it is theoretically possible to vary the radius of curvature of pultrusion dies during the pultrusion process, enabling the possibility of varying the outer diameter and the intersection node-to-node distance along the length of a tube, the current state-of-the-art does not accommodate such a design. While it would also be possible to vary the cross-sectional area of each member along their length, it is considered undesirable as it would negatively affect the fibre volume content for a pultrusion-based process. Instead, it is recommended to construct an iso-truss structure in stages, being connected by a structure that is to be envisioned and produced in future research. ... Read more

To expand the use of additive manufacturing in aerospace towards more critical applications, it is required to design parts in a damage tolerant context. Therefore, the damage tolerance of additive manufactured multiple load path structures is assessed by analysing the fatigue life and damage propagation of components with increasing redundancy. An experimental approach is chosen, whereby specimens with 1, 9 and 81 parallel struts are tested. A decreased fatigue life is found for the specimens with more but thinner struts. This decrease is attributed to manufacturing related effects that occur upon producing smaller elements. The failure of the multiple load path structures showed a step-wise pattern. Due to this, the decreased variation in fatigue life and decreased sensitivity to initial damage, multiple load path structures are more damage tolerant. However, in design a balanced decision should be made upon applying these structures, due to the decreased fatigue life. ... Read more

Global and local aviation traffic is growing while economic and performance pressures on the industry are increasing. As a consequence, airlines try to maximise their fleet utilization. Airline operators and Maintenance, Repair and Overhaul (MRO) providers therefore require as much insight as possible in factors affecting component reliability and availability. Reliability analysis in literature rarely considers the existence of a relation between explanatory variables and component reliability, and includes strict assumptions on independence of events and underlying distributions. This disregards the complex nature of aircraft operations, where the probability of an event may be influenced by various operational and maintenance factors. This research develops new insights from operational and maintenance data about the impact of operating environment and ageing of components and fleet on reliability of the components by incorporating these factors in an extension of the Cox regression model. The research was performed in cooperation with KLM Engineering & Maintenance, a Dutch MRO company. Examination of results obtained from analysing historical data of a set of three components with respect to installations and removals indicate that the natural environment at the hub airport, maintenance history of components, the age of the aircraft on which the component is installed and different modification designs are useful significant predictors of the time-on-wing duration of the component. ... Read more

This thesis presents a model that is able to predict fatigue crack growth and damage directionality in non-conventional Fibre Metal Laminates (FMLs) in CentreCracked Tension (CCT) specimens. Non-conventional FMLs encompass all FMLs other than standardised ones such as GLARE. FMLs can be made non-conventional by using multiple fibre types, any fibre orientation, multiple alloy types or thicknesses, or a combination thereof. These characteristics provide much more tailorability than standardised FMLs and thereby extend the applicability of FMLs to, for example, door corner reinforcements and wing structures. Contrary to standardised FMLs, the damage in non-conventional FMLs is non-uniform, necessitating the ability to compute the crack growth rate in the metal layers and the delamination at the metal-fibre interfaces separately. ... Read more

The superyacht industry faces an increasing trend of larger dimensions, more open spaces, larger hull openings and more exotic shapes. This puts more effort on the structural design and especially for superyacht longitudinal stiffness is important, since the luxurious interior and delicate systems installed in a superyachts are not allowed to cause creaking noises or be damaged. A method is developed that can provide global and local deformations in operational sea conditions to use for risk assessment and provide guidance on clearances or connections that should be used for interior installment. Wave-induced loads are calculated with a linear response analysis in combination with a regular equivalent design wave. The yacht hull is modelled as a 1D Timoshenko beam including shear deformations and torsion for which good agreement is found with a detailed 3D FE model with shear deformations accounting for 20% to the vertical displacement.

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Incorporating carbon nanomaterials such as carbon nanotubes into a polymer matrix not only enhances the mechanical properties of the composite, but also induces good electrical properties. This makes carbon nanocomposite interesting for potential electronic applications, such as electromagnetic interference shielding by means of creating housings for electronic devices. One potential option of producing carbon nanocomposites is via injection molding, which is widely used in the plastics industry since it is a fast and cost effective method to mass-produce plastic parts.

Looking at the current state-of-the-art literature a lot of research in this area can be found. It has been identified that injection molding is not beneficial for high electrical properties of the composite and it leads to a non-uniform in-plane distribution of the electrical properties. Moreover treatments such as annealing have been described to enhance the electrical properties of the composites. However some shortcomings in the current research have been identified.

Hence this master thesis research aims at eliminating those shortcomings by characterizing the electrical properties of different injection-molded nanocomposites and their in-plane distribution. Moreover it has been investigated how additional treatments such as below melt temperature annealing and dielectricphoresis enhance the electrical properties and their in-plane distribution.
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EX-CORE, a novel foam core material developed by Donkervoort Automobielen B.V., allows the creation of complexly shaped sandwich structures in a one-shot out-of-autoclave manufacturing process. Products with small tolerances and high surface quality on all surfaces can be obtained. The EX-CORE technology has achieved its intended goal at Donkervoort of saving cost and time for the production of sandwich structures for their cars. Now Donkervoort has the ambition to further develop EX-CORE for larger scale automotive manufacturing. To make the EX-CORE technology competitive with other composite production processes, the cycle time of several hours should be reduced to several minutes. The present work contributes to this development by re-engineering the EX-CORE foam composition such that cure cycle time reductions can be achieved. ... Read more

Besides building ultra-lightweight sportscars, Donkervoort Automobielen B.V. is developing a novel core material to be applied in complex shaped composite sandwich structures. This material goes by the name of X-Core and has the unique capability of generating the pressure required for facesheet consolidation, enabling a one-shot manufacturing process for the first time. The present research has focused on the phenomena present during the manufacturing process of the foam. In-situ temperature measurements have been carried out to gain a deeper understanding of the thermal behaviour of the material. A numerical model, based on a transient finite difference method, was then constructed to predict the temperature distribution in the material during its cure under different processing conditions, material compositions and cure cycles. The proposed model can now be applied in fine-tuning cure-cycles required to attain certain desirable X-Core properties. ... Read more

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. ... Read more

Fatigue is the weakening of a material or structure due to cyclic loading and unloading. As such fatigue is very important in engineering fields like aerospace, where structures are exposed to cyclic loads. Therefore theories on the initiation and propagation of fatigue have been extensively researched In the past century. The main Fatigue Crack Growth (FCG) prediction models are based on a Stress Intensity Factor (SIF), ΔK. Representing FCG data as a function of this SIF causes a stress ratio (R-)effect, which is accounted for by means of plasticity induced crack closure. Crack closure causes the crack to close before a zero tensile load is applied, as such influencing the effective SIF. If FCG data is presented as a function of the effective SIF ΔKeff instead of ΔK, the data correlates very well and the R-effect disappears.
However, the theories based on a SIF and crack closure have recently been subject of discussion. The prediction models using ΔK for similitude are empirically derived and thus do not have any physical explanation. Furthermore ΔK has been derived for quasi-static loading conditions and as such it cannot be blindly adopted for fatigue loading conditions. Besides there is a lot of confusion about the phenomenon (plasticity induced) crack closure, load-displacement observations attributed to crack closure could for instance also be attributed to residual compressive stresses. Especially early test results in vacuum environment do not agree with theories based on SIF and crack closure.
An alternative proposed in literature is to approach fatigue from a Strain Energy Release (SER) perspective. This theory approaches fatigue conform the laws of thermodynamics, and claims that not the amount of energy released under quasi-static load conditions should be considered, but the energy released during a complete fatigue load cycle. It also claims that the R-effect is only an artefact of choosing ΔK for similitude. Treating fatigue as a SER dominated phenomenon instead of a SIF dominated phenomenon, might result in a proper description, prediction and understanding of fatigue.
As such the first goal of this research was to investigate if ΔK is a correct similitude parameter for FCG. This was investigated by comparing experimental results in air and vacuum. According to conventional fatigue theories based on SIF, there should be no difference between air and vacuum. Experiments were designed and similar test conditions were applied with the only difference the environment tested in. Experimental results in air showed -as expected- a clear R-effect that could be accounted for by the plasticity induced crack closure corrections proposed in literature. However, the results in vacuum did not show this R-effect, while the results of crack opening experiments and plasticity did not differ compared to results of experiments in air. It was therefore concluded that ΔK is improper to use as similitude parameter for FCG prediction... ... Read more

Splicing is a method for joining Fibre Metal Laminate (FML) panels in which, at the location of the joint, metal sheets are overlapped to form a Damage Tolerant (DT) bond. This joining method is successfully applied in aircraft structures, but has one main disadvantage; it cannot be used in structures with significant double curvature. To qualify FMLs for these specific locations as well, a different joining method is required. With this in mind, the idea of Friction Stir Welded (FSW-ed) FMLs was born. By FSW-ing individual metal sheets together before lay-up, it is possible to create FML structures with the required double curvature. This research was aimed at developing the DT design principles for successful application o f t h i s concept in aircraft structures. In order to reach this goal, a step-by-step DT compliance plan was created. This plan started with the identification of analytical methodologies for predicting the DT performance of the joint. In the following steps, the relations between the DT properties of FSW-ed Glare 3-3/2-0.4 and standard Glare 3-3/2-0.4 were determined experimentally, and used to design different concepts that met the requirements from the compliance plan. Out of the four concepts, the idea with the highest value in terms of cost-effectiveness was determined, which was subsequently compared to other materials typically used in the aerospace industry. Experimental results show that cracks grow faster inand residual strength is lower ofthe FSWed version of the laminate. To bring the DT performance back to the level of the standard laminate, additional layers of material are necessary at the location of the joint. The concept that does this in the most cost-effective way for Glare 3-3/2-0.4, is a joint with an inter-laminar aluminum doubler of the same thickness as the other metal layers. Compared to the spliced version of the laminate, the FSW-concept is significantly more expensive. When looking at the DT performance compared to other materials, only certain carbon-fibre reinforced plastics have better properties. ... Read more