Growing competitiveness in the launcher market is driving metallic propellant tanks toward tighter mass limits, increasing the need for reliable buckling prediction under combined axial compression and internal pressurization. Thin-walled cylinders are imperfection-sensitive, and current practice relies on conservative knockdown factors derived mainly from unpressurized tests. This work evaluates alternative nonlinear imperfection modeling approaches for pressurized launcher tank segments, with an emphasis on reliability and welding-induced imperfection signatures.

Five imperfection-sensitive strategies were assessed using NASA Shell Buckling Knockdown Factor Project cylinders at 0, 2, and 4 bar, including SPLA, MPLA, EIA, MGI, and a distributed-force perturbation approach (DFPA). Reliability was quantified using the coefficient of variation, Kendall’s W, and the intraclass correlation coefficient.

Results show that pressurization reduces imperfection sensitivity by increasing geometric stiffness. Distributed and multiple-perturbation methods were the most stable across pressures, whereas localized approaches exhibited strong pressure sensitivity. Accurate pressurized buckling prediction, therefore, requires pressure-aware imperfection mechanisms.
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Automated Fiber Placement (AFP) is a manufacturing process used to produce composite structures, mainly in the aerospace industry, where a robotic system deposits one or more long-fiber tapes on a mold or surface by applying pressure and high temperature to the material. Currently, AFP-manufactured components are mostly manually inspected by operators or using post-production Non-Destructive Testing (NDT). These methods are time-consuming and often have low reliability. For these reasons, online monitoring systems are being adopted, which are technologies capable of detecting defects while the component is being manufactured. However, these systems still require human operators to fix the defects or to change process parameters to avoid them.
This thesis addresses this gap by developing an Adaptive Process Improvement System (APIS) for AFP, which consists of a closed-loop approach for defect mitigation. Central to the system is a profilometer sensor integrated directly onto the AFP machine. This sensor, coupled with an embedded defect detection software, automatically acquires geometric and defect data from the deposited layer, which are then used to generate a detailed defect visualization and a quantitative defect report. Prior to the algorithm design, a comprehensive foundational analysis was conducted to quantify the relationship between AFP process parameters and the formation of specific defects. This correlation analysis established the necessary knowledge base by determining which parameter adjustments cause specific improvements in laminate quality.
The system was validated through a series of deposition tests on the AFP machine at the Airbus Composite Technology Center. Following the production and scanning of a ply, the defect report is analyzed, and the system autonomously adjusts the process parameters for the immediate subsequent layer. This is performed by the APIS algorithm, developed using Python 3.12.9. The results are highly promising: for each subsequent layer, the improved process parameters consistently led to a measurable improvement in laminate quality, quantified by a significant reduction in the frequency and severity of defects. The successful implementation of the system demonstrates the feasibility of achieving fully autonomous, adaptive control in AFP, representing an important step toward Industry 4.0 integration for high-performance composite manufacturing. ... Read more

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

Double-walled vessels are recognized as an effective storage solution for liquid hydrogen (LH2) due to their superior thermal insulation. Similar to a thermos flask, the vacuum space between the inner cryogenic vessel and the outer vacuum shell prevents convective heat transfer, which would otherwise result in the rapid boil-off of the stored LH2. A critical component of this technology is the inner support structure which supports the inner vessel within the outer vacuum shell. It must be robust enough to handle operational loads and potential crash events specific to aviation applications, prevent excessive thermo-mechanical stresses caused by the contracting inner vessel, and minimize heat transfer through conduction. Despite its importance, there is a noticeable lack of comprehensive designs and research addressing this component, particularly in the context of aviation.

The primary objective of this thesis is to develop a design methodology for creating effective inner support structures for double-walled vessel technology. The research is grounded in a practical context through a collaboration with AeroDelft, a student team at TU Delft currently retrofitting a Sling 4 aircraft for hydrogen-powered electric flight. As part of the next milestone in their Project Phoenix, AeroDelft aims to store 6 kg of LH2 in a double-walled vessel to meet the mission's requirements.

To begin, functional, operational, and constraint requirements were established for the inner support structure. A baseline design for the inner vessel and outer shell was then developed. Subsequently, four distinct inner support structure concepts were introduced, each with its own design intents and key considerations. These concepts were subjected to various analyses, including modal, thermo-mechanical, crash loads, and heat leakage, to assess their viability and ability to meet essential functional requirements. To determine the most performative design(s), the concepts were evaluated and compared based on the following performance metrics: gravimetric efficiency, heat leakage, safety, and feasibility of manufacturing and assembly.

The analyses demonstrated that all four design concepts meet the essential functional requirements, providing a solid foundation for further development or potential prototyping. While the focus was on a vessel designed for a small aircraft, the methodology and design insights are applicable to larger systems. Hence, this research contributes to advancing cryogenic storage solutions for hydrogen-powered aviation.
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In this study recyclable Twin Matrix Composites (TMC) have been developed and analysed. The reinforcements of these composites are pultrdued rods, which are made from carbon fiber and Bisphenol A Epoxy. These rods are embbed in a secondary matrix which is made from a bio-based epoxy resin and recyclamine curing agents.
This study focuses on the interlaminar properties of these TMCs and how they are impacted by recycling. The results indicate that the change in rod/secondary-matrix interface due to recycling is insignificant. This suggests that these TMCs can be considered as favourable condidates in for sustainable composite industries. ... Read more

Presently, there exists no “off-the-shelf” option for power generation on the order of magnitude necessary for sustaining a long-term human presence on the surface of Mars. In this thesis work, an investigation was performed to determine the optimal design for a large-scale, static, autonomously deployable, lightweight Martian surface solar array. A principle aim of the design study was to articulate a concept whose stowage volume and mass performance is, at the very least, comparable to that of the Compact Telescoping Surface Array (CTSA) which was developed by the National Aeronautics and Space Administration (NASA) in 2016 to address the same challenge. Divided into two main sections, the first portion of this research consisted of a conceptual design phase which resulted in the generation of numerous different deployable solar array concepts. Through detailed analysis as well as cross-comparison, the Stripped Array concept was determined to likely be the only concept that can outperform the CTSA. At a high level, the Stripped Array is a square shaped, monolithic deployable array whose solar array membrane subassembly is divided into strips of varying length. It deploys above a Martian lander and is supported at its center by additional payload on the vehicle’s payload deck as well as at its corners by four telescoping composite booms which are evenly spaced around the perimeter of the landing vehicle. A main reason for the Stripped Array’s improvement in volume and mass performance is based on the reduction in deployment length and in total number of telescoping supports. Furthermore, the stripped membrane configuration in conjunction with the quad slip wrapping stowage method results in low stowed volumes by comparison to the other concepts. The second portion of this research consisted of a number of preliminary sensitivity studies to further characterize the Stripped Array concept. Specifically, system response to changes in total array area, level of pretension, and sizing of various subcomponents of the solar array membrane was evaluated. Furthermore, a preliminary study was performed to understand the effect of solar array membrane pre-tension, level of gravitational loading, supporting architecture cross-sectional sizing, and assumed support conditions on assembly stresses, deflections, and natural frequencies. ... Read more

C/C-SiC is a type of ceramic matrix composite, which consists of a silicon carbide matrix phase, combined with reinforcing carbon fibres. This material has high specific strength and stiffness, good damage tolerance, as well as excellent thermal properties. It is commonly applied in environments where these properties are utilized, such as thermal protection systems, engine components and refractory industry parts. Thus, also rocket nozzles, which contain a highly mechanically and thermally stressed environment. This thesis aims to add to the research on C/C-SiC for rocket nozzle applications. Specifically, using pitch-based short fibers as a reinforcing stage. This has the potential to have manufacturing, cost and performance benefits over other materials, however, this has never before been developed. The influence of manufacturing parameters was quantified, where it was found that temperature cycle, pressure application and resin application have a significant influence on part properties. Also, the effect of the composition parameters of fibre length, fibre type, volume fraction and resin type was investigated on microstructural, mechanical and thermal properties. Based on this, extrapolation could be done, and an optimal material defined. This knowledge was combined in the design and planning of a proof-of-concept rocket nozzle from short fiber C/C-SiC material. ... Read more

The use of Grid-stiffened structures has been increasing in the space industry over the last decade. Thanks to it is high specific mechanical properties and excellent damage tolerance characteristics, researchers also started looking into the potential of using them for aeronautical applications. However, not much has been done to investigate the reduction in strength after barely visible impact damage and visible impact damage, and how much energy is needed to cause such damage, which is an important requirement for aircraft certification. In this project, a grid-stiffened replica of an existing reference cargo drone is created, and the design is tested to check its compliance with the requirements. This involved modelling of the design, manufacturing of test coupons, impact and mechanical tests, and model validation. The results showed a possible weight reduction, with no major reduction in strength observed with impacting using the cut-off energy level set by the manufacturer. ... Read more

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

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. ... Read more

In a bid to increase additive manufacturing (AM) technology readiness, this study researched feasibility of AM technology application in the next generation secondary flight control systems. Taking a state-of-the-art certification framework and technology into account, a selection tool was created and used to survey the high lift and thrust reverser systems for the most suitable demonstrator part. A thrust reverser lever, the selected part was then redesigned to prove the AM technology benefits, for which a trade-off of 4 different designs and existing part was performed. The final concept showed a part count and weight reduction, which on a system level is negligible. Using analytical and numerical methods, technical feasibility of the design was proven. Nevertheless, while satisfactory, for future products a more sophisticated fatigue assessment method would be required if parts in more demanding load environments are to be considered. The recurring cost model for AM developed in the study has shown reduction in cost of the concept when compared to the existing components produced in a low-cost country. However, the AM business case is compromised when analysed against the true existing parts’ cost. Consequently, the research has shown that while the small low risk components are technically feasible and cost-competitive for AM production, the more radical technology application is needed to provide a step change in performance. ... 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

Paralympic sports are growing more popular. Besides the dedicated training of the athlete, technology is crucial to empower amputees to perform at their highest level. The recent carbon fibre Running-Specific- Prosthesis (RSP) have energy stored and return capabilities that allow runners with amputations to perform almost as able-bodied. However, due to the difference in power output between a biological ankle and a RSP, unilateral transtibial (UTT) amputees need to adjust their biomechanics to an asymmetric pattern. It is known that the stiffness of the blade has a great influence on the performance of the athlete. The main challenge was to find a method to prescribe the optimal stiffness for a particular athlete, that allows him/her to performthe best in a race. The current approach to advice a RSP is based on the bodyweight of the athlete and the coaches and athletes wishes. Nevertheless, as a result of the insufficient number of subjects and the difficulty to performa randomised control trial, there is limited evidence about the UTT athlete capability of adapting their muscle activity to different prosthesis stiffness and the optimal RSP stiffness for them. In order to investigate this, two main goals for this master thesis project were raised: to implement a musculoskeletal model of an UTT amputee athlete wearing a RSP and predict its optimal running biomechanics through predictive forward dynamic simulations; to find the optimal athlete-RSP stiffness combination that maximizes the running performance. Five different stiffness of a Flex-Run ¨Ossur (Reykjavík, Island) RSP were modelled and simulated for the maximumvelocity the model could reach. Results: firstly, the model could perform better with a middle-class RSP category. It enhanced the hip muscles to exert more power in the blade during the first part of the stance phase. However, the prosthetic leg generated 41.2% lower total average power, including the RSP power, than the intact leg. The RSP made up 24.8% of the total prosthetic leg power. Secondly, the intact leg benefited from an improved push-off of the prosthetic leg having a favourable landing that allowed to exert more power and propel the body into longer flight time than with low-class RSP categories. Still, the top speed of the model was far from what athlete can achieve, but the motion and kinetic data were comparable for low running speeds. Therefore, it could be concluded that a reasonable prediction of the optimal RSP stiffness for running at about 4.6 m/s was achieved. The presented biomechanical model could potentially be used to assist coaches and athletes to have a better idea of themost suitable RSP stiffness. ... Read more

The aim of this study is the assessment of the mechanical performance reduction due to manufacturing-induced gaps and voids (delaminations) in thermoplastic composite pipes. The effects of gaps are assessed based on the finite element modeling of an internal pressure load case and is validated by experimental tensile coupon testing. Results show a stress increase through-the-thickness in the layers having the same orientation, which depends linearly on the gap width. The assessment of voids is based on the modeling of external pressure and lateral crushing, in which the latter is also experimentally tested for validation purposes. No reduction in performance is observed for external pressure and an onset of delamination growth is observed for lateral crushing. A tool is proposed for a fast and computational inexpensive assessment of manufacturing-induced gaps in thermoplastic composite pipes to improve the design and manufacturing process and contribute to an improved integrity management system. ... Read more

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. ... Read more

Since the aerospace industry is continuously looking for new strong and lightweight solutions to existing aircraft parts, Fused Composite Manufacturing has much potential for future applications as it incorporates both the freedom of design and a continuous fiber reinforcement. The current state of the technology is of low maturity as engineering thermoplastics are of use with low Fiber Volume Content and part complexity is limited due 3-axis kinematics of the used printers.
As such, the research presented in this report aims to evaluate the feasibility of such FCM process with regard to aerospace applications by the integration and optimisation of a novel print head within a 6-axis industrial robot, capable of printing high performance prepreg filament in all arbitrary directions. ... Read more

To investigate the damage tolerance of a flexible tsunami barrier, the intralaminar fracture toughness of a plain weave cloth, consisting of Dyneema© fibers and a plastomer resin, has been investigated.
Fracture toughness tests have been performed on center cracked tensile specimens, with varying sizes and initial crack ratios, under quasi static loading. The tests showed nonlinear behavior at the crack tip, leading to crack-blunting, fibers shifting and matrix release. This is due to the low adhesion of the matrix with the fibers and the flexible nature of the cloth. General failure mode proved to be strength-dominant and therefore no critical stress intensity factor could be determined.
To predict the failure and of the cloth, a numerical simulation based on the peridynamic framework is proposed. The model includes the anisotropic elasticity of the cloth but not the nonlinear effects like fiber shifting. Therefore the strength of the cloth is eventually underestimated. ... Read more

An approach to optimizing variable stiffness laminates for strength is modified to allow for the optimization of curved structures. A density function to take in account the effect of gaps and overlaps during optimization created by fibre steering is found with the functional approximation method. The density plot of a plate for 2 standard cases is compared, after encountering complications an alternative solution is proposed with the finite element method. ... Read more

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. ... Read more