During this research, a new approach to predict impact damage was evaluated using the PAL-V Liberty’s propeller blade as the test subject. The purpose of this research was to provide a simple method for impact damage prediction which will support the certification activities of the PAL-V propeller.
This method involves conducting a threat assessment, a Probability of Detection analysis, executing ASTM D7136 impact and quasi-static tests on coupon samples and conducting quasi-static tests on the propeller blade itself. The results from these tests were used to create a two-mass model which can predict the contact force during a propeller impact event. This model was validated using impact test on the propeller blade.
The study conducted a series of ASTM D7136 impact tests and quasi-static tests on coupons, revealing that the coupons exhibited greater load-bearing capacity under impact loading compared to quasi-static loading. These tests also showed that the coupons have an increased stiffness when subjected to impact loading, requiring a multiplication factor of 1.47 to align their stiffness with quasi-static conditions.
The research also involved determining boundary conditions for propeller tests, which led to the development of a custom clamping mechanism. During the quasi-static tests, the differences in stiffness between coupon and propeller tests were identified. These coefficients served as the basis for a predictive
model involving a two-mass, spring and damper system, with parameters derived from coupon tests and the propeller quasi-static tests. After performing the validation impact tests on the propeller blade, it was determined that this model successfully predicted contact forces within 13% of actual test values.
The research demonstrated the potential to predict impact energy requirements for barely visible impact damage, without the use of FEA. The model’s accuracy, while it can be improved, is sufficient to predict impact events effectively, offering a simpler alternative to complex FEA models.

This project aims at developing a model to predict the damage initiation and propagation in a cylindrical filament-wound cord-rubber structure under internal pressurization using non-linear FEA, and is conducted in cooperation with TANIQ BV, Netherlands.
Cord-reinforced rubber composites are used in several safety-critical industries such as oil and gas and civil plumbing. Despite their widespread use, limited research is available that focuses on the single-cycle damage phenomenon that may occur in events such as over-pressurization.

The aim of this project is to close this knowledge gap by developing a theory that accounts for the key damage modes present in CRC structures. This involves experimental studies for material characterization and identification of relevant damage modes, the creation of a novel fibre overlap model that accurately replicates the meso-level filament-wound structure, and translation of the experimentally verified damage modes into functional damage initiation and propagation laws using a global-local FEA model. Verification of the created damage model is done experimentally on samples manufactured and tested at TANIQ, with differences between model predictions and experimental burst pressures being $\approx 6.5\%$. This is a marked improvement over Taniq's current FEA model, which overpredicts the solution by $\approx 27\%$.

The successful implementation of this model would help industries like TANIQ build efficient, strong, and lightweight rubber composite parts for various industries, thus adapting aerospace design principles to the development of more commonplace apparatus.

This research investigates the role of how Finite Element simulation models reproduced progressively crushed Glass Fiber Reinforced Polymer (GFRP) parts. The proposed work is motivated by the research questions concerning what are the relevant critical modeling strategies that accurately reproduce the behavior of in-plane crushed laminated composite parts with LS-Dyna, how will the simulation model be evaluated following the modeling strategies, and which are the main similarities and dissimilarities among the result of the modeling strategies considered. The research objective is to develop detailed finite element simulation models for axially crushed GFRP composite parts which can represent complex damage modes by a methodical approach in a reasonable time with LS-Dyna explicit. Previous research has shown the necessity to calibrate many parameters with no physical meaning to correctly reproduce crushing. This research addresses these gaps by benchmarking two material models that are not characterized by such effects (*MAT_261, *MAT_262) in comparison with the one characteristic of such behavior, *MAT_54. The most important contribution is to the crashworthiness industry. To date, no research studies were found in the literature covering all the aspects described. This work demonstrates how to deploy such capabilities starting from simple numerical models, to vehicle parts. To illustrate these concepts, the necessary assumptions to create the models and how the parameters were identified have been described while choosing fully integrated shell and thick shell elements. The qualitative and quantitative criteria defined were necessary to systematically evaluate more than 200 simulations in comparison with available experimental data from Daimler AG. The significant findings from the research demonstrate that *MAT_261 and *MAT_262 are not subjected to strain localization phenomena, unlike *MAT_54. The developed set of parameters resulted in a low sensitivity of the *MAT_262 models concerning element size, lay-up or impact energy. Moreover, the research demonstrates that more accurate quantitative results than the current state of the art can be produced with a 5.0 mm element length against the general belief that fine-meshed and mesh convergence studies are required. Contrary to the expectations *MAT_261 demonstrated a low mean force in crushing although sharing the input parameters with *MAT_262 and similar damage laws. The developed models and set of *MAT_262 parameters can be deployed in full vehicle crash simulations with the plug-in possibility to evaluate new design variants. It is concluded that the findings provide support fulfilling the research objective.

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.

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.

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.

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.

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.

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.

As the demand on new lightweight materials increases due to economic and environmental reasons, fiber reinforced plastics seem an interesting solution. In order to maximize their potential, ways have to be found to introduce damage tolerant designs. To this end, in the present exercise, the damage caused by cyclic loading is investigated.
Cyclic loading causes loss of stiffness and strength of composite structures. In the present work a progressive damage analysis model has been built. Damage is tracked by a macroscopic failure criterion. Failure occurring at levels below the macroscopic level are captured by a degradation theory which requires S-N curves as input. An attempt is made to use S-N curves derived from static tests only. Stress solutions are obtained using a finite element package. In order to bring the macroscopic damage, degradation and stress solution parts together, a cycle jumping algorithm has been developed which minimizes the amount of FEM stress solutions required and the required amount of function evaluations.
In its current form, the model is able to properly predict the trend of stiffness and strength behavior. Showing that a model like this has potential. For the proper predictions of mag- nitudes, additional failure modes should be modeled and the usage of S-N curves obtained from large specimens for applying on smaller geometries (elements) should be reconsidered.

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.

Fibre-reinforced laminated composites are constructed layer-by-layer, allowing their material properties to be easily tailored relative to their isotropic counterparts (metallic alloys). Moreover, a composite structure with variable stiffness (VS) can be made by spatially tailoring stiffness across a laminate. This permits better load distribution within a structure, efficiently using a given material, and allow for lighter construction. Typically, the design of VS structures follows a bi-level procedure: first, the structure’s stiffness distribution is optimised using lamination parameters (LPs), and second, the stacking sequences (SS) of differently oriented fibres are designed to achieve the desired stiffness distribution. However, the designs envisioned using LPs are only sometimes exactly matched by the designed SS. The shortcomings faced during this conversion are called the ’Inverse Problem’. Upon reviewing the existing techniques in literature to handle the inverse problem, it was understood that converting LPs into SS is challenging without incurring substantial computational costs or imposing significant restrictions on allowable fibre orientations in the design. Such restrictions tend to under-utilise the directional properties of the fibres. Thus, there was a need to explore and develop better stiffness design methods for laminated composites by bridging the gap between LPs and SS in a computationally efficient way.

In response to this challenge, a hierarchical design framework was proposed to handle the Inverse Problem. Diverging from conventional methods that directly design the SS and try to match a given set of LPs, this framework divides the problem into two distinct stages. Initially, the focus is to use the In-Plane LPs and determine the number of layers in each orientation within a laminate, also called the Fibre Angle Distribution (FAD). Subsequently, the FAD serves as an interim solution, and the SS can be designed by using the Out-of-Plane LPs along with it. This problem partitioning enhances computational efficiency and offers potential benefits in solving the Inverse Problem more effectively. Given the time constraints inherent to a master thesis, the primary undertaking of this study was to efficiently design the FAD while accommodating a wide range of possible fibre orientations. To address this, a novel method using the Fast-Fourier Transform (FFT) was developed to facilitate FAD design with ply angle multiples of 15° (or [∆15° ] = [0, ±15, ±30, ±45, ±60, ±75, 90]). Moreover, empirical guidelines for SS design, such as the Symmetry and Balancing rule, were incorporated into the design step.

The primary contribution of this report is introducing an FFT-based method to design FADs, a novel addition to the existing body of research. Upon extensive testing, it was shown that this implementation could convert LPs into multiple unique FAD solutions in less than 0.3 seconds on a regular office laptop, outperforming other methods in literature by at least ten times. Furthermore, the implementation was also used to demonstrate the benefits of designing laminated composites using [∆15°] over the conventional [∆45°] orientations (or [0, ±45, 90]). In light of the positive results, it is pointed out that the In-Plane LPs (and consequently the In-Plane stiffness) are known to be sensitive only to the FAD and not their SS. As such, the readers of this thesis are presented with a very computationally efficient approach for designing laminated composites for In-Plane Stiffness...

The specific properties of fibre reinforced laminated composite plates can be optimized by tailoring the local stacking sequences to approach the locally required stiffness and strength. Blending enforces continuation of some or all plies from one stacking sequence to another to ensure structural integrity and manufacturability. Effectivity in blending becomes important when the number of variables increases, also referred to as the curse of dimensionality. A CA-based blending strategy is proposed which evolves the local optima to a blended configuration. The optimal design provided by the CA-based algorithm, for a horse shoe pattern benchmark case, is comparable to the state-of-the art blending methods in terms of weight. A new benchmark problem is proposed, to prove the effectivity for blending a large number of sections. The computational effort of the CA-based algorithm increases linearly with the amount of sections, which solves the curse of dimensionality.

Straight fiber variable stiffness laminates use multiple overlapping patches to tailor the fiber orientations in particular regions of the laminate. A novel, automated framework for the design of manufacturable laminate has been developed using different stages. In the first and second stage an optimal stiffness distribution is determined using lamination parameters and converted to stacking sequences on a per region basis. In the third and fourth stages cellular automata and network theory are used to introduce cohesion between regions and comply with current manufacturing standards. Plates in uniaxial compression and cylinders in bending show an increase in buckling performance of 42% and 30% respectively. Such improvements do allow weight savings between 7-11% for these types of structures. When the additional cost of manufacturing and the cost-to-weight ratio for airlines are considered, these laminates already have the potential to significantly reduce the cost of air travel.

The development and production of carbon fiber reinforced plastic (CFRP) exterior parts with Class-A surface finish in the automotive industry comes with challenges. Next to the structural design of the components, the surface quality as well as the joining technique to the body-in-white and the Mercedes-AMG specific factory integration into the worldwide production lines of the Daimler AG need to be considered.
The aim of the thesis was to experimentally qualify an in-house developed open-mold polyurethane injection bonding technology to produce and bond a subframe structure in one process to the inside of a modular CFRP roof with Class-A surface finish. The qualification was done by means of experimental material and process verification and in close collaboration with the adhesives team at Daimler AG Sindelfingen.

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

In a strive to further improve the performance of Aircraft movables the performance of Carbon fibre PolyEtherKetoneKetone (C/PEKK) on component level was assessed in this study. In this study 3 concepts were designed for a fictitious Next Signle Aisle aircraft (NSA) rudder to perform a trade-off between the two composite materials and the two stiffening concepts. An existing C/PPS multi-rib rudder concept is used as a reference. Specified requirements were elaborated to create a C/PEKK based multi-rib rudder redesign. Two multi-rib concepts, each with a different minimum skin thickness, were made and compared. The weight and cost of these two concepts was found to be nearly equal. Alternative stiffening concepts for the multi-rib were generated in collaboration with experts. Grid-stiffening (GS) of the skin using a short fibre reinforced composite was selected. The GS skin allowed most of the ribs to be omitted so that part count and assembly effort could be reduced. The multi-rib concept proved to be the lightest, regardless of the used material. The Technology Readiness Level (TRL) of some manufacturing processes for C/PEKK is low and requires more development. The C/PEKK rudder shall be a viable option in the near future when all envisioned manufacturing concepts and welding of C/PEKK tape become available. The GS rudder requires more research and development. The short fibre material and manufacturing process of the grid have a low TRL and are not yet qualified. A discrete model of the GS skin is also required to better understand the behaviour of the rudder. Thus the GS rudder is expected to be a viable solution in the long term future.

The use of fiber-reinforced composites in the aerospace industry has increased over the past couple of decades thanks to their high specific properties. Fiber-reinforced composites also enable engineers to tailor the stacking sequence to satisfy the required stiffness or strength requirements. However, locally optimizing the stacking sequence of composite laminates introduces incompatibilities between the locally optimized sections which jeopardize the structural integrity of the panel. This highlights the importance of “laminate blending” which is a term given to problems that involve the local optimization of laminates while taking into account continuity guidelines to ensure manufacturability. In this work, a constant thickness blended demonstrator of 32 layers and 5x5 sections was designed, manufactured and tested for its stiffness and critical buckling load. The results were compared to a constant stiffness conventional laminate of the same geometry and weight. The critical buckling load of the blending demonstrator was 80.9% higher than that of its conventional counterpart and the stiffness was 93.75% higher.

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.

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.