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.

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.

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.

Variable Stiffness Laminates are created by spatially varying the fiber orientation resulting in designs that makes use of curved fibers rather than Uni-directional fibers to tailor the properties to design requirement. The advent of automated manufacturing methods such as Automated Fiber Placement and Tailored Fiber Placement has made variable stiffness laminate more realistic and attractive for use in aerospace and automotive sector. Importance of light weight designs in automotive sector has received new interest due to the stringent emissions rules and entry of designs based on alternative energy. Within this context, this thesis intends to create variable stiffness design for an automotive part to investigate the possible improvements in structural responses compared to a design based on conventional laminates. The design is done based on 2D Finite element analysis coupled with a convex optimization that helps to generate steered fiber designs optimized for strength, stiffness and buckling. One of the important load case studied here is the Inertia Relief. Inertia Relief method is a computationally efficient way of analyzing rigid bodies without doing a dynamic analysis. The method was implemented in the finite element framework and the responses from the analysis were taken for optimization.
Final optimization of the structure showed that significant improvement in the objective responses can be achieved by using variable stiffness laminates over a conventional laminate design (UD). The result also implies that reduction in weight can be achieved if a variable thickness optimization is to be done on the model.

Fibre Metal Laminates (FML) are hybrid composites, with the attempt to combine the advantages of metals and fibre reinforced plastics. Their promising properties are used locally in joining areas to reduce the structural weight. As the metal foils density, in this case a steel alloy, is much higher than the density of carbon plies, its amount should be kept minimal. Hence, the replacement of the laminas is done gradually creating a so called Transition Zone (TZ).

In this research, the focus is given to the influence of the TZ on the structural behavior in pin connected FMLs. In the investigation two different designs of TZ and two different starting positions of TZ (closer and further from the pin) are considered. First their effect on the laminates behavior is investigated with static bearing tests accompanied by Digital image Correlation (DIC) measurement, followed by a Finite Element Analysis for an in-depth look at the laminas behavior. Later includes the implementation of the Cuntze failure criterion for damage prediction. The studies revealed that the distance between load introduction and start of the TZ can be very short without affecting the load carrying capacity.

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.

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.