During the last two decades, the use of hydrogen (H₂) as fuel for aircraft applications has been drawing attention; more specifically, its storage in liquid state (LH₂), which is performed in extreme cryogenic temperatures (−253 °C), is a matter of research. The motivation for this effort is enhanced by the predicted growth of the aviation sector; however, it is estimated that this growth could be sustainable only if the strategies and objectives set by global organizations for the elimination of greenhouse gas emissions during the next decades, such as the European Green Deal, are taken into consideration and, consequently, technologies such as hydrogen fuel are promoted. Regarding LH₂ in aircraft, substantial effort is required to design, analyze and manufacture suitable tanks for efficient storage. Important tools in this process are computational methods provided by advanced engineering software (CAD/CAE). In the present work, a computational study with the finite element method is performed in order to parametrically analyze proper tanks, examining the effect of the LH₂ level stored as well as the tank geometric configuration. In the process, the need for powerful numerical models is demonstrated, owing to the highly non-linear dependence on temperature of the involved materials. The present numerical models’ efficiency could be further enhanced by integrating them as part of a total aircraft configuration design loop.

In wind turbines, blades are critical design members because performance depends on blade material, shape, twist angle, etc. The problem of internal, mechanical design and material selection for a prototypical high-power horizontal axis wind turbine blade under static, flap-wise loading is investigated in this study. At first a materials selection methodology has been proposed. A very detailed computational analysis based on finite element modes is developed representing the load-carrying box girder of the blade with a given airfoil shape, size, and the type and position of the interior load-bearing longitudinal beams–shear webs. Results concerning displacements and stresses are generated using both plane and shell elements with linear and nonlinear analyses.

Plastic deformation of micro- and nanoscale samples differs from macroscopic plasticity in two respects: (i) the flow stress of small samples depends on their size, and (ii) the scatter of plastic deformation behavior increases significantly. In this work, we focus on the scatter of plastic behavior. We statistically characterize the deformation process of micropillars using results from discrete dislocation dynamics (DDD) simulations. We then propose a stochastic microplasticity model that uses the extracted information to make statistical predictions regarding the micropillar stress-strain curves. This model aims to map the complex dynamics of interacting dislocations onto stochastic processes involving the continuum variables of stress and strain. Therefore, it combines a classical continuum description of the elastic-plastic problem with a stochastic description of plastic flow. We compare the model predictions with the underlying DDD simulations and outline potential future applications of the same modeling approach.

This article deals with the numerical study of composite beams in asymmetric four-point bending and the comparison of the induced results with experimental and numerical results. The measurement of the interlaminar shear strength of composite beams, an important design variable in many applications, may be suc-cessfully performed by the recently established asymmetric off-axis bending test. In order to obtain experimental results, specimens had been produced and tested to failure. A linear FEA is adopted throughout the composite beams to obtain the stress distributions in the beams and especially at the loading points and the supports where the stresses vary abruptly and present the most important discrepancies when compared with the classical theory. This is a main purpose of this article since the application of the FEA can elucidate the situation in these areas to a great extent. From the FEA, possible crack initiation positions are determined and compared with the corresponding results obtained from the experimental investigation. Also, a comparison between the experimental results of the deflections and the numerical values was carried out in order to estimate the declination.

Today, the offshore oil and gas and wind power industry is a heavily regulated segment, and current standards have established restrictions which yield a very limited weather window for submarine cable installations due to experience with cable failure in bad weather. There are two main limiting factors in current practice during cable installation of an S-lay configuration: the design criterion for the minimum allowable radius of curvature in the touch down point and the avoidance of axial compression in the touch down zone. Accurate assessment of the cable integrity during offshore installation has drawn great attention and is related to the existing available analysis and design tools. The main purpose of this paper is to develop and propose a quick and easy custom-made analysis tool, which is able to export similar results as sophisticated finite element analysis software. The developed tool utilizes analytical equations of a catenary-type submarine structure extended to account for varying cross-sections with different weights and/or stiffnesses, as is the real practice. A comparative study is presented in this paper to evaluate the significance for the modeling of the “out of water” cable segment required for accurate safety factor quantification during a laying operation. The efficiency and accuracy of the proposed tool are proven through a validation study comparing the results and the computational effort and time with commercial finite element analysis software. The analysis error in the case of not modeling the “out of water” cable part is significant, especially in shallow water areas, which proves the importance of using the proposed analysis tool.

Wind energy stands as one of the most important renewable energy sources. Large scale wind turbine blades are mainly based on fiber reinforced polymer composites, as an efficient way to further improve their performance reducing the weight of their blades. The problem of the microstructure material failure of the interior support mechanism for a – high power – horizontal axis wind turbine blade is investigated in this study. A finite element model is developed, simulating the load-bearing box girder of the blade with a given airfoil shape, size, type, and position of the interior longitudinal beams and shear-webs. Previous work showed the challenging topics of material properties, design, computational analysis techniques, and load response of a blade cross-section. In order to shed some light at a local level, a comparison of the most common composite blade materials concerning stress distributions and also displacements, which are critical for optimal blade design, is presented. A failure criterion is applied based on the shell finite element analysis of the model, in order to demonstrate the stress levels throughout every ply of the composite materials of the box girder and locate the initiation of fracture. Failure results concerning both glass and carbon materials are presented.