This paper presents recent research, concerning some preliminary design guidelines to be applied in GFRP composite sandwich panels, for civil engineering applications. For more than a decade, the foundations of preliminary design of concrete, wood and steel structures, have been fully established in structural design codes and technical recommendations. Since FRP structures at the moment possess no standard design code, its preliminary design guidelines are nowhere to be found. This work pretends to fill this gap in knowledge, by providing simple and clear design guidelines to be applied in classical known GFRP composite sandwich panels, more specifically in home buildings. Just like in concrete structures, for GFRP structures one of the most unfavourable design state is the serviceability, mainly due to the long term deflection. Therefore, this long term deflection will be used to estimate the minimum span/height ratio necessary to “indirectly” verify the serviceability state. This is performed using an extensive parametric analysis: of the span beam model; type of materials; type of support; load levels; and geometrical properties. In this work in order to correctly estimate the flexural and shear deflection, the Carrera Unified Formulation is used, therefore no simplified shear correction factor is needed.

A Deform^TM-3D analysis was used to illustrate the effect of strain rate on isothermal deformation (forging) of X20CrMoV121 steel. The simulation process was conducted at an isothermal temperature of 850 °C and varying the strain rates of 1.9 s^-1, 2 s^-1 and 3 s^-1. The results of temperature, strain and stress distribution at various strain rates were reported. The strain/stress distribution exhibited a heterogeneous distribution, indicating inhomogeneity during hot forging. It was also shown that the deformation inhomogeneity decreased with the increase in the strain rate. The results are comparable to experimental publications, indicating that Deform^TM-3D is an effective tool for finite element analysis of hot deformation processes.

The satellite structural mass is considered a crucial parameter during the process of satellite structural design. Sandwich structures acquire a considerable role in minimizing such mass while maintaining structural integrity. This article discusses the structural configuration, design, and analysis of a small satellite. A small Earth remote sensing satellite is chosen from the published data as a case study. Its structural design configuration is of a rectangular box that is based upon metallic alloys. Through a comprehensive study, the most suitable design configuration for the given mission is selected. A contribution has been made in developing a novel hexagonal primary structure that is based upon Aluminum honeycomb sandwich panels. The satellite configuration process and structural design procedure are thoroughly presented. The finite element modeling of honeycomb sandwich panels according to sandwich theory is introduced. Such modeling is validated numerically in comparison with published data. The analysis process is implemented using finite element analysis considering the loads during the ground and launch phases. The proposed structural design results in a significant mass reduction of 15% when compared with the baseline case study.

In this research, an investigation was carried out through experimentation and numerical modeling to evaluate the cracking pressure induced due to corrosion of reinforcement for different cover thicknesses, grades of concrete and bar locations. The model was also used to determine the patterns of crack for a different number of bars and the effect of bar diameter on cracking pressure. The critical pressure was measured experimentally by applying hydraulic pressure through a hole in concrete cubes of 150 mm. Abaqus 6.14 was used as a modeling platform. From the experimentation and numerical modeling, it was found that with the increase of cover thickness the critical pressure was increased irrespective of bar locations. A lower cracking pressure was observed for corner bar with respect to the sidebar. On the other hand, with the increase in bar diameter, a decrease in cracking pressure was observed. The critical pressure observed was also increased with higher grades of concrete. For corner bars with cover thickness 37.5 mm, the critical pressure was found as 6-10 MPa and it increased up to 17 MPa for the cover thickness of 64 mm for different grades of concrete. On the other hand, for other bar location with the cover thickness of 37.5 mm and 64 mm, the pressure required to initiate crack was about 7.6 MPa and 14.8 MPa, respectively, for C20 grade concrete.

An experimental analysis of the effect of gamma and X-ray irradiation with dose rate 0.25-6mSv/h on low-density polyethylene (LDPE) and PMMA samples is presented. The focus of attention is on their DC conductivity as a dielectric of a capacitor. This system is based on the discharge of a capacitor by radioactive radiation through ionization of the dielectric consists of an inner electrode of the capacitor. The experimental setup contains a special electronic circuit in which polymer samples are placed as dielectric of parallel-plate capacitor which is connected to electrodes and a high voltage power supply is in series with other components of the circuit. It is understood that the resistance of polymers varies with the applied voltage and absorbed gamma ray dose from 137Cs with 0.661 MeV energy. The influences of this parameter on LDPE and PMMA electrical properties as a result of polarization of dielectric are also presented. The experimental results show elevation of LDPE and PMMA electric conduction properties as irradiation dose rate increases. Indications of predominance of charge accumulation are also observed.

Growth of the volumes of dangerous and critical welded metal structures constructed under low temperatures imposes additional requirements on the mechanical properties of the weld joints, particularly, on the impact resistance of the weld joint and on the stability of its values. It can be achieved by using coated electrodes with ultradisperse powders of alloying elements in the coating. To develop new improved welding materials we need to optimize the systems of weld metal alloying to meet the increasingly stringent requirements to the welding-operational characteristics. Introduction of a complex ultradisperse powder (Al₂O₃, SiO₂, TiO₂, Ni) into the electrode coating applied for manual metal-arc welding ensures more stable process of electrode metal fusing and its transfer into the welding bath, improves the performance characteristics of the welded metal.

Fabric Formworks which are made using textile sheets such as Polyolefin, Polyesters/Polyethylene Terephthalate, nylon and Polypropylene are being used instead of conventional formworks in the construction industry. This article summarises significant studies and provides an updated review of references on the structural performance of fabric formworks over the last decade. The survey showed that they could be categorised into seven themes; namely, “Feasibility studies and manufacturing methods of complex structural elements”; “Finite element modelling, structural optimizing and form-finding themes”; “Pneumatic / Vacuumatic formwork theme”; “Durability, sustainability, efficiency and quality improvement”; “Cable-net fabric formwork theme”; “Stay-in-place structural formworks theme”; and “Review papers”. These categories comprise about 25%, 17%, 15%, 15%, 10%, 6% and 6% of related studies respectively.

In this paper, the severe plastic deformation method (SPD) known as constrained groove pressing (CGP) was applied to produce ultrafine-grained microstructure in IF steel sheets. In the CGP technique, samples are subjected to repetitive shear deformation under the plane strain deformation condition using the constrained grooved and flat dies. For assessment of microstructure and mechanical properties of the CGPed IF steel sheet, several testing such as: uniaxial tensile test, hardness measurements, scanning electron microscopy (SEM) and X-ray diffraction analysis have been utilized. Finally, it was observed that the grains are significantly refined after the 16-step pressing of the interstitial free (IF) steel sheets. The grains were reduced from 45µm to 243 nm after four passes.

When a satellite is in orbit, micro vibration generated by its actuators (such as reaction wheels, deployable mechanisms, etc.) will affect the imaging quality of the camera. Viscoelastic materials are utilized as passive isolators to reduce these micro vibrations due to their simple construction and excellent energy dissipation capacity, A finite element model of the entire satellite as well as the camera is constructed using the ABAQUS software and then four reaction wheels are included as the sources of micro-vibrations and their forces are added to the model. To isolate these vibrations, four square sorbothane pads are designed and added in the finite element model as viscoelastic dampers located under the camera, between the camera and satellite bus. The generalized Maxwell model is employed to describe the dynamic properties of the viscoelastic elements in the ABAQUS software. Finally, by analyzing and comparing the dynamic responses of the system with and without the viscoelastic sorbothane pads, it is realized that this isolation system can effectively reduce the reaction wheel micro-vibrations on the camera and subsequently increase the image quality.

Strain-softening material models have conventionally had a pathological mesh sensitivity in finite element simulations and composite materials are indifferent to this problem. Spurious localization is inherent to the structural problem in strain-driven softening. This limitation is caused as the partial differential equations (that govern the structural problem) become ill-posed as the tangent modulus becomes negative, for which uniqueness of the solution with respect to the spatial discretization is lost. This causes the numerical results to unrealistically concentrate in a single layer of elements. A basic theory of overcoming mesh sensitivity is the non-local continuum theory. In this work, three different non-local models with isotropic weight function have been proposed and implemented to work in conjunction with a composite micro-mechanical material model. The effect of a weighing function in each of these formulations has been studied in detail. All three non-local formulations have been observed to produce a nice smeared effect of damage unlike the local damage models.