Sandwich Components Research Articles

Electrode-Level Modeling of Silicon Anodes for Improved Design

Silicon is an ideal active material for lithium-ion battery anodes, due to its low potential and high theoretical capacity. However, extreme volume changes during lithiation and delithiation make reversibility and long cycle life difficult challenges. To properly understand these volume changes, a detailed electrochemical model is needed. Much previous modeling work has focused on particle-level effects such as intra-particle diffusion and cracking. Beyond this, some efforts have successfully utilized pseudo-2-dimensional (P2D) models to evaluate electrode-level phenomena — such as stress distribution and changes in electrode thickness and electrochemical potential. Nevertheless, some essential physics is still missing.Here, we present a new P2D model with improvements that provide a deeper level of understanding of porous silicon anode property changes during lithiation, to enable improved electrode design. Important among these improvements are the use of local state of lithiation as opposed to electrode average state of lithiation to better capture porosity and ionic conductivity changes; an effective electrolyte reservoir that properly addresses electrolyte volume-change requirements; advection of electrolyte and solid-state Li; and an extensive electrode-level plastic deformation model that has a dramatic effect on the model’s predictions.We use this model to test the efficacy of various electrode and cell design decisions. The model can make recommendations on casing design such as rigidity and thickness and the effect of other cell sandwich components e.g. different layers thickness on the electrochemical performance of the cell. Furthermore, using the revised swelling behavior predictions given by the mechanical model, we can provide recommendations for initial electrode porosity and binder volume fraction. Finally, the model as a whole allows us to provide recommendations that will accommodate particle expansion with the least detriment to ionic conductivity at various C-rates. Figure 1

Consumption of beef sandwiches in the United States and contributions to intake of energy and select nutrients.

Sandwiches are commonly consumed in the United States. This study summarizes contributions of beef sandwiches to energy and select nutrient intakes. Beef sandwiches were categorized as beef burger sandwiches (hamburgers or cheeseburgers) and non-burger beef sandwiches. Per capita and per user consumption of beef sandwiches (total and by type) and contributions to total nutrient intakes from beef and non-beef sandwich components were estimated for the population ages ≥2 years (n = 15,984) participating in WWEIA/NHANES, 2013-2016. On any given day, 21.4% of the population consumed a beef sandwich. Among all Americans, beef sandwiches provided 6.3% of mean energy intake and accounted for approximately 10% of the population's mean intake of vitamin B12 and saturated fat, 9% of protein and sodium, 7% of iron, 6% of choline, and 5% of potassium. Among beef sandwich consumers, beef sandwiches accounted for 26.2% of mean energy intake on a day of consumption. The beef component of sandwiches accounted for the majority of vitamin B12, choline, and protein, non-beef components accounted for the majority of sodium, iron, and potassium, and beef and non-beef components made similar contributions to saturated fat. Hamburgers provided consumers the lowest energy, sodium, and saturated fat intake, while non-burger sandwiches provided the highest intake of these nutrients. Beef sandwiches are an important source of energy, protein, vitamin B12, iron, and choline, and like other sandwiches, are also a source of sodium and saturated fat. Americans could enhance nutrient contributions from sandwiches by selecting lean meat and limiting use of saturated fat- or sodium-rich non-beef components.

Determining the influence of sandwich-type components on the load of a hatch cover in a universal open wagon

The object of the study reported here is the processes of occurrence, perception, and redistribution of loads in the improved structure of the hatch cover in a universal open wagon. In order to reduce the load on the cover of an open wagon hatch, and, accordingly, to improve its strength, it is proposed to improve its design by introducing sandwich components. The thickness of the sheets that form the hatch cover has been determined. The dynamic loading of the hatch cover in the vertical plane was studied. It was found that the accelerations acting on the hatch cover with the proposed improvement are almost 20 % lower than those acting on the typical structure. The basic strength indicators of the hatch cover under the operational modes of its load have been determined. The results of the calculation showed that the maximum stresses in the hatch cover are 22 % lower than permissible ones. In addition, within the framework of the study, the main indicators of the dynamics of the open wagon equipped with the proposed structure of hatch covers were determined. The movement of the open wagon under the condition of movement in an empty state is rated as "good". At the same time, the maximum accelerations in the center of mass of the supporting structure of an open wagon were 4.6 m/s2, and the coefficient of vertical dynamics was about 0.6. Special features of the results within the framework of this study are that the proposed improvement of the hatch cover helps improve its strength by reducing the dynamic load, and not by strengthening the structure. The scope of practical application of the results is the engineering industry, in particular, railroad transport. The conditions for the practical use of the research results are the use of energy-absorbing material in the sandwich-type components that form the hatch cover. The study reported here could contribute to devising recommendations for the construction of components in the structures of modern freight cars, thereby reducing the costs of maintaining them in operation, as well as increasing the profitability of railroad transportation

Numerical Modelling of the Thermoforming Behaviour of Thermoplastic Honeycomb Composite Sandwich Laminates.

Lightweight component design is effectively achievable through sandwich structures; many past research studies in the aerospace and racing sectors (since the 1920s) have proven it. To extend their application into the automotive and other transport industries, manufacturing cycle times must be reduced. This can be achieved by sandwich materials made of continuous fibre-reinforced thermoplastic (CFRTP) cover layers and thermoplastic honeycomb cores. To widen the application of flat thermoplastic-based sandwich panels into complex parts, a novel forming technology was developed by the Fraunhofer Institute of Microstructure of Materials and Systems (IMWS). Manufacturing defects like wrinkling and surface waviness should be minimised to achieve high reproducibility of the sandwich components. Studying different manufacturing parameters and their influence on the final part is complex and challenging to analyse through experiments, as it is time-consuming. Therefore, a finite element (FE) modelling approach is implemented to reduce such efforts. Initially, a thermoforming model is developed and validated with experimental results to check its reliability. Further, different simulations are performed to optimise the novel sandwich-forming process. In this study, a thermoplastic sandwich made of polypropylene (PP) honeycomb core and polypropylene glass fibre (PP/GF) cross-ply as cover layers was used, and its numerical model was executed in LS-DYNA software release R11.2.1.

Modelling and bending analysis of a 3D-printed sandwich structure with an auxetic star-4 core

Quasi-static 3-point bending of additive manufactured sandwich components with auxetic star-4 cores was investigated to obtain information on the influence of geometry parameters of the auxetic structure on the stress distribution of the face sheets. Experiments were carried out on specimens manufactured by fused deposition modelling from a PLA polymer to verify a simulation model for analyses. A hyperelastic material model was used in the finite element models to describe the elastic material behaviour and a hardening model to consider plasticity. Nanoindentation tests on the printed structures were conducted to identify the material parameters with modelling the nanoindentation procedure using the finite element method and applying automated optimisation techniques. This approach enabled an accurate reproduction of the nanoindentation tests in the simulations. The derived models for analysing the auxetic geometry have shown that the stress distribution in the face sheets of the sandwich components can be noticeably influenced with targeted changing the wall thicknesses of the auxetic star-4 structure. The simulations have also made it apparent that more effort is required to take into account the influences of the printing process on the deformation behaviour of the sandwich structure in the simulation model.

Review of: "Nanochemical electrochemical sensors and a method called as say sandwich component Three"

Review of: "Nanochemical electrochemical sensors and a method called as say sandwich component Three"

Impact analysis of compression preloaded honeycomb sandwich structures

Honeycomb cores made of phenol resin impregnated paper are widely used in sandwich structures of aircraft. Owing to the rather weak core material, this kind of sandwich is prone to a range of damages as a result of impact loading which may accidentally occur during operation. When employed in aircraft these structures have to be damage tolerant. This means barely visible damages have to be considered in the structural design process. In the standard design process for damage tolerant aircraft structures especially the effect of impacts has to be considered but is mostly investigated on unloaded sandwich components. However, aircraft structures are not completely stress free, even when the aircraft is in parking position. At least the structural weight will cause a permanent static preload. In the literature there are only few investigations dealing with the impact behaviour of preloaded honeycomb sandwich structures. In general, studies on composite structures have shown that tension preloads lead to higher structural impact resistance, while prestressing in compression reduces mechanical properties such as impact strength and stiffness of the structure. For this reason, a compression preload is considered as the more critical load case. In order to evaluate the effect of static compression preloads an experimental study on five different honeycomb sandwich configurations was conducted. The experimental investigations showed that even low preloads cause a higher structural damage area, which results in a lower residual strength of the structure. The results indicated that it is recommendable to consider structural compression preloads in the aircraft structural design process.

Postfire performance of pultruded wood-cored GFRP sandwich beams

Wood-cored sandwich components have been extensively used in constructions of buildings and bridges. However, the existing studies on the postfire behavior of these components are very limited. This study aims to quantitatively evaluate the postfire residual properties of the pultruded wood-cored GFRP sandwich (PWGS) beams. This paper mainly comprises three parts: (i) review of fire experiment of the PWGS beams; (ii) postfire bending experiments conducted on the PWGS beams with different fire scenarios and (iii) numerical study on thermal and postfire thermomechanical responses. It was found the failure modes mainly depended on the number of exposed sides and the fire damage degree. For the three-sided fire-exposed specimens (except for the one with a 25 mm-thick calcium silica board), the progressive tension rapture of the charred fibers was the dominant failure mode. The other specimens, however, exhibited the brittle in-plane shear failure of the web. Moreover, after cooling down from 250 °C to 20 °C, the GFRP and wood exhibited 68 % and 35 % of recoveries of elastic modulus respectively. A three-dimensional thermal model with kinetic thermophysical sub-models considering heat transfer, water evaporation and decomposition was developed. The developed thermal model accurately predicted the temperature responses and charring profiles. Furthermore, a thermomechanical model considering the material damage was developed to accurately predict the elastic modulus distribution, postfire residual bending capacity and failure modes. This study provides the basis for the retrofit and the reinforcement of the fire-damaged PWGS beams. In the future, study on the fire resistance of the PWGS components in fire will be required.

Low-Velocity Impact Damage Quantification on Sandwich Panels by Thermographic and Ultrasonic Procedures

Composite sandwich structures are widely used for their mechanical properties combined to lightweight. However, damage area quantification caused by low velocity impacts represents generally a crucial task in sandwich composites. In the last years, recent advantages of thermographic devices offer new promising and different real-time industrial and engineering applications where lower computation time, accuracy of results and convenient cost are required. The present research deals with the comparison of standard or latest image-processing methods proposed for pulsed thermography regarding their suitability for determining the impact damage area in sandwich materials made of Aluminium core an a GFRP laminated skins. The Infra-Red processed results are compared with the advanced ultrasonic Phased array method commonly employed in the industrial Non-Destructive Testing. Specifically, the damage area quantification is performed by means of an appropriate MATLAB binarization algorithm for the post-processing of acquired thermal and ultrasonic maps. The data results verify the effectiveness of the image-processing thermographic technique combined to advanced processing approaches for the quantitative assessment of impact damage in sandwich component.

An experimental facility for detailed studies on energy absorbing components subjected to blast loading

AbstractDeformable components such as sandwich structures possess promising properties for use in protection systems. Detailed studies on energy absorption and fluid–structure interaction effects are necessary for the application of deformable sandwich structures in blast resistant design. In this paper, an existing shock tube facility has been extended with a transparent section to observe and measure fluid flow and the structural response of deformable components during transient dynamic loading. The extension was instrumented with pressure sensors and load cells to measure the pressure and force transmitted through the component during testing. The transparent design allows the use of optical measurement techniques. Here, high‐speed cameras were used both for digital image correlation and background‐oriented schlieren imaging. Tests with free‐standing plates and sandwich components were performed. A strong dependency was observed between the plate mass, and thus the velocity of the plates, and the pressure measured upstream and downstream of the components. The tests were simulated with a one‐dimensional numerical model for compressible shock flow with fluid–structure interaction. The numerical model accurately reproduced the shock flow and component displacements measured experimentally. Overall, the experimental set‐up presented in this study proved to be suitable for the detailed examination of deformable components subjected to airblast loading.

Computational Analysis of Sandwich Panels with Graded Foam Cores Subjected to Combined Blast and Fragment Impact Loading.

This study aimed to evaluate the performance of sandwich panels with graded foam cores of layered densities against combined blast and fragment impact loading, and to ascertain the optimal gradient of core configuration that would maximize the performance of sandwich panels against combined loading. First, based on a recently developed composite projectile, impact tests of the sandwich panels against simulated combined loading were conducted to provide a benchmark for the computational model. Second, a computational model, based on three-dimensional finite element simulation, was constructed and verified by means of a comparison of the numerically calculated and experimentally measured peak deflections of the back facesheet and the residual velocity of the penetrated fragment. Third, the structural response and energy absorption characteristics were examined, based on numerical simulations. Finally, the optimal gradient of core configuration was explored and numerically examined. The results indicated that the sandwich panel responded in a combined manner involving global deflection, local perforation and perforation hole enlargement. As the impact velocity increased, both the peak deflection of the back facesheet and the residual velocity of the penetrated fragment increased. The front facesheet was found to be the most important sandwich component in consuming the kinetic energy of the combined loading. Thus, the compaction of the foam core would be facilitated by placing the low-density foam at the front side. This would further provide a larger deflecting space for the front facesheet, thus reducing the deflection of the back facesheet. The gradient of core configuration was found to have limited influence on the anti-perforation ability of the sandwich panel. Parametric study indicated that the optimal gradient of foam core configuration was not sensitive to time delay between blast loading and fragment impact loading, but was sensitive to the asymmetrical facesheet of the sandwich panel.

Multi-functional SMC-aluminum battery tray to drive lightweight design

Functional integration and lightweight design are important tasks especially for modern electric vehicles. Development of multi-functional assemblies for the battery box of the future is one of the challenges in the field of electric mobility. The housing must perform many tasks: structural stiffening and sealing (waterproofness) as well as crash protection and thermal management for the batteries. In this paper results from a new developed multi-functional assembly of a SMC-aluminum battery tray will be presented and discussed. The outer housing shell is manufactured by forming SMC directly on an aluminum sandwich component in one stroke compression molding. Furthermore, passive temperature control functions are integrated into the core of the aluminum sandwich realized with switchable air-cooling and phase-change-material integrated into the foam. Additionally, sensors for structural health monitoring, temperature and humidity are integrated. Finally the process design and manufacturing tests will be explained.

Exploring Step-Heating and Lock-In Thermography NDT Using One-Sided Inspection on Low-Emissivity Composite Structures for New Rail Carbodies.

This paper aims to explore the qualification of step- and lock-in heating thermography as techniques capable of inspecting new composite rail carbodies following input and inspection requirements set by the rail manufacturing industry. Specifically, we studied (a) a monolithic CFRP sample (20 mm thickness) and (b) a CFRP-PET foam-CFRP sandwich (40 mm total thickness) component, that were manufactured with artificial defects, to replicate the side wall sections of a carbody. The samples proved to be very challenging to test using only one-sided inspection due to (1) exhibiting significant thickness compared to existing literature, (2) low surface emissivity and (3) that the foam core of the sandwich sample was a thermal insulating material. In addition, the sandwich sample was designed with defects on both skins. Both thermography techniques provided similar defect detection results, although step heating offered faster detection. In the case of the monolithic panel, defects up to 10 mm depth were detected, with minor detection of defects at 15 mm depth with a step-heating protocol between 90 s and 120 s overall acquisition, which was faster than the 140 s used with the lock-in technique. For the sandwich component only the front skin defects were detected, with both techniques using heating protocols between 70-120 s.

Fire performance of pultruded wood-cored GFRP sandwich components for building construction

Fire safety is significantly required for glass-fiber reinforced polymer (GFRP) sandwich composite structures since the GFRP skin and the core are normally sensitive to high temperatures. This study presents an investigation on the thermal responses, insulation performance, and charring behavior of the pultruded wood-cored GFRP sandwich (PWGS) components subjected to the ISO-834 fire. The PWGS specimens protected with calcium silica (CS) boards were exposed to one- or three-sides fire with the fire duration being 30 or 60 min. It was found that the GFRP skins without CS board protection were fully charred after the 30-min fire exposure. Nevertheless, the PWGS section exhibits good insulation. The average temperature rise of the unexposed surface of the PWGS sections without protection did not exceed 140 °C, satisfying the insulation requirement in specifications such as EN 1995-1-2, ASTM E119 and GB/T 9978.1. Further, the PWGS specimen with a 25 mm-thick CS board can survive without clear damage during the 60 min thee-sides fire exposure. In addition, the charring rate of the GFRP skin and the Douglas-fir core were summarized and discussed.

3D printed continuous fibre composite repair of sandwich structures

This study quantifies the effectiveness of the rapid repair of sandwich structures using 3D printed continuous fibre composite patches. The sandwich structures are representative of lightweight honeycomb structures typically found in contemporary helicopters. The samples were designed to produce failure in the facesheets due to tensile or compressive stresses. This was achieved by locating the damage and subsequently repairing it on either the lower or upper facesheets. The entire repair process, including patch manufacture, was completed within two and a half hours. In all cases, the 3D printed repair restored the full load bearing capacity of the damaged structure and the ultimate strength was equal to the pristine sample configuration. These experiments give confidence that a 3D printed continuous fibre patch repair process can fully restore structural strength in damaged sandwich components.

A Numerical and Experimental Investigation into the Impact Response of Sandwich Composites under Different Boundary Conditions

The paper reports the results of an experimental and numerical investigation into the effect of the support conditions on the low velocity impact behaviour of sandwich composite panels. Significant differences are observed experimentally between the structural and damage responses to impact of small-span and large-span sandwich panels. In particular, impact events on large-span panels generate lower peak forces, larger displacements and smaller damage sizes in comparison to small-span panels subjected to the same impact energy. The experimental results are employed to validate the capability of a finite element (FE) tool to simulate the impact behaviour of the sandwich panels for the different boundary conditions. The comparison of FE and experimental results shows that the model provides a good prediction of the structural response as well as of the extent and mechanisms of impact damage for both small-span and large-span lengths, thus demonstrating the potential of the FE tool for verification and design of sandwich components in real engineering applications.

Investigation of an Automated Potting Process for High Volume Insert Assembly in Honeycomb Structures

<div class="section abstract"><div class="htmlview paragraph">Threaded, potted inserts are commonly used as a standard connecting element for sandwich components, which are used for aircraft interior. Since they often offer the only detachable connection, they are used in very high quantities. To ensure a material bond between the inserts and the honeycomb structure, the joint is filled with adhesive. Despite the high number of inserts, this process is performed manually. Recent research has shown new approaches for automated gripping and placement of the inserts by an industrial robot that yield high potential for cost savings and increased productivity. Automated adhesive insertion, so-called potting, has not been considered so far but is an essential contribution to the full automation of the entire process chain. The amount of adhesive varies depending on the type of insert and its position on the honeycomb structure. During the potting process, it is also mandatory to prevent air inclusions, to fulfill safety requirements in the aviation industry. This paper presents an approach for automated potting to further increase the degree of automation during sandwich panel production. First, the range of insert types is analyzed and the joint geometries are investigated. Based on the derived requirements, an automation concept is introduced and a parameter study is carried out. Optimal parameters are derived which can be used for process control. Finally, the overall process capability is shown and evaluated using a flexible, automated system.</div></div>

Development of fly ash and slag based high-strength alkali-activated foam concrete

Foam concrete is a lightweight construction material with excellent thermal and acoustic insulation ability. It is widely used in building envelopes, partitioning walls, sandwich components, etc. However, the foam concrete applied most is made by Portland cement that consumes much energy and emits a large amount of CO2 during its production process. As a green binding material without clinker, the alkali-activated material fully utilizes fly ash, slag and other industrial solid wastes or by-products, which largely reduces CO2 emissions. In this paper, the fly ash and slag based alkali-activated foam concrete with a design density ranging from 200 kg/m3 to 1200 kg/m3 was developed. Based on the bubble dynamics theory, the mechanical behavior and the stability of bubbles in the mixture were analyzed, and a calculation method for judging the stability of bubbles in the mixture was proposed. According to the analysis and performance of prepared bubbles, Sodium dodecyl sulfate was selected as the foaming agent to prepare the foam concrete. The compressive strength of the developed foam concrete ranged from 0.50 MPa to 44.98 MPa while the flexural strength ranged from 0.22 MPa to 13.86 MPa, respectively, with respect to different densities. The results show that the mechanical strengths of alkali-activated foam concrete are higher than that of ordinary Portland cement based foam concrete with the same density. In addition, alkali-resistant glass fibers were used to improve the problem of the brittleness of low-density foam concrete. It was observed that the 0.5% volume fraction of fibers was optimal to improve the mechanical properties.

Survey on compression property of sandwich 3D printed PLA components

Additive Manufacturing (AM) is a trending technology to manufacture functional parts from 3D design to real-time products. Lightweight structure with expected mechanical property is a difficult task in conventional manufacturing. In aircraft, interior design parts should have high-strength parts with a low weight ratio. The high strength to low weight ratio can be developed using different materials, but the influenced factor is cost. Making a sandwich component is one of the best methods to fabricate the parts with high strength to low weight ratio. Sandwich structure is one type of design that can be fabricated using additive manufacturing with different materials. Sandwich structures comprise three components: a lightweight core and two face sheets at the top and bottom. Many materials can be used in this technique to produce sandwich parts, but this article focused on existing PLA and its composites. PLA is widely renowned for its characteristics and environmental awareness. This review is focused on the compression property investigation of the 3D printed Sandwich Structure and methods to improve the mechanical property of 3D printed parts.

Damage evolution in sandwich components at different extreme temperatures

Composites' structures are subjected to various environmental conditions during their service life. However, only a few papers are focalized on analysing damage history after impact at shallow temperatures and among them, even less concern sandwich components. Futhermore, since the effect of any degradation phenomena may not be visible to the naked eye, the evolution of the damage is followed with non-destructive techniquest. In this paper, the damage suffered by sandwich structure composites was evaluated by three NDT techniques: Ultrasound, Lock-in Thermography and speckle interferometry. Sandwich structures investigated consist of carbon fibre reinforced face sheets surrounding a PVC core. Indentation and penetration tests (U = 7.5J, 10.5 J and 12 J) were carried out at room temperature and −55°C, +70°C. After tests, damage extension and propagation has been evaluated in terms of indentation depth and delamination by NDT. The results provided useful information about the influence of extreme temperature on both impact properties and damage evolution in the system investigated.