Foam Core Thickness Research Articles

A numerical study on thermal-structural characteristics of cryogenic common bulkhead propellant tanks for various tank lengths and core thicknesses

Common bulkhead (CBH) propellant tanks have the advantage that its structural and space efficiency are high. The tank is a form in which an oxidizer tank and a fuel tank are integrally combined, and the oxidizer and fuel are separated by the CBH. The CBH propellant tank in which two tanks are integrated can reduce unnecessary space between the two tanks. However, there are other difficult problems regarding effectively designing the CBH propellant tanks even though there are structural and space benefit. This paper is a study on the thermal-structural characteristics of CBH tanks containing LOX/LH2 propellant. In order to conduct the thermal-structural analysis, the thermal analysis model was constructed using 2-dimensional axisymmetric elements to reflect the shape features of the tank, and the structural analysis model was built using 3-dimensional elements. The thermal-structural analysis was performed on the length of the bottom tank and the foam core thickness of the CBH. In the structural analysis of the tank, when the thermal load was ignored and only the pressure load was applied, there was a difference in the buckling load factor depending on the thickness of the CBH foam core, but as the thermal load was taken into consideration, there was also a difference in the bottom tank length. The analysis results show that the thermal-structural characteristics of the CBH propellant tank were influenced by the length of the bottom tank as well as the thickness of the foam core.

Failure mechanisms of asymmetric sandwich panels subjected to low-velocity impact: An explicit wave dominating damage model

Asymmetric sandwich panels (ASPs) with tapered transitions are effective configurations for connecting them with other structural elements. However, fiber reinforced composite panels are susceptible to impact events and thus it is imperative to gain a comprehensive understanding of the impact failure mechanisms of ASPs. This article investigates the failure mechanisms of ASPs subjected to low-velocity impacts experimentally and numerically. Low-velocity impact tests are conducted at two energy levels to induce barely visible impact damage (BVID) and visible impact damage (VID). A non-linear finite element (FE) model is developed to elucidate the damage behavior and failure mechanisms of ASPs. The numerical results are compared with experimental data to validate the FE model. Additionally, a parametric study is undertaken to explore the failure mechanisms of ASPs subjected to penetration. This study also investigates the influence of impactor diameter, impactor angle, foam core thickness, face sheet stacking sequence, and face sheet thickness on impact response through numerical simulations. The reported results hold potential significance for safety design ASPs.

Failure analysis of sandwich beams under three-point bending based on theoretical and numerical models

Abstract This article presents a comprehensive study on the failure behavior of foam core sandwich beams under three-point bending using theoretical analysis and finite element methods. A displacement formula for the foam sandwich beam is derived, considering the shear deformation of the foam core. Based on this formula, the deflection is obtained using energy and Rayleigh–Ritz methods. The failure loads of face yielding, core shearing, and indentation are combined to construct a failure mechanism map. The proposed theoretical model is then compared with existing theoretical analyses, demonstrating higher prediction accuracy. To investigate nonlinear damage and size effects, a series of finite element analyses is conducted. The results suggest that increasing the face sheet thickness has a greater impact on the ultimate load capacity, while the foam core thickness is more effective in enhancing bending stiffness.

Analytical study on the dynamic response of foam-core sandwich plate under wedge impact

In this paper, the dynamic responses of sandwich plate with foam core subjected to wedge impact are theoretically investigated. An analytical model of fully clamped foam-core sandwich plate under low-velocity wedge impact is developed based on the approximate yield criteria and rigid-perfectly plastic theory. Besides, the horizontal impact experiments and numerical simulations of polyvinyl chloride (PVC) foam-core sandwich plates were conducted to verify the accuracy of analytical prediction model. Results show that the analytical prediction results of foam-core sandwich plate under wedge impact such as the permanent deformations and impact force as well as deformation distribution are consistent with the experimental and numerical results. Furthermore, the geometrical parameters such as wedge width and aspect ratio of sandwich plate as well as foam core thickness on the dynamic responses are theoretically performed. Results showed that the deformation reaches to maximum with aspect ratio of 1and the permanent deformation declines with the increase of wedge width and foam core thickness.

The effect of different structural designs on impact resistance to carbon fiber foam sandwich structures

Abstract The development of the composite materials in the past decades has made the composite materials more and more widely used in various engineering fields. The mechanical properties of the composite materials are gradually improved, especially the impact resistance. In this article, the damage of carbon fiber foam sandwich structure (material grade: W-3021FF/H60) under different sandwich thicknesses and impact energies was studied. Ultrasonic C-scan was used to measure the depth and area of impact damage area. Finally, the impact energy and foam core thickness on impact damage was analyzed by test results. The results show that the impact damage depth and area of foam sandwich structure were positively related to the impact energy, and with the increase in the impact energy, the growth rate of damage depth and damage area changes; the greater the thickness of the foam core was, the stronger the span-direction guiding energy for impact energy, the larger the damage area and the smaller the damage depth. Under the same energy, the more the layers of carbon fiber cloth with the foam sandwich structure, the larger the impact damage depth and the smaller the impact damage area. The proportion of ±45° ply in the foam sandwich structure can improve its impact resistance.

Impact penetration and perforation performance of square sandwich panels with EPS foam core

This paper addresses the impact penetration and perforation behaviour of sandwich panels having a low density core expanded polystyrene foam (EPS) bonded to two aluminum (6061-T6) face-sheets. The effects of foam and plate thicknesses on the impact energy absorption of sandwich panels were also investigated. The dynamic response of panels was analyzed using the explicit finite element method. The foam core material was modeled as a crushable foam material with ductile damage, and the metal face-sheets as Johnson-Cook (JC) material. The cohesive response of the adhesive interface was considered using cohesive zone model. The analyses showed that the impact energy, face-sheet and foam core thickness affected significantly failure modes, contact force levels and histories. The low-speed impact tests of the sandwich panels with different face-sheet and foam core thicknesses showed similar contact force histories, energy absorption ability and deformation modes to those of finite element analyses.

Flexural deformation behavior of carbon fiber reinforced aluminium hybrid foam sandwich structure

Aluminium hybrid foam (HF) core sandwich structures with carbon fiber-cold setting resin as face sheets have been made. The flexural properties and energy absorption of these sandwich structures have been analyzed through three-point bending (3 PB) test. It is found that with the use of a double-layer carbon fiber sheet, the flexural load carrying capacity of the sandwich structure increases up to eight times as compared to that of bare foam (BF) structure. Whereas, the bending stiffness of the structure is nine times to that of BFs and energy absorption is 58% more than that of BF. It is also found that with the increase in foam core thickness the flexural load carrying capacity, bending stiffness and energy absorption capacity of the sandwich structure increases significantly. The specific strength and bending stiffness increase as compared to that of face sheet due to the addition of foam at the core. The deformation behavior of different sandwich structures was analyzed to investigate the different modes of failure during bending.

Mechanical performance of marine sandwich composites subjected to flatwise compression and flexural loading: Effect of resin pins

Mechanical performance of marine sandwich panels comprising E-glass/vinyl ester face sheets and perforated poly-vinyl chloride foam core was evaluated and compared with conventional foam core sandwich panels. Circular holes through the foam core thickness were drilled with 12 different arrangements in square patterns and the holes were filled with the resin during the infusion process which created the through-the-thickness solid resin pins. The effect of each pattern on the flatwise compression and core shear properties of the sandwich panels were experimentally investigated. The three-point bending maximum failure load of perforated foam core sandwich panels was increased over 133.8% by increasing the diameter of the resin pins at the expense of increased panel weight up to 67%. The flatwise compression stress to induce core crushing was significantly increased by reinforcing the resin pins.

Energy Absorption Capacity of Basalt Sandwich Composite Cylinder Subjected to Axial Compression Loadings

In this report presented the investigation of axial progressive compression on sandwich composite cylinder made from basalt fibre reinforced composite tube as skins and polyurethane (EPU) foam as core of the structure. The effect of braid orientation angle of the sandwich skins and foam core thickness were evaluated on the parameter performance namely peak force, average force, total energy absorption, crush force efficiency, and specific energy absorption. The primary failure mode observed was progressive failure fibre cracking and tube’s wall folding and crumping. Experiment result showed that the effect of outer wall braid angle of sandwich tube structure was the dominant factor contributed to high energy absorption capacity. Furthermore, the foam thickness has no significant influences on the SEA value; however, the total diameter size of sandwich tube skins was.

Impact responses of sandwich panels with fibre metal laminate skins and aluminium foam core

Low velocity impact responses of a newly developed sandwich panel with aluminium foam core and fibre metal laminate (FML) skins, comprised of aluminium sheets and plain woven E glass fibres, are investigated in this paper. Drop weight impact tests were conducted and the effect of the thickness of foam core and FML skin on the impact response of the panels was investigated via the experimental study. A finite element model is also developed and validated against the experiments to prove the effectiveness and accuracy for analyzing the impact responses of the sandwich panels under low-velocity impact. The research findings are summarized and concluded finally.

Flexural behaviour of fibre-reinforced polymer–aluminium sandwich curtain walls

A new type of fibre-reinforced polymer–aluminium sandwich curtain wall panel, which consists of layers of aluminium plate, fibre-reinforced polymer plate, foam core and gypsum board, was proposed to achieve high strength and stiffness, efficient energy saving and good fire resistance for the modern curtain wall systems in buildings. An experimental study was conducted to investigate the flexural behaviour of the fibre-reinforced polymer–aluminium composite curtain wall panels. Three groups of large-scale specimens with different thickness of foam core with and without a phase change material layer were tested under uniformly distributed loads. The test results showed that due to the asymmetric arrangement of sandwich layers, the loading directions had a significant effect on the flexural behaviour of the panels with and without a phase change material layer. It was also shown that with the increase of the foam core thickness, the flexural behaviour of panels was significantly improved. In addition, the phase change material layer had little effect on the flexural behaviour of the sandwich panels under and beyond the serviceability conditions, but significantly reduced the serviceability strength.

Blast resistance and design of sandwich cylinder with graded foam cores based on the Voronoi algorithm

Blast resistance and design of sandwich cylinder with graded foam cores are investigated using numerical simulations. The finite element (FE) model is constructed based on the random Voronoi algorithm, and validated by experimental results. The deformation process of sandwich cylinder subjected to blast loading is simulated using the ABAQUS/Explicit software. Subsequently, parametric studies are carried out to analyze the effects of explosive charge, thicknesses of face-sheet and core, and core gradient on deformation pattern, plastic dissipation of the core, and maximum radial deflection (MRD) of the outer face-sheet. The cylinder structure with high plastic dissipation and low MRD is a good choice for protecting persons and objects located on the outside of the cylinder from the internal blast. The results show that the blast resistance increases with the foam core thickness increasing. However, the plastic dissipation of core and the MRD of outer face-sheet are two conflicting objectives to evaluate blast resistance for other parameters.

One-Way Slab of Structural Insulated Panel Strengthened with FRP

In order to promote the usage of structural insulated panels (SIP) as floor and roof for residential buildings, the bending capacity of SIP should be improved. In this paper, fiber reinforced polymer sheets were used as strengthening materials. The new variation of SIPs, which is called Fiber Reinforced Structural Insulated Panel (FSIP), was tested in this paper. Five one-way slabs were subjected to uniformly distributed loads till failure. It is observed that the flexural bearing capacity and stiffness of the slabs were affected by the thickness of foam core and the strength of FRP sheet. By strengthened with FRP sheets, the one-way slab of structural insulated panel can be used for floor and roof in residential and light commercial buildings.

Experimental analysis to improve energy absorption properties of rectangular metal section subjected to axial loading

This paper aimed to study the aluminiumalloy foam core with mild steel tubes. The aluminium foam was made with LM25 aluminium alloy 15wt% silicon carbideparticle. Aluminium foam core thickness of (18×18) mm was used for making mild steel foam filled tube. The mild steel foam filled tubes were tested in Universal Testing Machine. The energy absorption rate per unit volume was noted that 11.78 to 15.00 MJ/m3 and 12.49 to 17.33 MJ/m3 empty and foam filledmildsteeltubei.e.rectangularshape respectively. This work also describes the compression movementsof mild steel tube and foamfilled tube with foam, variable strain rate between 10-3/s to 10/s at room temperature. The compressive deformation behaviour of thisLM25 aluminium alloy foam filled mild steeltubeand empty mild steel tube was examined in order to evaluate its specific energy absorption. It is also noted that foam filled mild steel tubes stress strain diagram exhibited more energy absorption properties.

Thickness Effect of Polyurethane Foam Core on the Flexural Behaviour of Composite Sandwich Materials

This study explored the feasibility of flexural performance of composite sandwich material composed of various low density polyurethane foam core thickness sandwiched between GFRP skins. The mechanical behaviour of this material was assessed by carrying out a flexural testing. Each spesimen had a nominal dimensions of 110 mm x 30 mm x (c + 4 mm). These spesimens with various core thickness (c) of 2 mm. 5 mm. and 8 mm were then tested in three point bending according to ASTM C 393-00. This study revealed that. by incorporating the thickest core ( 8 mm ) . the bending strength decreases by 42.3 % compared to 5 mm core and it further decreases by 72.6 % compared to 2 mm core. The material stiffness showed positive trend for the thickest core (8 mm). it increases by 53.1 % and 78.1 % compared to 5 mm core and 2 mm core respectively. Low shear modulus of polyurethane foam core contributed to the low bending strength of composite sandwich material with 8 mm core. This was further confirmed by failure analysis under optical microscope which revealed that core shear failure was the dominant failure mechanism for 8 mm core. Meanwhile the dominant failure mechanism for 2 mm core and 5 mm core was microbuckling which confirm the high modulus of GFRP skin. The material stiffness was affected by the high modulus of GFRP skin and the core thickness.

Experimental study on the compression-after-impact behavior of foam-core sandwich panels

This paper presents the experimental results pertaining to the deformation, failure mode, failure mechanism and residual strength for the compression-after-impact tests of woven polymer-based foam-core sandwich panels. Sandwich panels with impact-type damage, inflicted via low-velocity impact, were tested to failure in compression. The optical strain measurement system ARAMIS was used to obtain the complete non-uniform strain and displacement fields of the damaged face-sheet. Consequently, damage in the face-sheets was characterized by fractography. It has been found that the dominant damage mechanism is kink band in the impacted face-sheets due to fiber plastic micro-buckling. Besides, the effects of impactor diameter, impact energy, face-sheet thickness and foam core thickness on the residual strength under in-plane compressive loading were studied. This study will be useful for characterizing and predicting the residual compressive strength and understanding the failure mechanism of woven polymer-based foam-core sandwich panel.

Dynamic response of spherical sandwich shells with metallic foam core under external air blast loading – Numerical simulation

The dynamic response of spherical sandwich shells with aluminum face sheets and aluminum foam core under external air blast loadings were investigated numerically by employing the LS-DYNA. To calibrate the numerical model, the experiments of cylindrical sandwich shells were modeled. And the numerical results have a good agreement with the experiment data. The calibrated numerical model was used to simulate the dynamic response of spherical sandwich shells subjected to the external air blast loadings. It is found that the spherical sandwich shells have a better performance than that of the cylindrical sandwich shells in resisting the blast loadings. The structural dynamic response process has been divided into three specific stages and the deformation modes have been classified and discussed systematically. According to parametric studies, it is concluded that with the decrease of radius of curvature, increase of the thickness of foam core and face sheets and decrease of blast intensity, the blast-resistance is increasing obviously; keeping the thickness summation of front and back face sheet almost constant, a big thickness of front face sheet will improve the blast-resistance performance. These simulations findings can guide well the theoretical study and optimal design of spherical sandwich structures subjected to external blast loading.

Improving the Dynamical Behaviour of a Laser Cutting Equipment by Using a Carbon Fibre Composite Main Structural Runway Frame

In order to improve the dynamic behaviour of an industrial laser cutting equipment a sandwich solution, using a carbon fibre reinforced polymer (CFRP) and polyester foam core, was implemented to construct its main runway structural frame, which supports the cutting head and major laser beam mirrors and lens. Nowadays, the commercial competiveness of laser cutting equipments is considerable enhanced by their higher cutting speed and precision, as well as, cost. With the recent available higher power laser beam generators and swifter motors quicker and powerful cuts may be already done. However, at accelerations of 3 and 4 g’s already enabled by linear motors, the lack of stiffness and high mass and consequent inertia of the traditional runway structural frames, made from steel and/or aluminium, do not allow achieving high required cutting precisions. Thus, the present study considered replacing those conventional materials by much lighter advanced CRFP composites to improve the dynamic performance of an existing laser cutting equipment. Advanced numeric Finite Element Method (FEM) calculations by using the ANSYS package software were made to verify the static and dynamic behaviours of the new composite structural frame and compare them to simulations made with the currently used steel solution. The composite structural frame processing method has been also studied and defined in this work. Furthermore, the composite laminate has been optimised by defining the better number of stacking layers and fibre orientations to be used, as well as, the foam core thickness. The failure of the new sandwich structural composite runway frame has been verified through the Tsai-Wu criterion. Finally, an economic analysis of the viability of the new composite solution adopted will be also presented.

Experimental and numerical study on the low-velocity impact behavior of foam-core sandwich panels

This paper presents the results of an experimental and numerical study on the low-velocity impact behavior of foam-core sandwich panels. Panels with polyurethane foam core and plain weave carbon fabric laminated face-sheets were subjected to low-velocity impact with hemispherical steel impactors of different diameters at various energy levels. Digital image correlation technique (a non-contact measuring system) was used to measure the real-time displacement and velocity of the impactor, and the back surface out-of-plane panel deflection time-history. A load sensor was used to record the contact force time-history. Non-destructive inspection and destructive sectioning methods were used to evaluate the internal and external damage on the sandwich panels after impact. The effects of impact variables such as impactor diameter, impact energy, and sandwich panel configuration parameters, such as face-sheet thickness and foam core thickness on the impact behavior and resulting impact damage states were studied. Based on the generalized Schapery theory, a progressive damage model is developed to describe the nonlinear behavior of plain weave carbon laminates during impact. The foam core was modeled as a crushable foam material. Coupon tests were conducted to determine the input parameters for the progressive damage model and the foam crushing properties. Three-dimensional finite element models were implemented to analyze the impact response incorporating the progressive damage model. Results from the numerical models were found to agree well with experimental observations.

Buckling of a thin-walled cylindrical shell with foam core under axial compression

This paper investigates the effect of partially filled foam core on the behavior of buckling in a thin-walled cylindrical shell. Previous studies have focused on 100% infill or simply used a fixed thickness of foam core. However, this may not be the optimum arrangement in terms of design. To further investigate this, a theoretical analysis is carried out using the Rayleigh–Ritz approximation, and a new formula is proposed to predict the critical buckling stress of an infill ranging from 0% up to 100% rigid. The proposed formula agrees well with works reported in the literature. It also shows that filling a foam core in a thin-walled cylindrical shell can enhance its resistance to buckling failure. Meanwhile, a simplified formula is provided to the practicing engineer. The paper concludes that an excessive increase in foam core thickness beyond 10% of outer radius is inefficient due to extra cost and weight.