Foam Core Research Articles

Three-Layered Annular Plate Made of Functionally Graded Material Under a Static Temperature Field

The presented problem considers the static temperature analysis of a three-layered, annular plate with heterogeneous facings made of material with radially variable parameters. They are defined by the accepted exponent functions. The plate is composed of thin metal facings and a thicker foam core. The plate is loaded with a flat temperature field with a gradient directed across the plate radius. Using the approximation finite-difference method, the eigen-value problem is solved in order to calculate the temperature differences between plate edges, which cause a loss of plate stability. Taking into account the different material and geometrical parameters, the critical temperature state parameters are evaluated. The meaning of the mixed system of parameters connected with the plate shape geometry, dimensions of the plate-transversal structure, and with the gradation of the material in the radial direction on the thermal response of the composite plate have been found. Numerous results of numerical calculations show the responses of the examined composite plate with facings made of the heterogeneously directed material.

Method to improve the bonding strength of polyethylene terephthalate core with glass fiber reinforced skins in a sandwich composite

AbstractComposite materials provide an alternative to conventional structural materials. Sandwich composites show high bending strength and superior strength‐to‐weight ratio. The major drawback in sandwich composites is debonding of skin from core, that causes failure of a component during the usage at different loads. To overcome this issue, the current work identifies a solution of introducing nylon screws (M6 × 32) to adhere firmly the skins consisting of glass fibers with PET (Polyethylene Terephthalate) core. The sandwich composites were fabricated by vacuum infusion process. Two flat sandwich composites were fabricated; one with nylon screws placed perpendicular to the skin and the other a plain sandwich composite. Mechanical characteristics of the specimens such as fracture toughness, flexural strength and shear strength were studied. Specimens with nylon screws showed 21.78% more fracture toughness compared to plain specimen. The presence of screws acts as hindrance to the propagation of cracks in the interfacial region resulting in the enhancement of debonding resistance of the specimens. Also, sandwich specimens with nylon screws exhibited 136% and 142% improvement in flexural and shear strength respectively when compared to plain sandwich specimens. The investigation of scanning electron microscope (SEM) images of tested specimens indicates strong interfacial bonding between skin and the core of specimens with nylon screws.Highlights Introduction of light‐weight nylon screws in z‐direction enhanced the bonding between face sheets and foam core. Sandwich composites with nylon screws exhibited superior bending and shear strength compared to plain specimens. Crack propagation in the interfacial region is restricted by the presence of nylon screws. Investigation of fractured specimens indicated a strong interfacial bonding in the specimens with screws.

Design of continuously radial density-graded aluminum foam with unidirectional and bidirectional and study on blast resistance of sandwich tube

This work focuses on investigation of the internal blast resistance of metal sandwich tubes with continuously radial density-graded aluminum foam cores. Based on the 3D-Voronoi technology in polar coordinates, unidirectionally and bidirectionally continuously density-graded aluminum foam were developed for the cores of sandwich tubes in Finite Element (FE) model. And the correctness of core gradient was verified by comparing theoretical design with the actual value generated by FE model. Effects of core density distribution and core density gradient on blast resistance of sandwich tubes were explored and identified. The results indicate that, when the core density gradient is constant, the sandwich tube with negative-gradient core exhibits the smallest maximum deformation of the outer tube, while the negative-middle-low-gradient core tube shows the highest specific energy absorption ( SEA). For negative-gradient core tube, as the core density gradient increases, the maximum deformation of the outer tube decreases significantly, with only slight reduction of the structural SEA. For negative-middle-low-gradient core tube, as the core density gradient increases, the maximum deformation of the outer tube decreases, while the SEA increases.

Enhanced microwave absorption of sandwich panels with magnetized carbon fiber corrugated array reinforced PMI foam core

AbstractIntegrating periodic array structures made of metal wires or conductive inks into the foam core of electromagnetic (EM) wave absorbing sandwich panels can significantly improve broadband absorption performance. However, the complex fabrication process and poor corrosion resistance of these materials limit their practical applications. This work innovatively introduces magnetized carbon fiber (CF) into PMI foam, simultaneously achieving broadband absorption and lightweight characteristics of the sandwich structure through the design of array structure and fiber bundle geometry. Simulation analysis compared the EM absorption performance of sandwich panels with carbonyl iron powder (CIP)/CF tape and helical twisted CIP/CF rope corrugated arrays, determining the optimal array structure parameters, which were then experimentally validated. The experimental results align with the simulations, showing that CIP/CF rope corrugated arrays with an amplitude of 10 mm, a cycle length of 15 mm, and an array spacing of 15 mm provide optimal absorption performance, with a reflection loss below −10 dB across the 9–18 GHz frequency range and a maximum absorption of −33.9 dB at 17 GHz. Finally, the absorption mechanism of these sandwich structures is discussed, highlighting how the synergistic effects between the electromagnetic properties and structural morphology of CIP/CF enhance the absorption performance of the EM absorbing sandwich panel.

Effect of Films on In‐Mold Decoration and Microcellular Foaming Injection Molding Parts: Cell Structure, Surface, Warpage, and Mechanical Properties

ABSTRACTThe in‐mold decoration and microcellular foaming injection molding (IMD‐MIM) process was proposed to solve the apparent quality problem of polypropylene in microcellular foaming injection molding. Based on physical experiments and finite element simulation, stainless steel (ST) and polyethylene glycol terephthalate (PET) decorative films were selected for analysis, and the influence of the type and thickness of the decorative films on the cell structure, surface morphology, warpage deformation, and mechanical properties was revealed. The results show that the surface quality of the samples coated is significantly improved, and the asymmetric temperature field caused by the films changes the structure and distribution of the cells. The cell density on the coated side is higher than that on the non‐coated side, and the average cell diameter is smaller, and the foam core layer is shifted to the coated side. The warpage caused by ST film is larger, up to 2.836 mm. With the intervention of ST film and PET film, the impact properties of the samples have little change, but the tensile and flexural properties of the foamed samples have been effectively improved. The tensile strength increased by 28.6% and 25.9%, while the flexural strength increased by 28.6% and 28.1%, respectively. This study provides new insights into the comprehensive optimization of the structure and performance of polypropylene microcellular foaming materials and provides support for the development and application of lightweight materials in the future.

Recycled PET foam core sandwich panels with reinforced hybrid composite facesheets: A sustainable approach for enhanced impact resistance

This research explores the Low-Velocity Impact behavior of thermoplastic composite sandwich panels with 100% recycled Polyethylene Terephthalate (PET) foam sourced from post-consumer plastic water bottles. Being recognized as a reliable technique, hybridization using stainless-steel mesh layers was employed to reinforce the panels’ composite facesheets of sandwich panels accessible for modular housing, cold storage rooms and cargo trucks. Adequate impregnation of the reinforcement metallic mesh layer alongside proper skin-to-core adhesion was accomplished by optimizing a two-phase compression molding method. The effect of hybridization on impact response of sandwich panels with two different PET foam core thicknesses, and stacking sequence were evaluated. It was revealed that reinforcing the impacted surface of the composite sandwich panels significantly increased the perforation threshold. Moreover, analyzing the post-impact section view of the samples indicated that hybridization modified the damage propagation response of the PET foam core sandwich composites, through which the energy absorption capacity was improved.

Dynamic instability and nonlinear response analysis of nanocomposite sandwich arches with viscoelastic cores

This paper presents a comprehensive study of the nonlinear dynamic behavior and snap-through phenomena in sandwich arch structures with viscoelastic cores and carbon nanotube-reinforced nanocomposite face sheets. Subjected to uniform time-dependent pressure shocks, these arches exhibit complex snap-through behavior critical for practical engineering applications. Utilizing third-order shear deformation theory, the study accurately captures nonlinear behaviors. The viscoelastic core, modeled with the Kelvin-Voigt law, enhances damping and reduces vibration amplitudes. Numerical solutions are obtained using a Chebyshev-based Ritz method, Newmark integration, and Newton-Raphson method. The Budiansky-Ruth criterion evaluates dynamic buckling loads. Key findings include significant instability near buckling loads, increased buckling loads and vibration damping due to viscoelastic effects, reduced buckling loads with foam cores, improved performance with CNTs, and more pronounced CNT effects with greater deflections. Additional conclusions highlight the sensitivity of dynamic snap-through to geometric parameters and the superior accuracy of the proposed approach compared to traditional models. This research advances the understanding and design strategies for nonlinear sandwich arch structures, enhancing predictive capabilities in complex structural systems.

Extending the Natural Neighbour Radial Point Interpolation Meshless Method to the Multiscale Analysis of Sandwich Beams with Polyurethane Foam Core

This work investigates the mechanical behaviour of sandwich beams with cellular cores using a multiscale approach combined with a meshless method, the Natural Neighbour Radial Point Interpolation Method (NNRPIM). The analysis is divided into two steps, aiming to analyse the efficiency of NNRPIM formulation when combined with homogenisation techniques for a multiscale computational framework of large-scale sandwich beam problems. In the first step, the cellular core material undergoes a controlled modification process in which circular holes are introduced into bulk polyurethane foam (PUF) to create materials with varying volume fractions. Subsequently, a homogenisation technique is combined with NNRPIM to determine the homogenised mechanical properties of these PUF materials with different porosities. In this step, NNRPIM solutions are compared with high-order FEM simulations. While the results demonstrate that RPIM can approximate high-order FEM solutions, it is observed that the computational cost increases significantly when aiming for comparable smoothness in the approximations. The second step applies the homogenised mechanical properties obtained in the first step to analyse large-scale sandwich beam problems with both homogeneous and functionally graded cores. The results reveal the capability of NNRPIM to closely replicate the solutions obtained from FEM analyses. Furthermore, an analysis of stress distributions along the beam thickness highlights a tendency for some NNRPIM formulations to yield slightly lower stress values near the domain boundaries. However, convergence towards agreement among different formulations is observed with mesh refinement. The findings of this study show that NNRPIM can be used as an alternative numerical method to FEM for analysing sandwich structures.

Impact responses of steel–concrete–steel–gradient aluminum foam energy absorbing panels: Experimental and numerical studies

A novel steel–concrete–steel–gradient aluminum foam energy absorbing panel (SCSGF-EAP) has been proposed for improving the impact resistance of existing structures. The impact resistant performances of the SCSGF-EAP were evaluated through the drop weight impact tests and numerical simulations. The varying thickness of gradient aluminum foam and concrete core was considered in the drop weight impact tests. All the specimens presented a consistent failure mode, which included local indentation and global flexure of SCS panel and crushing of gradient aluminum foam. The Finite Element (FE) model was developed through adopting LS-DYNA for studying the impact resistance of SCSGF-EAP, and the comparisons exhibited that numerical results agreed well with experimental data. The internal energy of different components of specimen was determined by numerical model, and the gradient aluminum foam absorbed the majority of the impact energy. Finally, parametric studies were adopted to determine influences of the initial momentum and kinetic energy of impactor, as well as the density of gradient aluminum foam and impact location on the impact response of SCSGF-EAP.

Post impact flexural behavior investigation of hybrid foam-core sandwich composites at extreme Arctic temperature

This study explores the post-impact bending behavior and failure mechanisms in hybrid sandwich composites made of Carbon Fiber Reinforced Polymer (CFRP) and Glass Fiber Reinforced Polymer (GFRP). Flexural tests conducted at both ambient room temperature and low temperature Arctic conditions reveal a significant enhancement in flexural performance when GFRP layer is incorporated on the outer side of the hybrid composite. The investigation utilizes images from testing to elucidate damage modes, including fiber and matrix cracking in the composite facesheet, as well as core shearing and debonding in the Polyvinyl Chloride (PVC) foam core. Residual flexural properties are notably influenced by stacking sequence, facesheet compressive properties, pre-existing impact damage and temperature conditions. Analytical predictions, validated experimentally, highlight the effect of stacking sequence, low temperature, and impact energy on flexural collapse modes, with competing failure modes such as indentation and core shear. Collapse maps indicate that room temperature specimens predominantly collapse through indentation, while diverse collapse mechanisms emerge due to facesheet thickness, rigidity, and degraded tensile strength. The study aims to provide fundamental insights for future composite designs tailored for Arctic applications.

Thermoplastic composite sandwich panels with recycled PET foam core: A manufacturing process assessment

This study attempts to modify two distinct lamination processes of double-belt and compression molding to produce environmentally sustainable full thermoplastic sandwich panels. A precise assessment of fabrication parameters was conducted to ensure the quality of sandwich panels made of glass/Polypropylene composite skin and 100% recycled PET foam core sourced from consumer waste bottles. Evaluations of the skin-to-core adhesion properties revealed that the PET foam density in conjunction with the fabrication approach can affect the layers’ bonding. The formation of satisfactory interlayer connection under controlled process parameters was confirmed by Peel-off and flatwise tensile test results. Moreover, complementary three-point bending analyses highlighted deviations in panel performance. Panels manufactured by the compression molding method exhibited superior load-bearing capacity compared to those made via a double-belt machine. These observations are attributed to the inherent nature of the lamination procedures, taking single or multiple thermal treatment phases to fabricate the sandwich panels. Finally, the findings suggest that despite potential slight quality degradation, the production continuity capability of the double-belt method makes it a viable option for meeting industry requirements.

Evaluation of mechanical properties and energy absorption of polyurethane foam core sandwich panels with kevlar/basalt-epoxy laminates as face sheets

Evaluation of mechanical properties and energy absorption of polyurethane foam core sandwich panels with kevlar/basalt-epoxy laminates as face sheets

The Impact of 3D Printing Technology on the Improvement of External Wall Thermal Efficiency—An Experimental Study

Three-dimensional printing technology continues to evolve, enabling new applications in manufacturing. Extensive research in the field of biomimetics underscores the significant impact of the internal geometry of building envelopes on their thermal performance. Although 3D printing holds great promise for improving thermal efficiency in construction, its full potential has yet to be realized, and the thermal performance of printed building components remains unexplored. The aim of this paper is to experimentally examine the thermal insulation characteristics of prototype cellular materials created using 3D additive manufacturing technologies (SLS and DLP). This study concentrates on exploring advanced thermal insulation solutions that could enhance the energy efficiency of buildings, cooling systems, appliances, or equipment. To this end, virtual models of sandwich composites with an open-cell foam core modeled after a Kelvin cell were created. They were characterized by a constant porosity of 0.95 and a pore diameter of the inner core of the composites of 6 mm. The independent variables included the different material from which the composites were made, the non-uniform number of layers in the composite (one, two, three, and five layers) and the total thickness of the composite (20, 40, 60, 80, and 100 mm). The impact of three independent parameters defining the prototype composite on its thermal insulation properties was assessed, including the heat flux (q) and the heat transfer coefficient (U). According to the experimental tests, a five-layer composite with a thickness of 100 mm made of soybean oil-based resin obtained the lowest coefficient with a value of U = 0.147 W/m2·K.

Low-velocity impact of clamped Y-shaped sandwich beams with metal foam core

This study aims to analytically and numerically investigate the dynamic behavior of clamped foam-filled Y-shaped sandwich beams subjected to low-velocity impact. Using the yield criterion for the foam-filled Y-shaped sandwich structure, a theoretical model is proposed. The bound and the analytical solution of low-velocity impact (LVI) of the foam-filled Y-shaped sandwich beam (FYSB) are obtained. Numerical computations are conducted to study the dynamic behavior of FYSB subjected to LVI. Analytical predications are in agreement with numerical. Subsequently, an in-depth analysis is undertaken employing a theoretical model to discuss the influences of parameters such as the Y-shaped plate angle, impact location, foam strength on the dynamic behavior of the FYSB. It is shown that for the given deflection, the impact force diminishes as the impact location progressively approaches the mid-span, and increases with increasing foam strength, Y-shaped plate angle, face-sheet thickness and striker mass. The analytical model can be used to predict the dynamic response of the FYSB subjected to LVI.

Nonlinear temperature dependent and visco-elastic foundation effects on the free vibration of functionally graded sandwich plates with ceramic foam core

This paper investigates the vibrations of a functionally graded sandwich plate (FG sandwich plate) with a ceramic foam core resting on a viscoelastic foundation. The focus is on the influence of temperature changes on sandwich plates that have foam core and FG face sheet on the free vibration. The damping coefficient and different schemes of sandwich plate have been considered in the current work. The analysis uses a quasi-3D theory, which reduces the number of unknown displacements and simplifies the equations by incorporating integral terms. Two models are employed to represent the non-uniformity of the ceramic foam core. To account for the influence of the supporting layer, a viscoelastic foundation is included. The governing equations are derived using Hamilton’s principle and solved using the Navier solution method. The paper comprehensively discusses how the volume fraction index k, geometric properties, ceramic foam distribution, viscoelastic foundation, and different temperature rise profiles impact the vibration response of the FG sandwich plate.

Wall sandwich panels with steel facings and PUR foam core under transverse loading: Experimental testing and numerical model calibration

Light weight panels are largely used for the envelope (wall assembly, roofing system) of different kind of buildings. Under extreme loading conditions, like external explosions, the walls may suffer extensive damage, under either positive or negative pressures. The study presented in the paper describes the results obtained on wall sandwich panels tested for transverse loading until complete failure. The panels are arranged as single span systems supported on side rails and loaded at the mid-span. After a quasi-linear response, the maximum bending capacity is reached. At this point, the panels have a sudden drop in capacity, associated with the rapid wrinkling of the face in compression. If the end fasteners have adequate resistance, catenary stage develops, and the ultimate capacity can be significantly higher than the peak bending capacity. Flexibility of the lateral restraints significantly influence the initiation of catenary action and the ultimate capacity of sandwich panels. Numerical models were calibrated using the structural analysis and design program SAP2000. This may allow professionals to integrate more quickly the wall models into the structural design even for extreme loading conditions.

Dynamic Response of Gradient Aluminum Foam Sandwich Tubes under External Explosive Loads.

In this paper, we numerically investigate the dynamic response and explosion resistance of gradient aluminum foam sandwich tubes subjected to external blast loads. Based on 3D-Voronoi technology, we construct density-graded aluminum foam cores to systematically explore the influence of core density distribution, density gradient, and average relative density on the protective performance of these structures. Our primary objective is to identify optimal design parameters that maximize explosion mitigation capabilities while balancing energy absorption and specific energy absorption capacities. The research results show that a positive gradient core configuration exhibits superior anti-explosion performance, significantly outperforming its uniform and negatively graded counterparts, particularly when the gradient value is substantial. For the positive gradient cores, an increase in the gradient value leads to a corresponding enhancement in explosion resistance. Conversely, in negatively graded cores, a higher gradient value diminishes the anti-explosion performance. Furthermore, while augmenting the relative density of the core layer does improve the overall explosion resistance of the sandwich tube, it comes at the cost of reduced energy absorption and specific energy absorption capabilities, highlighting the need for a delicate balance among these competing factors.

Dynamic Response of Fiber-Metal Laminates Sandwich Beams under Uniform Blast Loading.

In this work, theoretical and numerical studies of the dynamic response of a fiber-metal laminate (FML) sandwich beam under uniform blast loading are conducted. On the basis of a modified rigid-plastic material model, the analytical solutions for the maximum deflection and the structural response time of FML sandwich beams with metal foam core are obtained. Finite element analysis is carried out by using ABAQUS software, and the numerical simulations corroborate the analytical predictions effectively. The study further examines the impact of the metal volume fraction, the metal strength factor between the metal layer and the composite material layer, the foam strength factor of the metal foam core to the composite material layer, and the foam density factor on the structural response. Findings reveal that these parameters influence the dynamic response of fiber-metal laminate (FML) sandwich beams to varying degrees. The developed analytical model demonstrates its capability to accurately forecast the dynamic behavior of fiber-metal laminate (FML) sandwich beams under uniform blast loading. The theoretical model in this article is a simplified model and cannot consider details such as damage, debonding, and the influence of layer angles in experiments. It is necessary to establish a refined theoretical model that can consider the microstructure and failure of composite materials in the future.

Multiscale Analysis of Sandwich Beams with Polyurethane Foam Core: A Comparative Study of Finite Element Methods and Radial Point Interpolation Method.

This study presents a comprehensive multiscale analysis of sandwich beams with a polyurethane foam (PUF) core, delivering a numerical comparison between finite element methods (FEMs) and a meshless method: the radial point interpolation method (RPIM). This work aims to combine RPIM with homogenisation techniques for multiscale analysis, being divided in two phases. In the first phase, bulk PUF material was modified by incorporating circular holes to create PUFs with varying volume fractions. Then, using a homogenisation technique coupled with FEM and four versions of RPIM, the homogenised mechanical properties of distinct PUF with different volume fractions were determined. It was observed that RPIM formulations, with higher-order integration schemes, are capable of approximating the solution and field smoothness of high-order FEM formulations. However, seeking a comparable field smoothness represents prohibitive computational costs for RPIM formulations. In a second phase, the obtained homogenised mechanical properties were applied to large-scale sandwich beam problems with homogeneous and approximately functionally graded cores, showing RPIM's capability to closely approximate FEM results. The analysis of stress distributions along the thickness of the beam highlighted RPIM's tendency to yield lower stress values near domain edges, albeit with convergence towards agreement among different formulations. It was found that RPIM formulations with lower nodal connectivity are very efficient, balancing computational cost and accuracy. Overall, this study shows RPIM's viability as an alternative to FEM for addressing practical elasticity applications.

Impact response and compression-after-impact properties of foam-core sandwich composites incorporating scrap tyre rubber particles

Integrating scrap rubber particles as fillers into polymer matrix composites offers a cost effective and environmentally sustainable pathway to manage tyre waste through the creation of value-added products. This research explores the low-velocity impact (LVI) response and compression after impact (CAI) properties of rubberised foam-core glass fibre-reinforced epoxy (GFRE) sandwich composites. Syntactic foam cores integrated with rubber particles were manufactured using vacuum-assisted resin transfer moulding (VARTM). The compression properties of rubberised foam core, vital for resisting impact damage during LVI, were examined. Results show more than 40% reduction in compression strength and modulus of the syntactic foam upon the inclusion of 33 wt.% rubber particles. The LVI response and residual compression properties of rubberised foam-core composites were also evaluated. Rubberised foam cores caused a marginal reduction in the peak impact force and led to approximately 60% reduction in the delamination area. The pre-impact compression strength was unaffected by rubber particles within the core as the GFRE face sheets carried most of the compression load. Post-impact compression strength was slightly higher in rubberised foam-core composites due to reduced delamination. Digital Image Correlation (DIC) analysis tracking of the strain evolution during CAI experiments revealed the stress-raising effect of the impact damaged region. This study showcases sustainable scrap tyre management through the inclusion of rubber particles into foam-core composites without substantially reducing in-plane compression properties before or after low-velocity impact.