Papers by Keyword: Sandwich Structure

Abstract: Growing environmental awareness and the challenges posed by climate change have driven the development of sustainable composites to reduce dependence on fossil resources and mitigate ecological impacts. Conventional composites, despite their high mechanical performance, are constrained by greenhouse gas emissions and limited recyclability, motivating the adoption of “green composites” based on natural fibers, recycled constituents, and bio-based resins. This study presents a sustainable sandwich composite integrating flax fibers, a bio-based epoxy matrix, and a recycled PET foam core. Flexural performance was evaluated through finite element analysis (FEA) in ANSYS Workbench and validated by three-point bending tests. The results show that the 3C specimen achieved a maximum load of 579.92 N, with a deviation of 4.2% from simulation at 6 mm deflection, and all tested specimens exhibited discrepancies below 5%. These findings confirm the suitability of the developed composites for structural applications such as UAV wings, aligning high mechanical performance with environmental sustainability.

Abstract: This study examines the potential to customize the bending and transverse shear behavior of aluminum honeycomb sandwich panels by introducing sinusoidal perturbations to their cell walls. Finite element analysis is used to investigate the effect of varying the amplitude and frequency of the introduced perturbations on the flexural and transverse shear stiffness and strength of perturbed aluminum cores. Results show that increasing the amplitude and frequency of the perturbations generally decreases the flexural and transverse shear stiffness and yield strength. Local deformations in the perturbed cores indicate that imposing perturbations encouraged the development of localized deformations in the curved cell walls, which increased the perturbed cores' compliance. The transverse shear and flexural responses at the highest frequencies and amplitudes exhibited a very smooth and compliant behavior compared to the unperturbed cores. The response of the perturbed cores can be attractive for applications involving impact energy mitigation, as they demonstrate an enhanced capacity to reduce and limit the force transmitted through them.

Abstract: In designing materials to resist impact and penetrations, numerical simulation offers effective means to ascertain impact mechanism close to practical experimental procedures. This work presents penetration characteristics of water as an inter-layer between ultra-high strength steel sandwich structure. Residual velocities for both monolithic and sandwiched structures have been investigated. In the case of the monolithic structure, good agreement was found between experimental and simulation results in reducing projectile initial velocity of 854 m/s to obtained residual velocities of 487 m/s and 460 m/s respectively. Energy dissipation capability of water as an interlayer has also been investigated. Water, proving very effective in decreasing projectile velocity of 390 m/s to zero in a 2 mm steel-2 mm water – 2 mm steel sandwich system. Numerical simulation has been carried out using Ansys Explicit / Autodyn – a commercial software based on finite element method which is very effective in solving non-linear problems. Lagrange elements were used in the discretization of both the water and steel media.

Abstract: High speed feed axes are a key for increasing the productivity of machine tools. It requires high acceleration and causes jerk, which excites the machine structure and negatively affects the process quality. One approach to reduce those machine vibrations are passive dampers such as particle-filled hollow spheres (PHS). PHSs dissipate vibration energy through relative motion and friction between particles among themselves and the sphere. Compounds of PHS as core of sandwich materials allow structure-integrated damping of machine tool components and for maintaining a high specific stiffness at the same time. The complex interactions within each sphere lead to nonlinear damping. As of today, precise predictions on how PHSs influence the overall machine behavior are not possible. This prognosis is essential for establishing the material in any machine structure. The paper investigates the damping properties of PHSs in a spindle box of a machine tool. The experimental and numeric analysis demonstrates the nonlinear behavior and shows the reaction of the spindle box under external excitation. The result shows that the damping of the spindle box with PHSs is frequency and amplitude dependent. The damping of PHSs is domain with increased parts of them deformed during vibration.

Abstract: There exist some problems in the crash box and anti-collision beam sandwich structure, such as monotone deformation pattern and uneconomical energy absorption performance. In order to raise the deformation capacity and energy absorption performance of sandwich structure, centrosymmetric reentrant honeycomb (CRH) and hexagonal centrosymmetric reentrant honeycomb (HCRH) are proposed based on auxetic reentrant honeycomb (ARH) in this work. Based on HCRH, four kinds of transverse combination structures and two kinds of longitudinal combination structures are obtained. The results of specific energy absorption show that the energy absorption capacity of the angular contact homodromous combination structure (ACOC) is about 3 times that of the other three transverse combination structures. Compared with longitudinal heterodromous combination structure (LHEC), the energy absorption capacity of longitudinal homodromous combination structure (LHOC) is improved by 72.7%.

Abstract: Improvement of mechanical properties of light-weight corrugated core sandwich structures is a big demand in aerospace applications. Among these applications, space vehicles which encounter pressure loads and severe aerodynamic heating during ascent and reentry. The open-cell corrugated core is useful for active cooling of the sandwich structures. In this work, hybrid composite structural members with fiberglass corrugated core and carbon fiber skin facings were manufactured using vacuum bag technique. Different specimen configurations with rectangular cross-section area have been subjected to the load in the longitudinal direction of the corrugation and examined by edgewise compression test. The proposed testing has been applied to take advantage of the highest inertia of the specimen in such orientation. The test provides a basis for estimating the load carrying capacity when these structure members are used as individual webs in the aircraft interiors. Also as the core sheet is turned by 90° to the regular load direction, this structure member is similar to the so-called honeycomb when ordered in parallel rows and hence it is appropriate for floor sandwiching. In contrary to a honeycomb, this core consists of fiberglass laminate and therefore higher compressive resistance is associated. The results exhibit high values of both stiffness and ultimate compression force in the corrugation direction. For the rectangular area and the open corrugated contour, specific properties relative to the weight are extremely high. Also, the results and graphs indicate that there must be at least three corrugated ligaments with a trapezoidal cross section of 0.5” height and 63^o per cell to grantee stability under load and high absorbed energy in the non-linear stage as well.

Abstract: Jute fabric is well-known reinforcing material in composite science, however, there is a necessity to treat these fabrics to reduce moisture uptake and improve properties. Nevertheless, every modification increases the cost and reduces the possible applications. Presented research deals with an investigation of possibility to use untreated jute in various fabric weight as a reinforcing material in sandwich structures facings. Untreated jute reinforcements and two types of cork cores were saturated in one step during vacuum infusion creating a lightweight sandwich composite. All samples were mechanically tested in three-point bending test. Experimental results showed the most appropriate material combination and produced sandwich structure are proposed for design applications.

Abstract: Sandwich structures based on Fibre Reinforced Polymer (FRP) facesheet skins bonded with low density aluminium foam core are increasing in use in aerospace and marine industries. These structures are very sensitive to high velocity impact during the service. Therefore, it is necessary to study the energy absorption of the structures to ensure the reliability and safety in use. Experimental investigation of these transient events is expensive and time-consuming, and nowadays the use of numerical approaches is on the increase. Hence, the purpose of this paper is to develop a numerical model of sandwich panels with aluminium foam as a core and Glass, Carbon and Kevlar Fibre Reinforced polymer composite as faceplate, subjected to high velocity impact using ABAQUS/Explicit. The influence of individual elements of the sandwich panel on the energy absorption of the structures subjected to high velocity impact loading was analysed. Selection of suitable constitutive models and erosion criterion for the damage were discussed. The numerical models were validated with experimental data obtained from the scientific literature. Good agreement was obtained between the simulations and the experimental results. The contribution of the face sheet, foam core on the impact behaviour was evaluated by the analysis of the residual velocity, ballistic limit, and damaged area.

Abstract: Due to the significant and harmful effect of the global warming on our communities, health, and climate, the usage of sustainable, bio-based and green materials became an imperative. On the other hand, the utilization of waste and biomass resources for developing new bio based composite materials is attracting much attention for the environmental and socio economics. Therefore, in this study, bio based composite panels from TetraPack^® waste were developed. To enhance the mechanical and physical performances of TetraPak panels, sandwich structures were constructed. Mechanical and physical tests results showed significant improvements due to using sandwich structure in compare to No-skin structure. By comparing the developed TetraPak sandwich panels with the standard commercial particleboard, significant improvements in both mechanical and physical performances have been clearly observed. Consequently, the developed biocomposite TetraPak panels can be used in a wide variety of applications. Finely, this can be contributing in reducing environment contaminating, meanwhile introduce cheap and suitable product for different technical fields.

Abstract: Purpose of this study is investigation of energy absorption capability of the sandwich structures composed of combination of polystyrene and metal foam element and their suitability as new structure for design of protective helmets. Two types of the metal foams were experimentally tested and evaluated: Alporas (Shinko Wire Ltd., Japan) and Aluhab (Aluinvent Plc., Hungary). Samples of the sandwich structure are composed of two layers: bottom expanded polystyrene (EPS 200S) layer and upper metal foam layer which are glued together. Prepared samples are tested using a drop tower experiment to measure sample response (acceleration, reaction force) at different strain rates and energies. From acceleration/time history the Head Injury Criterion (HIC) is calculated as significant parameters in terms of protective helmets. Moreover, measured and derived characteristics are compared with pure EPS samples to obtain comparison of deformation behaviour between conventional structure for protective helmets and designed sandwich structures.