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This research study the energy absorption performance of aluminum core honeycomb sandwich panel (ACHSP) with filled and empty cores subjected to low-velocity impact testing, with diverse skins; (i) aluminum sheets, (ii) 5-ply epoxy glass composite, and (iii) 5-ply shear thickening fluid (STF)-impregnated glass fabrics. The prepared STF was 35 wt% and the impactor heights was selected at 100 and 500 mm to assess the effect of different impact velocities on the energy absorption capability of STF. The specific energy absorption (SEA) of the STF-filled ACHSP with 5-ply STF-impregnated fabrics skin (height of 500 mm) compared to STF-filled ACHSP with aluminum sheets skin and 5-ply epoxy glass composite skin have increased by 28.38 and 21.79%, respectively. In a fact of truth, when the external force is applied to the STF-filled ACHSP, the fluid transitions from a low-velocity to a high-velocity state instantly. This transition exerts forces on the suspended particles within the fluid. Actually, during the impact, the particles come into close contact and form temporary particle networks or chains. These networks increase the viscosity of the fluid, making it resistant to flow. The energy of the impact is then absorbed by the formation and reformation of these particles' networks. However, the SEA of STF-filled ACHSP at the height of 500 mm to empty ACHSP at the height of 100 mm have decreased significantly, and the energy absorption of STF-filled ACHSPs to corresponding empty ACHSPs have increased remarkably. [ABSTRACT FROM AUTHOR]

In this study, carbon fiber/thermoplastic (Elium®) honeycombs were manufactured using the resin infusion process in a customized metallic mold. Honeycomb cores, based on different carbon fiber layers, were manufactured to achieve four different fiber weight fraction composites. Two different types of specimens, based on a single honeycomb cell and five honeycomb cells, were prepared and subjected to compression loading. The results of these tests were compared with data from similar honeycomb structures based on carbon fiber–reinforced epoxy composite. It has been shown that the compressive strength and the specific energy absorption capacity of the honeycombs increase rapidly with increasing fiber weight fraction. The specific energy absorption capability of the novel thermoplastic honeycomb structures has been shown to be as high as 50 kJ/kg which compares favorably with other energy-absorbing core materials. The thermoplastic honeycomb specimens exhibited a similar specific energy absorption capability and an improved compressive strength compared to their epoxy counterparts. Furthermore, the CF/thermoplastic honeycombs exhibited enhanced structural stability and displayed a more uniform and progressive core failure mode than the longitudinal splitting observed in the CF/epoxy honeycombs. The honeycomb core that exhibited the best performance was then used to manufacture thermoplastic sandwich specimens based on CF/thermoplastic face sheets. Three point bend tests were conducted to determine the flexural strength of the sandwich samples and to identify the failure modes. Optical micrographs revealed that the flexural damage was primarily due to the core crushing and adhesive failure between the core and the composite skins. [ABSTRACT FROM AUTHOR]

The present paper explores different techniques for increasing flexural performance of composite sandwich panels made of hand-layup glass fiber reinforced polymer skins and low density closed cell polyurethane foam core. An experimental program compares the performance of simple panels face to the use of transversal and longitudinal internal glass fiber reinforced polymer ribs and the installation of a strain hardening cementitious base composite top layer over the panels. Based on the experimental results, finite element models are also developed to simulate the flexural behavior of tested panels and conducted an in depth analysis of the techniques studied. Obtained experimental and numerical results show that the use of internal glass fiber reinforced polymer ribs (especially in longitudinal direction) along with the use of strain hardening cementitious base composite significantly and effectively increases the flexural performance of sandwich panels. The high stiffness to weight ratio capacity of the panels attained by applying the proposed method enables its use in rehabilitation of historical places. Furthermore, the proposed techniques could be helpful for strengthening available composite sandwich panels. [ABSTRACT FROM AUTHOR]

The present paper explores a new modular floor prototype to be used in emergency houses. The prototype is composed of a frame structure made of glass-fibre-reinforced polymer tubular pultruded profiles, a slab made of sandwich panels with a polyurethane foam core and glass-fibre-reinforced polymer skins, and a tailored connection system that provides integrity between assembled components. A series of experimental tests are carried out including flexural tests on a single panel, on two and three connected panels, and on the assembled floor prototype. The behaviour of the panels is analysed when they are not considered part of the glass-fibre-reinforced polymer framed structure, namely the failure mechanisms and the efficiency of the proposed connection system between the panels. The performance of the floor prototype to support typical load conditions of residential houses is also assessed. Additionally, an analytical model was used to deeper study the behaviour of the developed sandwich panels, connection system and the modular floor prototype. [ABSTRACT FROM AUTHOR]

Currently, most cellular solid sandwich panel cores require multiple advanced manufacturing procedures that drive increasing costs for applications. Pumice is a naturally occurring cellular solid that exhibits a microstructure very similar to advanced ceramic foams. This work presents a manufacturing process for producing composite panels of pumice stones and epoxy binder. The cost and weight efficient structure is evaluated through mechanical testing and investigated for possible energy absorption applications. Mechanical performance as a function of relative density is presented and compared to currently available core materials, and scaling laws developed. [ABSTRACT FROM PUBLISHER]

This article describes the use of finite element analysis (FEA) for the simulation of the crushing response of glass fiber reinforced plastic (GRP) composite sandwich panels aimed to absorb collision energy. FEA is employed to predict the failure modes associated with the geometry of a triggering mechanism that is introduced in the foam-cored sandwich panels, and for analyses of the influence of the specimens' aspect ratio on the specific energy absorption of these panels. The formulated numerical models are found to be effective in reproducing the failure modes and crush zone morphology that is observed experimentally. The numerical results predict an optimum trigger geometry that marks the transition from a catastrophic face buckling (FB) failure to progressive crushing (PC) that dissipates large amounts of energy. They also show that there is not an apparent trend between the aspect ratio (size) of the panels and their specific energy absorption. [ABSTRACT FROM AUTHOR]

Analytical solutions for the deformation, penetration, and perforation of composite plates and sandwich panels subjected to quasi-static punch indentation and projectile impact are derived. Discrete spring-mass models are used to calculate the impact response of the composite plates and sandwich panels. Equivalent load resistance functions are obtained from the quasi-static analysis and adjusted for high strain rate. A generalized solution methodology for projectile impact of composite plates and sandwich panels are then proposed based on three key factors: (i) the contact load duration, (ii) the through-thickness transit time, and (iii) the lateral transit time. A two-dimensional wave propagation model is used to determine the ballistic limits of E-glass/polyester panels and GLARE fiber-metal laminates, and predicted values are found to be within 20 and 13% of the experimental results, respectively. A quasi-static impact model is used to predict the ballistic limit for E-glass/epoxy-aluminum honeycomb sandwich impacted by hemispherical nose projectile and the predicted values are within 11% of test results. [ABSTRACT FROM AUTHOR]

A new mathematical method and double Fourier series set of functions is developed to find out the local and global transverse and in-plane mode shapes, damped natural frequencies and modal loss factors in composite sandwich panels with multilayered laminated face sheets, viscoelastic flexible core and arbitrary boundary conditions. An improved high order sandwich plate theory IHSAPT) is applied to investigate the dynamic behavior of fiber reinforced plastic (FRP) sandwich thin and thick panels. The present analysis is very general and valid for any type of core, any type of boundary conditions as well as for the cases where the conditions at the upper face sheet are different from those at the lower one along the same edge. Interaction between static in-plane initial stress and dynamic response of a sandwich panel tire studied in this article. For different boundary conditions. solutions are obtained using the simple proposed identical double Fourier series functions rind Stokes's transformation technique. The effect of some parameters such as panel aspect ratio, thickness of core thickness of panel ratio, and initial in-plane stresses on dynamic response of composite sandwich panel are discussed and studied in detail. [ABSTRACT FROM AUTHOR]

A three-dimensional (3D) finite element analysis has been conducted to examine the local buckling behavior of foam-cored composite sandwich panels containing a face core debond. The influences of core stiffness and debond size and shape are examined. The core stiffness was found to have a profound influence on the local buckling load, especially for low modulus cores and smaller debonds. Panels with square debonds buckled at lower loads than those with circular debonds of the same dimension, and buckling loads for both circular and square debonds decreased with increased debond size. The results of the analysis were compared to local buckling loads determined experimentally. Reasonable agreement was found between the predicted and experimentally measured local buckling loads for both circular and square debonds. [ABSTRACT FROM AUTHOR]

This paper presents the results of an investigation of delamination failure at "exterior" ply drops in tension loaded sandwich panels with laminated composite face sheets. The thickness of composite laminates used as face sheets of sandwich panels is often increased locally around highly loaded locations such as joints, rivets, bolts or inserts. At the stations where such ply drops are made, the local bending stiffness of the face sheet laminates change discontinuously, thus inducing severe local bending effects. These local bending effects induce severe stress concentrations in the interfaces between the dropped plies/sub-laminates and the remaining face sheet laminates, and this may initiate delamination failure. The present paper suggests a simple approach for stress analysis and a simple "characteristic length" stress criterion for the prediction of delamination failure. An experimental investigation has been carried out, and the measured delamination loads compare well the theoretical predictions. [ABSTRACT FROM PUBLISHER]

Local regions of bond failure between face sheet and core are often observed when sandwich structures are exposed to low energy impacts. Similarly, impact loads frequently result in delaminations within the face sheets. In the absence of any delaminations in the sandwich structure the buckling strain of the debonded region is in this work shown to be the key parameter in assessing the structural integrity of a sandwich component in compression. The objective of this study was to predict the buckling of the debonded region and to investigate the parameters controlling this instability. A large number of analyses of the delamination buckling problem, which in many ways may appear similar to the debond problem, have been carried out in the past. However, the debond-buckling problem has not been addressed before and as shown in this work there are significant differences. The Finite Element method was found able to predict all the experimentally observed phenomena accurately. These calculations were expensive, and a simple one-dimensional closed form solution is proposed for qualitative parametric investigations. Effects of material properties and initial imperfections were examined. Analyses of the buckling of a delamination suggest that the effect of the core can be ignored. In contrast, the results presented in this paper show that the core cannot be ignored in the case of buckling of a debond nor can it be simulated in terms of simple boundary conditions. [ABSTRACT FROM PUBLISHER]