Fire reaction of sandwich panels with corrugated and honeycomb cores made from natural materials

2021 ◽  
pp. 109963622198923
Author(s):  
Avishek Chanda ◽  
Nam Kyeun Kim ◽  
Willsen Wijaya ◽  
Debes Bhattacharyya
Keyword(s):  
Heat Release ◽  
Ignition Time ◽  
Sandwich Panels ◽  
Radiata Pine ◽  
Core Material ◽  
Fire Performance ◽  
Time To Peak ◽  
The Core ◽  
Honeycomb Cores ◽  
Mechanical Performances

In recent years, the synthetic cores of sandwich panels have experienced an increase in demand to be replaced by environmentally friendly materials. Furthermore, with the stringent fire protocols introduced in the building codes due to recent fire incidents around the world, it is imperative to conduct fire performance studies for all structural materials. The mechanical performances of the different core structures in sandwich panels have been extensively studied and documented in the literature, although the influence of those core structures on the fire reaction properties has not yet been fully understood. The aim of this work is to experimentally investigate, for the first time, the effects of the core structures, namely, corrugated and honeycomb cores manufactured from flax reinforced polymeric composites and radiata pine plywood, on their flammability. A bench-scale cone calorimeter has been employed to measure the fire reaction properties of the two types of materials along with the subsequent effects of the core structures. The orientations of the cores were observed to significantly impact the performances of the samples under fire. The honeycomb cores, with the open cells exposed to the heat flux, generally had better fire performance compared to those of the corrugated cores with higher time to ignition (10 s or more) and time to peak heat release (65 s or more), having almost similar initial masses and peak heat release rates. Furthermore, among the two material systems, the plywood cores outperformed the flax-FRPP cores, specifically in ignition time, smoke production, total heat release and peak heat release rate. The results helped in confirming that the honeycomb cores have overall better fire performance and the use of plywood as the core material is viable even when fire is involved.

scholarly journals Fibers Networks as a New Type of Core Material. Processing and Mechanical Properties

2009 ◽  
Vol 1188 ◽  
Author(s):  
Laurent Mezeix ◽  
Christophe Bouvet ◽  
Serge Crézé ◽  
Dominique Poquillon
Keyword(s):  
Epoxy Resin ◽  
Carbon Fibers ◽  
Sandwich Panels ◽  
Open Architecture ◽  
Core Material ◽  
Cross Linking ◽  
Damping Capacity ◽  
The Core ◽  
Water Accumulation ◽  
Core Materials

AbstractMany different sandwich panels are used for aeronautical applications. Open and closed cell structured foam, balsa wood or honeycomb are often used as core materials. When the core material contains closed cells, water accumulation into the cell has to be taken into account. This phenomenon occurs when in service conditions lead to operate in humidity atmosphere. Then, water vapor from air naturally condenses on cold surfaces when the sandwich panel temperature decreases. This water accumulation might increase significantly the weight of the core material. Core with a ventilated structure helps to prevent this phenomenon. Periodic cellular metal (PCM) has been motivated by potential multifunctional applications that exploit their open architecture as well as their apparent superior strength and stiffness: pyramidal, lattice, Kagome truss or woven. One of the drawbacks of these materials is the expensive cost of the manufacturing. Recently, a novel type of sandwich has been developed with bonded metallic fibers as core material. This material presents attractive combination of properties like high specific stiffness, good damping capacity and energy absorption. Metal fibers bonded with a polymeric adhesive or fabricated in a mat-like form consolidated by solid state sintering. Entangled cross-linked carbon fibers have been also studied for using as core material by Laurent Mezeix. In the present study, ventilated core materials are elaborated from networks fibers. The simplicity of elaboration is one of the main advantages of this material. Multifunctional properties are given by mixing different sorts of fibers, by example adding fibers with good electrical conduction to give electrical conductivity properties. In this study network fibers as core material are elaborated using carbon fibers, glass fibers and stainless steel fibers. In aeronautical skins of sandwich panels used are often carbon/epoxy prepreg, so epoxy resin was used to cross-link fibers. The core thickness was chosen at 30 mm and fibers length was chosen at 40 mm. Entanglement, separation of filaments and cross-linking are obtained in a specific blower room. Fibers are introduced in the blower room, compressed air is applied and in same time epoxy resin is sprayed. Indeed one of the sandwich core material properties required is low density, so yarns size need to be decreased by separating filaments. Network fibers are introduced in a specific mould and then are compressed. The density obtained before epoxy spaying is 150 kg/m3. Finally samples are polymerized at 80°C for 2 hours in a furnace under laboratory air. Compressive behavior is study to determinate the influence of fibers natures and the effect of cross-linking. Reproducibility is also checked.

On the mechanisms of modal damping in FRP/honeycomb sandwich panels

2018 ◽  
Vol 25 (4) ◽  
pp. 649-660
Author(s):  
Aslan Abbasloo ◽  
Mohamad Reza Maheri
Keyword(s):  
Sandwich Panels ◽  
Shear Deformation Theory ◽  
Core Material ◽  
Honeycomb Core ◽  
The Core ◽  
Modal Damping ◽  
Reinforced Plastic ◽  
End Conditions ◽  
Modes Of Vibration ◽  
Bending Ratio

Abstract Sandwich panels made of fibre-reinforced plastic (FRP) skins and a honeycomb core can be effectively damped through the choice of the skin and especially of the core materials. Because the core is often highly damped, a lateral deflection that causes more shearing of the core than bending of the skin increases sandwich damping. Aside from the skin and the core material properties, the shearing/bending ratio depends on a number of other, often interacting, factors, including the sandwich planar as well as transverse dimensions, the particular modal pattern in which the panel vibrates and its relationship to the type of skin layup, as well as the panel end conditions. In the present work, using a simple, first-order shear deformation theory, damping results have been produced for simple modes of vibration of a sandwich panel comprising composite skins and a damped honeycomb core, demonstrating the mechanisms by which the above factors affect the FRP skin/honeycomb core sandwich damping.

Experimental Investigation of the Shear Cutting Behaviour of Sandwich Panels

2015 ◽  
Vol 825-826 ◽  
pp. 433-440 ◽  
Author(s):  
Philipp Stein ◽  
David Übelacker ◽  
Dirk Holke ◽  
Peter Groche
Keyword(s):  
Cutting Force ◽  
Sandwich Panels ◽  
Sheet Thickness ◽  
Cutting Parameters ◽  
Core Material ◽  
Burr Formation ◽  
Exhaust Emission ◽  
The Core ◽  
Design Engineers ◽  
The Face

Continually increasing exhaust emission standards for automobiles and an increasing environmental awareness push design engineers to develop new constructive and material concepts. So-called sandwich panels, consisting of stiff facings and light-weight cores, offer the possibility to combine properties of different materials synergistically. When processing large quantities, as is the case in the automotive industry commonly used manufacturing processes for cutting sandwich panels, like sawing or milling, are not applicable. A common manufacturing process to cut metal sheets in high quantities is shear cutting. However, pre-trials of shear cutting of sandwich panels have shown that it is not possible to achieve flawless cutting surfaces with current process layouts. Characteristic types of failure like high bending of the facings, delamination effects, burr formation and an undefined cracking of the core material were ascertained. Thus, in this study, the influence of cutting parameters, such as the clearance and the punch diameter, on these types of failure is examined. Five different clearances between 0.025 mm and 0.4 mm with two punch diameters, 8 mm and 32 mm, were investigated. In order to compare the influence of different materials, three commercially available sandwich panels were studied. The chosen sandwich panels differ both in the face sheet thickness and the core material. Finally, the shear cutting force is measured to identify a possible correlation between the cutting force and the face bending. As a result, optimal clearances to minimize the face bending are derived. Additionally, the influence of the core stiffness on the cutting force is determined.

scholarly journals Core failure in sandwich structures subjected to water slamming loads

2019 ◽  
Vol 21 (5) ◽  
pp. 1751-1772
Author(s):  
MA Battley ◽  
TD Allen
Keyword(s):  
Transverse Shear ◽  
High Speed ◽  
Failure Modes ◽  
Sandwich Panels ◽  
Core Material ◽  
Polymeric Foams ◽  
Failure Mechanics ◽  
The Core ◽  
High Elongation ◽  
Core Materials

Sandwich composite materials are widely used within the marine industry, particularly as hull panels. Water impact loads, known as slamming, can be very significant for these structures, particularly for high-speed craft. These loadings generate local regions of high transverse shear forces near panel boundaries, which can result in transverse shear failures of core materials. The transient nature of slamming loads can cause stress rates that are high enough to affect the strength of the core material, particularly for polymeric foams. Despite the significant body of work on the constitutive behaviour and failure mechanics of sandwich core materials, there is a lack of understanding of how core materials fail in transverse shear during slamming events. There is also only very limited knowledge of how the core shear strengths measured using standardised, often quasi-static material coupon testing relate to their behaviour in a panel-slamming situation. This paper contributes in two novel areas; controlled experimental characterisation of the failure mechanics of sandwich panels subjected to water slamming to understand and quantify the strength of different polymeric core materials, comparison of the failure modes and transverse shear strength of slam-loaded sandwich panels to predictions from material coupon properties. Core types include low, medium and high elongation polymeric foams. The results demonstrate that the more ductile foams perform better as panel structures under slamming relative to their quasi-static properties compared with the more brittle cores. Prediction of the strength of a panel is shown to be highly dependent on the load distribution and whether the static or dynamic core strength is considered. The results support empirical experience that ductile foams perform well under slamming loads, and that high-elongation materials can perform better in slamming situations than predicted by their quasi-static strengths.

Thermal Aging Effects on Fire Performance of the Cross-Linked Polyethylene Insulated Cable

2017 ◽  
Vol 898 ◽  
pp. 2399-2404 ◽  
Author(s):  
Jin Mei Li ◽  
Jia Qing Zhang ◽  
Qiang Li ◽  
Zi Dong Guo
Keyword(s):  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Thermal Aging ◽  
Ignition Time ◽  
Fire Performance ◽  
Aging Effects ◽  
Insulation Materials ◽  
Insulation Failure ◽  
Failure Temperature

To evaluate the fire performance of the cable in service, the ignition time, heat release rate and insulation failure parameters of the accelerated thermal aging cable on stimulated fire condition were studied. The results show that, the extended ignition time and decreasing peak of heat release rate of the cable in the early stage of aging are the addictive including the lubricant, plasticizer and anti-oxygen. In the aggravating of thermal aging, labile materials with low heating value will be exhausted, while the thermal stability of insulation sheath material decreases, its corresponding ignition time will start to shorten and initial peak of heat release rate will start to rise. The insulation failure temperature of the cable is related with the decomposition temperature of insulation materials of the cable by heating. In each aging stage, the decomposition temperatures of insulation materials by heating are all lower than the insulation failure temperature of the cable for about 10°C. The reason for the insulation failure of the cable is that the ambient heat , gives rise to the decomposition by heating of internal insulation materials of the cable through sheath materials finally under the thermal transmission effect.

Nonlinear thermo-mechanical behaviour of soft core sandwich panels – Creep effects

2018 ◽  
Vol 22 (8) ◽  
pp. 2629-2654
Author(s):  
Ehab Hamed ◽  
Yeoshua Frostig
Keyword(s):  
Sandwich Panels ◽  
Maxwell Model ◽  
Core Material ◽  
Internal Stresses ◽  
Structural Behaviour ◽  
Principle Of Superposition ◽  
The Core ◽  
Generalized Maxwell Model ◽  
The Face ◽  
Incremental Step

Sandwich panels can be subjected to significant changes in ambient temperature, which develop and sustain over certain time periods and lead to creep of the core material, and consequently to changes in the internal stresses and deformations with time. This paper deals with this issue with focus on the geometrically nonlinear aspects of structural behaviour. A theoretical model is developed, which combines the concepts of the principle of superposition of viscoelasticity, with the high-order sandwich theory (HSAPT), and the temperature dependency of the viscoelastic material properties. The nonlinear HSAPT formulation accounts for the deformability of the core in shear and through its thickness and it is based on large displacement kinematics of the face sheets. The convolution integral of viscoelasticity is converted into a rheological generalized Maxwell model after the expansion of the relaxation moduli into Prony series with temperature-dependence terms, which enables the solution of the governing equations through an incremental step-by-step time analysis without the need to store the response history. The capabilities of the model are demonstrated through numerical examples. It is shown that the creep of the core material can lead to bifurcation buckling of the sandwich panel under sustained temperatures that are smaller than the critical temperature obtained under an instantaneous increase of temperature.

Specific Properties of Novel Two-Dimensional Square Honeycomb Composite Structures

2014 ◽  
Vol 695 ◽  
pp. 694-698 ◽  
Author(s):  
Mohd Ruzaimi Mat Rejab ◽  
W.A.W. Hassan ◽  
Januar Parlaungan Siregar ◽  
Dandi Bachtiar
Keyword(s):  
Energy Absorption ◽  
Composite Structures ◽  
Sandwich Structures ◽  
Core Material ◽  
Foam Core ◽  
Specific Strength ◽  
The Core ◽  
Reinforced Plastic ◽  
Honeycomb Cores ◽  
Lightweight Core

Hexagonal honeycomb cores have found extensive applications particularly in the aerospace and naval industries. In view of the recent interest in novel strong and lightweight core architectures, square honeycomb cores were manufactured and tested under uniform lateral compression. A slotting technique has been used to manufacture the square honeycomb cores based on three different materials; glass fibre-reinforced plastic (GFRP), carbon fibre-reinforced plastic (CFRP) and self-reinforced polypropylene (SRPP). As semi-rigid polyvinyl chloride (PVC) foam was placed in each of unit cells to further stiffen the core structure. The core then was bonded to two skins to form a sandwich structure. The compressive responses of the sandwich structures were measured as a function of relative density. In this paper, particular focus is placed on examining the compression strength and energy absorption characteristics of the square honeycombs with and without the additional foam core. Comparisons in terms of specific strength and specific energy absorption have shown that the CFRP core offers excellent properties. The presence of the foam core significantly increases the energy absorption capability of overall structure and the SRPP core could potentially be used as an alternative lightweight core material in recyclable sandwich structures.

scholarly journals Vertically-aligned short E-glass fibre core sandwich composite: Production and evaluation

2021 ◽  
pp. 109963622199388
Author(s):  
Robbie White ◽  
Venkata R Machavaram ◽  
Benjamin A Fernando ◽  
Mark A Paget ◽  
Ashwini Prasad ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Glass Fibre ◽  
Failure Modes ◽  
Fibre Composite ◽  
Sandwich Panels ◽  
Sandwich Composite ◽  
Fibre Bundles ◽  
The Core ◽  
Vertically Aligned ◽  
Honeycomb Cores

This paper reports on the production and evaluation of a new class of “Z-axis” composite sandwich panel where the core consists of a dense array of vertically-aligned, 3 mm long E-glass fibre composite “beams”. The E-glass fibre bundles were aligned using electrostatic charging. A procedure was developed to retain the orientation of the short-fibre bundles whilst they were impregnated and cured with an epoxy/amine resin system. The skins were manufactured from 4-ply carbon/epoxy prepregs with a layup sequence of (0,90)s. The out-of-plane compressive strength of these Z-axis composites was found to be 25.2 and 15.2 times greater than equivalent sandwich panels made with Nomex® and aluminium honeycomb cores respectively. Their compressive strength was found to increase in proportion to the density of the core. Buckling and fracture of the vertically-aligned Z-axis composite were the predominant failure modes observed. The shear and flexural properties of the Z-axis composites were comparable to equivalent honeycomb sandwich panels manufactured from Nomex® and aluminium honeycomb cores.

scholarly journals Flame Retardancy of Lightweight Sandwich Composites

2021 ◽  
Vol 5 (10) ◽  
pp. 274
Author(s):  
Fabienne Samyn ◽  
Roland Adanmenou ◽  
Serge Bourbigot ◽  
Sophie Duquesne ◽  
Maude Jimenez ◽  
...  
Keyword(s):  
Heat Release ◽  
Flame Retardant ◽  
Unsaturated Polyester ◽  
Fire Retardant ◽  
Core Material ◽  
Sandwich Composite ◽  
Cone Calorimetry ◽  
The Core ◽  
The Matrix ◽  
Flame Retarded

This study proposes an innovative solution to flame-retard a sandwich composite made of unsaturated polyester resin, glass fibre skins and polyester nonwoven core material. The strategy uses the core material as flame-retardant carrier, while the resin is also flame-retarded with aluminum trihydroxide (ATH). A screening of the fire-retardant performances of the core materials, covered with different types of phosphorous flame-retardant additives (phosphate, phosphinate, phosphonate), was performed using cone calorimetry. The best candidate was selected and evaluated in the sandwich panel. Great performances were obtained with ammonium polyphosphate (AP422) at 262 g/m2. The core material, when tested alone, did not ignite, and when used in the laminate, improved the fire behaviour by decreasing the peak of heat release rate (pHRR) and the total heat release (THR): the second peak in HRR observed for the references (full glass monolith and sandwich with the untreated core) was suppressed in this case. This improvement is attributed to the interaction occurring between the two FR additives, which leads to the formation of aluminophosphates, as shown using Electron Probe Micro-Analysis (EPMA), X-Ray Diffraction (XRD) and solid-state 31P Nuclear Magnetic Resonance (NMR). The influence of the FR add-on on the core, as well as the ATH loading in the matrix, was studied separately to optimize the material performances in terms of smoke and heat release. The best compromise was obtained using AP422 at 182 g/m2 and 160 phr of ATH.

Homogenization of selective laser melting cellular material for impact performance simulation

2015 ◽  
Vol 6 (4) ◽  
pp. 439-450 ◽  
Author(s):  
G. Labeas ◽  
Evangelos Ptochos
Keyword(s):  
Selective Laser Melting ◽  
Failure Modes ◽  
Sandwich Structures ◽  
Sandwich Panels ◽  
Core Material ◽  
Laser Melting ◽  
Stress Strain ◽  
Content Type ◽  
The Core ◽  
Modelling Approaches

Purpose – The purpose of this paper is to present, the global behaviour of sandwich structures comprising cellular cores is predicted by finite element (FE) analysis. Two modelling approaches are investigated, providing different levels of accuracy; in both approaches, the sandwich structure is idealised as a layered stack with the skin modelled using shell elements; while the core is either modelled with fine detail using beam micro-elements representing the cell struts, or is modelled by three-dimensional solid elements after an appropriate core homogenisation. Design/methodology/approach – The applied homogenisation methodology, as well as the all important modelling issues are presented in detail. Experimental tests performed using a mass-drop testing machine are used for the successful validation of the simulation models. Findings – It was concluded that the core microscale models having detailed FE modelling of the core unit cells geometry with fine scale beam elements are suitable for the analysis of the core failure modes and the prediction of the basic core stiffness and strength properties. It was demonstrated that the homogenised core model provides significant advantages with respect to computing time and cost, although they require additional calculations in order to define the homogenised stress-strain curves. Research limitations/implications – Special microscale material tests are required for the determination of appropriate materials parameters of the core models, as steel selective laser melting (SLM) microstrut properties differ from the constitutive steel material ones, due to the core manufacturing SLM technique. Stress interactions were not taken into account in the homogenisation, as the applied core material model supports the introduction of independent stress-strain curves; however, the predicted load deflection results appeared to be very close to those obtained from the detailed core micromodels. Originality/value – The paper is original. The dynamic behaviour of conventional sandwich structures comprising conventional honeycomb type cores has been extensively studied, using simple mass-spring models, energy based models, as well as FE models. However, the response of sandwich panels with innovative SLM cellular cores has been limited. In the present paper, novel modelling approaches for the simulation of the structural response of sandwich panels having innovative open lattice cellular cores produced by SLM are investigated.

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