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.

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.

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.

The influence of different types of core materials on the impact behaviour of sandwich composites

2018 ◽  
pp. 78-83
Author(s):  
Cihan Kaboglu
Keyword(s):  
Sandwich Structures ◽  
Core Material ◽  
Sandwich Composite ◽  
Balsa Wood ◽  
Impact Behaviour ◽  
The Core ◽  
Glass Fibre Reinforced Polymer ◽  
Glass Fibre Reinforced ◽  
The Impact ◽  
Core Materials

Sandwich structures are popular in applications in which the weight of the component affects the efficiency, especially in the aviation and aerospace industries. This study aims to understand the impact behaviour of sandwich structures with different core materials. Sandwich structures are manufactured with glass fibre reinforced polymer skins and balsa wood, polyethylene terephthalate (PET) and polyvinyl chloride (PVC) core through resin infusion under flexible tools. Three different core materials were tested and compared using the damaged area of the back face of the sample. The effect of the core materials on the mechanical behaviour of the structures is crucial. The results showed that the microstructure of the core materials plays an important role, because althoughthe density of balsa wood is greater than the density of PET and PVC, the structures having PVC and PET as core materials undergo less damage than those having balsa wood as a core material. Keywords: Sandwich composite, impact behaviour, core materials.

Preparation and Properties of a Novel Water Soluble Core Material for the Resin Transfer Molding Process

2011 ◽  
Vol 306-307 ◽  
pp. 844-847
Author(s):  
Quan Zhou Li ◽  
Xiao Qing Wu
Keyword(s):  
Compressive Strength ◽  
Resin Transfer Molding ◽  
Water Soluble ◽  
Core Material ◽  
Molding Process ◽  
Transfer Molding ◽  
The Core ◽  
Rtm Process ◽  
Binder Solution ◽  
Core Materials

A novel water soluble core material composed of alumina, quartz sand, kaolin, gypsum powder and the solution of binders was prepared. The influence of different mass concentration of Polyethylene Glycol (PEG) binder solution and sodium silicate compounded (SS) binders solution on water soluble performance and compressive strength of the core materials was investigated, respectively. The results show that the compressive strength and solubility rate of the core materials, with the concentration of 30% of SS binders solution, are 1.023MPa and 0.24g/s respectively, which is satisfied for the requirements of Resin Transfer Molding (RTM) process completely.

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.

Effect of Envelope Films on Thermal Properties of Vacuum Insulation Panels with Glass Fiber

2011 ◽  
Vol 415-417 ◽  
pp. 859-864 ◽  
Author(s):  
Wang Ping Wu ◽  
Zhao Feng Chen ◽  
Jie Ming Zhou ◽  
Xue Yu Cheng
Keyword(s):  
Thermal Conductivity ◽  
Glass Fiber ◽  
Core Material ◽  
Type I ◽  
Type Ii ◽  
The Core ◽  
Vacuum Insulation ◽  
Porosity Ratio ◽  
Thermal Conductivities ◽  
Core Materials

The VIPs consist of the glass-fiber core material and two types of envelope film. The glass fiber was fabricated by a centrifugal blowing process. The core material was prepared by the wet method. The thermal conductivities of the materials were measured by the heat flow meter. The microstructure of the envelope film was observed by scanning electron microscopy. The porosity ratio and largest pore size diameters of the core materials are 92.27% and 20μm, respectively. The thermal conductivity of the VIP is about 8-10 times higher than that of the core materials. The thickness of type I and II envelope films are 45μm and 400μm, respectively. The thermal conductivities of the type I and type II envelope films are 0.11W/(m•K) and 0.69W/(m•K), respectively. The thermal conductivity of the VIP with type II envelope is higher than that of the VIP with type I envelope, which is attributed to the different structures and thickness of the envelope film.

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 Preparation and Self-Repairing Properties of Urea Formaldehyde-Coated Epoxy Resin Microcapsules

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Xiaoxing Yan ◽  
Yijuan Chang ◽  
Xingyu Qian
Keyword(s):  
Epoxy Resin ◽  
Deposition Time ◽  
Urea Formaldehyde ◽  
Coverage Rate ◽  
Core Material ◽  
Self Healing ◽  
Mass Ratio ◽  
Repair Rate ◽  
The Core ◽  
Five Factors

Urea formaldehyde resin-coated epoxy resin microcapsules were prepared by two-step in situ polymerization. The effects of five factors on the yield, coverage rate, repair rate, and morphology of the microcapsules were investigated by five factors and four levels of orthogonal test. These five factors were the mass ratio of the core to the wall material (Wcore:Wwall), the mass ratio of the emulsifier to the core material (Wemulsifier:Wcore), stirring rate, deposition time, and mass ratio of the emulsifier solution to the core material (Wemulsifier solution:Wcore). The ideal technological level of microcapsule synthesis was determined. According to the results of the range and variance of yield, coverage rate, and repair rate, the comprehensive properties of microcapsules became ideal. At this time, the Wcore:Wwall was 0.8 : 1, Wemulsifier:Wcore was 1 : 100, stirring rate was 600 r/min, deposition time was 32 h, and Wemulsifier solution:Wcore was 8 : 1. When the concentration of microcapsules in the epoxy resin was 10.0%, the self-repair rate was the best and the repair rate was 114.77%. This study is expected to provide a reference value for the preparation of a microcapsule self-healing technology and lay a foundation for the subsequent development of self-healing materials.

EFFECT OF ALLOYING ELEMENTS ON CORROSION POTENTIAL AND CORROSION PROPAGATION PROCESS OF MULTILAYER ALUMINUM-BRAZED SHEET

2019 ◽  
Vol 26 (07) ◽  
pp. 1850224
Author(s):  
LONGJUN GUO ◽  
JIHUI WANG ◽  
WENBIN HU ◽  
DEJING ZHOU
Keyword(s):  
Corrosion Potential ◽  
Ion Beam ◽  
Test Method ◽  
Alloying Elements ◽  
Core Material ◽  
Propagation Process ◽  
Exfoliation Corrosion ◽  
The Core ◽  
Corrosion Propagation ◽  
Core Materials

The cross-sectional depth microstructure profiles for a multilayer AA4045/AA3003*/AA4045 brazed sheet were observed and determined by focused ion beam-transmission electron microscopy (FIB-TEM) and energy dispersive spectrometer (EDS). The corrosion propagation of the multilayer brazed sheet in the sea water acidified accelerated test (SWAAT) was investigated by electrochemical impedance spectroscopy (EIS). The measured corrosion potentials of different layers of the multilayer aluminum sheet have been carried out according to ASTM G69-97 standard test method. To reveal the effect of the alloying elements on corrosion behavior, the theoretical corrosion potential of the band of dense precipitates (BDP) zone and core materials was also calculated according to the theoretical corrosion potential model. The electrochemical results showed that there were potential differences between the precipitates free zone (PFZ) and BDP zone as well as BDP zone and the core materials. The EIS test and equivalent circuits (EC) suggested that the capacitive time constant at low frequencies correspond to the corrosion of the BDP zone in the form of exfoliation corrosion. The corrosion propagation process could be identified into four stages: the dissolution of the eutectic [Formula: see text]-Al in the re-solidified cladding in the form of pitting corrosion; the corrosion of the primary [Formula: see text]-Al grain boundaries in the form of inter-granular corrosion (IGC); the corrosion of the BDP zone in the form of exfoliation corrosion; and the corrosion of the core material in the form of IGC.

Analysis of Physical and Mechanical Properties of A3003 Aluminum Honeycomb Core Sandwich Panels

2017 ◽  
Vol 867 ◽  
pp. 245-253 ◽  
Author(s):  
S. Rajkumar ◽  
B. Arulmurugan ◽  
M. Manikandan ◽  
R. Karthick ◽  
S. Kaviprasath
Keyword(s):  
Mechanical Properties ◽  
Sandwich Panels ◽  
Physical And Mechanical Properties ◽  
Honeycomb Core ◽  
Shear Moduli ◽  
The Core ◽  
Industrial Sectors ◽  
Aluminum Honeycomb ◽  
Strength And Stiffness ◽  
Core Materials

The demand for lightweight structures made of sandwich panels is ever increasing in many Industrial sectors. Numerous research efforts have been taken by various researchers in this area in terms of weight and cost reduction. Sandwich panel is a composite structure and it is an excellent alternative material in place of weight reduction without sacrificing its strength and stiffness characteristics. The geometrical characteristics of honeycomb core sandwich panels as well as their physical and mechanical properties such as compressive strength, flexural stiffness, core shear moduli, shear strength and stiffness are analyzed. The sandwich panels are available in various shapes and sizes to the service requirement. The commercially available sandwich panels have different core materials such as foams, FRPs and metallic and non metallic materials. The structure of the core typically varies as truss type and honeycomb. The face sheets and the core materials are bonded using thermo-set resins.

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