Light-weight sandwich panel honeycomb core with

Light-weight sandwich panel honeycomb core with hybrid carbon-glass fiber composite skin for electric vehicle application Sukmaji Indro Cahyono, Angit Widodo, Miftahul Anwar, Kuncoro Diharjo, Teguh Triyono, A. Hapid, and S. Kaleg Citation: AIP Conference Proceedings 1717, 040025 (2016); doi: 10.1063/1.4943468 View online: http://dx.doi.org/10.1063/1.4943468 View Table of Contents: http://scitation.aip.org/content/aip/proceeding/aipcp/1717?ver=pdfcov Published by the AIP Publishing Articles you may be interested in Properties of glass/carbon fiber reinforced epoxy hybrid polymer composites AIP Conf. Proc. 1728, 020238 (2016); 10.1063/1.4946289 Effect of temperature on the dynamic characteristics of the glass-carbon fiber hybrid composites AIP Conf. Proc. 1717, 040023 (2016); 10.1063/1.4943466 Damping of flexural vibrations in glass fibre composite plates and honeycomb sandwich panels containing indentations of power-law profile Proc. Mtgs. Acoust. 18, 030004 (2014); 10.1121/1.4776154 Damping of flexural vibrations in glass fiber composite plates and honeycomb sandwich panels containing indentations of power-law profile J. Acoust. Soc. Am. 132, 2041 (2012); 10.1121/1.4755506 Acoustical characteristics of honeycomb sandwich composite panels. J. Acoust. Soc. Am. 129, 2415 (2011); 10.1121/1.3587879

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Light-weight Sandwich Panel Honeycomb Core with Hybrid Carbon-Glass Fiber Composite Skin for Electric Vehicle Application Sukmaji Indro Cahyono1,a), Angit Widodo2,b), Miftahul Anwar1,c), Kuncoro Diharjo1,d), Teguh Triyono1,e), A Hapid2,f) , S Kaleg2, g) 1

Department of mechanical engineering Sebelas Maret University. Jl.Ir.Sutami 36A, Kentingan, Surakarta 57126, Central Java, Indonesia 2 Power electricity and mechatronic research center LIPI Jl.Sangkuriang komplek LIPI, Bandung 40135, west Java, Indonesia a)

Corresponding author: [email protected] b) [email protected], c) [email protected], d) [email protected]. e) [email protected] f) [email protected], g) [email protected]

Abstract. The carbon fiber reinforced plastic (CFRP) composite is relative high cost material in current manufacturing process of electric vehicle body structure. Sandwich panels consisting polypropylene (PP) honeycomb core with hybrid carbon-glass fiber composite skin were investigated. The aim of present paper was evaluate the flexural properties and bending rigidity of various volume fraction carbon-glass fiber composite skins with the honeycomb core. The flexural properties and cost of panels were compared to the reported values of solid hybrid Carbon/Glass FRP used for the frame body structure of electric vehicle. The finite element model of represented sandwich panel was established to characterize the flexural properties of material using homogenization technique. Finally, simplified model was employed to crashworthiness analysis for engine hood of the body electric vehicle structure. The good cost-electiveness of honeycomb core with hybrid carbon-glass fiber skin has the potential to be used as a light-weight alternative material in body electric vehicle fabricated.

INTRODUCTION The recent trends in vehicle design are toward lightweight of vehicles to improve energy efficiency and reduce gas emissions. However, for a decade, the trends are toward higher safety performance, comfort level, highefficiency and low cost, which all major demands. Therefore the weight of vehicle must be light to reduce energy consumption and reserve collision safety requirements. The vehicle safety capacity is observed to protect passage in car accident from front-end collision [1,2,3,4]. The side members of the front-end vehicles body are mainly strength materials that absorb energy by received axis loading. The light weight material such as aluminum and carbon fiber reinforce plastic (CFRP) have been used in automotive industries due to its material properties, but the production cost is relative high. Previous research, hybrid carbon-glass fibers (HCGF) composite in certain volume fraction have reach optimal material properties with a reasonable production cost [1,2]. The application of the hybrid carbon-glass fiber to build component of the body electric car has been done. It made of fully fiber composite with two layer profile sheet; outer body and inner body. Outer and inner bodies are attached by resin bonding and aluminum rivet as joining. The space between outer and inner body are varied by profile shape, the average space distance are 50 mm. The electric car component such as engine hood, floor and battery pack cover are need lower thick layer/single layer of composite, stronger structure and high impact energy absorber. Honeycomb sandwich is conducted to solve this problem. Honeycomb sandwich structure consist of a thick layer (core) intercalated between thin-stiff layers (skin). Honeycomb sandwich core are cellular solid [2, 4] that used void to decrease mass, while maintain qualities of

Sustainable Energy and Advanced Materials AIP Conf. Proc. 1717, 040025-1–040025-5; doi: 10.1063/1.4943468 © 2016 AIP Publishing LLC 978-0-7354-1365-8/$30.00

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stiffness and energy absorption. Honeycomb sandwich composite are increasingly being used to replace traditional material in highly loaded application such as automotive [4, 5, 6]. The present paper was evaluated the flexural properties and bending rigidity of various volume fraction hybrid carbon-glass fiber composite skins with the honeycomb core. The combination Honeycomb sandwich and HCGF has the potential to be used as a light weight material.

EXPERIMENT STUDIES Material specification and composite sandwich fabrication Specifications of raw material are listed in table 1. Multi-purpose epoxy resin BQTN 157 and methyl ethyl ketone peroxide (Mexpo) catalyst was used as matrix of specimens. The 8 mm Polypropylene (PP) honeycomb as sandwich core, uniform woven carbon fiber and non-uniform glass fiber as filler is purchased in PT.Justus Kimia Raya Semarang Indonesia. Material CFRP GFRP

TABLE 1. Tensile modulus and tensile strength Tensile modulus (GPa) Tensile Strength (MPa) 50,2-147 597-2390 9,1-26,7 108-321

Polypropylene honeycomb core height 8 mm is chosen due to its strong and flexibility in bending load to create car body profile. Honeycomb PP cannot be applied on angle profile of car body due to the maximum bending angle is limited. The both of surface layer the honeycomb have a thin sheet of woven PP to reduce resin trap inside the honeycomb core. The resin trap should be avoided to reduce weight and to raise accuracy of mixing ratio fillermatrix.

FIGURE 1. Manufacturing process of sandwich panel honeycomb core with hybrid carbon-glass fiber composite skin by hand lay-up method

The fabrication of specimens started by calculate volume fraction ratio all component; carbon/glass fiber and mixing resin-catalyst to make lower skin of honeycomb, see fig.1. Hybrid composite skins are made by hand lay-up method and then put the PP-honeycomb core above it, press it until the thickness of composite skin become 3 mm and hold until dry. The upper composite skin is also made by similar method. Finishing step is cut the specimen following standard test and put inside oven in 65oC for 30 minutes to get optimal dry, see fig.2.


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(b)

FIGURE 2. (a) Schematic diagram of a sandwich panel honeycomb core with hybrid carbon-glass fiber composite skin, (b) photo of three specimens and PP core of sandwich panel.

Sandwich panel honeycomb core with hybrid carbon-glass fiber composite skin Experiment on flexural properties and bending rigidity of was performed in order to provide higher the mechanical properties and to decrease the fabrication cost. A specimen consists of from bottom side a uniform woven carbon fiber sheet, non-uniform glass fiber, PP woven, PP honeycomb, PP woven, non-uniform glass fiber and a uniform woven carbon fiber sheet. The non-uniform glass fiber thickness is varied according to the expected volume fraction ratio of carbon/glass fiber. The variables of volume fraction ratio of carbon/glass fiber are 20/80%, 30/70% and 50/50%. Hybrid carbon-glass fiber composite as honeycomb skin are put on above and below PP honeycomb fig.1. The volume ratio of hybrid fiber/polyester resin is constant 60/40 % for all variables. The higher volume fraction of glass fiber means the volume fraction of carbon fiber is decreased. The carbon fiber tensile strength and the cost are higher than glass fiber, but the weight of the carbon fiber is lower than glass fiber [1].

EXPERIMENTAL DESIGN AND TESTING The honeycomb core shear properties were tested in accordance with ASTM C273/C273M-07a. Flexural properties of sandwich panel hybrid carbon/glass fiber composite with honeycomb core were tested according with ASTM D7250-06 and using ASTM c393-94 as standard loading on universal testing machine. The geometry of sandwich panel for flexural testing is 60mm wide and 160mm long. Three Point Bending test schematic configuration is described in fig.3. To prevent premature damage due to stress concentration, three steel loading blocks are covered by rubber pads.

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(b)

FIGURE 3. Physical and flexural properties of the hybrid carbon-glass fiber composite/honeycomb core sandwich panels are tested by using universal testing machine, (a) Three Point Bending test schematic configuration and dimension and (b) the universal testing machine.

RESULT AND DISCUSION Every variable is repeated five times to rise-up the accuracy of the test. Figure 4 (a) and (b) show similar trend that lower volume fraction ratio of carbon fiber are affected decrease to the tensile strength and tensile modulus. Compare with CFRP and GFRP properties table 1, the tensile modulus of the test result is in the middle of them. The experiment of three point bending test was conducted. Figure 4 (c) also shows that, lower volume fraction ratio of carbon fiber FRP affected the decrease of bending load.


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(b)

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FIGURE 4. Tensile strength of hybrid carbon/glass fiber composite (a). Tensile modulus of hybrid carbon/glass fiber composite (b). The three point bending test result of hybrid carbon-glass fiber composite/honeycomb core sandwich panels (c). The raw bending test data of 50/50% volume fraction ratio carbon/glass FRP comes from universal testing machine.

Structural simulation of engine hood electric car Crash simulation is conducted to improve the performance of applied sandwitch honeycomb composite material . The structure of honeycomb core are 5 mm hexagonal. To reduced error caused by size of mesh and rise complecity of the structure. The honeycomb model for structural simulation is simplified by single solid layer. Structure Figure 5(a) showed that carbon/glass FRP without honeycomb panel are more elastic, this mechanical properties become problem when it used to build a body electric vehicle. It need thicker, heavy and also cost. In fig.6 (a) safety factor of carbon/glass fiber composite without honeycomb panel is under 5 when the crush loads more than 30kN. It means the sandwich honeycomb core panel with hybrid carbon/glass fiber is safer.

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(b)

FIGURE 5. Varied crash load in the structural simulation are resulted; (a) Trend line graph of maximum displacement are increased if the crash loads are increased. (b) The maximum stress of sandwich honeycomb panel in varied crash load.


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(b)

FIGURE 6. (a) The Safety factor is decrease while the crash load is increased. (b) The distribution crash force simulation in engine hood of body electric vehicle.

CONCLUSION The mechanical properties of hybrid carbon/glass fiber, both of tensile strength and tensile modulus are better than GFRP and also lower price compare with fully CFRP. The hybrid carbon/glass fiber with PP honeycomb panels are more rigid than C/G-FRP without honeycomb. This is suitable for engine hood of body electric vehicle. Compare with the present manufacturing, the engine hood body feel plastic, weak and need thicker layer/profile to solve it. From structural simulation, the addition of sandwich panel are effected the factor of safety increase. It means the structure is stronger than without sandwich panel. The addition of sandwich panel also effected the material become rigid, The impact test is needed to know the energy absorber of sandwich.

ACKNOWLEDGMENT Grand-in-Aid from Ministry of Research Education and Culture 339/UN27.11/PL/2015)

Republic Indonesia

(PUSNAS

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