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IJRMET Vol. 4, IssuE spl - 1, NoV 2013 - ApRIl 2014

w w w . i j r m e t . c o m InternatIonal Journal of research In MechanIcal engIneerIng & technology 19

ISSN : 2249-5762 (Online) | ISSN : 2249-5770 (Print)

Numerical Simulation to Study the Effect of Core Type on Impact Performance of Honeycomb Sandwich Panel

1Ch. Naresh, 2A. Gopi Chand, 3K. Sunil Ratna Kumar, 4P.S.B.Chowdary1,3,4Dept. of ME, Sir C.R.Reddy College of Engineering, Eluru, AP, India

2Dept. of ME, Sri Venkateswara University College of Engg., S. V. University, Tirupathi, AP, India

AbstractHoneycomb sandwich panels are finding a lot of application in current day to day scenario. They are being used in submarines in deep under water to aero planes in the air. The advantage of using the honeycomb sandwich panels is their high strength to weight ratio. Modelling the impact behaviour of the sandwich panels provides valuable information during design of the panels. In the current work, dynamic behaviour of the sandwich panels is modelled when the panels are subjected to impact loading. The effect of core shape on the behaviour of the panels during impact loading is studied numerically by using FE techniques. Simulations are carried out using Ansys workbench. The results are compared to that of a plate. It is found that in sandwich panels, the failure is due to local indentation while that of a plain sheet is due to global deformation. Also in sandwich panels it is found that the failure is only the face sheet taking the impact.

KeywordsCopper, Stainless Steel, Pro-E and Ansys

I. IntroductionSandwich panels are having a wide area of applications. They are used in under water vehicles, Automobiles, Railways and in aircrafts. Euro-Composites [16] in their presentation detailed the use of honeycomb structures in railways. David [8] performed and extensive literature survey regarding the use of composite materials in high speed rail cars. U.S. Department of Transportation [9] investigated the use of composite panels in aviation sector. Hexcel Composites [11] in their technical report also detailed the applications of honeycomb sandwich panels. The main advantage of the sandwich panels comes from their high strength to weight ratio. This is because of the structure of the sandwich panels. A sandwich panel consists of a core sandwiched between two facing sheets. Fig. 1 shows three types of sandwich panels: Corrugated, Foamed and Honeycomb sandwich panels. It can be observed that in each, the core is sandwiched between two facing sheets. Most generally, the core material is a soft materials like aluminium, copper etc. while the facing materials are hard materials like Stainless steel, Mild steel, Aluminium (when aluminium core is used). The main advantage of the sandwich panels is their low weigh, high stiffness, high durability and production cost savings [11]. Numerical investigation into the behaviour of the sandwich panels is very much necessary for design purposes. A lot of investigation has been carried out in this regard. Numerical formulations for modelling the behaviour of sandwich panels under static loading are presented in [11] along with examples.

Fig. 1 (a): Corrugated Sandwich Panel

Fig. 1(b): Foamed Sandwich Panel

Fig. 1(c): Honeycomb Sandwich Panel

Using these expressions various stiffness constants can be evaluated. Achilles Petras [13] investigated the failure modes of sandwich beams of GFRP panels and Nomex honeycombs. Failure mode map for loading under 3 - Point bending, is constructed showing the dependence on failure mode map and load on the ratio of skin thickness to span length and Honeycomb relative density. High - Order Sandwich Beam Theory (HOSBT) applied to study the response of the beam under 3 - Point bending. Contact stress distribution between the interface and the top skin as well as its importance in the indentation process investigated. James G. Ratcliffe, et al [15] developed a 1-dimensional material model was developed for simulating the transverse (thickness-direction) loading and unloading response of aluminium honeycomb structure. The model is implemented in ABAQUS using UMAT models. Comparison of these analysis results with data from these experiments shows overall good agreement. These models are specifically used for quasi-static bending. I. G. Masters and K. Evans [14] proposed mathematical models using which elastic constants of honeycomb sandwich panels can be evaluated. These constants were further used to predict the behaviour of the sandwich panels.According to Horrigan and Aitken [12], the main drawback of sandwich structure is its low resistance to impact damage and the extent to which the strength of the structure is reduced under compressive loading. A continuum damage model is used by them to model crushing due to impact. The material behaviour in compression is described by a combination of three constitutive models namely elastic, continuum damage and inelastic strain accumulation. Chang Qi, et al [2] studied the dynamic behaviour of honeycomb sandwich panels with reentrant auxetic honeycomb core under high velocity projectile impact. It is found that the core’s negative poisson’s ratio is the cause of its best ballistic resistance. Gopi Chand, et al [3] studied the behaviour of honeycomb sandwich panel under 3-point bending both experimentally and numerically. FE simulations are performed on the model. Solid

IJRMET Vol. 4, IssuE spl - 1, NoV 2013- ApRIl 2014 ISSN : 2249-5762 (Online) | ISSN : 2249-5770 (Print)

w w w . i j r m e t . c o m 20 InternatIonal Journal of research In MechanIcal engIneerIng & technology

elements are used during simulation. The numerical formulation discussed by them showed good agreements with FE simulation results. Castanié [4] proposed a multi-level approach to study the behaviour of honeycomb sandwich panel response under low impact loading. Kantha Rao, et al [5] compared the bending behaviour of Aluminium honeycomb sandwich panel with that of a plain aluminium sheet when both are subjected to 3 – point bending. Using FE simulations He Lee [6] simulated the impact of a rigid ball on aluminium honeycomb sandwich panel. Paulius GRIŠKEVICIUS, et al [7] performed an experimental investigation of deformation behaviour of sandwich structures with honeycomb core in the cases of quasi-static and dynamic loading in this study. During the study, the composites are made of non – metallic materials. Numerical modelling by finite element method of sandwich structures behaviour under impact loading was performed. Haydn N. G. Wadley studied the response of square honeycomb structures when subjected to underwater impact loading. Aboura, et al [1] performed simulations for studying the response of a card board corrugated composite panels using both solid and shell elements. He found that the results of both showed not much difference except that the use of solid elements is computational intensive. In the current work, investigation is carried out to study the effect of core shape on the behaviour of sandwich panel when subjected to impact loading. Two core types are considered and the responses of these panels are compared to that of a plain sheet of equal weight and dimensions.

II. Problem DefinitionImpact can be defined a large force acting for a very small time [17]. Designing for impact resistance is a major factor. Experimental testing is a costly process. Simulations prove to be handy during this situation. In the current work, as mentioned in the previous section, the effect of cell shape during impact loading is studied. For this purpose two different core shapes are considered, namely, square and hexagonal cores. Fig. 2 shows the two cores with dimensions. The aim of the work is to find which core has best response. These results are also compared with that of a plain SS sheet having same weight and dimensions (length and width) as that of the square honeycomb panel.

Fig. 2: (a). Square Honeycomb structure

Fig. 2(b): Hexagonal Honeycomb Structure

III. Materials and Boundary ConditionsThe face sheets are assigned with Stainless steel and the core is assigned copper material. The impact load is assumed to be acting at the middle of the panel. The models are created in Pro/E and then imported into Ansys Workbench. Meshing is performed in Ansys using solid elements. Fig. 3 (a), (b) & (c) show the meshed models. Fig. 2 shows the loading and boundary conditions. Fig. 4 shows the variation of the force with time. Three magnitudes of impact are considered during the analysis: 1kN, 2kN and 5kN. Transient analysis is performed to study the impact behaviour of the panels. Results are presented in the next section.

Fig. 3(a): Meshed Model of the Square Honeycomb Core

Fig. 3(b): Meshed Model of Hexagonal Honeycomb Core




Fig. 3(c): Meshed Model of Plate

Fig. 4: Variation of Impact Force With Time

IV. Results and DiscussionsTransient analysis is performed on each model for each load. The responses of each model for each load are studied. Initially for 1kN load, the displacement and stresses are compared for three cases. During the comparison, it was found that the deformation was more for Simple Sheet. The deformation is about 1.2 mm which is more when compared to that of hexagonal honeycomb sandwich (0.742mm) and Square Honeycomb (0.404mm) panels. Also from the deformation plots, it is observed that the deformation was global for simple sheet while the deformation is local for honeycomb sandwich panels. Deformation plots of various panels at this load are given in fig. 6.

Fig. 5: Deformation of 3 Panels Under 1kN Impact Loading

Fig. 6(a): Deformation of Plain Sheet Under 1kN Impact Loading

Fig. 6(b): Deformation of Hexagonal Sandwich Panel Under 1kN Impact Loading

Fig. 6(c): Deformation of Plain Sheet Under 1kN Impact Loading

Since deformation is only local in honeycomb sandwich panels, it is decided to go with further loading of the sandwich panels. The response of these panels were studied under 2kN and 5kN loads. During this study, it was found that the deformations were more in Hexagonal honeycomb than when compared to that of Square honeycomb. This is mainly because of the larger cell area for the same cell side length in hexagonal honeycomb when compare to that of square honeycomb. Fig. 7(a) shows the comparative graphs

IJRMET Vol. 4, IssuE spl - 1, NoV 2013- ApRIl 2014 ISSN : 2249-5762 (Online) | ISSN : 2249-5770 (Print)

w w w . i j r m e t . c o m 22 InternatIonal Journal of research In MechanIcal engIneerIng & technology

for deformation in both the cases for various loads. It may be noted that the high deformation observed in both the panels was on the load bearing face sheet while on the other side, the deformation was minimum indicating the deformation to be local. This can be observed in deformation plots for hexagonal honeycomb panel in fig. 8. Fig. 7(b) show the stress plots for both hexagonal and square honeycomb sandwich panels. It can be seen that the stresses are also higher for hexagonal honeycomb sandwich panels. This is mainly because of large deformation in load bearing facing sheet for hexagonal honeycomb sandwich panel which is due to larger cell area when compared to that of square honeycomb sandwich panel. Based on the results and comparative plots, it can be observed that the square honeycomb sandwich panels have better response when compared to that of hexagonal honeycomb sandwich panels

Fig. 7(a): Deformation Comparison for Square and Hexagonal Honeycomb Panels

Fig. 7(b): Stress Comparison for Square and Hexagonal Honeycomb Panels

Fig. 8(a): Deformation on the Load Bearing Face Sheet in Hexagonal Honeycomb Sandwich Panels (Deformation is 0.74mm)

Fig. 8(b): Deformation on the Non - Load Bearing Face Sheet in Hexagonal Honeycomb Sandwich Panels (Deformation is 0.42mm)

V. ConclusionA study of dynamic response of Square and Hexagonal honeycomb sandwich panels subjected to impact loading is performed in this work. The models are created in pro/e and then imported into Ansys. Impact load may be defined as a large force acting for a very small time. Thus to study the behaviour, transient analysis is performed. The analysis is carried on plain sheet, hexagonal honeycomb and square honeycomb sandwich panels. During the study at load of 1kN, it is observed that the deformation was high and global for plain sheet while local for the sandwich panel. In other words, the sandwich panels were subjected to local indentation. Further investigation was carried out into behaviour of honeycomb sandwich panels for higher loads which showed that square honeycomb sandwich panels showed lower deformation and stresses when compared to hexagonal sandwich panels indicating a better performance of the square honeycomb sandwich panels. Also during the study it is observed that the indentation is only on the load bearing face sheet while there is lesser deformation on the other face sheet.

References[1] Z. Aboura, N. Talbi, S. Allaoui, M.L Benzeggagh,"Elastic

behavior of corrugated cardboard: Experiments and Modeling", Composite Structures, 63(1), pp. 53-62, 2013.

[2] Chang Qi, Shu Yang, DongWang, Li-Jun Yang,"Ballistic Resistance of Honeycomb Sandwich Panels under In-Plane High-Velocity Impact", The Scientific World Journal, 2013.

[3] A.Gpoichand, R.Mohanrao, N.V.S Sankar, G.Rama Balaji, P.Sandeep Kumar,"Design and Analysis of Copper Honeycomb Sandwich Structure", International Journal of Engineering and Advanced Technology, 2(4), pp. 635-638, 2013.

[4] B. Castanié, Y. Aminanda, C. Schwob,"Modeling of Impact on Sandwich Structures for Fast Maintenance loops", ICAS 2012.

[5] K. Kantha Rao, K. Jayathirtha Rao, A.G.Sarwade, B.Madhava Varma,"Bending Behavior of Aluminum Honeycomb Sandwich Panels", International Journal of Engineering and Advanced Technology, 1(4), pp. 268 - 272, 2012.




[6] He Lei,"Composite Sandwich Structures With honeycomb Core Subjected To Impact", Graduate School of Clemson University, Master’s Thesis, 2012

[7] Paulius GRIŠKEVICIUS, Daiva ZELENIAKIENE, Vitalis LEIŠIS, Marian OSTROWSKI,"Experimental and Numerical Study of Impact Energy Absorption of Safety Important Honeycomb Core Sandwich Structures", Materials Science, 16(2), pp. 119 - 123, 2010.

[8] David Wennberg,"A Light Weight Car Body for High-Speed Trains", 2009.

[9] Federal Aviation Administration,"Structural Testing and Analysis of Honeycomb Sandwich Composite Fuselage Panels", U.S. Department of Transportation, 2008.

[10] Haydn N. G. Wadley, Kumar P. Dharmasena, Doug T. Queheillalt, Yungchia Chen, Philip Dudt, David Knight, Ken Kiddy, Zhenyu Xue, Ashkan Vaziri,"Dynamic Compression of Square Honeyccomb structures during underwater impulse loading", Journal of Mechanics of Materials, 2(10), pp. 2025-2048, 2007.

[11] Hexcel Composites,"HexWebTM Honeycomb design technology", Technical Report, 2000.

[12] D.P.W. Horrigan, R.R Aitken,"Finite Element Analysis of Impact Damaged Honeycomb Structures", LUSAS User conference, 1999.

[13] Achilles Petras,"Design of sandwich structures", Robinson College, Cambridge University, Doctoral Thesis, 1998.

[14] I. G. Masters, K. E. Evans,"Models for the elastic deformation of honeycombs", Composite Structures, 35, pp. 403-422, 1996.

[15] James G. Ratcliffe, Michael W. Czabaj, Wade C. Jackson, "A Model for Simulating the Response of Aluminum Honeycomb Structure to Transverse Loading", Proceedings of the American Society for Composites – Twenty-Seventh Technical Conference

[16] EURO-COMPOSITES, "Presentation RAIL", www.euro-composites.com

[17] [Online] Available: http://www.en.wikipedia.org/wiki/Impact_%28mechanics%29

Ch.Naresh was born in Antervedi kara in India, on Feb 10, 1988. He was graduated from Sagi Ramakrishnam Raju Engineering College, Bhimavaram in 2010 and student of M.E MACHINE DESIGN at SIR C.R Reddy college of Engineering, India. His areas of interest are Design, Strength of Materials related topics.

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