Effect of Cell Size on the Fundamental Natural Frequency of FRP Honeycomb Sandwich Panels

Sourabha S. Havaldar, Ramesh S Sharma, Arul Prakash M. D. Antony, Mohan Bangaru

Department of Mechanical Engineering, PES Institute of Technology, Bangalore.
Department of Production Technology, Madras Institute of Technology, Chennai, India.

DOI: 10.4236/jmmce.2012.117048                

Abstract

In the present work, the effect of hexagonal cell size of the core on the fundamental natural frequency of FRP honey-comb sandwich panels has been analyzed both experimentally and by finite element technique. Experimental Modal tests were conducted on hexagonal cell honeycombs ranging in size from 8 mm to 20 mm maintaining the facing thickness constant at around 1mm with two different boundary conditions viz C-F-F-F and C-F-C-F. The traditional “strike method” has been used to measure the vibration properties. The modal characteristics of the specimens have been obtained by studying its impulse response. Each specimen has been subjected to impulses through a hard tipped hammer which is provided with a force transducer and the response has been measured through the accelerometer. The impulse and the response are processed through a computer aided FFT Analyzing test system in order to extract the modal parameters with the aid of software. Theoretical investigations have been attempted with appropriate assumptions to understand the behavior of the honeycomb sandwich panels during dynamic loading and to validate experimental results. Finite Element modeling has been done treating the facing as an orthotropic laminate and Core as orthotropic with different elastic constants as recommended in the literature. The results are presented which show that the theoretical model can accurately predict the fundamental frequency and how honeycombs with difference cell size will perform under dynamic loads.

Keywords

Honeycomb; Modal Testing; FRP; Impulse; Frequency

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	P.H.W.Tsang and P.A.Lagace, “Failure Mechanisms of Impact-Damaged Sandwich Panels under Uniaxial Compression,” 35th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference, Hilton Head, SC, Apr.1994, pp 745-754
[2]	P.A. Lagace and J.E.Williamson, “Contribution of the Core and Facesheet to the Impact Damage Resistance of Composite Sandwich Panels,” 10th DOD/NASA/FAA Conference on Fibrous Composites in Structural Design, Apr. 1994, pp. II53–II74.
[3]	W.S. Burton and A.K. Noor, “Assessment of Computational Models for Sandwich Panels and Shells,” Comp. Meth. Appl. Mech. & Eng., vol. 124, pp. 125–151, 1995.
[4]	W.S. Burton and A.K. Noor, “Assessment of Continuum Models for Sandwich Panel and Honeycomb Cores,” Comp. Meth. Appl. Mech. & Eng., vol. 145, pp. 341–360, 1997.
[5]	T.G. Nieh, “Processing and Modeling of Cellular Solids for Light-weight Structures,” Lawrence Livermore National Lab. Report UCRL-ID-129666, Dec. 1997.
[6]	M.R. Maheri and R.D. Adams, “Steady-state Flexural Vibration Damping of Honeycomb Sandwich Beams,” Composites Science & Technology (UK), vol.53, no.3,pp.333–347, 1994.
[7]	W. Goldsmith and J.L. Sackman, “An Experimental Study of Energy Absorption in impact on Sandwich Plates,” Int, J. Imp. Imp. Eng., vol.12,pp. 241-262,1992.
[8]	W. Goldsmith and J.L. Sackman, “Dynamic Energy Absorption of Sandwich Structures by Inelastic Deformation,” Technical Report: AFOSRTR-91-033, Bolling AFB, DC,Feb. 1991.
[9]	M.K. Neilsen, “Continuum Representations of Cellular Solids.” DOET Technical Report No. Sand-93-1287, Washington, DC Sept. 1993.
[10]	R.D. Adams and M.R. Maheri, “Dynamic Shear Properties of Structural Honeycomb Materials,” Composites Science and Technology (UK), vol. 47, pp. 15–23, 1993.
[11]	Qunli Liu and Yi Zhao, “Role of Anisotropic Core in Vibration Properties of Honeycomb Sandwich Panels”, Journal of Thermoplastic Composite MATERIALS, Vol.15—Jan 2002.
[12]	Robert D Blevins, “Formulas for natural frequencies and mode shape”, Van Nostrand Reinhold company, USA,1979
[13]	XLA Li-Juan, JIN Xian-fing, Wang Yang-bao, “The equivalent analysis of Honeycomb sandwich plates for satellite structure”, www.mscsoft-ware.com, 2001.