Structural Performance of Eco-Core Sandwich Panels

  • Kunigal ShivakumarEmail author
  • Huanchun Chen


Eco-Core, a fire resistant core material for sandwich composite structures developed under the US Navy (ONR) program, was used to study its performance as a sandwich beam with glass/vinyl ester face sheet. Performance of Eco-Core was compared with balsa and PVC core sandwich panels. Test specimens were designed to simulate shear, flexural, and edgewise compression loadings. These tests were conducted on Eco-Core as well as balsa and PVC sandwich composite specimens. Failure loads and modes were compared with each other and the analytical prediction. Both Eco-Core and balsa cored sandwich beams had similar failure modes in all three test conditions. In the case of transversely loaded (four-point) beams Eco-Core specimens failed by core shear for span/depth (S/d) ratio less than 4 and the failure mode changed to core tension for S/d >4. This is attributed to weak tensile strength of the core material. An expression for core tension failure load based on beam theory was derived. On the other hand, ductile materials like PVC failed by core indentation. Under edgewise compression, face sheet microbuckling and general buckling are the two potential failure modes for Eco-Core and balsa core sandwich composites. For specimen length/depth ratio L/d <7 the failure is by face sheet microbuckling, for 7 ≤L/d ≤13 the failure is a combination of face sheet microbuckling, debonding and buckling, and for L/d >13 the failure is by general buckling. Predictions from the existing equations agreed well with the experiment for both core materials. For PVC core, wrinkling/shear buckling and general buckling are the potential failure modes. For L/d ≤8.5 the failure is wrinkling and for L/d >8.5 the failure is general buckling.


Failure Load Sandwich Panel Face Sheet Sandwich Beam Core Sandwich 
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The authors wish to thank the Office of Naval Research for financial support through grants #N00014-07-1-0465 and #N000140510532. Dr. Yapa Rajapakse was the technical monitor of the grants.


  1. 1.
    Olson K (2003) Keynote Lecture, Proceedings of 6th International Conference on Sandwich Structures, March 31–April 2, Fort Lauderdale, FLGoogle Scholar
  2. 2.
    Sorathia U, Perez I (2004) Improving the fire safety of composite materials for naval applications. SAMPE 2004, May 16–20, Long Beach, CAGoogle Scholar
  3. 3.
    Shivakumar KN, Argade SD, Sadler RL et al. (2006) Processing and properties of a lightweight fire resistant core material for sandwich structures. J Ad Maters 38(1):32–38Google Scholar
  4. 4.
    Argade S, Shivakumar K, Sadler R et al. (2004) Mechanical fire resistance properties of a core material. SAMPE, May 16–20, Long Beach Convention Center, Long Beach, CAGoogle Scholar
  5. 5.
    Shivakumar KN, Sharpe M, Sorathia U (2005) Modification of eco-core to enhance toughness and fire resistance. SAMPE-2005, Long Beach, CAGoogle Scholar
  6. 6.
    Sadler RL, Sharpe MM, Shivakumar KN (2008) Water immersion of eco-core and two other sandwich core materials. SAMPE 2008, May 18–22, Long Beach, CAGoogle Scholar
  7. 7.
    Allen HG (1969) Analysis and design of structural sandwich panels. Pergamon, OxfordGoogle Scholar
  8. 8.
    Zenkert D (1997) An introduction to sandwich construction. Chameleon, LondonGoogle Scholar
  9. 9.
    Swaminathan G, Shivakumar KN, Sharpe M (2006) Material property characterization of glass and carbon/vinyl ester composites. Compos Sci Technol 66(10):1399–1408CrossRefGoogle Scholar
  10. 10.
  11. 11.
  12. 12.
    Heath WG (2002) Sandwich construction, Part 2:The optimum design of flat sandwich panels. Aircraft Eng 33:163–176Google Scholar
  13. 13.
    Gdoutos EE, Daniel IM, Wang KA (2002) Compression facing wrinkling of composite sandwich structures. Mech Mater 35:511–522CrossRefGoogle Scholar
  14. 14.
    Sadler RL, Shivakumar KN, Sharpe MM (2002) Interlaminar fracture properties of split angle-ply composites. SAMPE 2002, Long Beach, CAGoogle Scholar
  15. 15.
    Soden PD (1996) Indentation of composite sandwich beams. J Strain Anal 31:353–360CrossRefGoogle Scholar
  16. 16.
    Gdoutos EE, Daniel IM, Wang KA (2002) Indentation failure in composite sandwich structures. Exp Mech 42(4):426–431CrossRefGoogle Scholar
  17. 17.
    Steeves CA, Fleck NA (2004) Collapse mechanisms of sandwich beams with composite faces and a foam core, loaded in three-point bending. Part I:Analytical models and minimum weight design. Int J Mech Sci 46:561–583CrossRefGoogle Scholar
  18. 18.
    Fleck NA, Sridhar I (2002) End compression of sandwich columns. Compos A 33:353–359CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media B.V. 2009

Authors and Affiliations

  1. 1.Center for Composite Materials Research, Department of Mechanical and Chemical EngineeringNorth Carolina A&T State UniversityGreensboroUSA

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