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The compressive response of carbon fiber composite pyramidal truss sandwich cores

K. Finnegan, G. Kooistra, H. N. G. Wadley and V. S. Deshpande

Abstract

Pyramidal truss sandwich cores with relative densities in the range 1 – 10 % have been made from carbon fiber reinforced polymer laminates using a snap-fitting method. The measured quasi-static uniaxial compressive strength increased with increasing from 1 to 11 MPa over the relative density range investigated here. A robust face-sheet/truss joint design was developed to suppress truss – face sheet node fracture. Core failure then occurred by either (i) Euler buckling () or (ii) delamination failure () of the struts. Micro-buckling failure of the struts was not observed in the experiments reported here. Analytical models for the collapse of the composite cores by Euler bucking, delamination failure and micro-buckling of the struts have been developed. Good agreement between the measurements and predictions based on the Euler buckling and delamination failure of the struts is obtained. The micro-buckling analysis indicates this mechanism of failure is not activated until delamination is suppressed. The measurements and predictions reported here indicate that composite cellular materials with a pyramidal micro-structure reside in a gap in the strength versus density material property space, providing new opportunities for lightweight, high strength structural design.


* Correspondence address, H. N. G. Wadley Department of Materials Science and Engineering 395 McCormick Road Wilsdorf Hall, P.O. Box 400745 Charlottesville, VVA 22904 Tel.: +1 434/982 5671 Fax: +1 434/9825677 E-mail:

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Published Online: 2013-06-11
Published in Print: 2007-12-01

© 2007, Carl Hanser Verlag, München