Advances in nonlinear buckling mode interaction modelling for sandwich struts with functionally graded cores

Abstract

Sandwich struts are a special class of three-layer composites where a soft compliant core is sandwiched between two thin stiff plates, offering high bending rigidity at low weight. Precisely because of this efficient configuration, such structures are prone to localized failures such as localized buckling and subsequently buckling induced delamination. Building on prior work (Hunt & Wadee, 1998 ; Wadee, Yiatros & Theofanous, 2010), the work herein is an analytical investigation of the effect of symmetric property gradation in the core on elastic buckling mode interaction in sandwich struts. Using density as a design parameter to functionally grade stiffness properties in the core, it can have an influence to the formation of the secondary bifurcation that leads to interactive buckling. Two mechanical models are presented based on the Total Potential Energy principle accounting for different shear deformable theories for the core, namely the Timoshenko Beam Theory (TBT) and the Reddy-Bickford Theory (RBT). Several different stiffness gradation profiles have been tested using the two mechanical models and their results compared to Finite Element simulations in ANSYS, exhibiting the merits of each model for each parametric study and highlighting the potential of stiffness gradation as a design parameter in buckling mitigation.

Hunt GW, Wadee MA. Localization and mode interaction in sandwich structures. InLocalization And Solitary Waves In Solid Mechanics 1999 (pp. 301-320). Wadee MA, Yiatros S, Theofanous M. Comparative studies of localized buckling in sandwich struts with different core bending models. International Journal of Non-Linear Mechanics. 2010 Mar 1;45(2):111-20.