Experimental validation of the modified couple stress Timoshenko beam theory for web-core sandwich panels

The paper presents experimental validation of the modified couple stress Timoshenko beam theory for web-core sandwich panels. The face and web-plates are assumed to be isotropic and to behave according to the kinematics of the Euler-Bernoulli beam theory. First, a modified couple stress theory for Timoshenko beams is reviewed. Then shear, bending and couple stress responses of homogenized web-core sandwich beams are examined. The developed theory is validated with experiments from open literature for beams in 3- and 4-point bending. The beams have 4, 9 and 15 unit cells along their length. It is seen that the developed theory is in excellent agreement with experiments. It is also seen that the theory converges to physically correct solutions in the cases of infinite and zero shear stiffness; while the first corresponds the case of Euler-Bernoulli sandwich beam, the second corresponds the case where the sandwich effect is lost and the bending is carried out purely by the bending of the faces. The paper also gives explicit expression for the couple stress stiffness in terms of unit cell dimensions and materials.