Holographic Evaluation of Warp in the Torsion of a Bar of Cellular Solid

Holographic methods are utilized to examine deformations in a cellular solid, polymethacrylamide closed cell foam. A square cross section bar is subjected to static torsional deformation. The warp deformation is observed to be less in a foam bar than in a homogeneous polymeric bar used as a control. The homogeneous bar obeys the predictions of classical elasticity. Behaviour of the foam bar is consistent with Cosserat elasticity. In a Cosserat solid, points in the continuum rotate as well as translate, and the material supports couple per unit area as well as force per unit area. Cosserat effects are important since they can lead to enhanced toughness