Assuming square, hexagonal, and random packed arrays of nonoverlapping identical parallel cylindrical voids dispersed in an aluminum matrix, we have calculated numerically the concentration dependence of the transverse Poisson's ratios. It was shown that the transverse Poisson's ratio of the hexagonal and random packed arrays approached 1 upon increasing the concentration of voids while the ratio of the square packed array along the principal continuation directions approached 0. Experimental measurements were carried out on rectangular aluminum bricks with identical cylindrical holes drilled in square and hexagonal packed arrays. Experimental results were in good agreement with numerical predictions. We then demonstrated, based on the numerical and experimental results, that by varying the spatial arrangement of the holes and their volume fraction, one can design and manufacture voided materials with a tailored Poisson's ratio between 0 and 1. In practice, those with a high Poisson's ratio, i.e., close to 1, can be used to amplify the lateral responses of the structures while those with a low one, i.e., close to 0, can largely attenuate the lateral responses and can therefore be used in situations where stringent lateral stability is needed.

No abstract

No abstract

It was recently proposed (Goussev, 0. A., Zeman, K. and Suter, U. W., J . Adhesion 56, 45 (1 996)) to characterize the joints between materials directly by the maximum bending moment, M,,,, borne just prior to delamination (delamination moment). This alternative to the energy-release-rate approach was first introduced for the blister test configuration. Here we extend this idea to a cantilever beam test. We suggest, therefore, to evaluate the bending moment in the cantilever-beam experimental setup with an elastic upper plate through direct measurement of the curvature of the upper plate in the vicinity of the separation line. For the profile measurement and determination of the exact location of the delamination line, the projection-moirC technique was employed. The methodology was tested on measurement of adhesion of an epoxy adhesive to steel. It was shown that the value of the maximum bending moment remains approximately constant during the delamination, indicating that this quantity is a physical characteristic of the joints between materials.