TECHNIQUES FOR THE MEASUREMENT OF THE FLEXURAL RIGIDITY OF THIN FILMS AND LAMINATES*

A method of measuring the flexural rigidity of thin films and laminates is described. The method employs the principle of the heavy elastica which relates flex-ural rigidity to the deflection of the material under its own weight. Results are presented of tests to determine the stiffness of plastic films and plastic-metal laminates for use in space structures experiments. Tests were performed on untreated and aluminized polyjethylene terephthalatej film, aluminum foil, and laminates of aluminum foil and polyjethylene terephtahlate) film or polypropylene film. The thickness of the materials ranged from 0.00018 inch (0.00046 cm) to 0.00270 inch (0.00691 cm). The weight effici-ency in flexure is presented, the efficiency of the aluminized polyethylene terephthalate] film (Echo I material) being taken as unity. It has been shown that the principle of the heavy elastica (including both the heart-loop and the cantilever methods) is valid for such determinations if the material does not have a static electric charge. Although higher stiffness can be obtained at the expense of more weight, the investigation showed that the rigidity can increase more rapidly than the weight. Compared with the Echo I material, the laminates had the highest efficien