Theoretical development of suitable test scenarios for the determination of the bending tensile strength of thin glass with or without influence of edges and their experimental implementation

Abstract

ABSTRACTThe use of thin glass in the field of electrical engineering for screens of mobile phones or laptops is well known and the necessary material requirements such the scratch resistance has been sufficiently researched. For applications in the building sector, however, the determination of the bending tensile strength of such thin glass necessary for structural design represents a new research topic. The test scenarios described in the standard series EN 1288 relevant for the determination of the bending tensile strength, such as the ring‐on‐ring test or the four‐point‐bending test, are not applicable for glass with a thickness of less than 3 mm. One reason is e.g. the high flexibility of the glass in case of four‐point‐bending tests. As a consequence, these test scenarios have to be adapted or new test scenarios have to be developed. The double‐ring bending tensile test was adapted in that the loading ring, e.g. was replaced by a pressure pad of soft elastomer. Thus, a constant stress distribution in the area under the pressure pad necessary for the determination of the probability of failure could be achieved. The four‐point‐bending test was replaced by test set‐ups in which the force is introduced in‐plane – parallel to the glass surface – as a membrane force in the glass and the glass is thereby deformed or bent until breakage analogous to a stability test. Another variant is bending with a constant bending radius. In this test set‐up, a circular arc is created by precise adjustment of the distance of the supported smaller straight edges and their rotation. Thus, the length of the edge, at which sets a constant bending moment can be increased. These alternative test scenarios were theoretically developed and analysed or partially experimentally investigated by means of test series. These experimental series serve to validate the theoretical development of suitable experimental scenarios and are intended to provide a first approach for a necessary adaptation of EN 1288.