Simple Testing System for Pure Bending Tests with Large Deflections

Abstract

The potential uses of new materials in structural elements are growing constantly. The focus is on the use of composites with high strengths and strains [1], among other properties. This means that their mechanical properties and failure modes need to be described. Bending tests are widely used for these purposes due to their advantages compared to other types of tests. In particular, pure bending tests are very useful when calculating mechanical parameters and failure modes. These tests do not superimpose different types of loading on the specimens and do not introduce shear stresses which often make the test difficult to carry out properly (for example, in sandwich beams that exhibit great changes in curvature and therefore have a small core thickness). Nonetheless, if long specimens with large allowable strains or curved specimens need to be tested, then traditional bending test methods may fail to apply; making the displacement of support points and load application necessary. This work proposes a pure bending test method that overcomes these disadvantages. It is based on a pulley system which, in addition to introducing the necessary rotations, allows the reduction of the distance between test specimen supports and guarantees pure bending. After the corresponding kinematic study that shows the foregoing, the tests carried out on a test specimen yield uniform characteristics known to confirm the validity of the design.