Double Beam Shear (DBS) – a new test method for determining interlaminar shear properties of composite laminates

A new test method, the Double Beam Shear (DBS), has been developed at Loughborough University for the determination of the interlaminar shear (ILS) mechanical properties of fibre-reinforced laminated composite materials. The DBS uses an intact beam specimen with three equal-spaced supports under two loaders in such a way that each loader is applied at the middle of two supports. Under such set-up, two longitudinal pure ILS sections are induced in the two inner regions where the corresponding bending stresses are zero. It has been validated extensively using various composite laminates including carbon and E-glass fibre reinforcements, each in more than one thickness. The overwhelming majority of the tested specimens failed consistently in one of the inner regions with interior delamination. The magnitudes of the obtained ILS strengths of the composite materials are significantly greater than the corresponding apparent ILS strengths produced by the Short Beam Method. The DBS is especially able to induce ILS failure in certain composite materials, in which the Short Beam Method is not able to. The DBS Method is simple and easy to use.