Determination of shear parameters of rigid foams with three rail shear test

In order to better understand the structural behavior of sandwich structures and to increase their performance, the shear modulus and shear strength values of the core materials used have to be determined accurately. Therefore in this study, the shear modulus and shear strength values of a lightweight polystyrene foam (PF) core material in the relevant material planes are obtained by performing three rail shear test (TRST). First, a rigid TRST apparatus had been manufactured. A total of 6 experiments had been performed; 3 for the strong plane and 3 for the weak plane. Using the experimental results obtained, the shear module of the PF core material are approximately calculated using the numerical and analytical models. ANSYS program is used for the numerical model and the classical beam theory is used for the analytical model, where shear deformation is also considered. The results obtained in this study show that TRST may be used to obtain the shear module but it should not be used to obtain the shear strength as the shear strength values obtained using this test are grossly in error.