Determination of Shear Modulus of Unidirectional Composite Laminae by Torsional Pendulum

Characterization of shear moduli of composite lamina by existing methods such as rail shear test, Arcan shear test, Iosipescu shear test, etc. has their disadvantages. Developing a simple and efficient method for characterizing the shear moduli of the composite lamina is the objective of this work. A composite specimen of unidirectional laminate clamped and suspended from one end and with a rod weight attached horizontally at the lower end was tested simply by twisting and releasing as a torsional pendulum. By measuring the period of the twisting oscillation, the shear modulus of the laminae can then be calculated via a theoretical relationship. Experiments were conducted on specimens with different widths and rod weights with different lengths. Data of period were fitted simultaneously, and the shear modulus was obtained with less than 4% errors in comparison with that offered by the material manufacturer. The sensitivities of the shear moduli to the measured period are discussed and evaluated. This work presents the technique of the torsional pendulum, a very simple and efficient technique for measuring the shear modulus of the composite lamina.