Vibrating membrane elastometer for reliable measurement of mechanical properties of metallic films

We describe an apparatus for measuring the biaxial mechanical properties of metallic films. A circular knife-edge support forms a drum-head geometry over which the film to be studied is stretched. The film’s tension is obtained from the frequency of its membrane modes, and its strain by using an optical technique. The biaxial modulus is obtained from the ratio of tension and strain. An electronic detection system is developed that regeneratively locks to the film’s resonant frequency. The system is also capable of measuring the film’s damping when the lock is switched off.