EXPERIMENTAL-TECHNIQUES FOR DYNAMIC CHARACTERIZATION OF COMPOSITE-MATERIALS

This research combines theoretical and experimental approaches for dynamic material characterization of composite materials. The samples studied include continuous fiber graphite/epoxy beams with various symmetric lay-up configurations. Included are laminated beams with the following lay-ups: [0(8)/90(8)]s, [90(8)/0(8)]s, [(45/0/ - 45)5]s and [(0/45/0/ - 45)3/90/0/0(1/2]s. The resonant dwell technique is used to determine the material damping and the real part of the dynamic flexural modulus of double cantilever beam specimens in the first mode of vibration over the frequency range 25 Hz to 300 Hz. The dynamic properties are determined as a function of the frequency of oscillation at room temperature. In addition, the Metravib Viscoanalyzer, based on off-resonance tests, is also used to provide another source of experimental data for comparison. Although the Viscoanalyzer was originally intended for testing viscoelastic polymers, the present research establishes the limits of applicability for composite materials, with particular emphasis on the three point bending test. Comparisons and limitations of both techniques are critically discussed.