FURTHER INVESTIGATIONS INTO THE MICRODYNAMICS OF WAVE PROPAGATION.
Annual summary rept. Jun 68-Jun 69,
WHITTAKER CORP SAN DIEGO CALIF RESEARCH AND DEVELOPMENT/SAN DIEGO
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This continuing analytical program is concerned with establishing equations to define wave propagation in unidirectional, multi-fiber reinforced composites. It was found that the exact solution and the approximate solution yield the same numerical results for displacements, stresses, and propagation velocities for a model of rotational symmetry. It was also found that only the fundamental propagative mode in a composite materials can propagate waves. The higher modes have cut-off frequencies below shich propagation is impossible. They are strongly attenuated just below the cut-off frequency, and immediately above it dispersion is very high. The more commonly used fiber composites materials, glass epoxy, may be used for an example. Those with a fiber content of 60 have a cut-off frequency of 10 times 10 to the sixth power cyclessecond for the first higher mode those with a fiber content of 80 have a cut-off frequency of 26 times 10 to the sixth power cyclessecond. It is therefore justifiable to use solutions in which the dynamics of the system are simplified or solutions which are approximated in such a way that they deal mainly with the fundamental mode. Author, modified-PL
- Laminates and Composite Materials