THERMOELASTIC DISSIPATION IN COMPOSITE THIN BEAMS. PART I: THEORY. PART II: EXPERIMENT.
Summary rept. Jun 65-Jan 66 and Jun-Sep 66,
MINNESOTA UNIV MINNEAPOLIS DEPT OF AERONAUTICS AND ENGINEERING MECHANICS
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Part I A general formula for thermoelastic loss coefficient for composite materials in free oscillation is derived, based on Tasis single-material analysis. This is related to Zeners beam and reed results, and a formula for laterally layered beams is found. A particular Zinc-Monel composite based on the experimental work in free-free oscillation is solved numerically, the results appearing as curves which show the increased damping obtained as compared to beams of one material or the other. Incidentally, the nature of Zeners approximations is justified by the small difference appearing between his beam predictions and the slight more exact results based on Tasis three-dimensional formula. Part II The thermoelastic effect as a means of energy dissipation in engineering materials has been studied by many authors. Among them Zener related this effect to the dissipation in thin beams excited in flexure. Other papers may be found on thermoelastic damping in beams and rods under axial excitation and plates under flexure. To this authors knowledge, however, no prior work has been conducted regarding thermoelastic dissipation in composite or laminated thin beams excited in flexure. In an endeavor to increase energy dissipation in thin beams excited in flexure, this report contains a qualitative discussion on one possible laminated configuration. Subsequent experimental studies were conducted to determine possible validity of these discussions. Author