Carbon fiber drive shaft

Claim 1

A tubular drive shaft having noise and vibration dampening characteristics, and capable of being rotated at a speed of at least 6000 rpm. without misalignment between its geometric axis and its axis of rotation, said shaft having a maximum longitudinal Young's modulus of elasticity of 8 × 10 6 psi. and comprising a composite of a plurality of layers of filamentary material in a solid resin matrix, said filamentary material being at least 20 percent by weight carbon fibers, with from at least 10 percent by weight to no more than 20 percent by weight of the filamentary material present being disposed parallel to the longitudinal axis of said shaft when filamentary material having a Young's modulus below 25 × 10 6 psi. is employed, the balance of said filamentary material being circumferentially and helically disposed about the longitudinal axis of the shaft, the fibers in the innermost and outermost layers being substantially circumferentially disposed about the longitudinal axis of the shaft at an angle of from 85° to 90° to a line parallel to the longitudinal axis of the shaft, said circumferentially disposed fibers containing carbon fibers, and the fibers of at least four intermediate layers between the innermost and outermost layers being helically disposed about the longitudinal axis at an angle of from 15° to 50° to a line parallel to the longitudinal axis of the shaft, with the fibers of each successive helical layer crossing the fibers of the previous helical layer at an angle of from 30° to 90°; the value of the formula EI/L.sup.4 for said shaft being no greater than 1, and the value of the formula EI/L.sup.4 DPt for said shaft being at least 40, wherein E is the longitudinal Young's modulus of the shaft (psi.), I is the second moment of area of the shaft (inches 4 ), L is the length of the shaft (inches), D is the mean diameter of the shaft (inches), P is the average density of the shaft wall (lb./in. 3 ), and t is the thickness of the shaft wall (inches).