Technique for measuring the complex elastic (young{3 s) modulus utilizing laser interferometry

Claim 1

A method for measuring the dynamic complex elastic modulus of a viscoelastic material comprising the steps of: fixedly mounting a prismatic rod of the material of length L at one of its ends; maintaining the rod at a predetermined temperature; introducing a sinusoidal longitudinal stress wave of a selected number of frequencies within a predetermined range of frequencies into the rod; measuring the deflection, UL, of the rod at its free end, at a point midway its length UL/2, and at a point one quarter of the length of the rod from its fixed end, UL/4, for each of the selected frequencies; A. for frequencies below the last maximum in R4 determine the complex elastic modulus, E* for the given frequency f according to the following relationship

Claim 2

A method for measuring the dynamic complex elastic modulus of a viscoelastic material comprising the steps of: fixedly mounting a prismatic rod of the material of length L at one of its ends; maintaining the rod at a predetermined temperature; introducing a sinusoidal longitudinal stress wave of a selected number of frequencies within a predetermined range of frequencies into the rod; measuring the deflection, UL, of the rod at its free end, at a point midway its length UL/2, and at a point one quarter of the length of the rod from its fixed end, UL/4, for each of the selected frequencies; A. for frequencies below the last maximum in R4 determine the complex elastic modulus, E* for the given frequency f according to the following relationship

Claim 3

An apparatus for measuring the displacement of a sample rod of viscoelastic material under sinusoidal longitudinal compression waves at lineal points critical for the determination of the dynamic complex modulus of elasticity of the material, comprising: an environmental housing for enclosing the sample rod and controlling the temperature thereof; means for securing one end of said rod in said environmental housing; means attached to the unconstrained end of the sample rod for introducing sinusoidal compression stress waves therein; means for producing a beam of collimated light and introducing the same into said environmental housing to impinge upon said sample rod; means for splitting said beam of collimated light into two beams, said means interposed along said beam of light; means for reflecting one of said split beams, mounted perpendicularly along the length of said sample rod, one for successively measuring the longitudinal displacement of said sample rod along the length thereof at the unconstrained end, another at a point midway along its length, and still another at a point one-quarter the length from the secured end; means for combining said split beams reflected from said reflecting means with the other of said split beams; and means for counting the interference fringes produced by the combining means thus determining the displacement of each of said reflecting means at the selected frequency.

Claim 4

An apparatus for measuring the displacement of a sample rod of viscoelastic material under sinusoidal longitudinal compression waves at lineal points critical for the determination of the dynamic complex modulus of elasticity of the material, comprising: an environmental housing for enclosing the sample rod and controlling the temperature thereof; means for securing one end of said rod in said environmental housing; means attached to the unconstrained end of the sample rod for introducing sinusoidal compression stress waves therein; means for producing a beam of collimated light and introducing the same into said environmental housing to impinge upon said sample rod; means for splitting said beam of collimated light into two beams, said means interposed along said beam of light; means for reflecting one of said split beams, mounted perpendicularly along the length of said sample rod, one for successively measuring the longitudinal displacement of said sample rod along the length thereof at the unconstrained end, another at a point midway along its length, and still another at a point one-quarter the length from the secured end; means for combining said split beams reflected from said reflecting means with the other of said split beams; and means for counting the interference fringes produced by the combining means thus determining the displacement of each of said reflecting means at the selected frequency.