ISSN: 1945-7553
CODEN: JTEVAB
Page Count: 3

Strain Measurement Techniques for Fiber Modulus Determination

Moore, RL
Technical associate and group leader, Lawrence Livermore Laboratory, University of California, Livermore, Calif.

Lepper, JK
Technical associate and group leader, Lawrence Livermore Laboratory, University of California, Livermore, Calif.

Abstract

Two techniques were employed to measure the tensile strain of Kevlar-49® organic fiber in an epoxy matrix. One, a direct averaging strain method, uses two linearly variable differential transformers whose hollow cores are supported by glass beads bonded to the fiber strand specimens. The other method is an indirect method using specimens of several gage lengths. The crosshead displacement for selected loads was determined for each gage length and the data were fit to a straight line by a least squares method and the unit strain calculated for each load.

The tensile modulus of the Kevlar-49® fiber strands was determined to be 20 × 10⁶ psi (138 × 10⁶ kPa). The variation of the averages between methods and within methods between specimens was less than five percent.

Keywords:
fibers, tensile properties, epoxy resins, modulus of elasticity, strain measurement, least squares method

Paper ID: JTE10094J
DOI: 10.1520/JTE10094J
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