Elastic constants of fiber-reinforced composites: a fresh measurement approach

Abstract

Composites reinforced with uniaxial fibers possess five independent elastic constants: C/sub 11/, C/sub 33/, C/sub 44/, C/sub 66/, and C/sub 13/. Measurements on a single specimen along principal axes give all the C/sub ij/ except C/sub 13/. To get C/sub 13/, a new approach is proposed that requires measurements only along principal directions: <100>. The approach also avoids the thin-plate problem, where measuring C/sub 22/ and C/sub 33/ may be difficult. A pulse-echo method is used to measure C/sub 11/, C/sub 44/, and C/sub 66/, and a resonance (kilohertz-frequency) method is used to measure two elastic compliances: S/sub 11/ and S/sub 33/. S/sub 44/ and S/sub 12/ come from simple formulas containing C/sub 44/ and C/sub 66/. S/sub 13/ comes from a relatively simple formula containing S/sub 11/, S/sub 12/, S/sub 33/, and C/sub 11/. The approach is applied to a graphite-magnesium composite.<>