3.2 Constitutive Relations for Advanced Composites
61
APPLIED FIELD
CURRENT PATH
FIBERS
RESIN MATRIX
C
R
EDDY−CURENT PATH
Fig. 3.1 How fiber-to-fiber contact allows transverse conduction (a). A possible AC equivalent
circuit for eddy-current flow (b)
Table 3.1 Summary of electrical properties of some composites [5]
Graphite-epoxy
Boron-epoxy
Kevlar
Permeability (μ R )
1
1
1
Permittivity ( R )
Indeterminate
5.6
3.6
DC Conductivity (S/m)
Longitudinal (σ L )
2 × 10 4
30
6 × 10 −9
Transverse (σ T )
100
2 × 10 −8
6 × 10 −9
Anisotropy ratio (σ L /σ T )
200
1.5 × 10 9
1
61
APPLIED FIELD
CURRENT PATH
FIBERS
RESIN MATRIX
C
R
EDDY−CURENT PATH
Fig. 3.1 How fiber-to-fiber contact allows transverse conduction (a). A possible AC equivalent
circuit for eddy-current flow (b)
Table 3.1 Summary of electrical properties of some composites [5]
Graphite-epoxy
Boron-epoxy
Kevlar
Permeability (μ R )
1
1
1
Permittivity ( R )
Indeterminate
5.6
3.6
DC Conductivity (S/m)
Longitudinal (σ L )
2 × 10 4
30
6 × 10 −9
Transverse (σ T )
100
2 × 10 −8
6 × 10 −9
Anisotropy ratio (σ L /σ T )
200
1.5 × 10 9
1