74
3 Modeling Composite Structures
Currents flowing orthogonally to the fiber direction penetrate more deeply into the sample.
Probe
X
Z
Fiber Direction
Current Flow
Current Flow
Fig. 3.11 Currents flowing orthogonally to the fiber direction penetrate more deeply into the
structure because of the extended skin depth
X
Z
Fiber Direction
Current Flow
Fig. 3.12 The ‘bent-plate’ phenomenon: currents flowing orthogonally to the fiber direction
penetrate more deeply into the structure because of the extended skin depth. This gives rise to
a z-directed current component. If the structure is thick enough in the z-direction, this component
should be large enough to produce a reliable estimate of the zz-component of the conductivity
tensor
In the anisotropic plate with which we are concerned, however, the x-component
of the electric field experiences a skin depth much smaller than that experienced
by the y-component (see Fig. 3.11), which means that the resulting eddy-currents
flow in a ‘bent-plate’ mode, as suggested by Fig. 3.12. This gives rise to a z-directed
field and current. It is this field, and the resulting current that allows us to infer the
zz-component of the conductivity tensor. We expect that the z-field becomes larger
with a thicker structure, allowing a more reliable estimate of σ z .
3 Modeling Composite Structures
Currents flowing orthogonally to the fiber direction penetrate more deeply into the sample.
Probe
X
Z
Fiber Direction
Current Flow
Current Flow
Fig. 3.11 Currents flowing orthogonally to the fiber direction penetrate more deeply into the
structure because of the extended skin depth
X
Z
Fiber Direction
Current Flow
Fig. 3.12 The ‘bent-plate’ phenomenon: currents flowing orthogonally to the fiber direction
penetrate more deeply into the structure because of the extended skin depth. This gives rise to
a z-directed current component. If the structure is thick enough in the z-direction, this component
should be large enough to produce a reliable estimate of the zz-component of the conductivity
tensor
In the anisotropic plate with which we are concerned, however, the x-component
of the electric field experiences a skin depth much smaller than that experienced
by the y-component (see Fig. 3.11), which means that the resulting eddy-currents
flow in a ‘bent-plate’ mode, as suggested by Fig. 3.12. This gives rise to a z-directed
field and current. It is this field, and the resulting current that allows us to infer the
zz-component of the conductivity tensor. We expect that the z-field becomes larger
with a thicker structure, allowing a more reliable estimate of σ z .