Chapter 3
Modeling Composite Structures
3.1 Background
Composite materials in the form of fiber-reinforced matrix materials as, for example,
graphite-epoxy, are being increasingly used in critical structures and structural components because of their high strength-to-weight ratio. In order to assess the integrity
of these structures, it is necessary to employ suitable methods for quantitative
NDE. One method uses eddy-currents; composite materials, however, are inherently
anisotropic, which means that many of the classical eddy-current technology and
design procedures are not applicable. In addition, composite materials vary widely
in their permittivities and conductivities, which means that new analyses must be
carried out to develop effective strategies for using eddy-currents in quantitative
NDE. A final problem is that there is a variety of potential failure modes in
composites, such as delaminations, fiber-breakage due to impact damage, flaws,
etc., some of which may not be readily detectable by eddy-currents [85]. In order to
complement empirical studies it is necessary to embark upon a rigorous quantitative
NDE program for composites to assess the role that eddy-currents play in it, and
especially to determine suitable inversion algorithms.
Eddy-current methods for the examination of carbon-fiber reinforced epoxy
resins and other composite materials have been discussed and analyzed by Owston
and Prakash [82, 83, 86, 87]. These analyses have been based on an ad hoc
equivalent circuit in which the composite test piece is regarded as being inductively
coupled to the probe, much as in the classical treatment of eddy-current evaluation
of metals. Though the technique gives a useful indication of the form of the results,
a more satisfactory approach, as Owston [83] points out, is to use a field-theoretic
analysis which is capable of giving exact results for a given model. A field-theoretic
analysis is also desirable when computing electromagnetic interactions for shielding
effectiveness of advanced composites in aircraft [132].
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
H. A. Sabbagh et al., Advanced Electromagnetic Models for Materials
Characterization and Nondestructive Evaluation, Scientific Computation,
https://doi.org/10.1007/978-3-030-67956-9_3
59
Modeling Composite Structures
3.1 Background
Composite materials in the form of fiber-reinforced matrix materials as, for example,
graphite-epoxy, are being increasingly used in critical structures and structural components because of their high strength-to-weight ratio. In order to assess the integrity
of these structures, it is necessary to employ suitable methods for quantitative
NDE. One method uses eddy-currents; composite materials, however, are inherently
anisotropic, which means that many of the classical eddy-current technology and
design procedures are not applicable. In addition, composite materials vary widely
in their permittivities and conductivities, which means that new analyses must be
carried out to develop effective strategies for using eddy-currents in quantitative
NDE. A final problem is that there is a variety of potential failure modes in
composites, such as delaminations, fiber-breakage due to impact damage, flaws,
etc., some of which may not be readily detectable by eddy-currents [85]. In order to
complement empirical studies it is necessary to embark upon a rigorous quantitative
NDE program for composites to assess the role that eddy-currents play in it, and
especially to determine suitable inversion algorithms.
Eddy-current methods for the examination of carbon-fiber reinforced epoxy
resins and other composite materials have been discussed and analyzed by Owston
and Prakash [82, 83, 86, 87]. These analyses have been based on an ad hoc
equivalent circuit in which the composite test piece is regarded as being inductively
coupled to the probe, much as in the classical treatment of eddy-current evaluation
of metals. Though the technique gives a useful indication of the form of the results,
a more satisfactory approach, as Owston [83] points out, is to use a field-theoretic
analysis which is capable of giving exact results for a given model. A field-theoretic
analysis is also desirable when computing electromagnetic interactions for shielding
effectiveness of advanced composites in aircraft [132].
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
H. A. Sabbagh et al., Advanced Electromagnetic Models for Materials
Characterization and Nondestructive Evaluation, Scientific Computation,
https://doi.org/10.1007/978-3-030-67956-9_3
59