Composite materials are widely used in a range of applications and theirreliability depends on the quality of manufactured structure. Defects can be producedin composite materials during the manufacturing and can also evolve over the entireservice life. A number of different defects can initiate during the manufacturing,adhesive bonding and repair process. For example, voids and interfacial debond can bevery detrimental to the performance of the composite structure. Debond at bondedjoints is often difficult to characterize (for example, “kissing bond”). Althoughprogress has been made in detection of defects using popular nondestructive methods,there are still significant challenges remain in quantifying the distribution of defectsand the corresponding property loss. The objective of this study is to explore effectsof defects (micro-void and debond) at interlaminar locations within the laminate andalso at adhesive joints. To study the effect of interlaminar defect, glass microspheresand Teflon inserts are used to create debond region between two carbon fiber plies. Onthe other hand, coatings of mold release agent and release films were used in theadhesive joint to mimic kissing bond between glass fiber substrates. We will use anew concept that heterogeneous charge polarization inside a material is related to themicrostructural degradation and can be quantified using Broadband DielectricSpectroscopy (BbDS) technique. Using both bulk and scanning mode, we can quantifythe distribution of dielectric properties. Corresponding mechanical property loss due todefects in the material has been determined and related to changes in dielectriccharacteristics such as changes is complex permittivity. Results show that realpermittivity captures the interfacial defect in both interlaminar and kissing bondexperiments. A 3D X-ray microscope will be used to validate experimentalobservations. Details of experimental results and observations are documented in thepaper.
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