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This work is a continuation of the research recently presented in [1] and [2] on the determination of residual thermal stresses in graphite/polyimide composites with and without externally applied bending loads. In the previous work [1, 2] a combined experimental and numerical methodology for the determination of the residual stresses in unidirectional graphite/PMR-15 composites based on X-ray diffraction (XRD) measurements of residual strains in embedded aluminum (Al) and silver (Ag) inclusions has been presented. In this research, the previously developed approach has been applied to evaluate the residual thermal interlaminar stresses in an 8 harness satin (8HS) woven graphite/PMR-15 composite. First, residual thermal stresses have been measured by XRD in aluminum inclusions embedded between the rst and second plies of a four-ply 8HS woven graphite/PMR-15 composite. The measurements have been conducted with the composite specimens subjected to four-point bending deformations. Second, viscoelastic computations of interlaminar residual stresses in the composite have been performed using classical laminated plate theory (CLPT) following the manufacturing procedure. Third, the residual strains and stresses in the inclusions have been numerically predicted using the viscoelastic Eshelby model for multiple spherical inclusions. Finally, the interlaminar residual stresses in the composite have been extracted from the XRD strains in the Al inclusions, again using the viscoelastic Eshelby model, and

The applicability of using flat composite plates and hollow core composite cylinders for moisture absorption testing of unidirectional glassr r r r rpolymer composites ( ) used in high voltage composite non-ceramic insulators was examined. Two main ( issues were addressed in this work. First, the effect of specimen geometry cylin-) ders vs. plates on moisture absorption by the composites was investigated both numerically and experimentally. Both classical Fickian and non-Fickian diffusions ( ) were considered. Subsequently, hollow core cylinders made up of ECR low seedglass fibers and epoxy resin were tested for their high voltage properties under controlled moisture diffusion conditions. The specimens were exposed to warm, moist air and their high voltage properties were ascertained using a modified ver-( ) sion of the ANSI test standard C29.11 Section 7.4.2 for water diffusion electrical testing. It was found that the behavior of the hollow core cylinder and flat plate composite specimens subjected to moisture compared reasonably well experimentally and very well numerically. From the high voltage tests, a direct correlation was found between the amount of moisture that had been absorbed by the specimens and the amount of leakage current that was detected. It was shown that using the thin walled composite cylinders leakage currents could be predicted based on the amount of absorbed moisture in the insulator composites. The predictions can be made based on relatively short term moisture data even if the diffusion process in the composites is anomalous in nature with long times required for full saturation. After additional verifications, considering other composite systems, the hollow core cylinder testing under controlled moisture and high voltage conditions could become a screening test for selecting suitable glassr r r r rpolymer composites for insulator applications.

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