Maciej Kumosa

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The purpose of this work is to establish the critical surface conditions leading to the initiation of stress corrosion cracks on the as supplied surfaces of three unidirectional Eglass/polymer composites with modified polyester, epoxy and vinyl ester resins subjected to a nitric acid solution without mechanical loads. The composite materials considered in(More)
] It was postulated in 1 , based on experimental evidence, that brittle fracture fail( ) ures of composite non-ceramic HV insulators could be caused by water and mechanical stresses. It was also claimed therein that the brittle fracture process was more likely to happen with water than acids. This postulation could be of major importance as its(More)
In this research the mechanical behavior of composite suspension insulators with crimped end-fittings manufactured by NGK has been evaluated. Two issues have been addressed in this study. Insulators crimped with the standard, high, reversed and constant high stress conditions have been analyzed for their crimping deformations, and the two and three(More)
An investigation was performed to determine whether corrosion resistant boron-free E-glass fibers could adequately prevent acid induced brittle fracture failures of high voltage composite insulator rods. Nine different rod compositions were tested at 45% of mechanical failure load in contact with 1 N nitric acid. Rods made out of commonly used E-glass(More)
The chemical environment responsible for the brittle fracture failure of composite ( ) non-ceramic insulators is determined. Also previously reported observations by the authors are verified. Five non-ceramic composite suspension insulators and one composite guide were subjected to FTIR analysis. Out of the six field failed units, five insulators showed(More)
In this paper, the most important results are presented and discussed from a multiyear interdisciplinary study directed toward the identification of the most suitable glass/polymer composite systems with the highest resistance to brittle fracture for high voltage composite insulator applications. Several unidirectional glass/polymer composite systems,(More)
This paper describes water diffusion into and electrical testing of unidirectional ( ) glass reinforced polymer GRP composite rods used as load bearing components ( ) in high voltage composite non-ceramic insulators. The tests were performed following ANSI standard C29.11 Section 7.4.2 that can be used to evaluate electrical properties of composites. The(More)
Recent evidence indicates that renin transgenic rats TGR(mRen2)27 (TGR) manifest increased activity of the central vasopressinergic system. Because one of the reasons for this finding could be an increased synthesis of vasopressin receptors, we determined in the present study expression of V1a and V1b vasopressin receptors (R) mRNA in the brain of TGR rats(More)
The effective conductivity of a fibrous composite is investigated using the Monte Carlo simulation scheme and the finite-element method. The conductive fibers are modeled as randomly distributed resistors in a nonconductive matrix. The gap elements are constructed between neighboring fibers to model the interfiber contact. The resistance of a gap element is(More)