Die elektrische Emission beim Versagen von Faserverbundwerkstoffen und ihren Komponenten

Abstract

Deformation and failure of fiber-reinforced materials (FRM) can cause electric charge displacements. This, consequently, leads to variations in the external electric field. These can be observed and recorded during the loading process without any contact to the sample. Analyzing, these signals named electric emission (EE) can be done individually and also statistically when an acoustic emission equipment is used. Fracture of carbon and glass fibers yields EE signals of large amplitudes, whereas the polycarbonate matrix material exhibits smaller ones. The signals obtained in a tensile test with the composite materials exceed the ones of the matrix material but do not attain those of the fiber material. From the shape of the EE signals conclusions can be made on the elementary fracture process. From these experiments it can be concluded that the EE method is a valuable tool with respect to the detection of failure occurence of composite materials as is the acousti emission technique. The EE Technique is a field method and does, therefore, not require any sample preparation. This makes it a low cost technique which can be possibly applied in the field as well as in the laboratory

Relation of Electromagnetic Emission and Crack Dynamics in Epoxy Resin Materials

“…The occurrence of this electromagnetic emission (EME) has been shown for almost any material and for various kinds of failure mechanisms [1][2][3][4][5][6][7][8][9]. The detection and analysis of EME can help to understand the complex processes of crack formation.…”

Measurement and Study of Electromagnetic Emission Generated by Tensile Fracture of Polymers and Carbon Fibres

“…all show a characteristic form of a fast exponential rise and a slow exponential decay which reflects the characteristic response of the applied sensor system to a step function in input voltage. Furthermore, all detected signals of carbon fibre fracture reported in [9,40] exhibit the same polarity. Figure 16a shows EME and AE signals detected during the fracture of a HM type carbon fibre.…”

“…EME measurements with capacitive probes during tensile tests of fibre bundles containing a few thousand carbon fibres have been conducted before and reported in [9,40]. The EME signals emitted by failure of single fibres before the failure of the whole bundle reported in these texts are dominated by the bandwidth of the applied sensor system, i.e.…”

“…As sources for the electromagnetic fields, the separation, displacement or movement of bound or free charges are considered. These effects have been shown for a variety of materials and source dimensions [1][2][3][9][10][11]. The emitted frequencies range from a few Hertz up to the terahertz regime, while the EME of induced or secondary effects like gas discharges between the crack sides may have even higher frequencies.…”

Nondestructive Testing of Polymers and Polymer–Matrix Composites

“…Fractoluminescence (193), that is, the emission of visible light, and electromagnetic emission from fracture of polymers or PMC (194) are now being investigated as NDT tools (195). Microwave testing is applicable to nonconducting materials (196) and used, for example, for exciting ultrasonic waves in PMC (197) or the characterization of anisotropic materials, such as short fiber-reinforced injection molded parts (198).…”