Noise diagnostics of advanced composite materials for structural applications
Our study is focused on noise diagnostics of an advanced composite material for structural applications called extren, which consists of a combination of a fibre glass reinforcement and a resin binder. Electromagnetic and acoustic emission signals appear during mechanical loading of the material under investigation. They carry information about micro-cracks generated in tested materials. We made long-time simultaneous multi-channel measurements of both signals for various loading conditions, carried out time development of noise spectrum, evaluated parameters of EME and AE events, studied their time development, correlations between them and made statistical analyses of signals and their parameters.
A COMPARISON OF DIFFERENT TYPES OF PROBES FOR DETECTING ELECTROMAGNETIC EMISSION
This paper deals with a comparison of different types of probes for detecting electromagnetic emission (EME). The matter of investigation is EME from a model which generates cracks of samples under load. This article provides a description of probes for EME measurement signals. The novelty of the approach lies in the fact that the physical model was used instead of real samples under uniaxial load of composite materials. The author also describes the experiment conducted for obtaining signals and analyses the digitized signals as waveforms and spectra. Appropriate conclusions were made according to the comparative analysis.
The peculiar thermo-structural behavior of the anionic lipid DMPG.
Aqueous dispersions of the anionic phospholipid dimyristoyl phosphatidylglycerol (DMPG), around 100 mM ionic strength, are known to exhibit a thermal behavior similar to that of the largely studied lipid dimyristoyl phosphatidylcholine (DMPC), which undergoes a gel to liquid crystalline phase transition at 23 degrees C, well characterized by differential scanning calorimetry (DSC), and other methods. However, at low ionic strength, DMPG has been shown to present a large gel-fluid transition region, ranging from 18 to 35 degrees C. This intermediate phase is optically transparent and characterized by a continuous change in membrane packing. Structural properties of the DMPG gel-fluid transition region will be discussed, based on results obtained by several techniques: electron spin resonance (ESR) of spin labels at the membrane surface and intercalated at different depths in the bilayer; light scattering; DSC; small angle X-ray scattering (SAXS); and fluorescence spectroscopy of probes in the bilayer.