AE in Polymeric Composites

Abstract

Polymeric composites comprise a wide range of materials consisting of continuous or discontinuous fibers, various particles, or combinations of these embedded in a polymer matrix. Beside technical polymer composites, biobased composites with biopolymers or natural fibers, or natural polymer composites such as wood are finding increasing use in structural applications. The complex, multi-scale morphology yields distinctly different mechanisms generating AE under thermo-mechanical loads or environmental exposure. Storage tanks and pressure vessels made from fiber-reinforced composites were among the first components for which AE testing yielded reliable assessments of structural integrity. The empirical Felicity-ratio is important for quantitative predictions of structural damage and remaining service life. Recent advances in AE signal analysis now contribute to improved source location accuracy and to the unambiguous identification of the underlying microscopic signal source mechanisms. AE testing of infrastructure and components tends to move from periodic inspection to continuous structural health or condition monitoring. This also applies to infrastructure made from polymeric composites as well as to structures or parts in the transportation industry. AE implemented for process monitoring related to polymeric composites shows potential for development of AEbased process control. This chapter first reviews the mechanisms generating AE in polymeric composites, then discusses progress in AE signal analysis for source location and identification of mechanisms and presents selected examples of established AE applications from the micro-to the macro-scale. This includes prediction and quantification of damage in materials and structures, and closes with prospects for developments of AE condition monitoring and process control.

Investigation of the Staging of Damage Accumulation in Polymer Composite Materials during Bending and Tensile Tests

“…Fourier spectra were calculated for the registered AE signals. Due to the fact that the noise frequencies are in range up to 20 kHz [7,14] and the informative part of AE signals spectrum for FGRP is in range up to 600 kHz, for the analysis of the registered signals the band of frequencies from 20 to 650 kHz was established [9]. After normalization, the resulting spectra were used for SOM training.…”

“…The characteristic of the registered AE performs according to such signal descriptors as amplitude [2], energy [12], peak [7] and median frequencies [13]. However, the assessment of only one parameter like median, peak or centroid frequency is often ineffective [4], therefore, it is necessary to obtain full information about their frequency components of the recorded AE signals [6,[14][15][16].…”