Quantification of failure mechanisms in mode-I loading of fiber reinforced plastics utilizing acoustic emission analysis

Abstract

Acoustic emission signals originating from interlaminar crack propagation in fiber reinforced composites were recorded during double cantilever beam testing. The acoustic emission signals detected during testing were analyzed by feature based pattern recognition techniques. In previous studies it was demonstrated that the presented approach for detection of distinct types of acoustic emission signals is suitable. The subsequent correlation of distinct acoustic emission signal types to microscopic failure mechanisms is based on two procedures. Firstly, the frequency of occurrence of the distinct signal types is correlated to different specimens' fracture surface microstructure. Secondly, a comparison is made between experimental signals and signals resulting from finite element simulations based on a validated model for simulation of acoustic emission signals of typical failure mechanisms in fiber reinforced plastics. A distinction is made between fiber breakage, matrix cracking and interface failure. It is demonstrated, that the feature values extracted from simulated signals coincide well with those of experimental signals. As a result the applicability of the acoustic emission signal classification method for analysis of failure in carbon fiber and glass fiber reinforced plastics under mode-I loading conditions has been demonstrated. The quantification of matrix cracking, interfacial failure and fiber breakage was evaluated by interpretation of the obtained distributions of acoustic emission signals types in terms of fracture mechanics. The accumulated acoustic emission signal amplitudes show strong correlation to the mechanical properties of the specimens. Moreover, the changes in contribution to the different failure types explain the observed variation in failure behavior of the individual specimens quantitatively.

Energy dissipation via acoustic emission in ductile crack initiation

“…related to stress wave propagation, due to inherent restrictions placed for example by the sensors. Nevertheless, such efforts provided empirical relations which were used to describe damage initiation and severity by several AE-defined features (Boler, 1990;Bosia et al, 2008;Jungk et al, 2006;King et al, 1981;Sause et al, 2012). The generation of AE from the fracture process has also been described based on the different types of produced waves.…”

Prediction of delamination growth in carbon/epoxy composites using a novel acoustic emission-based approach

“…Because of low strain energy required for the delamination initiation in mode I [7], this mode is the most critical mode of delamination and there are some conducted researches in literature regarding AE based condition monitoring of this mode [8][9][10][11][12].…”

Acoustic Emission

“…Moreover, the direct relation between particular cluster structures and respective AE source mechanisms needs to be validated in every experimental configuration. However, it has been demonstrated by various groups that the cluster strategy proposed in [125] works for source discrimination of AE signals of composite materials and wood fracture and in plant science [24,124,129,[137][138][139][140][141][142][143].…”

“…4.118a clearly different for the different sensor positions. Moreover, the feature range covered by the individual sensors spans the typical feature ranges also used to sort out failure types based on previous work [24,125,138,160]. For the OoP-source results seen in Fig.…”