This work aims at developing a new clustering method of acoustic emission (AE) signals, called In... more This work aims at developing a new clustering method of acoustic emission (AE) signals, called Incremental Clustering (IC), induced by damage mechanisms of glass fibre reinforced composite materials. The advantage of this method over other methods from literature is the capability to identify the signals carrying information and to provide the types of damage mechanisms without using additional expertise. To apply the method based on actual data, several specimens of glass fibre reinforced epoxy composites have been manufactured and subjected to specific mechanical tests. The developed method was compared to the k-means method that is extensively used to classify the \{AE\} signals. The reliability of the learning database was checked by the performance evaluation of the k Nearest Neighbours’ (kNN) classifiers. The kNN classifiers were trained by the training dataset and evaluated by the test dataset. The area under the receiver operating characteristic curves (AUC) was used as a criterion for evaluating the performance of classifiers. From specific mechanical tests, the \{IC\} method presented more advantages to successfully classify the \{AE\} signals and build a labelled learning database than the k-means method. The chronology of appearance of different damage mechanisms demonstrated the effectiveness of the incremental method. The powerful performance of the supervised method, characterized by values of \{AUC\} greater than 0.9 for each damage type, confirmed the reliability of the obtained learning database.
Composites Part A: Applied Science and Manufacturing, 2016
Abstract This paper aims at investigating the hybridisation effect on the diffusion kinetic and t... more Abstract This paper aims at investigating the hybridisation effect on the diffusion kinetic and the tensile mechanical behaviour of flax–glass fibres reinforced epoxy composites. For this purpose, hybrid composites composed of flax and glass fibre laminates with different stacking sequences were consolidated by compression moulding and subjected to environment ageing. The obtained results show that the water uptake and the diffusion coefficient are clearly reduced by the addition of glass fibre layers in flax laminate. The ageing conditions performed show that the flax–glass hybridisation presents a positive effect in a wet environment at low temperatures (∼20 °C) in the Young’s modulus and the tensile strength. For example, the Young’s modulus fell by 50% and 41% for hybrid laminates with 6% and 11% of glass fibres, and by 67% for the Flax laminate. However, the flax–glass hybridisation was not necessarily a relevant choice when the hybrid laminates were exposed in a wet environment at high temperatures. Indeed, at 55 °C, this hybridisation had a negative effect on the tensile strength and on the specific tensile strength.
Composites Part A: Applied Science and Manufacturing, 2016
Abstract This paper aims at assessing the experimental and analytical parameters of moisture diff... more Abstract This paper aims at assessing the experimental and analytical parameters of moisture diffusion of quasi-unidirectional and twill flax-fibres reinforced epoxy composites. The tested specimens of these composites were elaborated by hand lay-up technique at room temperature by using a vacuum moulding process. For several days, the samples were subjected to three ageing conditions, in order to evaluate the percentage of moisture uptake according to the ageing time. Next, the collected experimental data were analysed by using an optimisation program of Matlab software in order to identify the 3D diffusion parameters. The obtained results showed that the morphology and the anisotropy of flax fibres had a significant influence on the moisture diffusion. It also showed that moisture diffusion behaviour predicted by the 3D Fick model was in good agreement with the experimental results.
This paper aims to investigate the effect of hygrot hermal ageing on the mechanical properties of... more This paper aims to investigate the effect of hygrot hermal ageing on the mechanical properties of short Hemp Fibre Reinforced Polymers (HFRP) comp sites with different fibre contents (from 10% to 40%). Injected specimens were subjecte d to hygrothermal ageing with a relative humidity (RH) of 80% and a temperature of 25 °C. Th e water absorption and its effect on tensile properties of HFRP composites are investiga ted. The Acoustic Emission (AE) technique combined with electronic microscope obser vations were carried out to discriminate some damage mechanisms at the microscopic scale. F or the proposed hygrothermal ageing of HFRP composites, it is shown that the moisture a bsorption shows a quasi linear evolution according to the hemp-fibre content. Besides, no si gnificant effects on the mechanical characteristics of the studied composites were obse rved.
This work aims at developing a new clustering method of acoustic emission (AE) signals, called In... more This work aims at developing a new clustering method of acoustic emission (AE) signals, called Incremental Clustering (IC), induced by damage mechanisms of glass fibre reinforced composite materials. The advantage of this method over other methods from literature is the capability to identify the signals carrying information and to provide the types of damage mechanisms without using additional expertise. To apply the method based on actual data, several specimens of glass fibre reinforced epoxy composites have been manufactured and subjected to specific mechanical tests. The developed method was compared to the k-means method that is extensively used to classify the \{AE\} signals. The reliability of the learning database was checked by the performance evaluation of the k Nearest Neighbours’ (kNN) classifiers. The kNN classifiers were trained by the training dataset and evaluated by the test dataset. The area under the receiver operating characteristic curves (AUC) was used as a criterion for evaluating the performance of classifiers. From specific mechanical tests, the \{IC\} method presented more advantages to successfully classify the \{AE\} signals and build a labelled learning database than the k-means method. The chronology of appearance of different damage mechanisms demonstrated the effectiveness of the incremental method. The powerful performance of the supervised method, characterized by values of \{AUC\} greater than 0.9 for each damage type, confirmed the reliability of the obtained learning database.
Composites Part A: Applied Science and Manufacturing, 2016
Abstract This paper aims at investigating the hybridisation effect on the diffusion kinetic and t... more Abstract This paper aims at investigating the hybridisation effect on the diffusion kinetic and the tensile mechanical behaviour of flax–glass fibres reinforced epoxy composites. For this purpose, hybrid composites composed of flax and glass fibre laminates with different stacking sequences were consolidated by compression moulding and subjected to environment ageing. The obtained results show that the water uptake and the diffusion coefficient are clearly reduced by the addition of glass fibre layers in flax laminate. The ageing conditions performed show that the flax–glass hybridisation presents a positive effect in a wet environment at low temperatures (∼20 °C) in the Young’s modulus and the tensile strength. For example, the Young’s modulus fell by 50% and 41% for hybrid laminates with 6% and 11% of glass fibres, and by 67% for the Flax laminate. However, the flax–glass hybridisation was not necessarily a relevant choice when the hybrid laminates were exposed in a wet environment at high temperatures. Indeed, at 55 °C, this hybridisation had a negative effect on the tensile strength and on the specific tensile strength.
Composites Part A: Applied Science and Manufacturing, 2016
Abstract This paper aims at assessing the experimental and analytical parameters of moisture diff... more Abstract This paper aims at assessing the experimental and analytical parameters of moisture diffusion of quasi-unidirectional and twill flax-fibres reinforced epoxy composites. The tested specimens of these composites were elaborated by hand lay-up technique at room temperature by using a vacuum moulding process. For several days, the samples were subjected to three ageing conditions, in order to evaluate the percentage of moisture uptake according to the ageing time. Next, the collected experimental data were analysed by using an optimisation program of Matlab software in order to identify the 3D diffusion parameters. The obtained results showed that the morphology and the anisotropy of flax fibres had a significant influence on the moisture diffusion. It also showed that moisture diffusion behaviour predicted by the 3D Fick model was in good agreement with the experimental results.
This paper aims to investigate the effect of hygrot hermal ageing on the mechanical properties of... more This paper aims to investigate the effect of hygrot hermal ageing on the mechanical properties of short Hemp Fibre Reinforced Polymers (HFRP) comp sites with different fibre contents (from 10% to 40%). Injected specimens were subjecte d to hygrothermal ageing with a relative humidity (RH) of 80% and a temperature of 25 °C. Th e water absorption and its effect on tensile properties of HFRP composites are investiga ted. The Acoustic Emission (AE) technique combined with electronic microscope obser vations were carried out to discriminate some damage mechanisms at the microscopic scale. F or the proposed hygrothermal ageing of HFRP composites, it is shown that the moisture a bsorption shows a quasi linear evolution according to the hemp-fibre content. Besides, no si gnificant effects on the mechanical characteristics of the studied composites were obse rved.
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