Health monitoring of sandwich composites with auxetic core subjected to indentation tests using acoustic emission

2021 ◽  
pp. 147592172110539
Author(s):  
Khawla Essassi ◽  
Jean-Luc Rebiere ◽  
Abderrahim EL Mahi ◽  
Mohamed Amine Ben souf ◽  
Anas Bouguecha ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Experimental Tests ◽  
Damage Mechanism ◽  
Recognition Algorithm ◽  
Acoustic Energy ◽  
Matrix Cracking ◽  
Sandwich Composite ◽  
Cumulative Number ◽  
The Core ◽  
Number Of Cells

The quasi-static indentation behavior of an eco-sandwich composite with auxetic core consisting of polylactic acid reinforced with flax fibers will be discussed in this article. The structures involved in the test were manufactured using 3D printing technique. Four configurations with different number of cells in the core, were tested. It is found that sandwiches with high number of cells are stiffer and dissipate more energy. Experimental tests were monitored with acoustic emission technique in order to detect the appearance and the evolution of damage behavior. An unsupervised pattern recognition algorithm was used to post process the acoustic emission signals. The classification is conducted using k-means algorithm. Results show that there are three different classes of events for each configuration, which are the core cracking, the matrix cracking and the fiber/matrix debonding. The evaluation of the contribution of each damage mechanism on the total amount of failure was deduced according to the amplitude range, the cumulative number of hits and the acoustic energy activity. Furthermore, macroscopic and microscopic observations were performed in order to correlate acoustic emission classes with the damage mechanisms observed.

scholarly journals Damage Propagation Analysis in the Single Lap Shear and Single Lap Shear-Riveted CFRP Joints by Acoustic Emission and Pattern Recognition Approach

Materials ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 3963
Author(s):  
Claudia Barile ◽  
Caterina Casavola ◽  
Giovanni Pappalettera ◽  
Paramsamy Kannan Vimalathithan
Keyword(s):  
Pattern Recognition ◽  
Acoustic Emission ◽  
Research Work ◽  
Amplitude Distribution ◽  
Acoustic Energy ◽  
Matrix Cracking ◽  
Cumulative Energy ◽  
Cfrp Laminates ◽  
Hybrid Joint ◽  
Lap Shear

An innovative way of using the Acoustic Emission (AE) technique is introduced in this research work. The ratio of recorded acoustic energy and the counts recorded for each acoustic event were used for characterizing Carbon Fiber Reinforced Plastic (CFRP) laminates adhesively bonded with and without mechanical fasteners. The cumulative counts and cumulative energy of the recorded acoustic events were used for identifying the critical points of failure under loading of these hybrid joint specimens. The peak amplitude distribution was used for identifying the different damage modes such as delamination, matrix cracking and fiber breakage, albeit, ineffectively. The new parameter energy per count was introduced in this work, which can successfully identify the different damage modes under loading. To differentiate the damage modes using the energy per count, they were clustered using k-means++ pattern recognition technique. The method introduced in this work can estimate the damage modes of the CFRP specimens.

scholarly journals Damage mode identification of Carbon fiber/Epoxy composites under fatigue process using acoustic emission monitoring

2021 ◽  
Vol 2125 (1) ◽  
pp. 012036
Author(s):  
Yi-Er Guo ◽  
De-Guang Shang ◽  
Lin-Xuan Zuo ◽  
Lin-Feng Qu ◽  
Di Cai ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Carbon Fiber ◽  
Shear Failure ◽  
Fatigue Behavior ◽  
Damage Mechanism ◽  
Matrix Cracking ◽  
Epoxy Composites ◽  
Interface Debonding ◽  
Accumulated Damage ◽  
Carbon Fiber Epoxy

Abstract In this paper, the static and fatigue behavior of carbon fiber/Epoxy composites laminate are investigated. The degradation and damage evolution in the composite laminate tests process were monitored using the acoustic emission technique. The acoustic signals collected during the tests were analyzed. The results of the acoustic emission signal accumulated during static and fatigue tests are compared in order to identify the accumulated damage mechanism of carbon fiber/Epoxy composites laminate. The accumulated damage is manifested by matrix cracking, fiber/matrix interface debonding, shear failure, delamination, and fiber break.

scholarly journals Damage mechanisms assessment of hybrid carbon/flax fibre composites using acoustic emission

2019 ◽  
Vol 283 ◽  
pp. 03003 ◽  
Author(s):  
Mariem Ben Ameur ◽  
Jean-Luc Rebiere ◽  
Abderrahim El Mahi ◽  
Moez Beyaoui ◽  
Moez Abdennadher ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Composite Laminates ◽  
Multivariable Analysis ◽  
Damage Mechanism ◽  
Tensile Tests ◽  
Flax Fibre ◽  
Acoustic Energy ◽  
Uniaxial Tensile ◽  
Damage Mechanisms ◽  
Hybrid Carbon

The purpose of the present experimental study is to describe the damage mechanisms occurring in epoxy matrix composites reinforced with hybrid carbon-flax fibres. The samples tested were consist of unidirectional carbon and flax fibre plies with different stacking sequences. Composite laminates were manufactured by hand lay-up process. The specimens were tested under uniaxial tensile loading. The tests carried out were monitored by the acoustic emission (AE) technique. The results obtained during the monotonic tensile tests were analyzed in order to identify the damage mechanisms evolutions. The recorded events were classified with the k-means algorithm which is a statistical multivariable analysis. In addition, it was an unsupervised classification according to temporal descriptors. The percentage of each damage mechanism to the global failure was evaluated by the hits number and the acoustic energy activity. The AE technique was correlated with scanning electron microscopy (SEM) observations to identify the typical damage mechanisms.

scholarly journals Damage Mechanism Evaluation of Large-Scale Concrete Structures Affected by Alkali-Silica Reaction Using Acoustic Emission

2018 ◽  
Vol 8 (11) ◽  
pp. 2148 ◽  
Author(s):  
Vafa Soltangharaei ◽  
Rafal Anay ◽  
Nolan Hayes ◽  
Lateef Assi ◽  
Yann Le Pape ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Nuclear Power ◽  
Power Plants ◽  
Large Scale ◽  
Concrete Structures ◽  
Volumetric Strain ◽  
Damage Mechanism ◽  
Recognition Algorithm ◽  
Alkali Silica Reaction ◽  
The Common

Alkali-silica reaction has caused damage to concrete structures, endangering structural serviceability and integrity. This is of concern in sensitive structures such as nuclear power plants. In this study, acoustic emission (AE) was employed as a structural health monitoring strategy in large-scale, reinforced concrete specimens affected by alkali-silica reaction with differing boundary conditions resembling the common conditions found in nuclear containments. An agglomerative hierarchical algorithm was utilized to classify the AE data based on energy-frequency based features. The AE signals were transferred into the frequency domain and the energies in several frequency bands were calculated and normalized to the total energy of signals. Principle component analysis was used to reduce feature redundancy. Then the selected principal components were considered as features in an input of the pattern recognition algorithm. The sensor located in the center of the confined specimen registered the largest portion of AE energy release, while in the unconfined specimen the energy is distributed more uniformly. This confirms the results of the volumetric strain, which shows that the expansion in the confined specimen is oriented along the thickness of the specimen.

scholarly journals Experimental Characterization for Failure Behavior of Woven Modified Carbon/Carbon Composites Under Pin-Loading

2020 ◽  
Author(s):  
Yanfeng Zhang ◽  
Zhengong Zhou ◽  
Zhiyong Tan
Keyword(s):  
Acoustic Emission ◽  
Failure Mode ◽  
Damage Mechanism ◽  
Diameter Ratio ◽  
Hole Diameter ◽  
Matrix Cracking ◽  
Interface Debonding ◽  
Failure Behavior ◽  
Carbon Composites ◽  
Emission Signal

Abstract An experimental approach of 5-harness satin woven silicon carbide modification carbon/carbon composites arranged in various geometrical configuration is presented in this paper. Seven types of samples divided into three groups were tested under pin-loading to examine the effects of width-to-hole diameter ratio (W/D), edge distance -to- hole diameter ratio (E/D) and hole diameter-to- thickness ratio (D/t) on the failure mode. To further enhance the understanding of failure propagation, damage mechanism was observed and assessed combining acoustic emission monitoring. From the experimental results and observations, it follows that the net tension and shearing out failure respectively switch to the bearing failure with the increasing ratio of W/D and E/D, while D/t hardly affect the failure mode. Major features of damage mechanism include matrix cracking, fiber buckling and pulling-out, interface debonding, delamination and fiber fracture corresponding to different acoustic emission signal ranges.

Static and dynamic response of sandwich beams with lattice and pantographic cores

2021 ◽  
pp. 109963622110338
Author(s):  
Yury Solyaev ◽  
Arseniy Babaytsev ◽  
Anastasia Ustenko ◽  
Andrey Ripetskiy ◽  
Alexander Volkov
Keyword(s):  
Mechanical Performance ◽  
Lattice Structure ◽  
Unit Length ◽  
Experimental Tests ◽  
Plane Geometry ◽  
Sandwich Beams ◽  
Static Tests ◽  
Three Point Bending ◽  
The Core ◽  
The Impact

Mechanical performance of 3d-printed polyamide sandwich beams with different type of the lattice cores is investigated. Four variants of the beams are considered, which differ in the type of connections between the elements in the lattice structure of the core. We consider the pantographic-type lattices formed by the two families of inclined beams placed with small offset and connected by stiff joints (variant 1), by hinges (variant 2) and made without joints (variant 3). The fourth type of the core has the standard plane geometry formed by the intersected beams lying in the same plane (variant 4). Experimental tests were performed for the localized indentation loading according to the three-point bending scheme with small span-to-thickness ratio. From the experiments we found that the plane geometry of variant 4 has the highest rigidity and the highest load bearing capacity in the static tests. However, other three variants of the pantographic-type cores (1–3) demonstrate the better performance under the impact loading. The impact strength of such structures are in 3.5–5 times higher than those one of variant 4 with almost the same mass per unit length. This result is validated by using numerical simulations and explained by the decrease of the stress concentration and the stress state triaxiality and also by the delocalization effects that arise in the pantographic-type cores.

Optimization of performance in multi-cell beams with different surface slopes for use in vehicle structure using a multi-objective evolutionary algorithm based on decomposition

2021 ◽  
pp. 146442072199784
Author(s):  
S Chahardoli ◽  
Mohammad Sheikh Ahmadi ◽  
TN Tran ◽  
Afrasyab Khan
Keyword(s):  
Decomposition Method ◽  
Experimental Tests ◽  
Surface Slope ◽  
Optimal Model ◽  
Degree Polynomial ◽  
Numerical Tests ◽  
Numerical Studies ◽  
Surface Slopes ◽  
Vehicle Structure ◽  
Number Of Cells

This study examined the effect of the upper surface slope and the number of cells in the side beams on the collapse properties using experimental and numerical tests. The numerical studies were conducted with LS-DYNA software, and the accuracy of numerical results was investigated by experimental tests. Using MATLAB software, the second-degree polynomial functions were obtained for the collapse properties of the specimens. Also, after the optimization by the decomposition method, the best mode was introduced for the specimens. The studies on collapse properties showed that increasing the number of cells leads to a decrease in all collapse properties, and increasing the upper surface slope leads to an increase in the collapse properties. Moreover, the optimization results by decomposition method showed that this method could suggest the most optimal model for multi-cell and sloping beams.

Cumulative acoustic emission energy for damage detection in composites reinforced by carbon fibers within low-cycle fatigue regime at various displacement amplitudes and rates

2021 ◽  
pp. 096739112098570
Author(s):  
Mohammad Azadi ◽  
Mohsen Alizadeh ◽  
Seyed Mohammad Jafari ◽  
Amin Farrokhabadi
Keyword(s):  
Acoustic Emission ◽  
Carbon Fibers ◽  
Polymer Matrix Composites ◽  
Low Cycle Fatigue ◽  
Energy Parameter ◽  
Fatigue Tests ◽  
Matrix Cracking ◽  
Matrix Composites ◽  
Cycle Fatigue ◽  
Cumulative Energy

In the present article, acoustic emission signals were utilized to predict the damage in polymer matrix composites, reinforced by carbon fibers, in the low-cycle fatigue regime. Displacement-controlled fatigue tests were performed on open-hole samples, under different conditions, at various displacement amplitudes of 5.5, 6.0, 6.5 and 7.0 mm and also under various displacement rates of 25, 50, 100 and 200 mm/min. After acquiring acoustic emission signals during cycles, two characteristic parameters were used, including the energy and the cumulative energy. Obtained results implied that the energy parameter of acoustic emission signals could be used only for the macroscopic damage, occurring at more than 65% of normalized fatigue cycles under different test conditions. However, the cumulative energy could properly predict both microscopic and macroscopic defects, at least two failure types, including matrix cracking at first cycles and the fiber breakage at last cycles. Besides, scanning electron microscopy images proved initially such claims under all loading conditions.

scholarly journals Experimental Tests for Measuring Individual Attentional Characteristics in Songbirds

Animals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 2233
Author(s):  
Loïc Pougnault ◽  
Hugo Cousillas ◽  
Christine Heyraud ◽  
Ludwig Huber ◽  
Martine Hausberger ◽  
...  
Keyword(s):  
Cognitive Processes ◽  
Comparative Research ◽  
Visual Stimuli ◽  
Experimental Tests ◽  
European Starling ◽  
Auditory Stimuli ◽  
The Core ◽  
Cognitive Studies ◽  
Individual Variations ◽  
Species Specific

Attention is defined as the ability to process selectively one aspect of the environment over others and is at the core of all cognitive processes such as learning, memorization, and categorization. Thus, evaluating and comparing attentional characteristics between individuals and according to situations is an important aspect of cognitive studies. Recent studies showed the interest of analyzing spontaneous attention in standardized situations, but data are still scarce, especially for songbirds. The present study adapted three tests of attention (towards visual non-social, visual social, and auditory stimuli) as tools for future comparative research in the European starling (Sturnus vulgaris), a species that is well known to present individual variations in social learning or engagement. Our results reveal that attentional characteristics (glances versus gazes) vary according to the stimulus broadcasted: more gazes towards unusual visual stimuli and species-specific auditory stimuli and more glances towards species-specific visual stimuli and hetero-specific auditory stimuli. This study revealing individual variations shows that these tests constitute a very useful and easy-to-use tool for evaluating spontaneous individual attentional characteristics and their modulation by a variety of factors. Our results also indicate that attentional skills are not a uniform concept and depend upon the modality and the stimulus type.

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