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![3: Failure modes in a composite ply [3].](profile/Rapee-Ujjin/publication/266608030/figure/fig3/AS:617417294237697@1524215162407/Failure-modes-in-a-composite-ply-3.png)
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![Figure 1.1: Examples of bolted joints in the JAS 39 Gripen [1].](profile/Rapee-Ujjin/publication/266608030/figure/fig1/AS:617417294241795@1524215162319/Examples-of-bolted-joints-in-the-JAS-39-Gripen-1_Q320.jpg)
![Figure 2.22: Cross sectional view of damage [43].](profile/Rapee-Ujjin/publication/266608030/figure/fig19/AS:617417298436096@1524215163063/Cross-sectional-view-of-damage-43_Q320.jpg)
350 words maximum: This thesis presents the results of an investigation of bearing failure at a loaded hole in carbon fibre composite laminates. The investigation included finite element analysis and a program of experimental testing for quasi-isotropic laminates, uni-directional laminates and laminates with fibres steered along pre-defined traject...
Citations
... <40 -Li and Zhao 14 Interface debonding 40-60 -Ageorges et al. 9 1-5 -Ujjin 17 10-15 -Ageorges et al. 9 60-65 -Barre and Benzeggagh 10 30-60 -Park et al. 16 40-50 - Ujjin 17 55-65 -Benmedakhene et al. 11 40-55 -Kotsikos et al. 18 Fibre breakage 75-90 -Ageorges et al. 9 5-20 -Ujjin 17 15-25 -Ageorges et al. 9 85-95 - Barre Journal of Reinforced Plastics and Composites 31 (7) characterise the various failure modes in composites, such as matrix cracking, fibre-matrix debonding, fibre fracture and delamination. For a loaded structure, elastic energy is produced and stored in the material. ...
... <40 -Li and Zhao 14 Interface debonding 40-60 -Ageorges et al. 9 1-5 -Ujjin 17 10-15 -Ageorges et al. 9 60-65 -Barre and Benzeggagh 10 30-60 -Park et al. 16 40-50 - Ujjin 17 55-65 -Benmedakhene et al. 11 40-55 -Kotsikos et al. 18 Fibre breakage 75-90 -Ageorges et al. 9 5-20 -Ujjin 17 15-25 -Ageorges et al. 9 85-95 - Barre Journal of Reinforced Plastics and Composites 31 (7) characterise the various failure modes in composites, such as matrix cracking, fibre-matrix debonding, fibre fracture and delamination. For a loaded structure, elastic energy is produced and stored in the material. ...
Modern day aerospace, automotive, marine, mechanical and civil structures rely on the advanced composites for their added benefits over conventional metallic structures. The complex damage process in composites involves various failure modes such as matrix cracking, fibre-matrix debonding, fibre fracture and delamination. This paper presents an acoustic emission technique for the failure characterisation of top-hat stiffener specimens using conventional piezoelectric acoustic emission sensors and modern fibre Bragg Gratings. Strain insensitive fibre Bragg Grating sensors are used in this experimental investigation to compare the performance of piezoelectric sensors for composite structures. This work has contributed to the development of an acoustic emission sensing system based on fibre Bragg Gratings. Main objectives of this work are to compare the sensing characteristics simultaneously in a composite structure with a surface-bonded acoustic emission–fibre Bragg Grating sensor and acoustic emission–piezoelectric sensor. The feasibility of the system is demonstrated in typical applications of in-situ structural health monitoring based on acoustic emission techniques.
Quasi-brittle materials such as composite laminates, concrete, and toughened ceramics are subject to size effects in which the nominal strength decreases with increasing specimen size. Analyzing the joining of such materials is very important. Mechanically bolted joints are a widely used and suitable method for joining composite laminates in aircraft materials. Two-parameter cohesive laws—linear, constant, and exponential—were implemented analytically to analyze tearing, bearing stress, and remotely applied stress. An extended 2-D finite element model was created to validate the remote applied stress. The model provides reasonably acceptable results that can be used as fast design data for the selection of such materials and optimization of composite bolted joints.
La technique de l’émission acoustique est une méthode passive et non destructive d’évaluation de l’état de santé des structures. Sous contrainte, les structures libèrent de l’énergie sous forme d’ondes transitoires appelées émissions acoustiques, portant les caractéristiques de leurs sources. Ces ondes sont représentées dans un espace commun
de descripteurs. Le nombre de sources et les descripteurs pertinents étant inconnus, pour différents sous-ensembles de descripteurs, un partitionnement est fait en faisant varier le nombre de clusters. La validation consiste à déterminer le nombre de clusters et le sous-ensemble de descripteurs pertinents. Cette validation a longtemps reposé sur des critères basés sur la forme des clusters, sans tenir compte de la chronologie de ces derniers. Dans cette thèse nous avons défini des critères de validation séquentiels dédiés à l’émission acoustique. Une méthode d’évaluation du partitionnement basée sur les histogrammes de déclenchement des clusters a également été proposée
pour un suivi chronologique des événements. Enfin un modèle de partitionnement partiellement supervisé a été proposé pour orienter le partitionnement avec des informations partielles. Ce modèle permet aussi de déterminer le nombre de clusters
naturels de façon automatique, sans l’intervention d’un critère.
Mots-clés : Validation du partitionnement, émission acoustique, incertitude, comparaison d’algorithmes, monitoring, SHM, CND
Bolted/pinned joints are common elements in many engineering structures and their failure can lead to catastrophic failure of these structures. Therefore, their strength prediction is essential for an accurate design of the joints and, consequently, for the reliable design of the structure. The main objective of this paper is to introduce an analytical model to predict the net-tension strength of mechanically fastened joints in isotropic quasi-brittle structures. The model is formulated based on the cohesive zone model. The effect of the material cohesive law, the contact stress distribution due to presence of the bolt, the specimen size and the hole radius to specimen width ratio on the strength of the joint are considered in the present model. The obtained predictions are compared with the available experimental results with good agreement. The present model is capable of introducing simple design charts for the bolted joints in structures made of isotropic quasi-brittle materials.
