The Experts below are selected from a list of 10671 Experts worldwide ranked by ideXlab platform
Nuri Ersoy - One of the best experts on this subject based on the ideXlab platform.
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damage mode identification in Transverse Crack tension specimens using acoustic emission and correlation with finite element progressive damage model
Composites Part B-engineering, 2019Co-Authors: Sina Ahmadvashaghbash, Nuri ErsoyAbstract:© 2018 Elsevier Ltd In this study, damage progression in unidirectional composite specimens is investigated. Transverse Crack Tension specimens are used to stimulate damage in a predetermined progressive sequence. Acoustic Emission (AE) registration technique and its location detection capability is used to identify and locate the damage modes during the tension tests. The k-means++ algorithm is applied to cluster similar AE events and obtain reliable correlations between the damage modes and AE characteristics. Damage modes at the end of interrupted tests are identified under an optical microscope and correlated with locations of AE clusters. It is seen that matrix Cracks have high amplitude and duration, whereas delaminations have low amplitude and mid-duration, and fibre breaks have high average frequency characteristics. A finite element analysis was performed to predict the progressive failure behaviour including intralaminar failure and delaminations. The correlations between the AE clusters and damage modes are validated with the finite element model.
Dong Ju Han - One of the best experts on this subject based on the ideXlab platform.
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vibration analysis of periodically time varying rotor system with Transverse Crack
Mechanical Systems and Signal Processing, 2007Co-Authors: Dong Ju HanAbstract:This paper proposes the vibration analysis for the periodically time-varying rotor system with Transverse Crack based on the complex modal analysis by introducing the modulated coordinates. From the feasibility of the Crack modeling by harmonically varying stiffness, for which the dynamic behaviors of breathing Crack depending on two modeling structures are investigated, the vibration analysis associated with modal characteristics, whirling, instability, directional frequency response functions (dFRFs) and directional spectrum (dS) is carried out. Using the feature of the reverse dFRFs strongly representing the effect of the Crack and the interpretation of the dS patterns, the effective method to identify the modes due to the presence or propagation of a Transverse Crack is suggested.
F. P. Van Der Meer - One of the best experts on this subject based on the ideXlab platform.
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The Transverse Crack Tension test revisited: An experimental and numerical study
Composite Structures, 2016Co-Authors: T. Scalici, F. P. Van Der Meer, Giovanna Pitarresi, Giuseppe Catalanotti, Alice ValenzaAbstract:Several problems arise when measuring the mode II interlaminar fracture toughness using a Transverse Crack Tension specimen; in particular, the fracture toughness depends on the geometry of the specimen and cannot be considered a material parameter. A preliminary experimental campaign was conducted on TCTs of different sizes but no fracture toughness was measured because the TCTs failed in an unacceptable way, invalidating the tests. A comprehensive numerical and experimental investigation is conducted to identify the main causes of this behaviour and a modification of the geometry of the specimen is proposed. It is believed that the obtained results represent a significant contribution in the understanding of the TCT test as a mode II characterization procedure and, at the same time, provide new guidelines to characterize the mode II Crack propagation under tensile loads.
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a numerical investigation into the size effect in the Transverse Crack tension test for mode ii delamination
Composites Part A-applied Science and Manufacturing, 2013Co-Authors: F. P. Van Der Meer, L J SluysAbstract:Abstract In experimental studies, a size effect has been measured for the fracture energy in the Transverse Crack tension test. This paper presents a numerical investigation into the cause of this size effect. A finite element model has been developed that includes delamination, friction and shear nonlinearity. After calibration of the model, the size effect was reproduced well. It is shown that shear nonlinearity and friction separately contribute to the measured size effect and that significant amplification of the size effect takes place because of their interaction. As a consequence of their interaction, the unstable Crack growth that was observed for the thicker specimens in the experiments is also present in the model results.
Alice Valenza - One of the best experts on this subject based on the ideXlab platform.
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The Transverse Crack Tension test revisited: An experimental and numerical study
Composite Structures, 2016Co-Authors: T. Scalici, F. P. Van Der Meer, Giovanna Pitarresi, Giuseppe Catalanotti, Alice ValenzaAbstract:Several problems arise when measuring the mode II interlaminar fracture toughness using a Transverse Crack Tension specimen; in particular, the fracture toughness depends on the geometry of the specimen and cannot be considered a material parameter. A preliminary experimental campaign was conducted on TCTs of different sizes but no fracture toughness was measured because the TCTs failed in an unacceptable way, invalidating the tests. A comprehensive numerical and experimental investigation is conducted to identify the main causes of this behaviour and a modification of the geometry of the specimen is proposed. It is believed that the obtained results represent a significant contribution in the understanding of the TCT test as a mode II characterization procedure and, at the same time, provide new guidelines to characterize the mode II Crack propagation under tensile loads.
Ramesh Talreja - One of the best experts on this subject based on the ideXlab platform.
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simulation of manufacturing induced fiber clustering and matrix voids and their effect on Transverse Crack formation in unidirectional composites
Composites Part A-applied Science and Manufacturing, 2019Co-Authors: Aswathi Sudhir, Ramesh TalrejaAbstract:Abstract This work is a contribution to the fields of computational micromechanics and virtual testing of fiber reinforced composite materials. Particular focus is on deriving trends related to the early failure events leading to Crack formation in unidirectional composites under Transverse tension. A simulation scheme is proposed to capture fiber clustering and matrix microvoids in a resin infusion process. A systematic procedure is developed to quantify these manufacturing induced defects in terms of fiber displacements (mobility) from an initially dry fiber bundle to the fully resin-infused composite. Using established methods for stochastic characterization of microstructures, the minimum size of a representative volume element (RVE) is estimated and its multiple realizations are used in an embedded cell model for finite element based computation of the local stress fields. Strain energy based point-failure criteria are then employed to ascertain occurrence of the most likely first failure mechanism. A matrix Crack is assumed to form by coalescence of the point-failures as precursors. Parametric studies are performed to clarify the effects of the degree of fiber clustering, the volume fraction of matrix microvoids and the constituent properties on Transverse Crack formation. Experimental data available in the literature support the predictions of the simulations.
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Transverse Crack formation in unidirectional plies predicted by means of a percolation concept
Composites Part A-applied Science and Manufacturing, 2019Co-Authors: L. Maragoni, Ramesh TalrejaAbstract:Abstract Transverse Crack formation in epoxy based unidirectional composites is treated by means of a percolation concept. A previously proposed criterion for brittle cavitation in epoxies is used as the criterion for fibre/matrix debonding. Then, neglecting the details of debond linkups, a Transverse Crack is assumed to form when the intensity of the linkup process crosses a threshold analogous to the percolation threshold. The predicted applied strain to Transverse Crack formation based on this assumption agrees well with experimental data. A parametric study is conducted to reveal the effects of thermal cooldown temperature, fibre volume fraction and fibre elastic properties on the percolation threshold for Transverse Crack formation.
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Transverse Crack formation in unidirectional composites by linking of fibre/matrix debond Cracks
Composites Part A-applied Science and Manufacturing, 2018Co-Authors: Linqi Zhuang, Ramesh Talreja, Janis VarnaAbstract:Abstract Plausible mechanisms of Transverse Crack formation in unidirectional (UD) composites under applied tension normal to fibres are investigated numerically using a finite element model. Two initial scenarios are considered: Scenario 1 where a pre-existing single fibre/matrix debond Crack kinks out into the matrix and induces fibre/matrix debonding at neighbouring fibres, and Scenario 2 where multiple pre-existing debond Cracks link up by the debond growth and Crack kink-out process. The 2-D finite element model consists of a circular region of matrix with a central fibre surrounded by six fibres in a hexagonal pattern. The region is embedded in a homogenized UD composite of rectangular outer boundary. Energy release rates (ERRs) of interface Cracks and kinked-out Cracks are calculated under applied tension normal to fibres. Results show that Scenario 2 is more likely to lead to formation of a Transverse Crack than Scenario 1. These results provide understanding of the roles of fibre clustering and fibre volume fraction on Transverse Crack formation in composites.
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Transverse Crack formation in unidirectional composites by linking of fibre matrix debond Cracks
Composites Part A-applied Science and Manufacturing, 2018Co-Authors: Ramesh Talreja, Linqi Zhuang, Janis VarnaAbstract:Abstract Plausible mechanisms of Transverse Crack formation in unidirectional (UD) composites under applied tension normal to fibres are investigated numerically using a finite element model. Two initial scenarios are considered: Scenario 1 where a pre-existing single fibre/matrix debond Crack kinks out into the matrix and induces fibre/matrix debonding at neighbouring fibres, and Scenario 2 where multiple pre-existing debond Cracks link up by the debond growth and Crack kink-out process. The 2-D finite element model consists of a circular region of matrix with a central fibre surrounded by six fibres in a hexagonal pattern. The region is embedded in a homogenized UD composite of rectangular outer boundary. Energy release rates (ERRs) of interface Cracks and kinked-out Cracks are calculated under applied tension normal to fibres. Results show that Scenario 2 is more likely to lead to formation of a Transverse Crack than Scenario 1. These results provide understanding of the roles of fibre clustering and fibre volume fraction on Transverse Crack formation in composites.
