The Experts below are selected from a list of 303777 Experts worldwide ranked by ideXlab platform
Ignace Verpoest - One of the best experts on this subject based on the ideXlab platform.
-
the effect of carbon nanotubes on the Damage Development in carbon fiber epoxy composites
Carbon, 2011Co-Authors: Niels De Greef, Larissa Gorbatikh, A Godara, Luca Mezzo, Stepan Vladimirovitch Lomov, Ignace VerpoestAbstract:Abstract The aim of this study is to investigate the effect of carbon nanotubes (CNTs) on the initiation and Development of Damage in a woven carbon fiber/epoxy composite under quasi-static tensile loading. The composite is produced using resin transfer moulding and contains 0.25 wt.% of CNTs in the matrix. The results in the fiber direction report no improvement of the Young’s modulus and a slight improvement of the strength and strain-to-failure. The most important result of the study is a notion that CNTs have a hindering effect on the formation of transverse cracks. The conclusion is drawn from a combined analysis of the acoustic emission measurements (reporting a pronounced shift of all Damage Development thresholds towards higher strains by more than 30%) and X-ray/SEM observations (revealing a lower crack density in the CNT modified composite). The same analysis also indicates that the mechanism of energy dissipation through transverse microcracking is partially replaced by another mechanism that promotes (distributed) Damage through fiber debonding.
-
Damage Development in woven carbon fiber epoxy composites modified with carbon nanotubes under tension in the bias direction
Composites Part A-applied Science and Manufacturing, 2011Co-Authors: Niels De Greef, Larissa Gorbatikh, Stepan Vladimirovitch Lomov, Ignace VerpoestAbstract:Abstract The study investigates the effect of carbon nanotubes (CNTs) on the Damage Development in a woven carbon fiber/epoxy composite under quasi-static tension in the bias direction. The composite is produced by the resin transfer molding and contains 0.25 wt.% of CNTs in the matrix. The tensile tests are carried out till different strain levels and are accompanied with acoustic emission (AE) registration. The nano-modified composite possesses a higher stiffness and strain-to-failure. It also exhibits a significantly increased AE activity, both in terms of the number of events and the energy level, but reveals a lower crack density. The combined analysis of the AE data and X-ray images indicates that in the nano-modified composite cracks progress through the material in smaller jumps than in the virgin composite. The crack faces in the composite with CNTs also display a fine web of secondary fractures, which is not detected in the virgin composite.
-
carbon composites based on multi axial multi ply stitched preforms part 6 fatigue behaviour at low loads stiffness degradation and Damage Development
Composites Part A-applied Science and Manufacturing, 2007Co-Authors: Katleen Vallons, Stepan Vladimirovitch Lomov, Mengmeng Zong, Ignace VerpoestAbstract:Abstract This article studies the fatigue properties of a carbon-fibre cross-ply non-crimp fabric reinforced epoxy composite. Tensile–tensile fatigue cycling was carried out at load levels corresponding to the onset of Damage in a static tensile test, in machine, cross and bias direction. Specimens in machine and cross direction did not fail up to 106 cycles; specimens in bias direction had an average fatigue life Nmax of 3 × 105 cycles. Stiffness degradation in bias direction samples was found to be more severe than in machine or cross direction. Damage Development in the samples was studied by means of X-ray photography and appears to show remarkable resemblance to the Development under a static tensile test and can be qualitatively compared to the behaviour of non-stitched UD laminates. Post-fatigue tensile tests were done at various stages of the fatigue life. Small differences in Damage onset strain level can be found. Failure strain of bias direction tested samples shows significant decrease upon cycling.
-
modelling of the interaction between matrix cracks and delaminations during impact of composite plates
Composites Science and Technology, 1996Co-Authors: Luc Lammerant, Ignace VerpoestAbstract:This paper discusses the investigation of the transverse impact of plate-like composite specimens. It focuses on the initiation of delaminations at matrix cracks and on the interaction of delaminations with matrix cracks. This study shows that an accurate prediction of the Development of matrix cracks and delaminations during impact requires the use of energy criteria, taking into account the appropriate fracture toughness values, depending on the interface and the mixed mode loading. Also, the accumulation of Damage in the plate has to be taken into account when predicting the Damage Development.
Omer Van Der Biest - One of the best experts on this subject based on the ideXlab platform.
-
transverse cracking and poisson s ratio reduction in cross ply carbon fibre reinforced polymers
Journal of Materials Science, 1999Co-Authors: M Surgeon, E Vanswijgenhoven, Martine Wevers, Omer Van Der BiestAbstract:Gradual Damage Development in carbon fibre-reinforced polymers (CFRP) and its effect on the mechanical properties have been important subjects of investigation for many years. Most authors have studied transverse matrix cracking in cross-ply lay-ups and used the longitudinal Young's modulus as an indicator of the extent of Damage Development. Reductions of typically only a few percent have been found at saturation crack spacing. Some authors have studied the effect of matrix cracking on Poisson's ratio. The results show large reductions, but few data are available on the evolution of Poisson's ratio throughout the process of gradual matrix cracking and on the influence of the 0°/90° ply thickness ratio. Moreover, none of the available models seems to accurately predict the quantitative evolution of Poisson's ratio. In this work the degradation of the longitudinal and the transverse properties of a number of cross-ply CFRP laminates due to transverse matrix cracking under longitudinal tension was studied. The longitudinal Young's modulus appeared to be less sensitive to Damage Development, in contrast to Poisson's ratio which exhibited significant reductions in all lay-ups. A micromechanical model, based on the shear lag theory, was developed to predict the evolution of Poisson's ratio and the effect of the 0°/90° ply thickness ratio. The correlation between experiment and theory was very satisfactory.
-
acoustic emission during tensile testing of sic fibre reinforced bmas glass ceramic composites
Composites Part A-applied Science and Manufacturing, 1997Co-Authors: M Surgeon, E Vanswijgenhoven, Martine Wevers, Omer Van Der BiestAbstract:One of the problems preventing the industrial application of ceramic-matrix composites is the lack of an efficient method to detect and discriminate among types of Damage occurring during service. With this in mind, the mechanical response, Damage Development and acoustic emission activity during monotonic tensile testing of a BMAS glass-ceramic matrix reinforced with SiC fibres have been investigated. Damage initiation and propagation were easily detected and evaluated using the acoustic emission technique. Comparing the acoustic emission activity characteristics in simple lay-ups with those of more complex lay-ups allowed discrimination between matrix microcracking, matrix macrocracking accompanied by interface debonding, and delamination cracking. In this way, the paper contributes to the Development of the acoustic emission technique for in situ monitoring of Damage Development in ceramic-matrix composites.
T J Marrow - One of the best experts on this subject based on the ideXlab platform.
-
Damage Development during flexural loading of a 5 directional braided c c sic composite characterized by x ray tomography and digital volume correlation
Ceramics International, 2019Co-Authors: Fan Wan, Rongjun Liu, Yanfei Wang, Yingbin Cao, Changrui Zhang, T J MarrowAbstract:Abstract In situ observations of Damage Development within 3-dimensional 5-directional braided carbon fiber reinforced carbon and silicon carbide (C/C-SiC) ceramic composites, fabricated by gaseous silicon infiltration (GSI) and precursor infiltration pyrolysis (PIP), have been obtained using laboratory X-ray computed tomography during in situ flexural tests. The GSI composite has a denser structure than that fabricated by PIP, but contains initial defects within the fiber bundles. The GSI composite ultimately failed due to fracture across the fiber bundles, while failure of the higher strength PIP composite propagated along the interface between the fiber bundle and matrix with a greater degree of fiber pullout. These differences arise from the higher process temperature and greater degree of matrix-fiber reaction of GSI compared to PIP. Digital volume correlation (DVC), applied to the tomographs, measured the 3-dimensional deformations and hence the specimen curvature. This demonstrated the significant reduction in elastic modulus caused by the Development of internal cracking with tensile strain in both materials.
-
in situ observation of compression Damage in a 3d needled punched carbon fiber silicon carbide ceramic matrix composite
Composite Structures, 2019Co-Authors: Yanfei Wang, Changrui Zhang, T J MarrowAbstract:Abstract Damage Development has been observed in situ within a 3-dimensional needle-punched carbon fiber reinforced carbon and silicon carbide (C/C-SiC) ceramic composite, as compressive loads were applied longitudinally, transversely and obliquely to its anisotropic structure. Laboratory X-ray computed tomographs were analyzed using digital volume correlation to measure the local strains. Cracks exist within the microstructure before the application of load, due to thermal strains, and their propagation is affected by the heterogeneous microstructure and the direction of loading. The punched carbon fiber needles are observed to restrict the propagation of Damage.
-
multi scale modeling of Damage Development in a thermal barrier coating
Surface & Coatings Technology, 2015Co-Authors: Luis Saucedomora, Karel Slamecka, U Thandavamoorthy, T J MarrowAbstract:A multi-scale Finite Element Microstructure MEshfree (FEMME) fracture model for quasi-brittle materials with complex microstructures is applied to simulate thermo-mechanical Damage in a plasma-sprayed thermal barrier coating system. This novel multi-scale technique for Damage simulation allows the influence of the microstructure of the yttria-stabilized zirconia top coat and the geometry of the bond coat and the thermally grown oxide layer to be considered with computational efficiency. Mechanical Damage, due to the thermal strain of an applied temperature difference, is predicted to decrease the top coat Young's modulus. The interaction between the evolution of Damage and temperatures within the top coat is also simulated, demonstrating the capability of this methodology to address coupled multi-scale problems.
Stephen R Hallett - One of the best experts on this subject based on the ideXlab platform.
-
an experimental investigation into quasi static and fatigue Damage Development in bolted hole specimens
Composites Part B-engineering, 2015Co-Authors: Oliver J Nixonpearson, Stephen R HallettAbstract:An extensive experimental program has been carried out to investigate and understand the sequence of Damage Development throughout the life of bolted-hole composite laminates under quasi-static loading and tensionetension fatigue. Quasi-isotropic carbon/epoxy laminates, with stacking sequence [452/902/452/02]S defined as ply scaled and [45/90/-45/0]2S defined as sub-laminate scaled, were used. Specimens were cycled at 5 Hz with various amplitudes to 1 � 10 6 cycles unless failure occurred prior to this limit. For all cases an R ratio of 0.1 was used. Bolt washer pressures of 23 MPa and 70 MPa were investigated. For the ply-level case, the quasi-static test showed both delamination and fibre-dominated pull-out failures for a washer pressure of 23 MPa, and pull-out failure only for 70 MPa. Delamination dominates in fatigue tests. For the sub-laminate case the tests failed by pull-out in both quasi-static and fatigue tests for all washer pressures. It is shown in this paper how the role of delamination is critical in the case of fatigue loading and how this interacts with bolt clamp-up forces. A number of tests were analysed for Damage using X-ray CT scanning and comparisons of Damage are made with tests from previous openhole studies. © 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license
-
an investigation into the Damage Development and residual strengths of open hole specimens in fatigue
Composites Part A-applied Science and Manufacturing, 2015Co-Authors: Oliver J Nixonpearson, Stephen R HallettAbstract:An extensive experimental program was carried out to investigate and understand the sequence of Damage Development throughout the life of open-hole composite laminates loaded in tension-tension fatigue. Quasiisotropic carbon/epoxy laminates, with stacking sequence [45 2 /90 2 /-45 2 /0 2 ] S , [45/90/-45/0] 2S and [45/90/-45/0] 4S were examined. These were selected on the basis that under quasi-static loading the [45 2 /90 2 /-45 2 /0 2 ] S configuration exhibited a delamination dominated mode of failure whilst the [45/90/-45/0] 2S and [45/90/-45/0] 4S configurations showed a fibre dominated failure mode, previously described as “pull-out” and “brittle” respectively. Specimens were fatigue loaded to 1x10 6 cycles or catastrophic failure, which ever
-
Damage Development in open hole composite specimens in fatigue part 2 numerical modelling
Composite Structures, 2013Co-Authors: Oliver J Nixonpearson, Stephen R Hallett, Paul W Harper, Luiz F KawashitaAbstract:This paper follows on from the experimental investigation in Part 1 that identified the Damage mechanisms and sequence in open hole tension specimens under fatigue loading. Here a finite element modelling approach is proposed for the simulation of this Damage Development which leads to the ability to predict overall failure. The models use a Paris-law based cohesive interface element to model delamination and matrix cracks and their interactions. When applied to the tests from Part 1 it was found that the predicted Damage process had a close match to that observed experimentally. Matrix cracking at the surface ply and initiation of matrix cracks in the subsequent plies lead to delamination through thickness, and ultimately to failure at the −45/0 interface. When run at different severities the model could predict an S–N curve which had good agreement to tests.
-
Damage Development in open hole composite specimens in fatigue part 1 experimental investigation
Composite Structures, 2013Co-Authors: Oliver J Nixonpearson, Stephen R Hallett, P J Withers, J RouseAbstract:Abstract An extensive experimental program has been carried out to investigate and understand the sequence of Damage Development throughout the life of open-hole quasi-isotropic IM7/8552 carbon-fibre/epoxy laminates loaded in tension–tension fatigue. Samples were initially quasi-statically loaded to failure to determine an average strength, σUTS. Specimens were then cyclically loaded at 5 Hz at various amplitudes to 1 × 10+6 cycles or to failure (15% loss of stiffness), which ever occurred first. Interrupted fatigue tests were carried out with peak amplitude at 60% of the ultimate static load (60% severity) in order to determine the 3D sequence of Damage events using X-ray Computed Tomography (CT). Matrix cracking at the surface ply and initiation of matrix cracks in the subsequent plies lead to delaminations that progress through the thickness, and ultimately to the propagation of delamination at the −45/0 interface all the way back towards the end tabs. The log (number of cycles to failure) decreased linearly as the maximum fatigue stress level increased.
Oliver J Nixonpearson - One of the best experts on this subject based on the ideXlab platform.
-
an experimental investigation into quasi static and fatigue Damage Development in bolted hole specimens
Composites Part B-engineering, 2015Co-Authors: Oliver J Nixonpearson, Stephen R HallettAbstract:An extensive experimental program has been carried out to investigate and understand the sequence of Damage Development throughout the life of bolted-hole composite laminates under quasi-static loading and tensionetension fatigue. Quasi-isotropic carbon/epoxy laminates, with stacking sequence [452/902/452/02]S defined as ply scaled and [45/90/-45/0]2S defined as sub-laminate scaled, were used. Specimens were cycled at 5 Hz with various amplitudes to 1 � 10 6 cycles unless failure occurred prior to this limit. For all cases an R ratio of 0.1 was used. Bolt washer pressures of 23 MPa and 70 MPa were investigated. For the ply-level case, the quasi-static test showed both delamination and fibre-dominated pull-out failures for a washer pressure of 23 MPa, and pull-out failure only for 70 MPa. Delamination dominates in fatigue tests. For the sub-laminate case the tests failed by pull-out in both quasi-static and fatigue tests for all washer pressures. It is shown in this paper how the role of delamination is critical in the case of fatigue loading and how this interacts with bolt clamp-up forces. A number of tests were analysed for Damage using X-ray CT scanning and comparisons of Damage are made with tests from previous openhole studies. © 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license
-
an investigation into the Damage Development and residual strengths of open hole specimens in fatigue
Composites Part A-applied Science and Manufacturing, 2015Co-Authors: Oliver J Nixonpearson, Stephen R HallettAbstract:An extensive experimental program was carried out to investigate and understand the sequence of Damage Development throughout the life of open-hole composite laminates loaded in tension-tension fatigue. Quasiisotropic carbon/epoxy laminates, with stacking sequence [45 2 /90 2 /-45 2 /0 2 ] S , [45/90/-45/0] 2S and [45/90/-45/0] 4S were examined. These were selected on the basis that under quasi-static loading the [45 2 /90 2 /-45 2 /0 2 ] S configuration exhibited a delamination dominated mode of failure whilst the [45/90/-45/0] 2S and [45/90/-45/0] 4S configurations showed a fibre dominated failure mode, previously described as “pull-out” and “brittle” respectively. Specimens were fatigue loaded to 1x10 6 cycles or catastrophic failure, which ever
-
Damage Development in open hole composite specimens in fatigue part 2 numerical modelling
Composite Structures, 2013Co-Authors: Oliver J Nixonpearson, Stephen R Hallett, Paul W Harper, Luiz F KawashitaAbstract:This paper follows on from the experimental investigation in Part 1 that identified the Damage mechanisms and sequence in open hole tension specimens under fatigue loading. Here a finite element modelling approach is proposed for the simulation of this Damage Development which leads to the ability to predict overall failure. The models use a Paris-law based cohesive interface element to model delamination and matrix cracks and their interactions. When applied to the tests from Part 1 it was found that the predicted Damage process had a close match to that observed experimentally. Matrix cracking at the surface ply and initiation of matrix cracks in the subsequent plies lead to delamination through thickness, and ultimately to failure at the −45/0 interface. When run at different severities the model could predict an S–N curve which had good agreement to tests.
-
Damage Development in open hole composite specimens in fatigue part 1 experimental investigation
Composite Structures, 2013Co-Authors: Oliver J Nixonpearson, Stephen R Hallett, P J Withers, J RouseAbstract:Abstract An extensive experimental program has been carried out to investigate and understand the sequence of Damage Development throughout the life of open-hole quasi-isotropic IM7/8552 carbon-fibre/epoxy laminates loaded in tension–tension fatigue. Samples were initially quasi-statically loaded to failure to determine an average strength, σUTS. Specimens were then cyclically loaded at 5 Hz at various amplitudes to 1 × 10+6 cycles or to failure (15% loss of stiffness), which ever occurred first. Interrupted fatigue tests were carried out with peak amplitude at 60% of the ultimate static load (60% severity) in order to determine the 3D sequence of Damage events using X-ray Computed Tomography (CT). Matrix cracking at the surface ply and initiation of matrix cracks in the subsequent plies lead to delaminations that progress through the thickness, and ultimately to the propagation of delamination at the −45/0 interface all the way back towards the end tabs. The log (number of cycles to failure) decreased linearly as the maximum fatigue stress level increased.
