The Experts below are selected from a list of 264 Experts worldwide ranked by ideXlab platform
Pete Linde - One of the best experts on this subject based on the ideXlab platform.
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effects of Ply Thickness and architecture on the strength of composite sub structures
Composite Structures, 2020Co-Authors: C Furtado, Rodrigo P Tavares, A Arteiro, J Xavie, Pete LindeAbstract:Abstract This work presents an experimental study on the effect of: Ply Thickness; Ply-level hybridization; and type of Ply architecture on the damage mechanisms that dominate failure and strength of multidirectional laminates. Nine effectively equivalent 0°dominated multidirectional laminates made from unidirectional carbon fibre tapes (UD), non-crimp fabrics (NCF) and spread-tow fabrics (STF) with Thickness ranging from 67 μ m to 268 μ m are defined and tested under plain strength tension and compression, open-hole tension and compression, filled-hole compression and tension-bearing. An overall improvement of the strengths with the decrease of Ply Thickness is observed for the UD and NCF laminates, but nearly no effect of Ply Thickness is detected for STF laminates. Ply-level hybridization, where thin off-axis plies are combined with thicker grade 0°plies contributes to the improvement of the laminate response, especially when thicker 0°plies are used. However, hybrid-Ply laminates are more sensitive to the loading direction and are, therefore, only suitable in structures where highly oriented loadings are expected. Fabric-based laminates do not show especial susceptibility to early failure compared to UD laminates. Their use can, therefore, be an economical solution that does not compromise the structural response, ensuring the weight benefits of composite materials at lower processing costs.
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a virtual testing based search for optimum compression after impact strength in thin laminates using Ply Thickness hybridization and unsymmetrical designs
Composites Science and Technology, 2020Co-Authors: A Sasikuma, Pete Linde, D Trias, J Costa, J Llobe, I R Coza, A TuroAbstract:In the quest to improve the compression after impact (CAI) strength of thin laminates, Ply-hybrid laminates (where plies of different Thicknesses are mixed) have been used in a previous study to mitigate the fibre failure and, consequently, improve the CAI strength. In the same study, hybrid laminates were proposed following qualitative design rules. In this paper, we systematically look for hybrid stacking sequences with improved damage tolerance by virtually testing all the laminates in a defined design space. While the laminates in the design space are made of intermediate and thick Ply grades, the baseline laminate has only intermediate grade plies. Using an in-house numerical model, we virtually tested, (impact and CAI at two impact energies), all the candidate stacking sequences. The best hybrid laminates considerably improved the CAI strength over the baseline (31% and 40% improvement for the symmetric and unsymmetrical hybrid laminates, respectively). One of the best hybrid laminates was then manufactured and tested experimentally to validate the approach. Through virtual testing, this study demonstrates the benefits of using Ply Thickness hybrid laminates and the feasibility of optimizing the stacking sequence for impact damage tolerance.
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is there a Ply Thickness effect on the mode i intralaminar fracture toughness of composite laminates
Theoretical and Applied Fracture Mechanics, 2020Co-Authors: P P Camanho, C Furtado, A Arteiro, Pete Linde, Ia L WardleAbstract:Abstract The apparent crack resistance curves associated with longitudinal tensile failure of carbon fibre reinforced epoxy composite systems with Ply Thicknesses of 0.075 mm, 0.134 mm and 0.268 mm are determined experimentally from the size effect law of geometrically similar double edge notch tension cross-Ply specimens. An increase in notched strength as a function of the Ply Thickness and a corresponding increase of the measured intralaminar fracture toughness is observed. This increase is shown to be a consequence of the appearance of split cracks in the thicker 0° plies in the vicinity of the notches. The numerical models developed demonstrate that if the notch blunting mechanisms are properly represented, the laminate strength is well predicted for a constant value of the Ply intralaminar fracture toughness. This supports the hypothesis that these mechanisms are responsible for the higher strength of the thicker plies, and that the intralaminar fracture toughness of the 0° plies should not be scaled with the Ply Thickness.
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effect of Ply Thickness and Ply level hybridization on the compression after impact strength of thin laminates
Composites Part A-applied Science and Manufacturing, 2019Co-Authors: A Sasikuma, Pete Linde, D Trias, J Costa, N Lanco, J OAbstract:There is a lack of research available on how thin laminates respond to impact and post impact loads, even though thin structures are used in present-day aircrafts. This experimental paper employs thick, standard and thin uni-directional plies to investigate the effect Ply Thickness has on thin laminates on their impact and compression after impact (CAI) response. Further, we propose two hybrid laminates where thick or standard plies are mixed with thin plies, respectively, in an effort to improve the CAI strength of thin laminates. Results reveal that, contrary to thick laminates, thin laminates made of only thin plies exhibit extensive fibre failure, leading to a considerably reduced CAI strength. Moreover, the hybrid laminate where thick 0° plies are mixed with thin plies improves the CAI strength by 40% over the thin Ply baseline laminate. Thus, hybridization with thin laminates appears to be an economic prospective in terms of improving damage tolerance.
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micro mechanical analysis of the effect of Ply Thickness on the transverse compressive strength of polymer composites
Composites Part A-applied Science and Manufacturing, 2015Co-Authors: A Arteiro, Pete Linde, G Catalanotti, Antonio R Melro, P P CamanhoAbstract:Abstract A micro-mechanical model is used to study the effect of Ply Thickness on constrained 90° plies subjected to transverse compressive loading ( in situ effect). For cross-Ply sublaminates with conventional, standard-Thickness 90° plies, failure is dominated by fibre–matrix interface cracking and large localised plastic deformation of the matrix, forming a localised band in a plane that is not aligned with the loading direction. Ultra-thin plies show a dispersed damage mechanism, combining wedge cracking with Ply fragmentation/separation. Moreover, a transverse crack suppression effect is clearly observed. To the authors’ knowledge, it is the first time an in situ effect in transverse compression has been identified. When comparing the results of the micro-mechanical model with the predictions from analytical models for the in situ effect, the same trends are obtained. These results also show that, for realistic Ply Thicknesses, these analytical models can be considered fairly accurate.
J Otsis - One of the best experts on this subject based on the ideXlab platform.
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towards aerospace grade thin Ply composites effect of Ply Thickness fibre matrix and interlayer toughening on strength and damage tolerance
Composites Science and Technology, 2018Co-Authors: Joel Cugnoni, R Amache, S Kohle, J Unne, E Krame, Clemens Dransfeld, W Smith, K Scobbie, L Sorense, J OtsisAbstract:Abstract Thin-Ply composites represent a promising approach to further improve the performance of carbon fibre composite structures thanks to their ability to delay the onset of matrix cracking and delamination up to the point of fibre dominated failure. However, this increased strength comes with a more brittle failure response which raises concerns on damage tolerance. Thus a careful material optimization is needed to address this trade-off. In this work, eight different formulations of thin-Ply composites ranging from low modulus to high modulus carbon fibres are evaluated to understand the effects of the fibre and matrix constituents on the onset of damage and strength in unnotched tensile (UNT) tests of quasi isotropic laminates for Ply Thicknesses between 300 and 30 microns. The obtained experimental data are combined in master curve diagrams for simplified material selection process. It is observed that certain thin-Ply composites with a Ply Thickness t 95% of the fibre strain). The newly developed composite is further optimized to improve damage tolerance by toughening the resin and selected interfaces. The effect of those modifications on damage tolerance are evaluated through compression strength after impact (CAI) tests and open hole tensile tests (OHT). It is found that an optimized interlayer toughened thin-Ply composite based on 68 microns plies of intermediate modulus fibre can reach both outstanding strength properties with comparable or better CAI and OHT strength compared to current aerospace grade composites.
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Ply Thickness dependence of the intralaminar fracture in thin Ply carbon epoxy laminates
Composites Part A-applied Science and Manufacturing, 2018Co-Authors: Guillaume Frossard, Joel Cugnoni, Th Gmu, J OtsisAbstract:Abstract The effect of Ply Thickness t in intralaminar fracture of unidirectional thin-Ply carbon-epoxy laminates is characterized by testing double cantilever beam (DCB) and compact tension (CT) specimens with different t. While the average intralaminar energy release rate (ERR) at initiation is found equal to the corresponding interlaminar values, the steady-state intralaminar ERRs, only reached in the DCB configuration, are approximately three times higher than the corresponding interlaminar values. Due to changes in the extent of bridging, intralaminar steady-state ERRs are ∼30% higher in thick-Ply (t = 0.150 mm) than in thin-Ply laminates (t = 0.030 mm). Thin-Ply composite laminates exhibit a faster ERR growth with crack length, and for DCB, reach steady-state at a much shorter crack extension than thick-Ply composites. Traction profiles, due to bridging, are identified using R-curves and implemented in cohesive element simulations to predict intralaminar fracture of DCB and CT specimens. The experimental and simulated load–displacement responses are in good agreement.
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mode i interlaminar fracture of carbon epoxy laminates effects of Ply Thickness
Composites Part A-applied Science and Manufacturing, 2016Co-Authors: Guillaume Frossard, Joel Cugnoni, Th Gmu, J OtsisAbstract:Abstract In this work, the influence of Ply Thickness on strain energy release rate (ERR) in delamination of carbon-epoxy laminates is addressed. Specimens with three Ply Thicknesses: 0.030, 0.075 and 0.150 mm are tested. While the ERR at onset of crack propagation is independent of Ply Thickness, the plateau level is much lower in thin-Ply laminates than in thicker Ply ones. This effect is attributed to changes in microstructure, caused by the tow spreading process involved in the fabrication of prepregs. Fiber and matrix rich regions observed only in thick Ply laminates promote the development of large bundles of bridging fibers which exert large closing forces, leading to higher ERR in thick-Ply laminates. Fiber bridging distribution is identified using an iterative procedure from R-curve results, and implemented in cohesive element models. This identification method provides reliable results, as the simulated load-displacement curves are in good agreement with experimental results.
Joel Cugnoni - One of the best experts on this subject based on the ideXlab platform.
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transverse cracking in the bulk and at the free edge of thin Ply composites experiments and multiscale modelling
Composites Part A-applied Science and Manufacturing, 2019Co-Authors: S Kohler, Raffael Amacher, Joel Cugnoni, John BotsisAbstract:Abstract Thin-Ply composites were shown to exhibit significantly delayed transverse cracking, but the linear onset of damage scaling with Ply Thickness reported by Amacher et al. (2014) did not correspond to the established LEFM based in situ strength model. This study further investigates this experimental behaviour by simultaneously comparing in situ free edge crack observation with acoustic emission measurements as well as performing ex-situ X-ray tomography observations of crack propagation. A multi-scale FE model was used to better understand the damage mechanisms at play, and showed a decreasing trend of the apparent toughness with decreasing Ply Thickness, which explains the deviation from the existing model. Transverse cracking at the free edges was observed to propagate quickly towards the center of the specimens for the thickest plies, while in the thinnest plies it is significantly delayed, up to a point where no cracks can reach the center of the sample before final failure.
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towards aerospace grade thin Ply composites effect of Ply Thickness fibre matrix and interlayer toughening on strength and damage tolerance
Composites Science and Technology, 2018Co-Authors: Joel Cugnoni, R Amache, S Kohle, J Unne, E Krame, Clemens Dransfeld, W Smith, K Scobbie, L Sorense, J OtsisAbstract:Abstract Thin-Ply composites represent a promising approach to further improve the performance of carbon fibre composite structures thanks to their ability to delay the onset of matrix cracking and delamination up to the point of fibre dominated failure. However, this increased strength comes with a more brittle failure response which raises concerns on damage tolerance. Thus a careful material optimization is needed to address this trade-off. In this work, eight different formulations of thin-Ply composites ranging from low modulus to high modulus carbon fibres are evaluated to understand the effects of the fibre and matrix constituents on the onset of damage and strength in unnotched tensile (UNT) tests of quasi isotropic laminates for Ply Thicknesses between 300 and 30 microns. The obtained experimental data are combined in master curve diagrams for simplified material selection process. It is observed that certain thin-Ply composites with a Ply Thickness t 95% of the fibre strain). The newly developed composite is further optimized to improve damage tolerance by toughening the resin and selected interfaces. The effect of those modifications on damage tolerance are evaluated through compression strength after impact (CAI) tests and open hole tensile tests (OHT). It is found that an optimized interlayer toughened thin-Ply composite based on 68 microns plies of intermediate modulus fibre can reach both outstanding strength properties with comparable or better CAI and OHT strength compared to current aerospace grade composites.
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Ply Thickness dependence of the intralaminar fracture in thin Ply carbon epoxy laminates
Composites Part A-applied Science and Manufacturing, 2018Co-Authors: Guillaume Frossard, Joel Cugnoni, Th Gmu, J OtsisAbstract:Abstract The effect of Ply Thickness t in intralaminar fracture of unidirectional thin-Ply carbon-epoxy laminates is characterized by testing double cantilever beam (DCB) and compact tension (CT) specimens with different t. While the average intralaminar energy release rate (ERR) at initiation is found equal to the corresponding interlaminar values, the steady-state intralaminar ERRs, only reached in the DCB configuration, are approximately three times higher than the corresponding interlaminar values. Due to changes in the extent of bridging, intralaminar steady-state ERRs are ∼30% higher in thick-Ply (t = 0.150 mm) than in thin-Ply laminates (t = 0.030 mm). Thin-Ply composite laminates exhibit a faster ERR growth with crack length, and for DCB, reach steady-state at a much shorter crack extension than thick-Ply composites. Traction profiles, due to bridging, are identified using R-curves and implemented in cohesive element simulations to predict intralaminar fracture of DCB and CT specimens. The experimental and simulated load–displacement responses are in good agreement.
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mode i interlaminar fracture of carbon epoxy laminates effects of Ply Thickness
Composites Part A-applied Science and Manufacturing, 2016Co-Authors: Guillaume Frossard, Joel Cugnoni, Th Gmu, J OtsisAbstract:Abstract In this work, the influence of Ply Thickness on strain energy release rate (ERR) in delamination of carbon-epoxy laminates is addressed. Specimens with three Ply Thicknesses: 0.030, 0.075 and 0.150 mm are tested. While the ERR at onset of crack propagation is independent of Ply Thickness, the plateau level is much lower in thin-Ply laminates than in thicker Ply ones. This effect is attributed to changes in microstructure, caused by the tow spreading process involved in the fabrication of prepregs. Fiber and matrix rich regions observed only in thick Ply laminates promote the development of large bundles of bridging fibers which exert large closing forces, leading to higher ERR in thick-Ply laminates. Fiber bridging distribution is identified using an iterative procedure from R-curve results, and implemented in cohesive element models. This identification method provides reliable results, as the simulated load-displacement curves are in good agreement with experimental results.
J Costa - One of the best experts on this subject based on the ideXlab platform.
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a virtual testing based search for optimum compression after impact strength in thin laminates using Ply Thickness hybridization and unsymmetrical designs
Composites Science and Technology, 2020Co-Authors: A Sasikuma, Pete Linde, D Trias, J Costa, J Llobe, I R Coza, A TuroAbstract:In the quest to improve the compression after impact (CAI) strength of thin laminates, Ply-hybrid laminates (where plies of different Thicknesses are mixed) have been used in a previous study to mitigate the fibre failure and, consequently, improve the CAI strength. In the same study, hybrid laminates were proposed following qualitative design rules. In this paper, we systematically look for hybrid stacking sequences with improved damage tolerance by virtually testing all the laminates in a defined design space. While the laminates in the design space are made of intermediate and thick Ply grades, the baseline laminate has only intermediate grade plies. Using an in-house numerical model, we virtually tested, (impact and CAI at two impact energies), all the candidate stacking sequences. The best hybrid laminates considerably improved the CAI strength over the baseline (31% and 40% improvement for the symmetric and unsymmetrical hybrid laminates, respectively). One of the best hybrid laminates was then manufactured and tested experimentally to validate the approach. Through virtual testing, this study demonstrates the benefits of using Ply Thickness hybrid laminates and the feasibility of optimizing the stacking sequence for impact damage tolerance.
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effect of Ply Thickness and Ply level hybridization on the compression after impact strength of thin laminates
Composites Part A-applied Science and Manufacturing, 2019Co-Authors: A Sasikuma, Pete Linde, D Trias, J Costa, N Lanco, J OAbstract:There is a lack of research available on how thin laminates respond to impact and post impact loads, even though thin structures are used in present-day aircrafts. This experimental paper employs thick, standard and thin uni-directional plies to investigate the effect Ply Thickness has on thin laminates on their impact and compression after impact (CAI) response. Further, we propose two hybrid laminates where thick or standard plies are mixed with thin plies, respectively, in an effort to improve the CAI strength of thin laminates. Results reveal that, contrary to thick laminates, thin laminates made of only thin plies exhibit extensive fibre failure, leading to a considerably reduced CAI strength. Moreover, the hybrid laminate where thick 0° plies are mixed with thin plies improves the CAI strength by 40% over the thin Ply baseline laminate. Thus, hybridization with thin laminates appears to be an economic prospective in terms of improving damage tolerance.
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a 3d tomographic investigation to elucidate the low velocity impact resistance tolerance and damage sequence of thin non crimp fabric laminates effect of Ply Thickness
Composites Part A-applied Science and Manufacturing, 2018Co-Authors: S M Garciarodriguez, J Costa, Anto Ardera, V Singery, D TriasAbstract:Abstract While thin-plies delay the onset of matrix cracking and improve certain in-plane mechanical properties, the effect they have on the out-of-plane response remains unclear. We compared the impact resistance, tolerance and sequence of failure events of thin laminates manufactured with thin- or standard-Ply non-crimp fabrics (fibre areal weight of 67 and 134 gsm per Ply). Damage initiation and propagation was detailed using (a) quasi-static indentation and impact tests at incremental energy levels and (b) X-ray tomography. The analysis revealed the damage mechanisms underlying the observed load drops in the force-displacement curves. In the indented specimens, the 3D post-process ascribed matrix cracks and delaminations to their corresponding plies/interfaces. Standard-Ply samples develop more extended delaminations and delay fibre failure, improving the load-carrying capacity and increasing compression after impact (CAI) strength by 27% for impact at 14 J.
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damage occurrence at edges of non crimp fabric thin Ply laminates under off axis uniaxial loading
Composites Science and Technology, 2014Co-Authors: G Guillame, Pete Linde, J Costa, A Turo, J Rena, J A MayugoAbstract:Thin-Ply based laminates are a promising development in composite materials and are expected in the near future to outperform conventional laminates in mechanical performance. A rational design with thin plies requires understanding the effect of Ply Thickness on each damage mechanism. This paper presents an experimental investigation into damage occurrence in a quasi-isotropic laminate made from thin-Ply, bi-axial, Non-Crimp-Fabric (NCF), under different off-axis uniaxial loadings. The NCF layers are positioned through the laminate Thickness creating two regions, namely THICK and THIN (with and without Ply clustering). Then, the onset and progress of three damage mechanisms (transverse matrix cracking, matrix crack induced delamination and free-edge delamination) for both regions are analyzed by monitoring the specimen’s free-edge. The results show that the critical region where damage occurs is that with Ply clustering (THICK), whereas delamination originating from matrix cracks or free edge effects are delayed or even suppressed in the THIN region.
P P Camanho - One of the best experts on this subject based on the ideXlab platform.
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is there a Ply Thickness effect on the mode i intralaminar fracture toughness of composite laminates
Theoretical and Applied Fracture Mechanics, 2020Co-Authors: P P Camanho, C Furtado, A Arteiro, Pete Linde, Ia L WardleAbstract:Abstract The apparent crack resistance curves associated with longitudinal tensile failure of carbon fibre reinforced epoxy composite systems with Ply Thicknesses of 0.075 mm, 0.134 mm and 0.268 mm are determined experimentally from the size effect law of geometrically similar double edge notch tension cross-Ply specimens. An increase in notched strength as a function of the Ply Thickness and a corresponding increase of the measured intralaminar fracture toughness is observed. This increase is shown to be a consequence of the appearance of split cracks in the thicker 0° plies in the vicinity of the notches. The numerical models developed demonstrate that if the notch blunting mechanisms are properly represented, the laminate strength is well predicted for a constant value of the Ply intralaminar fracture toughness. This supports the hypothesis that these mechanisms are responsible for the higher strength of the thicker plies, and that the intralaminar fracture toughness of the 0° plies should not be scaled with the Ply Thickness.
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micro mechanical analysis of the effect of Ply Thickness on the transverse compressive strength of polymer composites
Composites Part A-applied Science and Manufacturing, 2015Co-Authors: A Arteiro, Pete Linde, G Catalanotti, Antonio R Melro, P P CamanhoAbstract:Abstract A micro-mechanical model is used to study the effect of Ply Thickness on constrained 90° plies subjected to transverse compressive loading ( in situ effect). For cross-Ply sublaminates with conventional, standard-Thickness 90° plies, failure is dominated by fibre–matrix interface cracking and large localised plastic deformation of the matrix, forming a localised band in a plane that is not aligned with the loading direction. Ultra-thin plies show a dispersed damage mechanism, combining wedge cracking with Ply fragmentation/separation. Moreover, a transverse crack suppression effect is clearly observed. To the authors’ knowledge, it is the first time an in situ effect in transverse compression has been identified. When comparing the results of the micro-mechanical model with the predictions from analytical models for the in situ effect, the same trends are obtained. These results also show that, for realistic Ply Thicknesses, these analytical models can be considered fairly accurate.
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analytical modelling of transverse matrix cracking of θ 90n s composite laminates under multiaxial loading
Mechanics of Advanced Materials and Structures, 2010Co-Authors: Joan A. Mayugo, P Maimi, P P Camanho, Carlos G DavilaAbstract:An analytical model based on the analysis of a cracked unit cell of a composite laminate subjected to multiaxial loads is proposed to predict the onset and accumulation of transverse matrix cracks in the 90n plies of uniformly stressed {±θ/90n} s laminates. The model predicts the effect of matrix cracks on the stiffness of the laminate, as well as the ultimate failure of the laminate, and it accounts for the effect of the Ply Thickness on the Ply strength. Several examples describing the predictions of laminate response, from damage onset up to final failure under both uniaxial and multiaxial loads, are presented.
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prediction of in situ strengths and matrix cracking in composites under transverse tension and in plane shear
Composites Part A-applied Science and Manufacturing, 2006Co-Authors: P P Camanho, Carlos G Davila, S T Pinho, L Iannucci, P RobinsonAbstract:A criterion for matrix failure of laminated composite plies in transverse tension and in-plane shear is developed by examining the mechanics of transverse matrix crack growth. Matrix cracks are assumed to initiate from manufacturing defects and can propagate within planes parallel to the fiber direction and normal to the Ply mid-plane. Fracture mechanics models of cracks in unidirectional laminates, embedded plies and outer plies are used to determine the onset and direction of propagation of crack growth. The models for each Ply configuration relate Ply Thickness and Ply toughness to the corresponding in situ Ply strength. Calculated results for several materials are shown to correlate well with experimental results.