The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Ole Thybo Thomsen - One of the best experts on this subject based on the ideXlab platform.
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experimental investigation of interfacial crack arrest in sandwich beams subjected to fatigue loading using a novel crack arresting device
Journal of Sandwich Structures and Materials, 2019Co-Authors: Georgios Martakos, Jens Henrik Andreasen, Christian Berggreen, Ole Thybo ThomsenAbstract:A recently proposed face-sheet/Core Interface crack arresting device is implemented in sandwich beams and tested using the Sandwich Tear Test (STT) configuration. Fatigue loading conditions are applied to propagate the crack and determine the effect of the crack stopper on the fatigue growth rate and arrest of the crack. Digital image correlation is used through the duration of the fatigue experiment to track the strain evolution as the crack tip advances. The measured strains are related to crack tip propagation, arrest, and re-initiation of the crack. A finite element model is used to calculate the energy release rate, mode mixity and to simulate crack propagation and arrest of the crack. Finally the effectiveness of the crack arresting device is demonstrated on composite sandwich beams subjected to fatigue loading conditions.
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fracture behaviour at tri material junctions of crack stoppers in sandwich structures
Composite Structures, 2015Co-Authors: W Wang, Georgios Martakos, J M Dulieubarton, Jens Henrik Andreasen, Ole Thybo ThomsenAbstract:Abstract Inspired by a previously published peel stopper design for foam Cored composite sandwich structures, three novel markedly lighter peel stoppers were evaluated with respect to their ability to deflect and arrest propagating face debond cracks. Of the three novel peel stopper configurations, C1, C2 and C3, C1 was similar to the previous design, whereas C2 and C3 were modified with layers of glass fibre fabric extending from the peel stopper tip into the face sheet (C2) or into the face sheet/Core Interface (C3). The previous peel stopper was validated under mode II dominated conditions, but the novel designs were investigated under mode I dominated crack propagation conditions, which are of higher practical relevance. Both quasi-static and fatigue loading scenarios were investigated. The mechanisms controlling crack propagation at the internal peel stopper tip were studied using thermoelastic stress analysis (TSA) and finite element (FE) analysis. The TSA has revealed significant new information about the local stress fields in the vicinity of the tri-material junction (peel stopper tip) as well as the fracture process zone. Configuration C1 was unable to deflect debond cracks consistently, albeit it did so in most cases, whereas it was incapable of achieving crack arrest. C2 and C3 both performed better in that they consistently demonstrated the ability to deflect propagating cracks, whereas only C2 could arrest the cracks consistently as well. Detailed fracture mechanics analyses confirmed and explained the experimental observations.
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fracture behaviour at tri material junctions of crack stoppers in sandwich structures
Composite Structures, 2015Co-Authors: W Wang, Georgios Martakos, J M Dulieubarton, Jens Henrik Andreasen, Ole Thybo ThomsenAbstract:Abstract Inspired by a previously published peel stopper design for foam Cored composite sandwich structures, three novel markedly lighter peel stoppers were evaluated with respect to their ability to deflect and arrest propagating face debond cracks. Of the three novel peel stopper configurations, C1, C2 and C3, C1 was similar to the previous design, whereas C2 and C3 were modified with layers of glass fibre fabric extending from the peel stopper tip into the face sheet (C2) or into the face sheet/Core Interface (C3). The previous peel stopper was validated under mode II dominated conditions, but the novel designs were investigated under mode I dominated crack propagation conditions, which are of higher practical relevance. Both quasi-static and fatigue loading scenarios were investigated. The mechanisms controlling crack propagation at the internal peel stopper tip were studied using thermoelastic stress analysis (TSA) and finite element (FE) analysis. The TSA has revealed significant new information about the local stress fields in the vicinity of the tri-material junction (peel stopper tip) as well as the fracture process zone. Configuration C1 was unable to deflect debond cracks consistently, albeit it did so in most cases, whereas it was incapable of achieving crack arrest. C2 and C3 both performed better in that they consistently demonstrated the ability to deflect propagating cracks, whereas only C2 could arrest the cracks consistently as well. Detailed fracture mechanics analyses confirmed and explained the experimental observations.
Christian Berggreen - One of the best experts on this subject based on the ideXlab platform.
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experimental investigation of interfacial crack arrest in sandwich beams subjected to fatigue loading using a novel crack arresting device
Journal of Sandwich Structures and Materials, 2019Co-Authors: Georgios Martakos, Jens Henrik Andreasen, Christian Berggreen, Ole Thybo ThomsenAbstract:A recently proposed face-sheet/Core Interface crack arresting device is implemented in sandwich beams and tested using the Sandwich Tear Test (STT) configuration. Fatigue loading conditions are applied to propagate the crack and determine the effect of the crack stopper on the fatigue growth rate and arrest of the crack. Digital image correlation is used through the duration of the fatigue experiment to track the strain evolution as the crack tip advances. The measured strains are related to crack tip propagation, arrest, and re-initiation of the crack. A finite element model is used to calculate the energy release rate, mode mixity and to simulate crack propagation and arrest of the crack. Finally the effectiveness of the crack arresting device is demonstrated on composite sandwich beams subjected to fatigue loading conditions.
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the effects of shear and near tip deformations on Interface fracture of symmetric sandwich beams
Engineering Fracture Mechanics, 2018Co-Authors: Luca Barbieri, Roberta Massabo, Christian BerggreenAbstract:Abstract The effects of shear on energy release rate and mode mixity in a symmetric sandwich beam with isotropic layers and a debond crack at the face-sheet/Core Interface are investigated through a semi-analytic approach based on two-dimensional elasticity and linear elastic fracture mechanics. The semi-analytic expressions for the shear components of energy release rate and mode mixity phase angle which have been derived in Li et al. (2004) for bi-material beams are extended to sandwich beams and the necessary numerical coefficients derived through accurate finite element analyses. The expressions are combined with earlier results for sandwich beams subjected to bending moments and axial forces in order to obtain solutions for general loading conditions and for an extensive range of geometrical and material properties. The physical and mechanical significance of the terms of the energy release rate which depend on the shear forces are explained using structural mechanics concepts and introducing crack tip root rotations to account for the main effects of the near tip deformations. The results are applicable to laboratory specimens used for the characterization of the fracture properties of sandwich composites for civil, marine, energy and aeronautical applications, provided the lengths of the crack and the ligament ahead of the crack tip are above minimum lengths which are defined in the paper.
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the effects of shear and near tip deformations on Interface fracture of symmetric sandwich beams
arXiv: Soft Condensed Matter, 2018Co-Authors: Luca Barbieri, Roberta Massabo, Christian BerggreenAbstract:The effects of shear on energy release rate and mode mixity in a symmetric sandwich beam with isotropic layers and a debond crack at the face sheet/Core Interface are investigated through a semi-analytic approach based on two-dimensional elasticity and linear elastic fracture mechanics. Semi-analytic expressions are derived for the shear components of energy release rate and mode mixity phase angle which depend on four numerical coefficients derived through accurate finite element analyses. The expressions are combined with earlier results for three-layer configurations subjected to bending-moments and axial forces to obtain solutions for sandwich beams under general loading conditions and for an extensive range of geometrical and material properties. The results are applicable to laboratory specimens used for the characterization of the fracture properties of sandwich composites for civil, marine, energy and aeronautical applications, provided the lengths of the crack and the ligament ahead of the crack tip are above minimum lengths. The physical and mechanical significance of the terms of the energy release rate which depend on the shear forces are explained using structural mechanics concepts and introducing crack tip root rotations to account for the main effects of the near tip deformations.
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accelerated fatigue crack growth simulation in a bimaterial Interface
International Journal of Fatigue, 2011Co-Authors: Ramin Moslemian, Anette M Karlsson, Christian BerggreenAbstract:Abstract A method for accelerated simulation of fatigue crack growth in a bimaterial Interface (e.g. in a face/Core sandwich Interface) is proposed. To simulate fatigue crack growth, a routine is incorporated in the commercial finite element program ANSYS and a method to accelerate the simulation is implemented. The proposed method (the cycle jump technique) is based on conducting finite element analysis for a set of cycles to establish a trend line, extrapolating the trend line spanning many cycles, and use the extrapolated state as initial state for additional finite element simulations. A control criterion is utilized to ensure the accuracy of the cycle jumps. The inputs of the developed scheme are the crack growth rate as a function of energy release rate for discrete mode-mixities. If these relationships are available for a specific Interface, Interface fatigue crack growth in any structure with the same Interface can be simulated. Using this approach, fatigue crack growth in the face/Core Interface of a sandwich beam is simulated. Results of the simulation show that with fair accuracy, using the cycle jump technique, more than 65% reduction in computation time can be achieved. Results show that in highly nonlinear problems the control parameter needs to be chosen with care.
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face Core Interface fracture characterization of mixed mode bending sandwich specimens
Fatigue & Fracture of Engineering Materials & Structures, 2011Co-Authors: Amilcar Quispitupa, Christian Berggreen, Leif A. CarlssonAbstract:Debonding of the Core from the face sheets is a critical failure mode in sandwich structures. This paper presents an experimental study on face/Core debond fracture of foam Core sandwich specimens under a wide range of mixed mode loading conditions. Sandwich beams with E-glass fibre face sheets and PVC H45, H100 and H250 foam Core materials were evaluated. A methodology to perform precracking on fracture specimens in order to achieve a sharp and representative crack front is outlined. The mixed mode loading was controlled in the mixed mode bending (MMB) test rig by changing the loading application point (lever arm distance). Finite element analysis was performed to determine the mode-mixity at the crack tip. The results showed that the face/Core Interface fracture toughness increased with increased mode II loading. Post failure analysis of the fractured specimens revealed that the crack path depends on the mode-mixity at the crack tip, face sheet properties and Core density.
Tomasz Sadowski - One of the best experts on this subject based on the ideXlab platform.
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dynamic fracture analysis of sandwich composites with face sheet Core debond by the finite element method
2019Co-Authors: Vyacheslav N. Burlayenko, Holm Altenbach, Tomasz SadowskiAbstract:Numerical simulations using the finite element analyses within the code ABAQUS™ are used to study a dynamic fracture behaviour developing along the face sheet/Core Interface in sandwich panels. First, a virtual fracture test—the double cantilever sandwich beam subjected to uneven bending moments is simulated. In such analyses, the dynamic energy release rates and near-tip displacement and stress fields are extracted from finite element models developed within the two-dimensional elastodynamic theory and cohesive elements. These parameters are a basis for understanding the face sheet/Core Interface fracture in sandwich materials. Important computed results are that the inertia effects change the behaviour of fracture debonding parameters. Moreover, the analyses demonstrated the capability and the reliability of the finite element modelling technique for solving dynamic fracture mechanics problems. Also simulated and discussed is the dynamic Interface crack progression in the sandwich specimen. In the second part of the work, the computational models are modified for analysing dynamic fracture of sandwich panels. For this, tree-dimensional models of sandwich plates with a penny-shaped debonded zone have been elaborated. In all simulations, computations of dynamic Interface crack propagation are carried out in such a way when the crack history and inertial effects on cracking are direct outcomes of the analysis.
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Transient dynamic response of debonded sandwich plates predicted with finite element analysis
Meccanica, 2014Co-Authors: Vyacheslav N. Burlayenko, Tomasz SadowskiAbstract:Dynamic transient response of a composite sandwich plate with a penny-shaped debonded zone has been studied by using the finite element analysis within the ABAQUS/Explicit code in this paper. In order to accurately predict the response of the debonded sandwich plate to impulsive loading, contact–impact and sliding conditions along the damaged skin-to-Core Interface were imposed in the model through a kinematic predictor/corrector contact algorithm. The accuracy of the finite element (FE) model used was verified by comparing between numerical predictions and experimental data known in literature for the frequency spectrum of a cracked polycarbonate laminated beam containing a delamination. By analyzing nonlinear aspects of the transient dynamics of the sandwich plate, it is shown that the presence of the debond significantly alters its short-term response. In this respect, a considerable influence of contact events within the debonded region on the plate’s global dynamic response was found out. These results were presented in both time and frequency domains. The predictions performed also showed that the FE model applied would be useful for nondestructive evaluation of defects in composite sandwich plates, and for studying dynamic response of such plates to impact.
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influence of skin Core debonding on free vibration behavior of foam and honeycomb Cored sandwich plates
International Journal of Non-linear Mechanics, 2010Co-Authors: Vyacheslav N. Burlayenko, Tomasz SadowskiAbstract:The dynamic behavior of partially delaminated at the skin/Core Interface sandwich plates with flexible Cores is studied. The commercial finite element code ABAQUS is used to calculate natural frequencies and mode shapes of the sandwich plates containing a debonding zone. The influence of the debonding size, debonding location and types of debonding on the modal parameters of damaged sandwich plates with various boundary conditions is investigated. The results of dynamic analysis illustrated that they can be useful for analyzing practical problems related to the non-destructive damage detection of partially debonded sandwich plates.
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effective elastic properties of foam filled honeycomb Cores of sandwich panels
Composite Structures, 2010Co-Authors: Vyacheslav N. Burlayenko, Tomasz SadowskiAbstract:Abstract Filling with foams of honeycomb structures has been proposed as some enhancement of honeycomb-Cored sandwich material systems. The present study considers aluminum honeycomb Cores filled with polyvinyl chloride foams with the aim to predict their material elastic properties. The displacement-based homogeneous technique using 3D finite element analysis is applied to evaluate the effective elastic properties of foam-filled honeycomb Cores. The special attention is paid to stress predictions at the skin/Core Interface and the stress distributions within the honeycomb cell walls. The influence of the foam filler on distribution of local stresses within the cell is examined. The FE modelling is performed with the commercial available software ABAQUS. The structural benefits of the foam-filled honeycomb Cores are also discussed.
J M Dulieubarton - One of the best experts on this subject based on the ideXlab platform.
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fracture behaviour at tri material junctions of crack stoppers in sandwich structures
Composite Structures, 2015Co-Authors: W Wang, Georgios Martakos, J M Dulieubarton, Jens Henrik Andreasen, Ole Thybo ThomsenAbstract:Abstract Inspired by a previously published peel stopper design for foam Cored composite sandwich structures, three novel markedly lighter peel stoppers were evaluated with respect to their ability to deflect and arrest propagating face debond cracks. Of the three novel peel stopper configurations, C1, C2 and C3, C1 was similar to the previous design, whereas C2 and C3 were modified with layers of glass fibre fabric extending from the peel stopper tip into the face sheet (C2) or into the face sheet/Core Interface (C3). The previous peel stopper was validated under mode II dominated conditions, but the novel designs were investigated under mode I dominated crack propagation conditions, which are of higher practical relevance. Both quasi-static and fatigue loading scenarios were investigated. The mechanisms controlling crack propagation at the internal peel stopper tip were studied using thermoelastic stress analysis (TSA) and finite element (FE) analysis. The TSA has revealed significant new information about the local stress fields in the vicinity of the tri-material junction (peel stopper tip) as well as the fracture process zone. Configuration C1 was unable to deflect debond cracks consistently, albeit it did so in most cases, whereas it was incapable of achieving crack arrest. C2 and C3 both performed better in that they consistently demonstrated the ability to deflect propagating cracks, whereas only C2 could arrest the cracks consistently as well. Detailed fracture mechanics analyses confirmed and explained the experimental observations.
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fracture behaviour at tri material junctions of crack stoppers in sandwich structures
Composite Structures, 2015Co-Authors: W Wang, Georgios Martakos, J M Dulieubarton, Jens Henrik Andreasen, Ole Thybo ThomsenAbstract:Abstract Inspired by a previously published peel stopper design for foam Cored composite sandwich structures, three novel markedly lighter peel stoppers were evaluated with respect to their ability to deflect and arrest propagating face debond cracks. Of the three novel peel stopper configurations, C1, C2 and C3, C1 was similar to the previous design, whereas C2 and C3 were modified with layers of glass fibre fabric extending from the peel stopper tip into the face sheet (C2) or into the face sheet/Core Interface (C3). The previous peel stopper was validated under mode II dominated conditions, but the novel designs were investigated under mode I dominated crack propagation conditions, which are of higher practical relevance. Both quasi-static and fatigue loading scenarios were investigated. The mechanisms controlling crack propagation at the internal peel stopper tip were studied using thermoelastic stress analysis (TSA) and finite element (FE) analysis. The TSA has revealed significant new information about the local stress fields in the vicinity of the tri-material junction (peel stopper tip) as well as the fracture process zone. Configuration C1 was unable to deflect debond cracks consistently, albeit it did so in most cases, whereas it was incapable of achieving crack arrest. C2 and C3 both performed better in that they consistently demonstrated the ability to deflect propagating cracks, whereas only C2 could arrest the cracks consistently as well. Detailed fracture mechanics analyses confirmed and explained the experimental observations.
F Aviles - One of the best experts on this subject based on the ideXlab platform.
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a beam specimen to measure the face Core fracture toughness of sandwich materials under a tearing loading mode
International Journal of Mechanical Sciences, 2014Co-Authors: J A Rodriguezgonzalez, A Maypat, F AvilesAbstract:Abstract A new test specimen named the sandwich tearing beam (STB) is proposed as a fracture test method to measure the face/Core debond fracture toughness of sandwich materials loaded under mode III. The STB specimen consists of a sandwich beam made of a single laminated composite face sheet reinforced by a thick steel beam and bonded to the sandwich Core, which is adhesively bonded to the edge of a metal base plate allowing for rotations of the face sheet. The sandwich beam has an initial crack introduced at the face/Core Interface and a tearing force (parallel to the crack front) is applied at the free end of the face sheet which extends beyond the length of the Core. Finite element analysis (FEA) shows that the energy release rate distribution at the crack front of the STB specimen is highly dominated by loading mode III, with significant contributions of mode II only near the specimen edges. STB tests conducted to a steel beam-reinforced glass/vinyl ester face sheet bonded to an H100 PVC foam Core show that crack propagation occurs as a sub-Interface crack running parallel to the face/Core Interface. The measured compliance and face/Core mode III fracture toughness are in good agreement with FEA predictions.
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evaluation of the plate twist test to characterize mode iii fracture of sandwich panels with a face Core Interface crack
Engineering Fracture Mechanics, 2013Co-Authors: Adrian Hernandezperez, F Aviles, Leif A. CarlssonAbstract:Abstract Sandwich panels with a face/Core Interface edge crack loaded in torsion have been analyzed using finite element analysis (FEA) and experimental testing to characterize mode III delamination propagation. Symmetric sandwich panels with steel face sheets bonded to a high density (H250) PVC foam Core were considered. The test specimens were square plates of side length of 90 mm with 3 mm thick face sheets and Core thicknesses of 3, 12 and 25.4 mm supported at two corners and loaded in torsion by application of transverse loads at two diagonally opposite corners. The energy release rate (G) was determined from stress intensity factors calculated from the crack flank displacements. The results show dominant mode III crack loading. The mode III component of the energy release rate (GIII) was nearly uniform along the central region of the crack front and mode II contribution was only significant near the load introduction and support pins. The measured and calculated compliance for the sandwich panels examined agreed reasonable. The fracture toughness (Gc) determined from measured critical loads and the compliance calibration method was 119 ± 27 J/m2.