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Anthony M Waas - One of the best experts on this subject based on the ideXlab platform.
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Matrix crack interacting with a delamination in an impacted sandwich composite beam
Engineering Fracture Mechanics, 2016Co-Authors: Solver I. Thorsson, Jaspar Marek, Anthony M WaasAbstract:Abstract Delamination interacting with matrix cracking is a characteristic Failure mechanism that is observed in the damage evolution of laminated composites subjected to low velocity impact. This Failure mode can be studied in isolation by investigating the low velocity impact response of sandwich panels that have thin face sheets bonded to a core. In these panels, Failure is seen to initiate in the core (akin to the matrix) by cracking, leading to delamination between the core and the face sheet. Experimental and modeling results for the flexural response and Failure mechanisms of sandwich composite beams under three point bend loading, both for quasi-static and impact loading are presented. Digital image correlation (DIC) technique is used to obtain the surface strain field during the response event as well as capturing the onset of Failure. A 2D, plane strain finite element (FE) model using the Smeared Crack Approach (SCA) has been developed to predict the response, and to capture the Interactive Failure seen in the experiments. The FE model accurately captures the response seen in the experiments as well as the mode of Failure and the progression.
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Prediction of Low-velocity Impact Damage in Sandwich Composite Beams
56th AIAA ASCE AHS ASC Structures Structural Dynamics and Materials Conference, 2015Co-Authors: Solver I. Thorsson, Jaspar Marek, Anthony M WaasAbstract:A characteristic Failure mechanisms that is observed in the damage evolution of laminated composite beams subjected to low velocity impact is delamination interacting with matrix cracking. This Failure mode can be studied in isolation by investigating the low velocity impact response of sandwich panels where thin face sheets are bonded to a core. In these panels, Failure is seen to initiate in the core by cracking, leading to delamination between the core and the face sheet. Results for the flexural response and Failure mechanisms of sandwich composite beams under three point bend loading, both for quasi-static and dynamic loading are presented. Digital image correlation (DIC) technique is used to obtain the surface strain field during the response event as well as capturing the onset of Failure. A 2D, plane strain finite element (FE) model using the Smeared Crack Approach (SCA) has been developed to predict the response and Interactive Failure seen in the experiments. The FE model accurately captures the response seen in the experiments as well as the mode of Failure and the progression.
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Computational modeling of Failure in composite structures including uncertainties in material and geometrical properties
52nd AIAA ASME ASCE AHS ASC Structures Structural Dynamics and Materials Conference, 2011Co-Authors: Anthony M Waas, Peter A. Gustafson, Evan J. Pineda, Ravi S. RaveendraAbstract:This paper is concerned with a progressive Failure analysis methodology for fiber reinforced composite laminates combining various analytical models designed for investigating Failure mechanisms at different length scales. The methodology here employs a fundamental mechanism based approach to predict Failure or damage initiation with strong coupling between the multiple length scales. The discrete cohesive zone model elements are used to model the adhesion and delamination Failure at macroscale while Schapery theory, a continuum damage theory based on thermodynamics, is used to model material degradation occurring at the lamina level. Furthermore, the present numerical framework is incorporated with a probabilistic analysis module, based on the NEESUS software, to consider material variability and manufacturing inconsistencies. The combined analysis modules are implemented in a non-linear finite element code for modeling the progressive Failure of advanced composite structures. The proposed progressive Failure analysis methodology is applied to several cases for validating its capability of predicting the evolution of the Interactive Failure mechanisms in composite structures.
Tomasz Wierzbicki - One of the best experts on this subject based on the ideXlab platform.
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Interactive Failure in High Velocity Impact of Two Box Beams
Applied Mechanics and Biomedical Technology, 2003Co-Authors: Liang Xue, Li Zheng, Tomasz WierzbickiAbstract:The research reported in the present paper has been motivated mainly by the need of reconstructing the airplane impact damage of the WTC Towers. The initial phase of this catastrophic event was dominated by fracture, leading to breakup and fragmentation of the airplane and severance of a large number of external columns. However, the role of fracture has been de-emphasized in the recent attempt to reconstruct the 9/11 attack [1–3]. The objective of this paper is to raise the phenomenon of ductile fracture to the level of a main factor controlling the initial phase of the September 11th event. Our philosophy is similar to that employed by Lawver et al [4], but we are treating ductile fracture in a much more comprehensive way including the topics of material testing, calibration, validation and finite element implementation. A particular scenario considered is the impact of a corresponding section of the wing of the Boeing 767 into one external box column of a Twin Tower. Real dimensions are taken for the WTC column and the wing section is represented as a thin-walled box beam. Both members undergo extensive plastic deformation and fracture. In developing computer models, special attention was paid to the choice of the element type (shell vs. solid), contact algorithm, element removal (erosion) option, and above all the fracture criterion. Most calculations were done using LS-DYNA for several combinations of the equivalent strain to fracture of the aluminum alloy wing and the steel columns. In addition five ABAQUS runs were made with a newly developed criterion for ductile fracture with a cut-off value for negative triaxialities. Impact velocities considered ranged from 120 to 480 m/sec where 240 m/sec was the actual impact speed of the Boeing 767. It was found that the damage process is localized in the immediate velocity of the impact area. The fracture process initiates at the impacting flanges in the Mode III out-of-plane shear, continues down the webs as a combined shear/tension (tearing) and finally ends up as a tensile fracture of the rear flanges. While the airplane wing box was almost always completely cut, the WTC column was often partially penetrated for a wide range of the equivalent strain to fracture. It was also found that introducing a modified fracture locus changes the sequence of Failure pattern as well as the mode of fracture.Copyright © 2003 by ASME
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Interactive Failure of Two Impacting Beams
Journal of Engineering Mechanics, 2003Co-Authors: Xiaoqing Teng, Tomasz WierzbickiAbstract:A complete analysis of an inelastic beam-to-beam impact is presented. Both beams are of solid, rectangular cross-sections. The problem is formulated based on the momentum conservation and the kinematic and dynamic continuity conditions at the moving wavefront. Closed-form solutions are obtained for transient transverse velocities, deflection profiles, and tensile strains based on the moderately large deflection theory of the beam. Three different regimes of the solution are distinguished, depending on relative values of mass ratios and wave speed ratios. Critical impact velocities to break either of the beams are determined for both the striking and struck beams by assuming both beams fail by tensile necking. However, location of the fracture point depends on relative values of various parameters. It can be right in the contact zone or away from it. It is also shown that after one beam breaks, the other beam will deform further without breaking.
Xiao Chen - One of the best experts on this subject based on the ideXlab platform.
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Modeling multiple Failures of composite box beams used in wind turbine blades
Composite Structures, 2019Co-Authors: Xiao Chen, Jing Tang, Ke YangAbstract:Abstract Large composite structures, such as composite wind turbine blades, may exhibit multiple Failure modes that challenge the modeling strategies and methodologies designers adopt in finite element (FE) analysis. This study develops a comprehensive and general FE modeling method to simulate Interactive Failure process of composite box beams used in wind turbine blades. The composite box beams are the primary loading-carrying members and could show different Failure modes due to competing Failure mechanisms. A continuum-damage mechanics based progressive Failure analysis approach is developed in three-dimensional stress/strain domain to simulate Failure behavior of the box beams. Structural nonlinearities associated with geometry, materials and contact are included. The material Failures considered in this study are composite Failure with three material Failure modes, foam core crushing and adhesive Failure. The in-plane shear stress versus strain relation of unidirectional composites is included in the material damage model. Comprehensive comparisons are made between numerical simulations and experimental observations with respect to strain response, ultimate loads, Failure modes and Failure progress. The modeling approach is found to be capable of predicting both strength and Failure of box beams with reasonable accuracy and it exhibits great potential to predict Failure response of composite wind turbine blades.
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Revisiting the structural collapse of a 52.3 m composite wind turbine blade in a full-scale bending test
Wind Energy, 2017Co-Authors: Xiao Chen, Xiaolu ZhaoAbstract:Full-scale structural tests enable an in-depth understanding of how composite blades respond to specific applied loads. Blade strength can be validated, and necessary modifications can be made to improve structural performance and/or reduce blade weight. This study revisits the structural collapse of a 52.3 m composite blade with new research content. Specifically, the present work examines the chain of events captured in the video record of the blade collapse and provides direct phenomenological evidence of how the blade collapsed in its ultimate limit state. In addition, three-dimensional strains are investigated by reconstructing the root transition region of the blade using solid brick elements in a finite element analysis. The strain components responsible for particular Failure characteristics are identified. The structural response of the blade is investigated numerically. Interactive Failure phenomena associated with strains, local buckling and material Failure are examined in detail. The study shows that local buckling of the sandwich panels with unbalanced construction drives progressive Failure of the composite materials and eventually leads to blade collapse owing to significant Failure of the load-carrying spar cap. Design modifications of the blade are proposed and validated with the test of a new blade. With respect to the latest DNV GL standard, this study notes a possible method to predict delamination and skin/core debonding Failures. This study also recommends the use of three-dimensional solid elements in finite element analysis, especially when the strength and Failure of large blades are of concern. Copyright © 2017 John Wiley & Sons, Ltd.
Ajay Bharule - One of the best experts on this subject based on the ideXlab platform.
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computer aided design and analysis of swing jaw plate of jaw crusher
2009Co-Authors: Ajay BharuleAbstract:Traditionally, stiffness of swing plates has not been varied with changes in rock strength. Rock strength has only been of interest because of the need to know the maximum force exerted by the toggle for energy considerations. Thus a swing plate, stiff enough to crush taconite with an unconfined compressive strength (q_u) of up to 308 MPa, may be overdesigned (and, most importantly, overweight) for crushing a softer fragmental limestone, amphibolites. Design of lighter weight jaw crushers will require a more precise accounting of the stresses and deflections in the crushing plates than is available with traditional techniques. Efforts to decrease energy consumed in crushing have lead to consideration of decreasing the weight of the swing plate of jaw crushers for easily crushed material. In the present work the design of the swing jaw plate using point-load deformation Failure (PDF) relationships along with Interactive Failure of rock particles as a model for such a weight reduction. The design of the corrugated swing jaw plate is carried out by using CAD i.e. jaw crusher plate has been solid modeled by using CatiaV5R15. The calculated dimensions are validated with the drawing of reputed manufacturers. Finite Element Analysis of jaw plates are carried out by using ALGOR V19 software. Computerization of the theoretical design calculations of jaw plates of the jaw crusher has been carried out. The computerized program facilitates for quick design of the plates of the jaw crusher. The different comparisons of corrugated swing jaw plates behavior, calculated with the traditional and the new FEA Failure models with stiffeners, shows that some 10-25% savings in plate weight may be possible.
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computer aided design and analysis of swing jaw plate of jaw crusher
2009Co-Authors: Ajay BharuleAbstract:Traditionally, stiffness of swing plates has not been varied with changes in rock strength. Rock strength has only been of interest because of the need to know the maximum force exerted by the toggle for energy considerations. Thus a swing plate, stiff enough to crush taconite with an unconfined compressive strength (q_u) of up to 308 MPa, may be overdesigned (and, most importantly, overweight) for crushing a softer fragmental limestone, amphibolites. Design of lighter weight jaw crushers will require a more precise accounting of the stresses and deflections in the crushing plates than is available with traditional techniques. Efforts to decrease energy consumed in crushing have lead to consideration of decreasing the weight of the swing plate of jaw crushers for easily crushed material. In the present work the design of the swing jaw plate using point-load deformation Failure (PDF) relationships along with Interactive Failure of rock particles as a model for such a weight reduction. The design of the corrugated swing jaw plate is carried out by using CAD i.e. jaw crusher plate has been solid modeled by using CatiaV5R15. The calculated dimensions are validated with the drawing of reputed manufacturers. Finite Element Analysis of jaw plates are carried out by using ALGOR V19 software. Computerization of the theoretical design calculations of jaw plates of the jaw crusher has been carried out. The computerized program facilitates for quick design of the plates of the jaw crusher. The different comparisons of corrugated swing jaw plates behavior, calculated with the traditional and the new FEA Failure models with stiffeners, shows that some 10-25% savings in plate weight may be possible.
L J Hartsmith - One of the best experts on this subject based on the ideXlab platform.
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a re examination of the analysis of in plane matrix Failures in fibrous composite laminates
Composites Science and Technology, 1996Co-Authors: L J HartsmithAbstract:Abstract Rational analysis methods are presented to cover, separately, possible brittle fracture and ductile yield Failures of the matrix in fibre/polymer composite materials subjected to purely in-plane loads. The models cover both carbon fibres, which customarily fail before the matrix, and glass-fibre composites in which the matrix usually fails first. Delaminations, both at edges and from damage, are excluded, because they need quite different analyses. Customary progressive-Failure and ply-discounting analyses are shown to be erroneous, because one cannot characterize a fracture-mechanics problem with strength-of-material analyses. An explanation is provided for why, unlike fibre Failures and matrix yielding, matrix cracking cannot be assessed on a ply-by-ply basis. There is an interaction with adjacent plies which can act as crack stoppers. In other words, not even the classical laminate theory is valid when the matrix really cracks. Gaps in the understanding of the subject, in regard to residual thermal stresses, are identified. A distinction is drawn between conventional carbon-fibre/polymer composites, for which even a crude analysis of matrix Failures can suffice because only structurally insignificant matrix microcracking precedes the fibre Failures in properly designed laminates and in glass-fibre-reinforced plastics in which the matrix really can fail first. In metal-matrix composites, a far more accurate model will be needed because the matrix then carries most of the load. The knowledge of this subject 30 years ago is shown to be far superior to what is commonly used to analyse composite materials today and it is suggested that the introduction of the many abstract mathematical Interactive Failure criteria, valid only for truly homogeneous anisotropic materials, was largely responsible for this.