The Experts below are selected from a list of 2433 Experts worldwide ranked by ideXlab platform
Robert K. Goldberg - One of the best experts on this subject based on the ideXlab platform.
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Implementation and validation of a three-dimensional plasticity-based deformation model for orthotropic composites
Composites Part A: Applied Science and Manufacturing, 2016Co-Authors: Canio Hoffarth, Robert K. Goldberg, Subramaniam Rajan, Duane M. Revilock, Kelly S. Carney, Paul Dubois, Gunther BlankenhornAbstract:Abstract A new orthotropic elasto-plastic constitutive model has been developed to predict the inelastic response of composite materials under high velocity impact conditions. The model is driven by experimental stress-strain curve data stored as tabular input allowing for a very general material description. The theoretical details of the elasto-plastic deformation part of the material model are briefly summarized. This summary is then followed by details of the numerical implementation of the model as MAT213 (suitable for use with solid elements) into the commercial transient dynamic finite element code, LS-DYNA. The theoretical basis and the numerical implementation of the constitutive model are validated by using two sets of validation tests involving a widely used unidirectional composite, T800/F3900 - composite laminates used in Coupon Level tests and a low velocity impact test on a flat panel. Results show that the implementation is efficient, robust and accurate.
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Modification of a Macromechanical Finite Element–Based Model for Impact Analysis of Triaxially Braided Composites
Journal of Aerospace Engineering, 2012Co-Authors: Robert K. Goldberg, Brina Blinzler, Wieslaw K. BiniendaAbstract:Abstract A macro Level finite element-based model has been developed to simulate the mechanical and impact response of triaxially-braided polymer matrix composites. In the analytical model, the triaxial braid architecture is simulated by using four parallel shell elements, each of which is modeled as a laminated composite. For the current analytical approach, each shell element is considered to be a smeared homogeneous material. The commercial transient dynamic finite element code LS-DYNA is used to conduct the simulations, and a continuum damage mechanics model internal to LS-DYNA is used as the material constitutive model. The constitutive model requires stiffness and strength properties of an equivalent unidirectional composite. Simplified micromechanics methods are used to determine the equivalent stiffness properties, and results from Coupon Level tests on the braided composite are utilized to back out the required strength properties. Simulations of quasi-static Coupon tests of several representative braided composites are conducted to demonstrate the correlation of the model. Impact simulations of a represented braided composites are conducted to demonstrate the capability of the model to predict the penetration velocity and damage patterns obtained experimentally.
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Characterization and Analysis of Triaxially Braided Polymer Composites under Static and Impact Loads
Earth and Space 2012, 2012Co-Authors: Robert K. Goldberg, Lee W Kohlman, Gary D. Roberts, Brina Blinzler, Wieslaw K. BiniendaAbstract:In order to design impact resistant aerospace components made of triaxially braided polymer matrix composite materials, a need exists to have reliable impact simulation methods and a detailed understanding of the material behavior. Traditional test methods and specimen designs have yielded unrealistic material property data due to features such as edge damage. To overcome these deficiencies, various alternative testing geometries such as notched flat Coupons have been examined to alleviate difficulties observed with standard test methods. The results from the Coupon Level tests have been used to characterize and validate a macro Level finite element based model which can be used to simulate the mechanical and impact response of the braided composites. In the analytical model, the triaxial braid architecture is simulated by using four parallel shell elements, each of which is modeled as a laminated composite. Currently, each shell element is considered to be a smeared homogeneous material. Simplified micromechanics techniques and lamination theory are used to determine the equivalent stiffness properties of each shell element, and results from the Coupon Level tests on the braided composite are used to back out the strength properties of each shell element. Recent improvements to the model the incorporation of strain rate effects into the model. Simulations of ballistic impact tests have been carried out to investigate and verify the analysis approach.
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Investigation of a Macromechanical Approach to Analyzing Triaxially-Braided Polymer Composites
AIAA Journal, 2011Co-Authors: Robert K. Goldberg, Brina Blinzler, Wieslaw K. BiniendaAbstract:A macro Level finite element-based model has been developed to simulate the mechanical and impact response of triaxially-braided polymer matrix composites. In the analytical model, the triaxial braid architecture is simulated by using four parallel shell elements, each of which is modeled as a laminated composite. The commercial transient dynamic finite element code LS-DYNA is used to conduct the simulations, and a continuum damage mechanics model internal to LS-DYNA is used as the material constitutive model. The material stiffness and strength values required for the constitutive model are determined based on Coupon Level tests on the braided composite. Simulations of quasi-static Coupon tests of a representative braided composite are conducted. Varying the strength values that are input to the material model is found to have a significant influence on the effective material response predicted by the finite element analysis, sometimes in ways that at first glance appear non-intuitive. A parametric study involving the input strength parameters provides guidance on how the analysis model can be improved.
Wieslaw K. Binienda - One of the best experts on this subject based on the ideXlab platform.
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Modification of a Macromechanical Finite Element–Based Model for Impact Analysis of Triaxially Braided Composites
Journal of Aerospace Engineering, 2012Co-Authors: Robert K. Goldberg, Brina Blinzler, Wieslaw K. BiniendaAbstract:Abstract A macro Level finite element-based model has been developed to simulate the mechanical and impact response of triaxially-braided polymer matrix composites. In the analytical model, the triaxial braid architecture is simulated by using four parallel shell elements, each of which is modeled as a laminated composite. For the current analytical approach, each shell element is considered to be a smeared homogeneous material. The commercial transient dynamic finite element code LS-DYNA is used to conduct the simulations, and a continuum damage mechanics model internal to LS-DYNA is used as the material constitutive model. The constitutive model requires stiffness and strength properties of an equivalent unidirectional composite. Simplified micromechanics methods are used to determine the equivalent stiffness properties, and results from Coupon Level tests on the braided composite are utilized to back out the required strength properties. Simulations of quasi-static Coupon tests of several representative braided composites are conducted to demonstrate the correlation of the model. Impact simulations of a represented braided composites are conducted to demonstrate the capability of the model to predict the penetration velocity and damage patterns obtained experimentally.
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Characterization and Analysis of Triaxially Braided Polymer Composites under Static and Impact Loads
Earth and Space 2012, 2012Co-Authors: Robert K. Goldberg, Lee W Kohlman, Gary D. Roberts, Brina Blinzler, Wieslaw K. BiniendaAbstract:In order to design impact resistant aerospace components made of triaxially braided polymer matrix composite materials, a need exists to have reliable impact simulation methods and a detailed understanding of the material behavior. Traditional test methods and specimen designs have yielded unrealistic material property data due to features such as edge damage. To overcome these deficiencies, various alternative testing geometries such as notched flat Coupons have been examined to alleviate difficulties observed with standard test methods. The results from the Coupon Level tests have been used to characterize and validate a macro Level finite element based model which can be used to simulate the mechanical and impact response of the braided composites. In the analytical model, the triaxial braid architecture is simulated by using four parallel shell elements, each of which is modeled as a laminated composite. Currently, each shell element is considered to be a smeared homogeneous material. Simplified micromechanics techniques and lamination theory are used to determine the equivalent stiffness properties of each shell element, and results from the Coupon Level tests on the braided composite are used to back out the strength properties of each shell element. Recent improvements to the model the incorporation of strain rate effects into the model. Simulations of ballistic impact tests have been carried out to investigate and verify the analysis approach.
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Investigation of a Macromechanical Approach to Analyzing Triaxially-Braided Polymer Composites
AIAA Journal, 2011Co-Authors: Robert K. Goldberg, Brina Blinzler, Wieslaw K. BiniendaAbstract:A macro Level finite element-based model has been developed to simulate the mechanical and impact response of triaxially-braided polymer matrix composites. In the analytical model, the triaxial braid architecture is simulated by using four parallel shell elements, each of which is modeled as a laminated composite. The commercial transient dynamic finite element code LS-DYNA is used to conduct the simulations, and a continuum damage mechanics model internal to LS-DYNA is used as the material constitutive model. The material stiffness and strength values required for the constitutive model are determined based on Coupon Level tests on the braided composite. Simulations of quasi-static Coupon tests of a representative braided composite are conducted. Varying the strength values that are input to the material model is found to have a significant influence on the effective material response predicted by the finite element analysis, sometimes in ways that at first glance appear non-intuitive. A parametric study involving the input strength parameters provides guidance on how the analysis model can be improved.
Anthony M. Waas - One of the best experts on this subject based on the ideXlab platform.
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The EST Model for Predicting Progressive Damage and Failure of Open Hole Bending Specimens
57th AIAA ASCE AHS ASC Structures Structural Dynamics and Materials Conference, 2016Co-Authors: Ashith P K Joseph, Anthony M. Waas, Evan J. PinedaAbstract:Progressive damage and failure in open hole composite laminate Coupons subjected to flexural loading is modeled using Enhanced Schapery Theory (EST). Previous studies have demonstrated that EST can accurately predict the strength of open hole Coupons under remote tensile and compressive loading states. This homogenized modeling approach uses single composite shell elements to represent the entire laminate in the thickness direction and significantly reduces computational cost. Therefore, when delaminations are not of concern or are active in the post-peak regime, the version of EST presented here is a good engineering tool for predicting deformation response. Standard Coupon Level tests provides all the input data needed for the model and they are interpreted in conjunction with finite element (FE) based simulations. Open hole bending test results of three different IM7/8552 carbon fiber composite layups agree well with EST predictions. The model is able to accurately capture the curvature change and deformation localization in the specimen at and during the post catastrophic load drop event.
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A Unified Model for Predicting the Open Hole Tensile and Compressive Strengths of Composite Laminates for Aerospace Applications
54th AIAA ASME ASCE AHS ASC Structures Structural Dynamics and Materials Conference, 2013Co-Authors: Paul Davidson, Evan J. Pineda, Christian Heinrich, Anthony M. WaasAbstract:The open hole tensile and compressive strengths are important design parameters in qualifying fiber reinforced laminates for a wide variety of structural applications in the aerospace industry. In this paper, we present a unified model that can be used for predicting both these strengths (tensile and compressive) using the same set of Coupon Level, material property data. As a prelude to the unified computational model that follows, simplified approaches, referred to as "zeroth order", "first order", etc. with increasing Levels of fidelity are first presented. The results and methods presented are practical and validated against experimental data. They serve as an introductory step in establishing a virtual building block, bottom-up approach to designing future airframe structures with composite materials. The results are useful for aerospace design engineers, particularly those that deal with airframe design.
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predictions of delamination of a stiffened panel using a cohesive zone model
51st AIAA ASME ASCE AHS ASC Structures Structural Dynamics and Materials Conference<BR> 18th AIAA ASME AHS Adaptive Structures Conference<BR&, 2010Co-Authors: Peter A Gustafson, Anthony M. WaasAbstract:The ability of a nite element cohesive zone model to predict delamination in a sti ened structural component is investigated. A sti ened panel was proposed as a validation test for T650/AFR-PE4/FM680-1 material system cohesive zone parameters that were determined in Coupon Level tests. Models of the panel were constructed using two methods including the discrete cohesive zone element and the Abaqus R COH3D8 element to simulate adhesive failure. The test was found to be insensitive for validation of implicit models. The model and experimental failure loads were found to over-predict the experimental failure load by about 10%; the displacement at failure over-predicted by a larger margin. The discrepancies are discussed. The Coupon Level tests for determining the adhesive parameters are also summarized.
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Failure Analysis of Adhesively Bonded Structures: From Coupon Level Data to Structural Level Predictions and Verification
International Journal of Fracture, 2005Co-Authors: Jaeung Chung, Anthony M. Waas, Khaled W. Shahwan, Jessica A. Schroeder, Raymond G. Boeman, Vlastimil Kunc, Lynn B. KlettAbstract:This paper presents a predictive methodology and verification through experiment for the analysis and failure of adhesively bonded, hat stiffened structures using Coupon Level input data. The hats were made of steel and carbon fiber reinforced polymer composite, respectively, and bonded to steel adherends. A critical strain energy release rate criterion was used to predict the failure loads of the structure. To account for significant geometrical changes observed in the structural Level test, an adaptive virtual crack closure technique based on an updated local coordinate system at the crack tip was developed to calculate the strain energy release rates. Input data for critical strain energy release rates as a function of mode mixity was obtained by carrying out Coupon Level mixed mode fracture tests using the Fernlund–Spelt (FS) test fixture. The predicted loads at failure, along with strains at different locations, were compared with those measured from the structural Level tests. The predictions were found to agree well with measurements for multiple replicates of adhesively bonded hat-stiffened structures made with steel hat/adhesive/steel and composite hat/adhesive/steel, thus validating the proposed methodology for failure prediction.
Tobias Wille - One of the best experts on this subject based on the ideXlab platform.
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An analytical scaling approach for low-velocity impact on composite structures
Composite Structures, 2018Co-Authors: Raffael Marius Bogenfeld, Janko Kreikemeier, Tobias WilleAbstract:Abstract For the analysis of low-velocity impact, this work provides an analytic scaling approach, permitting to analyze structural impact scenarios on a small reference Coupon. Thus, the numerical prediction of impact damage on large structures through high-fidelity methods is made possible. Yet, the massive computational effort needed for these virtual tests even on a Coupon Level means a major challenge to their application in the design process of a structure. To reduce the computational effort, local analysis approaches consider only damage-prone areas for an actual damage analysis. Our approach permits the analysis of structural impact scenarios on a much smaller reference Coupon that represents the damage-prone area. An analytical spring-mass model transfers the impact parameters between the structural and the Coupon Level. For this purpose, the spring-mass model captures the impact-damage state by a scalar parameter. The transfer between the reference Coupon and the structure is based on the equivalence of this damage parameter. Thus, a Coupon simulation or Coupon test result is given validity for a structural impact scenario. So, based on a single Coupon simulation, areal impact assessment of a structure is made possible. This methodology is validated through experiments and a demonstrated on a generic aircraft door structure.
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Innovative Testing Methods on Specimen and Component Level
Adaptive tolerant and efficient composite structures, 2012Co-Authors: Falk Odermann, Tobias WilleAbstract:In general, tests can be divided into four categories: parameter estimation (e.g. material strength), phenomenological investigation, validation and qualification. According to this classification tests are carried out on a structural or component Level and on a Coupon Level. For structural testing a Buckling Test Facility, a Variable Component Test Facility and a thermo-mechanical test field are described. Furthermore, information is given on specimen Level tests with devices for standard test machines: Stringer Pull-off Device and 3D-Biax Device.
Brina Blinzler - One of the best experts on this subject based on the ideXlab platform.
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Modification of a Macromechanical Finite Element–Based Model for Impact Analysis of Triaxially Braided Composites
Journal of Aerospace Engineering, 2012Co-Authors: Robert K. Goldberg, Brina Blinzler, Wieslaw K. BiniendaAbstract:Abstract A macro Level finite element-based model has been developed to simulate the mechanical and impact response of triaxially-braided polymer matrix composites. In the analytical model, the triaxial braid architecture is simulated by using four parallel shell elements, each of which is modeled as a laminated composite. For the current analytical approach, each shell element is considered to be a smeared homogeneous material. The commercial transient dynamic finite element code LS-DYNA is used to conduct the simulations, and a continuum damage mechanics model internal to LS-DYNA is used as the material constitutive model. The constitutive model requires stiffness and strength properties of an equivalent unidirectional composite. Simplified micromechanics methods are used to determine the equivalent stiffness properties, and results from Coupon Level tests on the braided composite are utilized to back out the required strength properties. Simulations of quasi-static Coupon tests of several representative braided composites are conducted to demonstrate the correlation of the model. Impact simulations of a represented braided composites are conducted to demonstrate the capability of the model to predict the penetration velocity and damage patterns obtained experimentally.
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Characterization and Analysis of Triaxially Braided Polymer Composites under Static and Impact Loads
Earth and Space 2012, 2012Co-Authors: Robert K. Goldberg, Lee W Kohlman, Gary D. Roberts, Brina Blinzler, Wieslaw K. BiniendaAbstract:In order to design impact resistant aerospace components made of triaxially braided polymer matrix composite materials, a need exists to have reliable impact simulation methods and a detailed understanding of the material behavior. Traditional test methods and specimen designs have yielded unrealistic material property data due to features such as edge damage. To overcome these deficiencies, various alternative testing geometries such as notched flat Coupons have been examined to alleviate difficulties observed with standard test methods. The results from the Coupon Level tests have been used to characterize and validate a macro Level finite element based model which can be used to simulate the mechanical and impact response of the braided composites. In the analytical model, the triaxial braid architecture is simulated by using four parallel shell elements, each of which is modeled as a laminated composite. Currently, each shell element is considered to be a smeared homogeneous material. Simplified micromechanics techniques and lamination theory are used to determine the equivalent stiffness properties of each shell element, and results from the Coupon Level tests on the braided composite are used to back out the strength properties of each shell element. Recent improvements to the model the incorporation of strain rate effects into the model. Simulations of ballistic impact tests have been carried out to investigate and verify the analysis approach.
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Investigation of a Macromechanical Approach to Analyzing Triaxially-Braided Polymer Composites
AIAA Journal, 2011Co-Authors: Robert K. Goldberg, Brina Blinzler, Wieslaw K. BiniendaAbstract:A macro Level finite element-based model has been developed to simulate the mechanical and impact response of triaxially-braided polymer matrix composites. In the analytical model, the triaxial braid architecture is simulated by using four parallel shell elements, each of which is modeled as a laminated composite. The commercial transient dynamic finite element code LS-DYNA is used to conduct the simulations, and a continuum damage mechanics model internal to LS-DYNA is used as the material constitutive model. The material stiffness and strength values required for the constitutive model are determined based on Coupon Level tests on the braided composite. Simulations of quasi-static Coupon tests of a representative braided composite are conducted. Varying the strength values that are input to the material model is found to have a significant influence on the effective material response predicted by the finite element analysis, sometimes in ways that at first glance appear non-intuitive. A parametric study involving the input strength parameters provides guidance on how the analysis model can be improved.
