Download or read book Rate Dependent Deformation and Strength Analysis of Polymer Matrix Composites written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-04 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt: A research program is being undertaken to develop rate dependent deformation and failure models for the analysis of polymer matrix composite materials. In previous work in this program, strain-rate dependent inelastic constitutive equations used to analyze polymers have been implemented into a mechanics of materials based composite micromechanics method. In the current work, modifications to the micromechanics model have been implemented to improve the calculation of the effective inelastic strain. Additionally, modifications to the polymer constitutive model are discussed in which pressure dependence is incorporated into the equations in order to improve the calculation of constituent and composite shear stresses. The Hashin failure criterion is implemented into the analysis method to allow for the calculation of ply level failure stresses. The deformation response and failure stresses for two representative uniaxial polymer matrix composites, IM7/977-2 and AS4-PEEK, are predicted for varying strain rates and fiber orientations. The predicted results compare favorably to experimentally obtained values.Goldberg, Robert K. and Stouffer, Donald C.Glenn Research CenterPOLYMER MATRIX COMPOSITES; DEFORMATION; STRAIN RATE; FAILURE ANALYSIS; MICROMECHANICS; PRESSURE DEPENDENCE; SHEAR STRESS; FIBER ORIENTATION; FAILURE; CONSTITUTIVE EQUATIONS; CRITERIA

Download or read book Rate Dependent Deformation and Strength Analysis of Polymer Matrix Composites written by and published by . This book was released on 1999 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Strain Rate Dependent Deformation and Strength Modeling of a Polymer Matrix Composite Utilizing a Micromechanics Approach written by Robert Keith Goldberg and published by . This book was released on 1999 with total page 88 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Implementation of Laminate Theory Into Strain Rate Dependent Micromechanics Analysis of Polymer Matrix Composites written by Robert K. Goldberg and published by . This book was released on 2000 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Strain Rate Dependent Deformation and Strength Modeling of a Polymer Matrix Composite Utilizing a Micromechanics Approach written by Robert K. Goldberg and published by . This book was released on 1999 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Strain Rate Dependent Modeling of Polymer Matrix Composites written by Robert K. Goldberg and published by . This book was released on 1999 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Nonlinear Strain Rate Dependent Composite Model for Explicit Finite Element Analysis written by Xiahua Zheng and published by . This book was released on 2006 with total page 340 pages. Available in PDF, EPUB and Kindle. Book excerpt: "With the increasing application of fiber reinforced polymer matrix composites in the aerospace industry, a composite model that has the capability to capture the nonlinear, strain rate dependent deformation behavior of the materials is desired for finite element analysis. Polymers are believed to be the major contributors to the nonlinearity and rate dependence of the composites. In this study, the nonlinear, rate dependent constitutive polymer model developed by Goldberg has been modified to incorporate the rate dependence of the elastic modulus and a simple damage model is proposed to improve its unloading prediction. The polymer constitutive equations are then implemented within a strength of materials based micromechanics method in order to predict the nonlinear, strain rate dependent deformation of the composite. Strain rate dependent failure criteria and post failure progressive damage model are incorporated into the composite model. The polymer and the composite models are implemented into a commercially available explicit finite element code, LS-DYNA, as user defined materials (UMATs). The deformation behaviors of several representative polymers and two polymer matrix composites of various fiber configurations are simulated in LS-DYNA with the UMATs for a wide range of strain rates, and the numerical results agree well with the experimental data. To expand the application of the unidirectional lamina based composite UMAT, braiding/weaving with through-thickness integration points method is proposed with examples to simulate the deformation behavior of textile composites."--Iii-iv.

Download or read book Incorporation of Mean Stress Effects Into the Micromechanical Analysis of the High Strain Rate Response of Polymer Matrix Composites written by and published by . This book was released on 2002 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book High Strain Rate Deformation Modeling of a Polymer Matrix Composite written by and published by . This book was released on 1998 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Incorporation of Mean Stress Effects Into the Micromechanical Analysis of the High Strain Rate Response of Polymer Matrix Composites written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt: The results presented here are part of an ongoing research program, to develop strain rate dependent deformation and failure models for the analysis of polymer matrix composites subject to high strain rate impact loads. A micromechanics approach is employed in this work, in which state variable constitutive equations originally developed for metals have been modified to model the deformation of the polymer matrix, and a strength of materials based micromechanics method is used to predict the effective response of the composite. In the analysis of the inelastic deformation of the polymer matrix, the definitions of the effective stress and effective inelastic strain have been modified in order to account for the effect of hydrostatic stresses, which are significant in polymers. Two representative polymers, a toughened epoxy and a brittle epoxy, are characterized through the use of data from tensile and shear tests across a variety of strain rates. Results computed by using the developed constitutive equations correlate well with data generated via experiments. The procedure used to incorporate the constitutive equations within a micromechanics method is presented, and sample calculations of the deformation response of a composite for various fiber orientations and strain rates are discussed.Goldberg, Robert K. and Roberts, Gary D. and Gilat, AmosGlenn Research CenterCONSTITUTIVE EQUATIONS; DEFORMATION; IMPACT LOADS; MICROMECHANICS; POLYMER MATRIX COMPOSITES; STRAIN RATE; BRITTLENESS; EPOXY RESINS; FAILURE ANALYSIS; FIBER ORIENTATION; HYDROSTATICS; MATRIX MATERIALS; TENSILE TESTS; SHEAR PROPERTIES

Download or read book Implementation of Fiber Substructuring Into Strain Rate Dependent Micromechanics Analysis of Polymer Matrix Composites written by and published by . This book was released on 2001 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book High Strain Rate Deformation Modeling of a Polymer Matrix Composite Part 1 Matrix Constitutive Equations written by National Aeronautics and Space Adm Nasa and published by . This book was released on 2018-10-18 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recently applications have exposed polymer matrix composite materials to very high strain rate loading conditions, requiring an ability to understand and predict the material behavior under these extreme conditions. In this first paper of a two part report, background information is presented, along with the constitutive equations which will be used to model the rate dependent nonlinear deformation response of the polymer matrix. Strain rate dependent inelastic constitutive models which were originally developed to model the viscoplastic deformation of metals have been adapted to model the nonlinear viscoelastic deformation of polymers. The modified equations were correlated by analyzing the tensile/ compressive response of both 977-2 toughened epoxy matrix and PEEK thermoplastic matrix over a variety of strain rates. For the cases examined, the modified constitutive equations appear to do an adequate job of modeling the polymer deformation response. A second follow-up paper will describe the implementation of the polymer deformation model into a composite micromechanical model, to allow for the modeling of the nonlinear, rate dependent deformation response of polymer matrix composites. Goldberg, Robert K. and Stouffer, Donald C. Glenn Research Center RTOP 523-24-13...

Download or read book Computational Simulation of the High Strain Rate Tensile Response of Polymer Matrix Composites written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-19 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: A research program is underway to develop strain rate dependent deformation and failure models for the analysis of polymer matrix composites subject to high strain rate impact loads. Under these types of loading conditions, the material response can be highly strain rate dependent and nonlinear. State variable constitutive equations based on a viscoplasticity approach have been developed to model the deformation of the polymer matrix. The constitutive equations are then combined with a mechanics of materials based micromechanics model which utilizes fiber substructuring to predict the effective mechanical and thermal response of the composite. To verify the analytical model, tensile stress-strain curves are predicted for a representative composite over strain rates ranging from around 1 x 10(exp -5)/sec to approximately 400/sec. The analytical predictions compare favorably to experimentally obtained values both qualitatively and quantitatively. Effective elastic and thermal constants are predicted for another composite, and compared to finite element results. Goldberg, Robert K. Glenn Research Center NASA/TM-2002-211489, E-13257, NAS 1.15:211489

Download or read book High Strain Rate Deformation Modeling of a Polymer Matrix Composite Part 2 Composite Micromechanical Model written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-05 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recently applications have exposed polymer matrix composite materials to very high strain rate loading conditions, requiring an ability to understand and predict the material behavior under these extreme conditions. In this second paper of a two part report, a three-dimensional composite micromechanical model is described which allows for the analysis of the rate dependent, nonlinear deformation response of a polymer matrix composite. Strain rate dependent inelastic constitutive equations utilized to model the deformation response of a polymer are implemented within the micromechanics method. The deformation response of two representative laminated carbon fiber reinforced composite materials with varying fiber orientation has been predicted using the described technique. The predicted results compare favorably to both experimental values and the response predicted by the Generalized Method of Cells, a well-established micromechanics analysis method. Goldberg, Robert K. and Stouffer, Donald C. Glenn Research Center RTOP 523-24-13...

Download or read book Computational Simulation of the High Strain Rate Tensile Response of Polymer Matrix Composites written by and published by . This book was released on 2002 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Implementation of Fiber Substructuring Into Strain Rate Dependent Micromechanics Analysis of Polymer Matrix Composites written by National Aeronautics and Space Adm Nasa and published by Independently Published. This book was released on 2018-09-15 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt: A research program is in progress to develop strain rate dependent deformation and failure models for the analysis of polymer matrix composites subject to impact loads. Previously, strain rate dependent inelastic constitutive equations developed to model the polymer matrix were incorporated into a mechanics of materials based micromechanics method. In the current work, the micromechanics method is revised such that the composite unit cell is divided into a number of slices. Micromechanics equations are then developed for each slice, with laminate theory applied to determine the elastic properties, effective stresses and effective inelastic strains for the unit cell. Verification studies are conducted using two representative polymer matrix composites with a nonlinear, strain rate dependent deformation response. The computed results compare well to experimentally obtained values.Goldberg, Robert K.Glenn Research CenterDEFORMATION; ELASTIC PROPERTIES; FAILURE ANALYSIS; POLYMER MATRIX COMPOSITES; NUMERICAL ANALYSIS; CONSTITUTIVE EQUATIONS; STRAIN RATE; NONLINEARITY; MICROMECHANICS; LAMINATES; IMPACT LOADS

Download or read book Experimental and Computational Characterization of the High Strain Rate Tensile Response of Polymer Matrix Composites written by RK. Goldberg and published by . This book was released on 2003 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: A research program is underway to experimentally characterize the strain rate dependent deformation and failure response of polymer matrix composites subject to high strain rate impact loads and to develop strain rate dependent deformation and failure models for the analysis of these types of materials. State variable constitutive equations based on a viscoplasticity approach have been developed to model the deformation of the polymer matrix. The constitutive equations are then combined with a mechanics of materials based micromechanics model which utilizes fiber substructuring to predict the effective mechanical and thermal response of the composite. Tensile stress-strain curves for a representative composite are obtained experimentally for strain rates ranging from quasi-static to several hundred per second. The developed numerical procedure is also used to compute the deformation response. The predictions compare favorably to the experimentally obtained values both qualitatively and quantitatively. Effective elastic and thermal constants are predicted for another composite, and compared to finite element results.