Microplane Model for Fracturing Damage of Triaxially Braided Fiber-Polymer Composites

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
Ferhun C. Caner ◽  
Zdeněk P. Bažant ◽  
Christian G. Hoover ◽  
Anthony M. Waas ◽  
Khaled W. Shahwan
Keyword(s):  
Present Model ◽  
Material Model ◽  
Multiscale Model ◽  
Stress And Strain ◽  
Band Model ◽  
Braided Composites ◽  
Microplane Model ◽  
Explicit Finite Element ◽  
Crack Band ◽  
Strain Tensors

A material model for the fracturing behavior for braided composites is developed and implemented in a material subroutine for use in the commercial explicit finite element code ABAQUS. The subroutine is based on the microplane model in which the constitutive behavior is defined not in terms of stress and strain tensors and their invariants but in terms of stress and strain vectors in the material mesostructure called the “microplanes.” This is a semi-multiscale model, which captures the interactions between inelastic phenomena such as cracking, splitting, and frictional slipping occurring on planes of various orientations though not the interactions at a distance. To avoid spurious mesh sensitivity due to softening, the crack band model is adopted. Its band width, related to the material characteristic length, serves as the localization limiter. It is shown that the model can realistically predict the orthotropic elastic constants and the strength limits. More importantly, the present model can also fit the tests of size effect on the strength of notched specimens and the post-peak behavior, which have been conducted for this purpose. When used in the ABAQUS software, the model gives a realistic picture of the axial crushing of a braided tube by a divergent plug.

Linear elastic eigenstates of the compliance tensor for trigonal crystals

2000 ◽  
Vol 215 (1) ◽  
pp. 1-9 ◽  
Author(s):  
P.S. Theocaris ◽  
D.P. Sokolis
Keyword(s):  
Strain Energy ◽  
Elastic Strain Energy ◽  
Symmetric Tensor ◽  
Stress And Strain ◽  
Linear Elastic ◽  
Trigonal System ◽  
Compliance Tensor ◽  
Characteristic Values ◽  
Strain Tensors ◽  
Elastic Strain Energy Density

The spectral decomposition of the compliance fourth-rank tensor, representative of a trigonal crystalline or other anisotropic medium, is offered in this paper, and its characteristic values and idempotent fourth-rank tensors are established, with respect to the Cartesian tensor components. Consequently, it is proven that the idempotent tensors serve to analyse the second-rank symmetric tensor space into orthogonal subspaces, resolving the stress and strain tensors for the trigonal medium into their eigentensors, and, finally, decomposing the total elastic strain energy density into distinct, autonomous components. Finally, bounds on the values of the compliance tensor components for the trigonal system, dictated by the classical thermodynamical argument for the elastic potential to be positive definite, are estimated by imposing the characteristic values of the compliance tensor to be strictly positive.

Strength Simulation of Woven Fabric Composite Materials With Material Nonlinearity Using Micromechanics Based Model

2000 ◽  
Author(s):  
A. Tabiei ◽  
G. Song ◽  
Y. Jiang
Keyword(s):  
Finite Element ◽  
Shear Failure ◽  
Material Model ◽  
Failure Criteria ◽  
Woven Fabric ◽  
Woven Composites ◽  
Explicit Finite Element ◽  
Representative Cell ◽  
Pure Matrix ◽  
Transverse Failure

Abstract The objective of the current investigation is to predict failure strength of woven composites, which considers the two-dimensional extent of woven fabric, based on micro-mechanics. The formulation has an interface with nonlinear finite element codes. At each load increment, global stresses and strains are communicated to the representative cell and subsequently distributed to each subcell. Once stresses and strains are associated to a subcell they can be distributed to each constituent of the subcell (i.e. fill, warp, and resin). Consequently micro-failure criteria (MFC) are defined for each constituents of a subcell and the proper stiffness degradation is modeled. Different stages of failure such as warp transverse failure, fill transverse failure, failure of pure matrix in longitudinal and shear, shear failure in fill and warp, and fiber in fill and warp in longitudinal tension are considered. Good correlation is observed between the predicted and the experimental results presented in the published literature. This material model is suitable for implicit failure analysis under static loads and is being modified for explicit finite element codes to deal with problems such as crashworthiness and impact.

MATHEMATICAL MODEL OF MATERIALS OF STRUCTURES AND ELEMENTS OF RESTORED SOIL DAMS FOR NUMERICAL CALCULATIONS

2021 ◽  
pp. 46-51
Author(s):  
V. YA. ZHARNITSKIY ◽  
◽  
A. P. SMIRNOV
Keyword(s):  
Negative Impact ◽  
Emergency Situation ◽  
Numerical Calculations ◽  
Stress And Strain ◽  
Operational Parameters ◽  
Reliable Operation ◽  
Operational Factors ◽  
Materials Used ◽  
Technical Operation ◽  
Strain Tensors

Identified in the process of analyzing the operation of the structure, in the conditions of its operation, allow to assess the actual reserves of the bearing capacity of the structure and take effective measures to restore the operational parameters. The main criteria influencing the choice of mathematical models of materials for structures and elements of soil dams are more consistent with the model of the equation of state connecting the components of stress and strain tensors, as well as the rate of their change, which are obtained and tested for numerical calculations and have a full set of constants for materials used in the calculations of earth dams, the choice of their structures (concrete,reinforced concrete, soils, etc.). Reliable operation of soil dams is possible only if all proper conditions are met. The causes of dam accidents and their damage must be known not only to eliminate errors at the design and construction stages, but also during their operation. In order to exclude the negative impact of operational factors on the safety of soil HTS, it is necessary not only to strictly observe the rules of technical operation and take measures to exclude the possibility of an emergency situation during technological operations at facilities, but also to have methods for predictive justification of the restoration of strength and operational indicators of structures and elements of soil dams.

Finite Element Modeling of Non-Orthogonal Loosely Woven Fabrics in Advanced Occupant Restraint Systems

2001 ◽  
Author(s):  
Romil R. Tanov ◽  
Marlin Brueggert
Keyword(s):  
Finite Element ◽  
Material Model ◽  
General Purpose ◽  
Woven Fabrics ◽  
Element Analysis ◽  
Correct Operation ◽  
Explicit Finite Element ◽  
Analysis Scheme ◽  
Occupant Restraint Systems ◽  
Protection Devices

Abstract The behavior of loosely woven fabrics differs significantly from other types of woven fabrics. Its unique characteristics have been successfully utilized for the correct operation of some recently developed occupant protection devices for the automotive and heavy machine and truck industry. However, this behavior cannot be efficiently modeled using the currently available material models within a finite element analysis scheme. Therefore, the aim of this work is to present the basics of a formulation of a material model for the analysis of loosely woven fabrics and its implementation in a general-purpose explicit finite element code. To assess the performance of the model, results from the simulation are presented and compared to real test data.

A Continuum Damage Model for Functionalized Graphene Membranes Based on Atomistic Simulations

2017 ◽  
Vol 754 ◽  
pp. 173-176
Author(s):  
Ivano Benedetti ◽  
R.A. Soler-Crespo ◽  
A. Pedivellano ◽  
Wei Gao ◽  
H.D. Espinosa
Keyword(s):  
Continuum Model ◽  
Damage Model ◽  
Atomistic Simulations ◽  
Band Model ◽  
Continuum Damage ◽  
Two Phase ◽  
Elastic Continuum ◽  
Continuum Damage Model ◽  
Crack Band ◽  
Hyper Elastic

A continuum model for GO membranes is developed in this study. The model is built representing the membrane as a two-dimensional, heterogeneous, two-phase continuum and the constitutive behavior of each phase (graphitic or oxidized) is built based on DFTB simulations of representative patches. A hyper-elastic continuum model is employed for the graphene areas, while a continuum damage model is more adequate for representing the behavior of oxidized regions. A finite element implementation for GO membranes subjected to degradation and failure is then implemented and, to avoid localization instabilities and spurious mesh sensitivity, a simple crack band model is adopted. The developed implementation is then used to investigate the existence of GO nano-representative volume elements.

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