scholarly journals Thermo-Viscoelastic Response of 3D Braided Composites Based on a Novel FsMsFE Method

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 271
Author(s):  
Jun-Jun Zhai ◽  
Xiang-Xia Kong ◽  
Lu-Chen Wang
Keyword(s):  
Finite Element ◽  
Cell Model ◽  
Structural Parameters ◽  
Thermal Relaxation ◽  
Viscoelastic Behavior ◽  
Unit Cell ◽  
Time Dependent ◽  
3D Braided Composites ◽  
Equivalent Time ◽  
Representative Unit Cell

A homogenization-based five-step multi-scale finite element (FsMsFE) simulation framework is developed to describe the time-temperature-dependent viscoelastic behavior of 3D braided four-directional composites. The current analysis was performed via three-scale finite element models, the fiber/matrix (microscopic) representative unit cell (RUC) model, the yarn/matrix (mesoscopic) representative unit cell model, and the macroscopic solid model with homogeneous property. Coupling the time-temperature equivalence principle, multi-phase finite element approach, Laplace transformation and Prony series fitting technology, the character of the stress relaxation behaviors at three scales subject to variation in temperature is investigated, and the equivalent time-dependent thermal expansion coefficients (TTEC), the equivalent time-dependent thermal relaxation modulus (TTRM) under micro-scale and meso-scale were predicted. Furthermore, the impacts of temperature, structural parameters and relaxation time on the time-dependent thermo-viscoelastic properties of 3D braided four-directional composites were studied.

SEA model for structural acoustic coupling by means of periodic finite element models of the structural subsystems

2021 ◽  
Vol 263 (1) ◽  
pp. 5301-5309
Author(s):  
Luca Alimonti ◽  
Abderrazak Mejdi ◽  
Andrea Parrinello
Keyword(s):  
Finite Element ◽  
Numerical Approach ◽  
Unit Cell ◽  
Analytical Models ◽  
Finite Element Models ◽  
Fe Model ◽  
Acoustic Coupling ◽  
Representative Unit Cell ◽  
Definition Of ◽  
Acoustic Treatment

Statistical Energy Analysis (SEA) often relies on simplified analytical models to compute the parameters required to build the power balance equations of a coupled vibro-acoustic system. However, the vibro-acoustic of modern structural components, such as thick sandwich composites, ribbed panels, isogrids and metamaterials, is often too complex to be amenable to analytical developments without introducing further approximations. To overcome this limitation, a more general numerical approach is considered. It was shown in previous publications that, under the assumption that the structure is made of repetitions of a representative unit cell, a detailed Finite Element (FE) model of the unit cell can be used within a general and accurate numerical SEA framework. In this work, such framework is extended to account for structural-acoustic coupling. Resonant as well as non-resonant acoustic and structural paths are formulated. The effect of any acoustic treatment applied to coupling areas is considered by means of a Generalized Transfer Matrix (TM) approach. Moreover, the formulation employs a definition of pressure loads based on the wavenumber-frequency spectrum, hence allowing for general sources to be fully represented without simplifications. Validations cases are presented to show the effectiveness and generality of the approach.

Viscoelastic Finite Element Modeling of Bimodal High Density Polyethylene (HDPE) Piping Materials for Nuclear Safety-Related Applications

2010 ◽  
Author(s):  
Do-Jun Shim ◽  
Prabhat Krishnaswamy ◽  
Yunior Hioe ◽  
Sureshkumar Kalyanam
Keyword(s):  
Finite Element ◽  
Service Life ◽  
High Density Polyethylene ◽  
Viscoelastic Behavior ◽  
Time Dependent ◽  
Tensile Creep ◽  
Uniaxial Tensile ◽  
Fe Model ◽  
Creep Tests ◽  
Uniaxial Tensile Creep

The U.S. Nuclear Regulatory Commission (USNRC) has recently approved Relief Requests for the use of high density polyethylene (HDPE) piping in safety-related applications. The ASME Boiler and Pressure Vessel Code, meanwhile, has developed Code Case N-755 that defines the design and service life requirements for PE piping in nuclear plants though it has not as yet been approved by the USNRC. One of the issues of concern is premature failure of PE piping due to slow crack growth (SCG) that can initiate due to a combination of sustained loads, elevated temperatures, and a pre-existing defect. Understanding and predicting the SCG behavior is an essential step in developing a methodology for predicting the service life of PE piping. The first step in studying the failure process in a polymer under a constant sustained load is the selection of a suitable constitutive model to represent the time-dependent behavior of the material. In this paper, uniaxial tensile creep tests were performed for a bimodal HDPE (PE4710) piping material. This creep data was used to determine the viscoelastic material constants for this bimodal HDPE using a power-law creep model. These material constants were used in finite element (FE) analyses to study the viscoelastic behavior of the bimodal HDPE. As a first step, the FE model was verified by comparing the results from numerical simulations and experiments for a set of uniaxial tensile creep tests. The FE model was then applied to study the viscoelastic behavior of a SCG specimen. The time dependent stress and strain fields were investigated.

A Homogenization Scheme for Nonlinear Viscoelastic Behaviors of Particulate Reinforced Composites

2006 ◽  
Author(s):  
Jeong Sik Kim ◽  
Anastasia Muliana ◽  
Kamran Khan
Keyword(s):  
Effective Properties ◽  
Cell Model ◽  
Constitutive Relations ◽  
Micromechanical Model ◽  
Unit Cell ◽  
Time Dependent ◽  
Analytical Models ◽  
Fe Model ◽  
Micro Particles ◽  
Nonlinear Viscoelastic

The present study introduces a micromechanical model for predicting nonlinear viscoelastic responses of composite systems reinforced with solid spherical micro particles. The composite microstructures are simplified with uniformly distributed cubic particles over an infinite medium. The representative volume element (RVE) consists of a single particle embedded in the cubic matrix. One eighth unit-cell model with four particle and polymer subcells is generated. The solid spherical particle is modeled as linear elastic, while the polymer follows nonlinear viscoelastic material responses. The homogenized micromechanical relation is developed in terms of the average strains and stresses and satisfies traction continuity and displacement compatibility at the subcells' interfaces. The micromechanical model provides three-dimensional (3D) effective properties of homogeneous materials, while recognizing important micro-structural aspects and parameters of the heterogeneous medium. The micromechanical formulation is generalized to include an explicit time-scale for modeling time-dependent behavior and is designed to be compatible with general displacement based finite element (FE) analyses. Due to the nonlinear and time-dependent response in the polymeric matrix, the linearized micromechanical relations will often deviate from the nonlinear constitutive equations. Thus, the stress-strain correction scheme is formulated to satisfy both micromechanical and nonlinear constitutive relations. Experimental data and analytical models available in the literature are used to verify the capability of the above micromechanical model in predicting the overall nonlinear behaviors. Comparisons with detail unit-cell FE model are also presented.

scholarly journals Validity of Finite Element Unit Cell Model for Studying Yield Condition of Isotropic Porous Materials.

1995 ◽  
Vol 61 (591) ◽  
pp. 2435-2441
Author(s):  
Tomoyuki Sasaki ◽  
Moriaki Goya ◽  
Kiyohiro Miyagi ◽  
Shousuke Itomura ◽  
Toshiyasu Sueyoshi
Keyword(s):  
Finite Element ◽  
Porous Materials ◽  
Cell Model ◽  
Yield Condition ◽  
Unit Cell ◽  
Unit Cell Model

Orientation order parameters and effective conductivity of a 2-D solid with partially disordered array of circular inhomogeneities

2021 ◽  
pp. 108128652110243
Author(s):  
Volodymyr I Kushch ◽  
Igor Sevostianov
Keyword(s):  
Effective Conductivity ◽  
Cell Model ◽  
Structural Parameters ◽  
Quantitative Measure ◽  
Expansion Method ◽  
Multipole Expansion ◽  
Orientation Order ◽  
Multipole Expansion Method ◽  
Representative Unit Cell ◽  
Heterogeneous Solid

The paper focuses on the quantitative characterization of the microstructure of a two-dimensional heterogeneous solid with circular inhomogeneities that may vary from perfectly periodic arrangement to completely random one. This characterization is linked to the calculation of the effective conductivity of the material. The partially disordered system of disks is generated in the framework of the representative unit cell model using Metropolis algorithm. The orientation order metrics are taken as the structural parameters providing a quantitative measure of disorder, and their variation caused by the gradual disordering of the periodic system is assessed. The effective conductivity of the heterogeneous solid with partially disordered microstructure is evaluated by the multipole expansion method. It is shown that effective conductivity cannot be fully characterized by only one orientation order metric, and the required additional ones are identified.

Development of a Representative Unit Cell Model for Bi-axial NCF Composites

2007 ◽  
Vol 41 (7) ◽  
pp. 801-835 ◽  
Author(s):  
J.L. Oakeshott ◽  
L. Iannucci ◽  
P. Robinson
Keyword(s):  
Cell Model ◽  
Unit Cell ◽  
Unit Cell Model ◽  
Representative Unit Cell
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