Failure Prediction of Unidirectional Composites Undergoing Large Deformations1

2015 ◽  
Vol 82 (7) ◽  
Author(s):  
Jacob Aboudi ◽  
Konstantin Y. Volokh
Keyword(s):  
Strain Energy ◽  
Large Deformations ◽  
Static Stability ◽  
Energy Functions ◽  
Micromechanical Analysis ◽  
Hyperelastic Materials ◽  
Failure Envelopes ◽  
Special Cases ◽  
Enhanced Strain ◽  
Strain Energy Functions

In previous publications, strain-energy functions with limiters have been introduced for the prediction of onset of failure in monolithic isotropic hyperelastic materials. In the present investigation, such enhanced strain-energy functions whose ability to accumulate energy is limited have been incorporated with a finite strain micromechanical analysis. As a result, macroscopic constitutive equations have been established which are capable to predict the onset of loss of static stability in a hyperelastic phase of composite materials undergoing large deformations. The details of the micromechanical analysis, based on a tangential formulation, for composites with periodic microstructure are presented. The derived micromechanical analysis includes the capability to model a possible imperfect bonding between the composite’s constituents and to provide the field distribution in the composite. The micromechanical method is verified by comparison with analytical and finite difference solutions for porous hyperelastic materials that are valid in some special cases. Results are given for a rubberlike matrix characterized by softening hyperelasticity, reinforced by unidirectional nylon fibers. The response of the composite to various types of loadings is presented up to the onset of loss of static stability at a location within the hyperelastic rubber constituent, and initial failure envelopes are shown.

Finite Bending and Straightening of Hyperelastic Materials: Analytical Solution and FEM

2019 ◽  
Vol 11 (09) ◽  
pp. 1950084 ◽  
Author(s):  
Sara Sheikhi ◽  
Mohammad Shojaeifard ◽  
Mostafa Baghani
Keyword(s):  
Finite Element ◽  
Strain Energy ◽  
Strain Energy Function ◽  
Optimization Procedure ◽  
Element Analysis ◽  
Energy Functions ◽  
Hyperelastic Materials ◽  
Finite Bending ◽  
Strain Energy Functions ◽  
Analytical Approaches

In this research, an incompressible, isotropic, nonlinear elastic rectangular block and a circular cylindrical sector are studied under bending and straightening moments, respectively. Analytical approaches are presented on implementing of the left Cauchy–Green tensor and Cauchy stresses. In addition, finite element analysis of both problems is carried out using UHYPER user-defined subroutine in ABAQUS to verify the analytical methods. Four different invariant-based strain energy functions, including neo-Hookean, Mooney–Rivlin, Arruda–Boyce, and recently proposed polynomial Exp-Exp models, are examined, and the results are compared. Material parameters of silicon rubber for the strain energy functions are identified by applying an optimization procedure. Finite element method results confirmed the analytical approach with great compatibility. Results showed that the length of the unbent beam does not affect the stress. Likewise, the initial angle of curved structure does not affect the unbending moment and stresses. Moreover, the Exp-Exp model had a slightly different result rather than other strain energies, which means that this model is more conservative than its counterparts. Furthermore, the Exp-Exp strain energy function is calibrated for tissue-like phantom and is compared with experimental data.

Experimental and Numerical Study for Determining the Mechanical Properties of Automobile Weatherstrip Seals

2006 ◽  
Author(s):  
Emre Dikmen ◽  
Ipek Basdogan
Keyword(s):  
Finite Element ◽  
Finite Element Modeling ◽  
Test Data ◽  
Compression Test ◽  
Strain Energy ◽  
Energy Functions ◽  
Material Models ◽  
Compression Load ◽  
Hyperelastic Materials ◽  
Strain Energy Functions

Structural parts made of hyperelastic materials such as rubber mounts in automotive powertrains and weatherstrip seals are widely used in automotive and other engineering applications. In this study, compression load deflection (CLD) behavior of a highly non-linear type of joint, automotive weatherstrip seal made of Ethylene Propylene Diene Monomer (EPDM) sponge rubber is examined using finite element modeling techniques. The finite element modeling (FEM) results are then compared with the compression load deflection data obtained experimentally. The compression load deflection data for various punch velocities can be used to model the weatherstrip seal as a nonlinear spring-dashpot system with varying stiffness and damping coefficient proportional to the amount of compression. The weatherstrip seals should be modeled accurately in order to predict the dynamic performance of the automobiles under various load conditions. First part of the study includes modeling of the seal using various hyperelastic material models which are available in ANSYS. The strain energy functions’ coefficients required for the various material models are calculated using both linear and nonlinear least square fit procedures implemented in ANSYS for fitting the tension, shear and compression test data. After the coefficients are calculated, the compression test is performed in ANSYS using various hyperelastic material models. Second part of the study includes the compression experiment of weatherstrip seal with a robotic indenter specifically designed for measuring hyperelastic materials. The measured CLD data is then compared with the FEM results. The accuracy of using only simple tension test data to acquire the coefficients for strain energy functions is investigated and suitable strain energy functions to model compression of weatherstrip seal are determined. Additionally, Mullins Effect (stress softening) for this application is investigated using the compression experiments data.

Strain energy functions for filled elastomers

1965 ◽  
Vol 9 (7) ◽  
pp. 2565-2579 ◽  
Author(s):  
M. Shinozuka ◽  
A. M. Freudenthal
Keyword(s):  
Strain Energy ◽  
Energy Functions ◽  
Filled Elastomers ◽  
Strain Energy Functions

Large Deformations of a Rotating Solid Cylinder for Non-Gaussian Isotropic, Incompressible Hyperelastic Materials

2000 ◽  
Vol 68 (1) ◽  
pp. 115-117 ◽  
Author(s):  
C. O. Horgan ◽  
G. Saccomandi
Keyword(s):  
Angular Velocity ◽  
Strain Energy ◽  
Large Deformations ◽  
Rotating Cylinder ◽  
Solid Cylinder ◽  
Hyperelastic Materials ◽  
Steady Rotation ◽  
Non Gaussian ◽  
Limiting Value ◽  
Small Angular Velocity

The purpose of this research is to investigate the steady rotation of a solid cylinder for a class of strain-energy densities that are able to describe hardening phenomena in rubber. It is well known that use of the classic neo-Hookean strain energy gives rise to physically unrealistic response in this problem. In particular, solutions exist only for a sufficiently small angular velocity. As the velocity approaches this limiting value, the analysis predicts that the rotating cylinder collapses to a disk. It is shown here that this nonphysical behavior does not occur when generalized neo-Hookean models, which exhibit hardening at large deformations, are used.

On the Development of Volumetric Strain Energy Functions

1999 ◽  
Vol 67 (1) ◽  
pp. 17-21 ◽  
Author(s):  
S. Doll ◽  
K. Schweizerhof
Keyword(s):  
Strain Energy ◽  
Volumetric Strain ◽  
Strain Energy Function ◽  
Material Behavior ◽  
Additional Material ◽  
Energy Functions ◽  
Material Parameters ◽  
Physical Conditions ◽  
Starting Point ◽  
Strain Energy Functions

To describe elastic material behavior the starting point is the isochoric-volumetric decoupling of the strain energy function. The volumetric part is the central subject of this contribution. First, some volumetric functions given in the literature are discussed with respect to physical conditions, then three new volumetric functions are developed which fulfill all imposed conditions. One proposed function which contains two material parameters in addition to the compressibility parameter is treated in detail. Some parameter fits are carried out on the basis of well-known volumetric strain energy functions and experimental data. A generalization of the proposed function permits an unlimited number of additional material parameters.  Dedicated to Professor Franz Ziegler on the occasion of his 60th birthday. [S0021-8936(00)00901-6]

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