Nonlinear Elastic Behavior of Unidirectional Composites With Fiber Waviness Under Compressive Loading

1996 ◽  
Vol 118 (4) ◽  
pp. 561-570 ◽  
Author(s):  
H. M. Hsiao ◽  
I. M. Daniel
Keyword(s):  
Constitutive Relations ◽  
Compressive Loading ◽  
Nonlinear Material ◽  
Elastic Behavior ◽  
Compression Tests ◽  
Fiber Waviness ◽  
Unidirectional Composites ◽  
Nonlinear Stress ◽  
Material Nonlinear ◽  
Nonlinear Elastic

Nonlinear elastic behavior of unidirectional composites with fiber waviness under compressive loading was investigated theoretically and experimentally. Unidirectional carbon/epoxy composites with uniform, graded, and localized fiber waviness were studied. Complementary strain energy was used to derive the material nonlinear stress-strain relations. Nonlinear material properties obtained from shear and longitudinal and transverse compression tests were incorporated into the analysis. Compression tests of specimens with known fiber waviness were conducted to verify the constitutive relations. Experimental results were in good agreement with predictions based on the constitutive model.

Finite Deformation and Nonlinear Elastic Behavior of Flexible Composites

1988 ◽  
Vol 55 (1) ◽  
pp. 149-155 ◽  
Author(s):  
Shen-Yi Luo ◽  
Tsu-Wei Chou
Keyword(s):  
Present Theory ◽  
Elastic Behavior ◽  
Stress Strain ◽  
Flexible Composites ◽  
Elastomeric Matrix ◽  
Eulerian Description ◽  
Stress Strain Relation ◽  
Nonlinear Stress ◽  
Material Nonlinear ◽  
Nonlinear Elastic

The flexible composites discussed in this paper are composed of continuous fibers in an elastomeric matrix. The usable range of deformation of these composites is much larger than that of conventional rigid composites. Due to the material as well as geometric factors, the stress-strain relations for these composites are generally nonlinear under finite deformations. A constitutive model has been developed based upon the Eulerian description. The material nonlinear stress-strain relation is derived by using the stress energy density referring to the deformed volume. The stretching-shear coupling and the effects of the in-plane reorientation of fibers are also considered in the theoretical analysis. Comparisons are made between predictions of the present theory and experimental data for tirecord/rubber and Kevlar/silicone-elastomer flexible composite laminae; very good correlations have been found.

A New Constitutive Model for the Compressibility of Elastomers at Finite Deformations

2001 ◽  
Vol 74 (4) ◽  
pp. 541-559 ◽  
Author(s):  
Jeffrey E. Bischoff ◽  
Ellen M. Arruda ◽  
Karl Grosh
Keyword(s):  
Uniaxial Tension ◽  
Volume Change ◽  
Constitutive Models ◽  
Hydrostatic Compression ◽  
Constitutive Law ◽  
Elastic Behavior ◽  
Compression Tests ◽  
Volume Response ◽  
Using Data ◽  
Nonlinear Elastic

Abstract Although traditional constitutive models for rubbery elastic materials are incompressible, many materials that demonstrate nonlinear elastic behavior are somewhat compressible. Clearly important in hydrostatic deformations, compressibility can also significantly affect the response of elastomers in applications for which several boundaries are rigidly fixed, such as bushings, or triaxial states of stress are realized. Compressibility is also important for convergence of finite element simulations in which a rubbery elastic constitutive law is in use. Volume changes that reflect compressibility have been observed historically in both uniaxial tension and hydrostatic compression tests; however, there appear to be no data obtained from both types of tests on the same material by which to validate a compressible hyperelastic law. In this paper, we propose a new compressible hyperelastic constitutive law for elastomers and other rubbery materials in which entropy and internal energy changes contribute to the volume change. Using data from the literature, we show that this law is capable of reproducing both the pressure—volume response of elastomers in hydrostatic compression, as well as the stress—stretch and volume change—stretch data of elastomers in uniaxial tension.

Effect of Fiber Waviness on the Nonlinear Elastic Behavior of Flexible Composites

1988 ◽  
Vol 22 (11) ◽  
pp. 1004-1025 ◽  
Author(s):  
Chen-Ming Kuo ◽  
Kiyohisa Takahashi ◽  
Tsu-Wei Chou
Keyword(s):  
Elastic Behavior ◽  
Fiber Waviness ◽  
Flexible Composites ◽  
Nonlinear Elastic

EFFECTS OF PRECONDITIONING ON THE ELASTIC BEHAVIOR OF SKIN UNDER COMPRESSIVE LOADING

2003 ◽  
Vol 03 (03n04) ◽  
pp. 275-283 ◽  
Author(s):  
JOHN Z. WU ◽  
REN G. DONG ◽  
W. PAUL SMUTZ ◽  
AARON W. SCHOPPER
Keyword(s):  
Compressive Loading ◽  
Tensile Tests ◽  
Elastic Behavior ◽  
Mechanical Parameters ◽  
Compression Tests ◽  
Skin Sample ◽  
Physiological Loading ◽  
Compressive Testing ◽  
Skin Samples ◽  
Compressive Tests

In physiological loading conditions, the skin tissues are, sometimes, loaded compressively. The mechanical characteristics of skins in tension have been studied intensively, while those in compression have not been studied thoroughly. Previous studies suggested that, in order to obtain repeatable mechanical parameters, the skin sample should be properly preconditioned in the tensile tests. The present study is to investigate if the skin sample should be preconditioned in the compressive tests. Pigskins were used in the present study. Compression tests were performed in confined and unconfined loading configurations and at four different loading speeds (0.5, 1.0, 40, and 400 μm/s). Our results show that skin samples should be preconditioned in compressive tests, to obtain repeatable mechanical parameters. The necessary number of the loading cycles in the preconditioning treatment for compressive testing is less than that for tensile testing. Our findings indicate that the skin samples reach repeatable mechanical behavior after 3–4 loading cycles, independent of the loading rate and loading configurations (confined or unconfined compressions).

Strip Extensiometry for Comparison of the Mechanical Response of Bovine, Rabbit, and Human Corneas

1992 ◽  
Vol 114 (2) ◽  
pp. 202-215 ◽  
Author(s):  
David A. Hoeltzel ◽  
Peter Altman ◽  
Kurt Buzard ◽  
Kang-il Choe
Keyword(s):  
Relative Humidity ◽  
Constitutive Relations ◽  
Elastic Behavior ◽  
Stress Strain ◽  
Elapsed Time ◽  
Time Period ◽  
Nonlinear Stress ◽  
Tangent Moduli ◽  
Significant Difference ◽  
Percent Relative Humidity

Specimens of bovine, rabbit, and human corneas were systematically tested in uniaxial tension to experimentally determine their effective nonlinear stress-strain relations, and hysteresis. Cyclic tensile tests were performed over the physiologic load range of the cornea, up to a maximum of 10 percent strain beyond slack strain. Dimensional changes to corneal test specimens, due to varying laboratory environmental conditions, were also assessed. The measured stress-strain data was found to closely fit exponential power function relations typical of collagenous tissues when appropriate account was taken of specimen slack strain. These constitutive relations are very similar for rabbit, human and bovine corneas; there was no significant difference between the species after preconditioning by one cycle. The uniaxial stress strain curves for all species behave similarly in that their tangent moduli increase at high loads and decrease at low loads as a function of cycling. In the bovine and rabbit data, there is a general trend towards more elastic behavior from the first to second cycles, but there is little variation in these parameters from the second to third cycles. In comparison, the human data demonstrates relatively little change between cycles. Increases in width of corneal test specimens, up to a maximum of 2 percent were found to occur under 95 percent relative humidity test conditions over 10 minutes elapsed time test periods, while specimens which were exposed to normal laboratory conditions (45 percent RH) were found to shrink in width up to a maximum of 9.5 percent over the same elapsed time period. The thickness of the test specimens were observed to decrease by 3 percent in 95 percent relative humidity and by 12 percent in 45 percent relative humidity over the same elapsed time period.

Development of a Multibody Model to Predict the Settling Point and Interfacial Pressure Distribution in a Seat–Occupant System

2015 ◽  
Vol 10 (3) ◽  
Author(s):  
Yousof Azizi ◽  
Tarun Puri ◽  
Anil K. Bajaj ◽  
Patricia Davies
Keyword(s):  
Viscoelastic Model ◽  
Viscoelastic Behavior ◽  
Elastic Behavior ◽  
Type Model ◽  
Model Parameters ◽  
Force Distribution ◽  
Compression Tests ◽  
Static Compression ◽  
Multibody Model ◽  
Nonlinear Elastic

The location of the hip-joint (H-Point) of a seat occupant is an important design specification which directly affects the seat static comfort. Most car seats are made of polyurethane foam and so the location of the H-Point is dependent on the quasi-static behavior of foam. In this research, a previously developed model of the seat–occupant system is refined by incorporating an improved foam model which is used to study seat and occupant interactions and the location of occupant’s H-Point. The seat is represented by a series of discrete nonlinear viscoelastic elements that characterize the seating foam behavior. The nonlinear elastic behavior of these elements is expressed by a higher order polynomial while their viscoelastic behavior is described by a hereditary type model with parameters that are functions of the compression rate. The nonlinear elastic and viscoelastic model parameters were estimated previously using data obtained from a series of quasi-static compression tests on a car seat foam sample. The occupant behavior is described by a constrained two-dimensional multibody model with five degrees of freedom. A Lagrangian formulation is used to derive the governing equations for the seat–occupant model. These differential equations are solved numerically to obtain the H-Point location. These results are then used to calculate the force distribution at the seat and occupant interfaces. The force distribution at the seat–occupant interface is also investigated experimentally and is found to match qualitatively with the results obtained using the seat–occupant model.

Elastic-Inelastic Self-Consistent Model for Polycrystals

2002 ◽  
Vol 69 (3) ◽  
pp. 309-316 ◽  
Author(s):  
A. Abdul-Latif ◽  
J. P. Dingli ◽  
K. Saanouni
Keyword(s):  
Complex Loading ◽  
Small Strain ◽  
Elastic Behavior ◽  
Inelastic Behavior ◽  
Surface Evolution ◽  
Heterogeneous Distribution ◽  
Strain Behavior ◽  
Loading Paths ◽  
Nonlinear Stress ◽  
Nonlinear Elastic

Based on a well-established nonincremental interaction law for fully anisotropic and compressible elastic-inelastic behavior of polycrystals, tangent formulation-based and simplified interaction laws, of softened nature, are derived to describe the nonlinear elastic-inelastic behavior of fcc polycrystals under different loading paths. Within the framework of small strain hypothesis, the elastic behavior, which is defined at granular level, is assumed to be isotropic, uniform, and compressible neglecting the grain rotation. The heterogeneous inelastic deformation is microscopically determined using the slip theory. In addition, the granular elastic behavior and its heterogeneous distribution from grain to grain within a polycrystal are taken into account. Comparisons between these two approaches show that the simplified one is more suitable to describe the overall responses of polycrystals notably under multiaxial loading paths. Nonlinear stress-strain behavior of polycrystals under complex loading, especially a cyclic one, is of particular interest in proposed modeling. The simplified model describes fairly well the yield surface evolution after a certain inelastic prestraining and the principle cyclic features such as Bauschinger effect, additional hardening, etc.

scholarly journals Black rubber and the non-linear elastic response of scale invariant solids

2020 ◽  
Vol 2020 (9) ◽  
Author(s):  
Matteo Baggioli ◽  
Víctor Cáncer Castillo ◽  
Oriol Pujolàs
Keyword(s):  
Strain Curve ◽  
Effective Field ◽  
Elastic Response ◽  
Elastic Behaviour ◽  
Scale Invariant ◽  
Stress Strain ◽  
Nonlinear Stress ◽  
Hyper Elastic ◽  
Simple Class ◽  
Nonlinear Elastic

Abstract We discuss the nonlinear elastic response in scale invariant solids. Following previous work, we split the analysis into two basic options: according to whether scale invariance (SI) is a manifest or a spontaneously broken symmetry. In the latter case, one can employ effective field theory methods, whereas in the former we use holographic methods. We focus on a simple class of holographic models that exhibit elastic behaviour, and obtain their nonlinear stress-strain curves as well as an estimate of the elasticity bounds — the maximum possible deformation in the elastic (reversible) regime. The bounds differ substantially in the manifest or spontaneously broken SI cases, even when the same stress- strain curve is assumed in both cases. Additionally, the hyper-elastic subset of models (that allow for large deformations) is found to have stress-strain curves akin to natural rubber. The holographic instances in this category, which we dub black rubber, display richer stress- strain curves — with two different power-law regimes at different magnitudes of the strain.

scholarly journals A set of measures for the systematic classification of the nonlinear elastic behavior of disparate rocks

2015 ◽  
Vol 120 (3) ◽  
pp. 1587-1604 ◽  
Author(s):  
Jacques Rivière ◽  
Parisa Shokouhi ◽  
Robert A. Guyer ◽  
Paul A. Johnson
Keyword(s):  
Elastic Behavior ◽  
Systematic Classification ◽  
Nonlinear Elastic
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