An empirical approach for the quantification of uniaxial compressive stress-strain of partially saturated granular media under high strain rates

Epoxy resin-based composite panels used for armors may be subjected to a wide range of operating temperatures (-55°C to 76°C) and high strain rates on the order of 103-104 s-1. Over the life cycle, various environmental factors also affect the resin properties and hence influence the performance of the composites. Therefore, it is critical to determine the stress-strain behavior of the epoxy resin over a wide range of strain rates and temperatures for accurate multi-scale modeling of composites and to investigate the influence of environmental aging on the resin properties. Additionally, the characterization of key mechanical properties such as yield stress, modulus, and energy absorption (i.e. area under the stress-strain curve) at varying temperatures and moisture can provide critical data to calculate the material operating limits. In this study, we characterize mechanical properties of neat epoxy resin, SC-15 (currently used in structural armor) and RDL-RDC using uniaxial compression testing. RDL-RDC, developed by Huntsman Corporation, has a glass transition temperature of ~ 120°C, compared to ~ 85°C of SC-15. A split Hopkinson pressure bar is used for high strain rate testing. Quasistatic testing is conducted using a screw-driven testing machine (Instron 4484) at 10-3 s-1 and 10-1 s-1 strain rates and varying temperatures. The yield stress is fit to a modified Eyring model over the varying strain rates at room temperature. For rapid investigation of resistance to environmental aging, accelerated aging tests are conducted by immersing the specimens in 100°C water for 48 hours. Specimens are conditioned in an environmental chamber at 76 °C and 88% RH until they reach equilibrium. Tests are then conducted at five different temperatures from 0°C to 95°C, and key mechanical properties are then plotted vs. temperature. The results presented are an important step towards developing a methodology to identify environmental operating conditions for composite ground vehicle applications.

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Determination of stress-strain characteristics at very high strain rates

Experimental Mechanics ◽

10.1007/bf02320419 ◽

1970 ◽

Vol 10 (9) ◽

pp. 370-376 ◽

Cited By ~ 108

Author(s):

C. K. H. Dharan ◽

F. E. Hauser

Keyword(s):

High Strain ◽

Strain Rates ◽

High Strain Rates ◽

Stress Strain ◽

Very High

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A Dynamic Mechanical Analysis of T2 Copper at High Strain Rates

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.812.38 ◽

2019 ◽

Vol 812 ◽

pp. 38-44

Author(s):

Shuai Chen ◽

Wen Bin Li ◽

Xiao Ming Wang ◽

Wen Jin Yao

Keyword(s):

Yield Strength ◽

Strain Rate ◽

High Strain ◽

Split Hopkinson Pressure Bar ◽

Pure Copper ◽

Dislocation Slip ◽

Strain Rates ◽

High Strain Rates ◽

Stress Strain ◽

Shpb Test

This work compares the pure copper (T2 copper)’s stress-strain relationship at different strain rates in the uni-axial tension test and Split Hopkinson Pressure Bar (SHPB) test. Small samples were utilized in the high strain rate SHPB test in which the accuracy was modified by numerical simulation. The experimental results showed that the T2 copper’s yield strength at high strain rates largely outweighed the quasi static yield strength. The flow stress in the stress-strain curves at different strain rates appeared to be divergent and increased with the increase in strain rates, showing great strain strengthening and strain rate hardening effects. Metallographic observation showed that the microstructure of T2 copper changed from equiaxed grains to twins and the interaction between the dislocation slip zone grain boundary and twins promoted the super plasticity distortion in T2 copper.

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Stress-Strain Behavior and Statistical Continuous Damage Model of Cement Mortar under High Strain Rates

Journal of Materials in Civil Engineering ◽

10.1061/(asce)mt.1943-5533.0000570 ◽

2013 ◽

Vol 25 (1) ◽

pp. 120-130 ◽

Cited By ~ 33

Author(s):

Jikai Zhou ◽

Xudong Chen

Keyword(s):

High Strain ◽

Cement Mortar ◽

Damage Model ◽

Strain Rates ◽

High Strain Rates ◽

Stress Strain ◽

Strain Behavior

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High Strain-Rate Compressive Behavior and Constitutive Modeling of Selected Polymers Using Modified Ramberg-Osgood Equation

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.566.80 ◽

2014 ◽

Vol 566 ◽

pp. 80-85

Author(s):

Kenji Nakai ◽

Takashi Yokoyama

Keyword(s):

High Strain Rate ◽

Strain Rate ◽

Compressive Stress ◽

Constitutive Modeling ◽

High Strain ◽

Strain Rates ◽

Stress Strain ◽

Strain Behavior ◽

Least Squares Fit ◽

Wide Range

The present paper is concerned with constitutive modeling of the compressive stress-strain behavior of selected polymers at strain rates from 10-3 to 103/s using a modified Ramberg-Osgood equation. High strain-rate compressive stress-strain curves up to strains of nearly 0.08 for four different commercially available extruded polymers were determined on the standard split Hopkinson pressure bar (SHPB). The low and intermediate strain-rate compressive stress-strain relations were measured in an Instron testing machine. Six parameters in the modified Ramberg-Osgood equation were determined by fitting to the experimental stress-strain data using a least-squares fit. It was shown that the monotonic compressive stress-strain behavior over a wide range of strain rates can successfully be described by the modified Ramberg-Osgood constitutive model. The limitations of the model were discussed.

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Characterization of a Ferritic Stainless Sheet Steel in Simple Shear and Uniaxial Tension at Different Strain Rates

Volume 8: Mechanics of Solids, Structures and Fluids; Vibration, Acoustics and Wave Propagation ◽

10.1115/imece2011-63141 ◽

2011 ◽

Cited By ~ 3

Author(s):

Matti Isakov ◽

Jeremy Seidt ◽

Kauko O¨stman ◽

Amos Gilat ◽

Veli-Tapani Kuokkala

Keyword(s):

Uniaxial Tension ◽

Simple Shear ◽

High Strain ◽

Image Correlation ◽

Materials Testing ◽

Strain Rates ◽

Test Results ◽

High Strain Rates ◽

Stress Strain

In this study the mechanical properties of ferritic stainless steel EN 1.4521 (AISI 444) were characterized in uniaxial tension and simple shear. The specimen geometries were designed so that tests could be carried out both with a conventional uniaxial materials testing machine and at high strain rates with the Tensile Hopkinson Split Bar method. During the tests, specimen surface deformation was measured using a three dimensional digital image correlation technique based on a two-camera stereovision setup. This technique allowed direct measurement of the specimen gauge section deformation during the test. Test results indicate that the selected approach is suitable for large strain plastic deformation characterization of ductile metals. The stress-strain data obtained from the simple shear tests shows a correlation with the tensile test results according to the von Mises effective stress-strain criterion. Since necking is absent in shear, test data can be obtained at considerably higher plastic strains than in tension. However, the final fracture occurs under a complex loading mode due to the distortion of the specimen geometry and multiaxial loading introduced by the simple shear arrangement. Test results also show that reliable material data can be obtained at high strain rates.

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