scholarly journals Strain rate-dependent large deformation inelastic behavior of an epoxy resin

2019 ◽  
Vol 54 (1) ◽  
pp. 71-87 ◽  
Author(s):  
Sandeep Tamrakar ◽  
Raja Ganesh ◽  
Subramani Sockalingam ◽  
Bazle Z (Gama) Haque ◽  
John W Gillespie
Keyword(s):  
Strain Rate ◽  
Epoxy Resin ◽  
Yield Stress ◽  
Split Hopkinson Pressure Bar ◽  
Testing Machine ◽  
Internal Heat ◽  
Characteristic Relaxation Time ◽  
Strain Rates ◽  
Temperature Dependent ◽  
Wide Range

The objective of this paper is to model high strain rate and temperature-dependent response of an epoxy resin (DER 353 and bis( p-aminocyclohexyl) methane (PACM-20)) undergoing large inelastic strains under uniaxial compression. The model is decomposed into two regimes defined by the rate and temperature-dependent yield stress. Prior to yield, the model accounts for viscoelastic behavior. Post yield inelastic response incorporates the effects of strain rate and temperature including thermal softening caused by internal heat generation. The yield stress is dependent on both temperature and strain rate and is described by the Ree–Erying equation. Key experiments over the strain rate range of 0.001–12,000/s are conducted using an Instron testing machine and a split Hopkinson pressure bar. The effects of temperature (25–120 ℃) on yield stress are studied at low strain rates (0.001–0.1/s). Stress-relaxation tests are also carried out under various applied strain rates and temperatures to obtain characteristic relaxation time and equilibrium stress. The model is in excellent agreement over a wide range of strain rates and temperatures including temperature in the range of the glass transition. Case studies for a wide range of monotonic and varying strain rates and large strains are included to illustrate the capabilities of the model.

STRAIN RATE EFFECTS ON COMPRESSIVE PROPERTIES OF A BIODEGRADABLE PLASTIC

2008 ◽  
Vol 22 (09n11) ◽  
pp. 1177-1182 ◽  
Author(s):  
MASAHIRO NISHIDA ◽  
KOICHI TANAKA ◽  
NORIOMI ITO
Keyword(s):  
Strain Rate ◽  
Split Hopkinson Pressure Bar ◽  
Testing Machine ◽  
Biodegradable Plastic ◽  
Strain Rates ◽  
Hopkinson Pressure Bar ◽  
Compressive Properties ◽  
Strain Rate Effects ◽  
Wide Range ◽  
Pressure Bar

The compressive properties of a biodegradable plastic were measured over a wide range of strain rates from 10−5 to 104 s −1, using a universal testing machine and a split Hopkinson pressure bar method. The yield stress of the biodegradable plastic increased with increasing strain rate and decreased with temperature and water absorption. Empirical equations for the yield stresses were derived for the strain rates from 10−5 to 103 s −1 and from 103 to 104 s −1, respectively.

INVESTIGATING THE INFLUENCE OF ENVIRONMENTAL CONDITIONING ON EPOXY RESINS AT QUASISTATIC AND HIGH STRAIN RATES FOR MATERIAL OPERATING LIMIT

2021 ◽  
Author(s):  
SAGAR M. DOSHI, SAGAR M. DOSHI, ◽  
NITHINKUMAR MANOHARAN ◽  
BAZLE Z. (GAMA) HAQUE, ◽  
JOSEPH DEITZEL ◽  
JOHN W. GILLESPIE, JR.
Keyword(s):  
Mechanical Properties ◽  
Epoxy Resin ◽  
Yield Stress ◽  
High Strain ◽  
Operating Conditions ◽  
Strain Rates ◽  
High Strain Rates ◽  
Stress Strain ◽  
Wide Range ◽  
Environmental Aging

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.

scholarly journals Dynamic Mechanical Characteristics and Constitutive Modeling of Rail Steel over a Wide Range of Temperatures and Strain Rates

2019 ◽  
Vol 2019 ◽  
pp. 1-15
Author(s):  
Peijie Liu ◽  
Yanming Quan ◽  
Guo Ding
Keyword(s):  
Strain Rate ◽  
Mechanical Behavior ◽  
Split Hopkinson Pressure Bar ◽  
Rail Steel ◽  
Strain Rates ◽  
Dynamic Mechanical ◽  
Flow Response ◽  
Strain And Strain Rate ◽  
Average Absolute Relative Error ◽  
Wide Range

Rail steel plays an indispensable role in the safety and stability of the railway system. Therefore, a suitable constitutive model is quite significant to understand the mechanical behavior of this material. Here, the compressive mechanical behavior of heat-treated U71Mn rail steel over a wide range of strain rates (0.001 s−1–10000 s−1) and temperatures (20°C–800°C) was systematically investigated via uniaxial quasistatic and dynamic tests. The split Hopkinson pressure bar (SHPB) apparatus was utilized to perform dynamic mechanical tests. The effects of temperature, strain, and strain rate on the dynamic compressive characteristics of U71Mn were discussed, respectively. The results indicate that the flow response of U71Mn is both temperature-sensitive and strain rate-sensitive. However, the influence of temperature on the flow response is more remarkable than that of strain rate. On the basis of the experimental data, the original and modified Johnson-Cook (JC) models of the studied material were established, respectively. Using correlation coefficient and average absolute relative error parameters, it is revealed that better agreement between the experimental and predicted stress is reached by the modified JC model, which demonstrates that the modified one can characterize the mechanical behavior of the studied material preferably.

Strain-Rate Dependence of Compressive Yield Strength of Titanium Grade 4 with Coarse-Grained and Ultrafine-Grained Structures: Experimental Results and Theoretical Calculation

2018 ◽  
Vol 1145 ◽  
pp. 100-105
Author(s):  
Ivan V. Smirnov ◽  
Alexander Y. Konstantinov
Keyword(s):  
Yield Strength ◽  
Strain Rate ◽  
Yield Stress ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Compression ◽  
Pure Titanium ◽  
Coarse Grained ◽  
Strain Rates ◽  
Ultrafine Grained ◽  
Titanium Grade

The nanocrystalline (NC) and ultrafine-grained (UFG) structures of metallic materials can lead to their extraordinary high strength. However, most of the papers on this topic consider deformation parameters of NC and UFG materials only for the case of quasi-static tensile tests. Characteristics of dynamic strength and fracture of such materials remain unexplored. This paper presents a study of the mechanical behavior of pure titanium Grade 4 with a coarse-grained (CG) and UFG structure under uniaxial compression with different strain rates. The UFG structure was provided using the method of equal-channel angular pressing. The dynamic compression was carried out on a setup with the Split-Hopkinson pressure bar. It is found that in the observed range of strain rates 10–3-3×103 s–1, the yield stress of the CG titanium increases by 20%, and does not exceed the yield stress of the UFG titanium. However, the yield stress of the UFG titanium remains close to a quasi-static value. It is shown that these strain-rate dependencies of the yield strength can be predicted by the incubation time approach. The calculated curves show that at strain rates above 104 s–1 the yield stress of the CG titanium becomes higher than the yield strength of the UFG titanium.

Studies on the Dynamic Compressive Properties of Open-Celled Aluminum Alloy Foams

2006 ◽  
Vol 306-308 ◽  
pp. 905-910 ◽  
Author(s):  
Zhi Hua Wang ◽  
Hong Wei Ma ◽  
Long Mao Zhao ◽  
Gui Tong Yang
Keyword(s):  
Yield Strength ◽  
Strain Rate ◽  
Split Hopkinson Pressure Bar ◽  
Strain Rates ◽  
Hopkinson Pressure Bar ◽  
Aluminum Foams ◽  
Wide Range ◽  
Split Hopkinson ◽  
Pressure Bar ◽  
Dynamic Loading Conditions

The compressive deformation behavior of open-cell aluminum foams with different densities and morphologies was assessed under quasi-static and dynamic loading conditions. High strain rate experiments were conducted using a split Hopkinson pressure bar technique at strain rates ranging from 500 to 1 2000 − s . The experimental results shown that the compressive stress-strain curves of aluminum foams also have the “ three regions” character appeared in general foam materials, namely elastic region, collapse region and densification regions. It is found that density is the primary variable characterizing the modulus and yield strength of foams and the cell appears to have a negligible effect on the strength of foams. It also is found that yield strength and energy absorption is almost insensitive to strain rate and deformation is spatially uniform for the open-celled aluminum foams, over a wide range of strain rates.

A new cooperative model for the prediction of compressive yield stress of polycarbonate nanocomposites considering strain rate, temperature, and agglomeration

2019 ◽  
Vol 53 (25) ◽  
pp. 3567-3575 ◽  
Author(s):  
Gholam H Majzoobi ◽  
H Malek-Mohammadi ◽  
J Payandehpeyman
Keyword(s):  
Strain Rate ◽  
Yield Stress ◽  
Split Hopkinson Pressure Bar ◽  
Filler Content ◽  
Direct Method ◽  
Current Model ◽  
Testing Machine ◽  
Injection Molding Process ◽  
Cooperative Model ◽  
Compressive Yield Stress

In this study, a new model was proposed to predict the compressive yield stress of polycarbonate nanocomposite reinforced by nanoparticles at different strain rates, temperatures, and filler contents. In addition, the proposed model makes it possible to calculate the critical filler content for which the agglomeration phenomena occur. For the validation of the model, a series of experiments were performed. At first, the modified nanoclay Cloisite 20A masterbatch was produced by a direct method using extrusion machine, and the graphene oxide masterbatch was produced by the solvent method. Then the composite samples were produced using the injection-molding process, and the compressive tests were performed at three temperatures under quasi-static and dynamic loadings using a universal testing machine and split Hopkinson pressure bar. The coefficients of the proposed modified cooperative model were calculated using the experimental results. The observations showed that the presented model could correlate the compressive yield stress of polycarbonate nanocomposites to strain rate, temperature, and filler content with sufficient accuracy. Furthermore, the agglomeration of nanoparticles in polymer matrix which is a critical issue in fabrication of the advanced nanocomposites is predictable by using the current model.

scholarly journals The Out-of-Plane Compression Response of Woven Thermoplastic Composites: Effects of Strain Rates and Temperature

Polymers ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 264
Author(s):  
Shiyu Wang ◽  
Lihua Wen ◽  
Jinyou Xiao ◽  
Ming Lei ◽  
Xiao Hou ◽  
...  
Keyword(s):  
Strain Rate ◽  
Elevated Temperatures ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Properties ◽  
Dynamic Compression ◽  
Polyphenylene Sulfide ◽  
Thermoplastic Composites ◽  
Strain Rates ◽  
Wide Range ◽  
Out Of Plane

The dynamic mechanical response of high-performance thermoplastic composites over a wide range of strain rates is a challenging research topic for extreme environmental survivability in the field of aerospace engineering. This paper investigates the evolution of the dynamic properties of woven thermoplastic composites with strain rate and damage process at elevated temperatures. Out-of-plane dynamic-compression tests of glass-fiber (GF)- and carbon-fiber (CF)-reinforced polyphenylene sulfide (PPS) composites were performed using a split Hopkinson pressure bar (SHPB). Results showed that thermoplastic composites possess strain-rate strengthening effects and high-temperature weakening dependence. GF/PPS and CF/PPS composites had the same strain-rate sensitivity (SRS) below the threshold strain rate. The softening of the matrix at elevated temperatures decreased the modulus but had little effect on strength. Some empirical formulations, including strain-rate and temperature effects, are proposed for more accurately predicting the out-of-plane dynamic-compression behavior of thermoplastic composites. Lastly, the final failure of the specimens was examined by scanning electron microscopy (SEM) to explore potential failure mechanisms, such as fiber-bundle shear fracture at high strain rates and stretch break at elevated temperatures.

Impact Compressive Failure of a Unidirectional Carbon/Epoxy Laminated Composite in Three Principal Material Directions

2012 ◽  
Vol 706-709 ◽  
pp. 799-804 ◽  
Author(s):  
Takashi Yokoyama
Keyword(s):  
Strain Rate ◽  
Split Hopkinson Pressure Bar ◽  
Testing Machine ◽  
Laminated Composite ◽  
Strain Rate Effect ◽  
Rate Effect ◽  
Failure Behavior ◽  
Strain Rates ◽  
Compressive Failure ◽  
The Impact

The impact compressive failure behavior of a unidirectional T700/2521 carbon/epoxy laminated composite in three principal material directions or fiber (1-), in-plane transverse (2-) and through-thickness (3-) directions is investigated on the conventional split Hopkinson pressure bar (SHPB). Cubic and rectangular block specimens with identical square cross section are machined from an about 10 mm thick composite laminate. The uniaxial compressive stress-strain curves up to failure at quasi-static and intermediate strain rates are measured on an Instron testing machine. It is shown that the ultimate compressive strength and strain exhibit no strain-rate effect in the 1-direction, but a slight strain-rate effect in the 2-and 3-direction over a range of strain rates from10-3to 103/s.

scholarly journals Dynamic behaviour of Al-Mg aluminum alloy at a wide range of strain rates

2018 ◽  
Vol 183 ◽  
pp. 02028
Author(s):  
Tsuyoshi Kami ◽  
Hiroyuki Yamada ◽  
Nagahisa Ogasawara
Keyword(s):  
Strain Rate ◽  
Pure Aluminum ◽  
Testing Machine ◽  
Rate Dependence ◽  
Strain Rate Dependence ◽  
Mg Alloy ◽  
Strain Rates ◽  
Positive Strain ◽  
Wide Range ◽  
The Impact

The effect of strain rate on mechanical properties of Al-2.3wt.%Mg alloy (AA5021) and commercial pure aluminum (purity 99.7wt.%: A1070) was investigated at room temperature. The tensile tests were conducted at strain rates from 1.0×10−4 to 1.0×103 s−1. The universal testing machine was used for strain rate 1.0×10-4 to 1.0×10−1 s−1. For the strain rate 1.0×100 s-1, the servohydraulic testing machine, which was developed by our laboratory, was used. The impact strain rate 1.0×103 s−1 was obtained using the split Hopkinson pressure bar method. The pure aluminum showed positive strain rate dependence of material strength at the investigated strain rates. In contrast, the Al-2.3wt.%Mg alloy showed the negative strain rate dependence at strain rates from 1.0×10−4 to 1.0×100 s−1. However, Al-2.3wt.%Mg alloy showed the positive strain rate dependence at strain rates from 1.0×100 to 1.0×103 s−1. It was surmised that the effect of dislocation locking by the solute Mg atoms became negligible at strain rate of approximately 1.0×100 s−1. It was confirmed that material properties for the Al-Mg alloy at the strain rate of 1.0×100 s−1 were important, since the strain rate dependence changed negative to positive around this strain rate.

Perforation Test as an Accuracy Evaluation Tool for a Constitutive Model of Austenitic Steel

2013 ◽  
Vol 58 (4) ◽  
pp. 1105-1110 ◽  
Author(s):  
W. Moćko ◽  
Z.L. Kowalewski
Keyword(s):  
Constitutive Model ◽  
Austenitic Steel ◽  
Relative Error ◽  
Split Hopkinson Pressure Bar ◽  
Testing Machine ◽  
New Method ◽  
Accuracy Evaluation ◽  
Strain Rates ◽  
Striker Velocity ◽  
Wide Range

Abstract In this paper, a new method for assessing the accuracy of a constitutive model is proposed. The method uses perforation test done by drop weight tower. The assessment is carried out by comparison of striker velocity curve obtained using experiment and FEM simulation. In order to validate proposed method the various constitutive equations were applied i.e. Johnson-Cook, Zerilli-Armstrong and the extended Rusinek-Klepaczko to model mechanical behaviour of X4CrMnN16-12 austenitic steel. The steel was characterized at wide range of strain and strain rates using servo-hydraulic testing machine and split Hopkinson pressure bar. The relative error calculated as a difference between measured and constitutive model based stress-strain curve was applied as a reference data (classic approach). Subsequently, it was compared with relative error determined on the basis of experimental and FEM calculated striker velocity (new approach). A good correlation between classic and a new method was found. Moreover, a new method of error assessment enables to validate constitutive equation in a wide range of strain rates and temperatures on the basis of a single experiment.

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