Viscoelastic Response and Adhesion Properties of Highly Filled Elastomers

1987 ◽  
Vol 60 (2) ◽  
pp. 227-244 ◽  
Author(s):  
R. G. Stacer ◽  
D. M. Husband ◽  
H. L. Stacer
Keyword(s):  
Fracture Energy ◽  
Contact Time ◽  
Loss Modulus ◽  
Viscoelastic Behavior ◽  
Small Deformation ◽  
Viscoelastic Response ◽  
Adhesion Properties ◽  
Adhesive Fracture ◽  
Filled Elastomers ◽  
Nonlinear Viscoelastic

Abstract The viscoelastic response of four highly-filled elastomers has been investigated. Small deformation dynamic testing of these materials reveals thay they are nonlinear viscoelastic, as well as thermorheologically complex. Nonlinear viscoelastic behavior was observed as a pronounced strain dependence in the range of 0.1 to 10%. The degree of this nonlinear response was quantified through a constitutive equation containing a single nonlinear factor; resultant nonlinear factors for the various materials were compared and evaluated. Thermorheologically complex behavior was displayed by slightly different shift coefficients to superpose G'′ and G″ data. An approach for calculating material resilience from the viscoelastic data was also developed and a nomographic technique presented for its application. A composite adhesive joint, consisting of two layers of a filled NBR compound bonded together by a filled putty interlayer, was also studied. It was found that both the adhesive fracture energy and the effect of interlayer thickness could be related to the loss modulus of the putty interlayer. Finally, the effect of contact time on bond strength was evaluated and results presented as a master curve of adhesive fracture energy vs. temperature-reduced contact time.

Nonlinear Viscoelastic Behavior of Active Fiber Composites

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Vahid Tajeddini ◽  
Hassene Ben Atitallah ◽  
Anastasia Muliana ◽  
Zoubeida Ounaies
Keyword(s):  
Stress Relaxation ◽  
Creep Deformation ◽  
Fiber Composite ◽  
Viscoelastic Behavior ◽  
Longitudinal Axis ◽  
Viscoelastic Response ◽  
Active Fiber ◽  
Nonlinear Viscoelastic ◽  
Nonlinear Viscoelastic Behavior ◽  
Analytical Approaches

In the present study, viscoelastic response of an active fiber composite (AFC) is investigated by conducting stress relaxation and creep deformation tests, and the quasi-linear viscoelastic (QLV) constitutive model is used to describe the viscoelastic response of the AFC. The AFC under study consists of unidirectional long piezoelectric ceramic fibers embedded in an epoxy polymer, encapsulated between two Kapton layers with interdigitated surface electrodes. The relaxation and creep experiments are performed by loading the AFC samples along the longitudinal axis of the fibers, under several strain and stress levels at three temperatures, namely 25 °C, 50 °C, and 75 °C. The experimental results reveal the nonlinear viscoelastic behavior of the composite. Next, simulation and prediction of the viscoelastic response, including stress relaxation and creep deformation of the material, are done by using semi-analytical QLV model in which a relaxation time-dependent function is used, which also depends on strain and temperature. The results from the model are compared with those from the experiments. In general, the experimental and simulation results are in good agreement, except in the case of some of the creep responses, where considerable discrepancies are seen between the experimental and analytical approaches. Possible reasons for these differences are discussed in details.

Peel Strength of Composite Layered Joints

1988 ◽  
Vol 61 (5) ◽  
pp. 794-811 ◽  
Author(s):  
H. L. Schreuder-Stacer
Keyword(s):  
Fracture Energy ◽  
Master Curve ◽  
Viscoelastic Response ◽  
Adhesive Failure ◽  
Master Curves ◽  
Universal Form ◽  
Adhesive Fracture ◽  
Wlf Equation ◽  
Failure Site ◽  
Low Rate

Abstract 1. Master curves of R/A/R (rubber/adhesive/rubber) type adhesion tests were generated by laterally shifting the rate curves of peel response with empirically determined shift factors. The universal form of the WLF Equation (3) did not shift the data into continuous master curves, due to the individual contributions of each deforming layer. 2. For the weakly-bonded A/EPM system, rate curves were shifted into good agreement using the universal form of the WLF relation and the Tg of EPM. However, in the case of EPM/A, shift factors calculated by the WLF Equation (3) did not create a smooth master curve. Lateral shifting produced a master curve of EPM/A peel response and resulted in experimentally determined shift factors which fell between the shift factors of the EPM and the adhesive. Apparently, the EPM substrate of low Tg completely dominated the viscoelastic response of the A/EPM joint and even exerted some influence over the debonding process for the EPM/A joint, where the detaching layer was comprised only of adhesive. 3. In the case of strongly bonded chloroprene systems, CR/A/CR data were shifted laterally, but the CR/A and A/CR data shifted well with log aT values calculated from the WLF equation. Adhesive and CR Tg's were within ten degrees, and the rubber layer therefore appeared to contribute little to the overall viscoelastic response of CR/A/CR and CR/A. 4. Detachment of EPM systems was entirely interfacial, except in regions of rate where the adhesive was forced to fail in an unfavorable mode (the low-rate EPM/A experiment and the high-rate A/EPM experiment). A distinct transition of interfacial failure was observed near the glass-transition temperature of the adhesive. As the adhesive failure site changed from substrate to backing, even at the same rate and temperature, a three-fold drop in adhesive fracture energy occurred. 5. CR systems debonded through cohesive rupture of the adhesive layer at low rates. Clean interfacial failure occurred at intermediate to high peel rates. A failure site transition occurred in the same rate and temperature region as the weakly-bonded transition. This failure site change was again associated with a three-fold drop in adhesive-fracture energy. However, the actual peel force difference resulting from this transition in CR/A/CR was on the order of 1000 N/m, while the weakly bonded EPM/A/EPM system experienced a drop of approximately 100 N/m. This disparity in the two transitions suggests that the driving mechanism for the substrate-to-backing failure change is not caused simply by added adhesive bending forces in the low-rate failure mode. 6. Relative contributions of each deforming material to the total peel response for an R/A/R system cannot be determined by examining the shift factor dependence upon temperature. However, R/A and A/R models of the R/A/R detachment modes illustrate the contributions of each layer: as the adhesive debonds from the substrate, both adhesive and rubber contribute to the viscoelastic response of peel, except in the case where both layers exhibit similar Tg's; during adhesive failure from the backing, only the rubber backing contributes to the peel response.

A Straightforward Procedure to Characterize Nonlinear Viscoelastic Response of Asphalt Concrete at High Temperatures

2018 ◽  
Vol 2672 (28) ◽  
pp. 481-492 ◽  
Author(s):  
Mohammad Bazzaz ◽  
Masoud K. Darabi ◽  
Dallas N. Little ◽  
Navneet Garg
Keyword(s):  
Asphalt Concrete ◽  
Viscoelastic Model ◽  
Viscoelastic Behavior ◽  
Deviatoric Stress ◽  
Creep Recovery ◽  
Viscoelastic Response ◽  
Nonlinear Viscoelastic ◽  
Wide Range ◽  
Stress Levels ◽  
Concrete Materials

This paper proposes a straightforward procedure to characterize the nonlinear viscoelastic response of asphalt concrete materials. Furthermore, a model is proposed to estimate the nonlinear viscoelastic parameters as a function of the triaxiality ratio, which accounts for both confinement and deviatoric stress levels. The simplified procedure allows for easy characterization of linear viscoelastic (LVE) and nonlinear viscoelastic (NVE) responses. First, Schapery’s nonlinear viscoelastic model is used to represent the viscoelastic behavior. Dynamic modulus tests are performed to calibrate LVE properties. Repeated creep-recovery tests at variable deviatoric stress levels (RCRT-VS) were designed and conducted to calibrate the nonlinear viscoelastic properties of four types of mixtures used in the Federal Aviation Administration’s National Airport Pavement and Materials Research Center test sections. The RCRT-VS were conducted at 55°C, 140 kPa initial confinement pressure, and wide range of deviatoric stress levels; mimicking the stress levels induced in a pavement structure under traffic. Once calibrated, the model was validated by comparing the model predictions and experimental measurements at different deviatoric stress levels. The predictions indicate that the proposed method is capable of characterizing NVE response of asphalt concrete materials.

Nonlinear Viscoelastic Finite Element Analysis of Adhesive Joints

1988 ◽  
Vol 16 (3) ◽  
pp. 146-170 ◽  
Author(s):  
S. Roy ◽  
J. N. Reddy
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Viscoelastic Behavior ◽  
Bonded Joints ◽  
Adhesively Bonded ◽  
Element Analysis ◽  
Adhesively Bonded Joints ◽  
Nonlinear Viscoelastic ◽  
Structural Failures ◽  
Updated Lagrangian

Abstract A good understanding of the process of adhesion from the mechanics viewpoint and the predictive capability for structural failures associated with adhesively bonded joints require a realistic modeling (both constitutive and kinematic) of the constituent materials. The present investigation deals with the development of an Updated Lagrangian formulation and the associated finite element analysis of adhesively bonded joints. The formulation accounts for the geometric nonlinearity of the adherends and the nonlinear viscoelastic behavior of the adhesive. Sample numerical problems are presented to show the stress and strain distributions in bonded joints.

Influence of κ-Carrageenan, Modified Starch and Inulin Addition on Rheological and Sensory Properties of Non-fat and Non-added Sugar Dairy Dessert

2020 ◽  
Vol 16 (4) ◽  
pp. 462-469
Author(s):  
Zhaleh Sheidaei ◽  
Bahareh Sarmadi ◽  
Seyede M. Hosseini ◽  
Fardin Javanmardi ◽  
Kianoush Khosravi-Darani ◽  
...  
Keyword(s):  
Storage Modulus ◽  
Loss Modulus ◽  
Viscoelastic Behavior ◽  
Textural Properties ◽  
Complex Viscosity ◽  
Sensory Properties ◽  
Modified Starch ◽  
Consumer Health ◽  
Added Sugar ◽  
Textural Parameters

<P>Background: The high amounts of fat, sugar and calorie existing in dairy desserts can lead to increase the risk of health problems. Therefore, the development of functional and dietary forms of these products can help the consumer health. </P><P> Objective: This study aims to investigate the effects of &#954;-carrageenan, modified starch and inulin addition on rheological and sensory properties of non-fat and non-added sugar dairy dessert. </P><P> Methods: In order to determine the viscoelastic behavior of samples, oscillatory test was carried out and the values of storage modulus (G′), loss modulus (G″), loss angle tangent (tan &#948;) and complex viscosity (&#951;*) were measured. TPA test was used for analysis of the desserts’ texture and textural parameters of samples containing different concentrations of carrageenan, starch and inulin were calculated. </P><P> Results: All treatments showed a viscoelastic gel structure with the storage modulus higher than the loss modulus values. Increasing amounts of &#954;-carrageenan and modified starch caused an increase in G′ and G″ as well as &#951;* and a decrease in tan &#948;. Also, firmness and cohesiveness were enhanced. The trained panelists gave the highest score to the treatment with 0.1% &#954;-carrageenan, 2.5% starch and 5.5% inulin (sucralose as constant = 0.25%) and this sample was the best treatment with desirable attributes for the production of non-fat and non-added sugar dairy dessert. </P><P> Conclusion: It can be concluded that the concentration of &#954;-carrageenan and starch strongly influenced the rheological and textural properties of dairy desserts, whereas the inulin content had little effect on these attributes.</P>

Identification of Nonlinear Viscoelastic Models of Flexible Polyurethane Foam From Uniaxial Compression Data

2016 ◽  
Vol 138 (2) ◽  
Author(s):  
Yousof Azizi ◽  
Patricia Davies ◽  
Anil K. Bajaj
Keyword(s):  
Uniaxial Compression ◽  
Viscoelastic Model ◽  
Viscoelastic Behavior ◽  
Model Parameters ◽  
Viscoelastic Models ◽  
Nonlinear Viscoelastic ◽  
Compression Data ◽  
Computationally Intensive ◽  
Nonlinear Viscoelastic Model ◽  
Flexible Polyurethane

Flexible polyethylene foam is used in many engineering applications. It exhibits nonlinear and viscoelastic behavior which makes it difficult to model. To date, several models have been developed to characterize the complex behavior of foams. These attempts include the computationally intensive microstructural models to continuum models that capture the macroscale behavior of the foam materials. In this research, a nonlinear viscoelastic model, which is an extension to previously developed models, is proposed and its ability to capture foam response in uniaxial compression is investigated. It is hypothesized that total stress can be decomposed into the sum of a nonlinear elastic component, modeled by a higher-order polynomial, and a nonlinear hereditary type viscoelastic component. System identification procedures were developed to estimate the model parameters using uniaxial cyclic compression data from experiments conducted at six different rates. The estimated model parameters for individual tests were used to develop a model with parameters that are a function of strain rates. The parameter estimation technique was modified to also develop a comprehensive model which captures the uniaxial behavior of all six tests. The performance of this model was compared to that of other nonlinear viscoelastic models.

On the Nonlinear Viscoelastic Behaviour of the PVC-Coated Fabric

2010 ◽  
Vol 160-162 ◽  
pp. 1476-1481 ◽  
Author(s):  
Wu Lian Zhang ◽  
Xin Ding ◽  
Xu Dong Yang
Keyword(s):  
Viscoelastic Model ◽  
Constitutive Relationship ◽  
Viscoelastic Behaviour ◽  
Viscoelastic Response ◽  
Nonlinear Parameters ◽  
Creep And Recovery ◽  
Nonlinear Viscoelastic ◽  
Coated Fabric ◽  
Nonlinear Viscoelastic Model

The nonlinear viscoelastic response of a PVC-Coated Fabric has been studied. For the needs of the present study, creep and recovery tests in tension of both the warp and the weft directions at the different stress levels were executed while measurements were made of the creep and recovery strain response of the system. For the description of the viscoelastic behaviour of the material, Schapery’s nonlinear viscoelastic model was used. For the description of the nonlinear viscoelastic response and the determination of the nonlinear parameters, a method by using a combination of analytical formulations and numerical procedures based on a modified version of Schapery’s constitutive relationship where an instantaneous plastic and a transient plastic terms were added, has been developed. The method has been successfully applied to the current tests.

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