No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
On the Mechanical Response of Chopped Glass/Urethane Resin Composite: Data and Model
Abstract
This report presents data on the creep response of a polymeric composite that is a candidate material for automotive applications. The above data were used to establish the basis for the mechanical characterization of the material's response over a wide range of stresses and temperatures, as well as under cyclic loading and due to exposure to distilled water. A constitutive model based upon fundamental principles of irreversible thermodynamics and continuum mechanics was employed to encompass the above mentioned database and to predict the response under more complex inputs. These latter tests verified the validity of the model.
... 2D models are the most computationally inexpensive option, using 1D linear beam elements to represent fibre bundles randomly distributed in 2D space. 7,[22][23][24][25][26] However, this approach overlooks fibre crimping and allows bundle-bundle penetration, as all bundles are deposited on the same plane, reducing accuracy. 2D models also tend to be over-stiff, as intersecting bundles are rigidly bonded at the intersection point, 25 which increases as the RVE thickness increases. ...
... This is an important failure mode captured by the current model, which is overlooked when representing the bundles as 1D beam elements. 7,[22][23][24][25][26] Tensile stress/strain curves from the FEA simulations are compared against experimental data 2 in Figure 12 for two fibre volume fractions. The curves closely match in terms of initial stiffness, onset of non-linearity, ultimate strength and ultimate strain. ...
A geometrical modelling scheme is presented to produce representative architectures for discontinuous fibre composites, enabling downstream modelling of mechanical properties. The model generates realistic random fibre architectures containing high filament count bundles (>3k) and high (∼50%) fibre volume fractions. Fibre bundles are modelled as thin shells using a multidimensional modelling strategy, in which fibre bundles are distributed and compacted to simulate pressure being applied from a matched mould tool. Finite element simulations are performed to benchmark the in-plane mechanical properties obtained from the numerical model against experimental data, with a detailed study presented to evaluate the tensile properties at various fibre volume fractions and specimen thicknesses. Tensile modulus predictions are in close agreement (less than 5% error) with experimental data at volume fractions below 45%. Ultimate tensile strength predictions are within 4.2% of the experimental data at volume fractions between 40 and 55%. This is a significant improvement over existing 2D modelling approaches, as the current model offers increased levels of fidelity, capturing dominant failure mechanisms and the influence of out-of-plane fibres.
... The TTSP concept has been used extensively in creep predictions of thermoplastics, including HDPE. Elahi and Weitsman 6,7 applied it to chopped glass/urethane composites. ...
The viscoelastic characterization of agro-filler based plastic composites is of paramount importance for these materials' long-term commercial success. To predict creep, it is imperative to derive a relationship between deformation, time, temperature, and stress. This work is the harbinger in modelling of the nonlinear creep behaviour of two-phase materials, where an extended "theory of mixtures" has been used to describe all the creep related parameters. The stress- and temperature-related shift factors were estimated in terms of the activation energy of the constituents. The combined effect of temperature and stress on creep strain was accommodated in a single analytical function where the interaction was shown to be additive. The model was validated under rigorous conditions and is unique because it describes creep not through curve fittings, but in terms of the creep constants of the constituents. This constitutive model is not only a vanguard in the prediction of long term creep of many biocomposites but also in the modelling of creep under step loading of temperature.
... Both of these equations are valid when there is a linear temperature shift in creep strain due to a change in the temperature. Elahi and Weitsman [18,19] used the concept of TTSP in their chopped glass/urethane composites, which implies the applicability and universality of this concept to composites. Many authors used the concept of vertical shift in semicrystalline plastics in conjunction with horizontal shift (TTSP), but the real cause for the vertical shift is not very clear [22]. ...
The viscoelastic characterization of agro-filler based plastic composites is of paramount importance for the material’s long-term commercial success. To predict creep, it is important to derive a relationship between deformation, time, temperature, relative humidity, and stress. Since temperature shift can interfere with stress shift in creep, the predictive model should incorporate the relationship between these two shifts. Rice husk-HDPE beams were subjected to creep and recovery in the flexural mode and stress/time/temperature-related creep behavior of the same was studied. Temperature-related creep constants and shift factors were determined for the material and the constants were compared against theoretical two-phase constants. The combined effect of temperature and stress on creep strain was accommodated in a single analytical function where the interaction was shown to be additive. This means that the stress equivalency of temperature is possible. This constitutive equation can predict creep in the long run. Although stress dependency is nonlinear, temperature dependency is linear and thermorheologically complex. The ‘single-phase’ material behavior (creep constants) was also compared with a ‘two-phase’ predictive model, where the creep constants were estimated with the ‘theory of mixtures’.
... Both of these equations are valid when there is a linear temperature shift in creep strain due to a change in the temperature. Elahi and Weitsman [18,19] used the concept of TTSP in their chopped glass/urethane composites, which implies the applicability and universality of this concept to composites. Many authors used the concept of vertical shift in semicrystalline plastics in conjunction with horizontal shift (TTSP), but the real cause for the vertical shift is not very clear [22]. ...
The viscoelastic characterization of agro-filler based plastic composites is of paramount importance for the material’s long-term commercial success. To predict creep, it is important to derive a relationship between deformation, time, temperature, relative humidity, and stress. Since temperature shift can interfere with stress shift in creep, the predictive model should incorporate the relationship between these two shifts. Rice husk-HDPE beams were subjected to creep and recovery in the flexural mode and stress/time/temperature-related creep behavior of the same was studied. Temperature-related creep constants and shift factors were determined for the material and the constants were compared against theoretical two-phase constants. The combined effect of temperature and stress on creep strain was accommodated in a single analytical function where the interaction was shown to be additive. This means that the stress equivalency of temperature is possible. This constitutive equation can predict creep in the long run. Although stress dependency is nonlinear, temperature dependency is linear and thermorheologically complex. The ‘single-phase’ material behavior (creep constants) was also compared with a ‘two-phase’ predictive model, where the creep constants were estimated with the ‘theory of mixtures’.
Current timber waterfront structures require the use of treated lumber to reduce environmental damage. Wood–plastic composites (WPCs) have been proposed as an alternative to treated timber due to their potential for reduced water absorption and degradation without chemical treatment. Even though WPCs are primarily made of wood (58% wood flour in the current case) their mechanical response to applied loads is quite different. The current study attempts to describe the time and temperature dependence of a commercial WPC formulation. Characterization of the formulation was undertaken by means of a series of creep and recovery tests. A Prony Series was used to describe the material’s time dependent compliance, where time was shifted with stress and temperature to describe the observed nonlinear response and temperature dependence. Damage effects were successfully correlated isothermally using an effective stress. The model was evaluated by comparing the behavior predicted by the model with experimental results in 3-point bending and fatigue.
This article concerns the mechanical response of random glass fiber strand swirl-mat/urethane matrix composite under static and cyclic loads as well as under elevated temperatures. The article presents an extensive amount of experimental data as well as predictions based upon a coupled damage/viscoelastic constitutive formulation generated specifically to model the behavior of the material at hand. Damage evolution relations are derived from an empirical relationship. This work extends previously published results.
The mechanical response of PMR-15 neat resin was investigated at 288?C. Monotonic loading/unloading tests performed at several constant stress rates revealed considerable rate dependence, especially on the unloading path. Effect of prior stress rate on creep behavior was evaluated in creep tests preceded by uninterrupted loading to a target stress. Creep response was dependent on the prior stress rate. Effect of loading history was studied in stepwise creep tests, where specimens were subjected to a constant stress rate loading followed by unloading to zero stress with intermittent creep periods during both loading and unloading. Comparison of creep strains accumulated during a stepwise creep test to those accumulated during creep preceded by uninterrupted loading indicate that the prior stress history affects the creep behavior. A nonlinear viscoelastic model (Schapery?s formulation) was characterized using creep and recovery tests. The model was verified by comparing the predictions with experimental results obtained in monotonic loading/unloading, single-step, and multi-step creep tests. The model qualitatively predicted creep response to single- and multi-step creep tests, including negative creep and creep rate reversal during unloading. However, predictions were not quantitatively accurate. The model was unable to accurately predict the recovery behavior and could not account for rate effects.
The inelastic deformation behavior of BMI-5250-4 neat resin, a high-temperature polymer, was investigated at 191°C. The effects of loading rate on monotonic stress–strain behavior as well as the effect of prior stress rate on creep behavior were explored. Positive nonlinear rate sensitivity was observed in monotonic loading. Creep response was found to be significantly influenced by prior stress rate. Effect of loading history on creep was studied in stepwise creep tests, where specimens were subjected to a constant stress rate loading followed by unloading to zero stress with intermittent creep periods during both loading and unloading. The strain-time behavior was strongly influenced by prior deformation history. Negative creep was observed on the unloading path. In addition, the behavior of the material was characterized in terms of a nonlinear viscoelastic model by means of creep and recovery tests at 191°C. The model was employed to predict the response of the material under monotonic loading/unloading and multi-step load histories. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
This article presents data on the creep response of a polymericcomposite that is a candidate material for automotive applications. Theabove data established the basis for the mechanical characterization ofmaterial''s response over a wide range of stresses and temperatures, aswell as under cyclic tensile loading. A constitutive model based uponfundamental principles of irreversible thermodynamics and continuummechanics was employed to encompass the abovementioned database and topredict the response under more complex inputs. These latter testsverified the validity of the model.
This article concerns certain aspects of the time-dependent response ofcross-ply polymeric composites consisting of stitched graphite fiberstrands embedded in urethane resin. Experimental data were collected atseveral levels of stress and temperature, as well as at various loadorientations. The time-dependent strains were shown to consist of thesum of a fully recoverable viscoelastic component and a permanentportion, which could be expressed empirically. The utility andshortcomings of the power-law creep form are being examined, suggestingthat its validity for making long term predictions may require that`short time' data must be collected over durations that exceed a certaintime-span.
The article presents several results that demonstrate thepredictive capabilities of some of the formulations employed therein.
Thesis (M.S.)--Washington State University, 2001. Includes bibliographical references.
ResearchGate has not been able to resolve any references for this publication.