Predicting the Creep Behavior of High Density Polyethylene Geogrid Using Stepped Isothermal Method

AbstractThermoplastic materials are increasingly used in demanding structural applications under, in some cases, long-term static loading over several decades. In this regard, the stepped isothermal method (SIM) with creep testing at stepwise increased temperature levels in combination with time-temperature superposition (TTSP) provides a very time efficient procedure for long-term creep characterization. In the present study, the creep behavior of an injection molded high-density polyethylene material (HDPE) was investigated by SIM in the thermally untreated state as well as after annealing.Due to experimental issues regarding the heating behavior of the specimens and non-linear viscoelastic behavior, particularly at elevated temperatures, bi-directional curve shifting was required in order to generate meaningful master curves for creep compliance. In a first step, an Arrhenius equation was used for the horizontal curve shifting, based on activation energies, determined in additional multi-frequency dynamic mechanical analysis (DMA). Continuous master curves were then obtained by empirical vertical shifting of the individual creep curve segments for the different temperature levels. In general, good agreement was observed between the resulting SIM master curves and the corresponding conventionally measured creep compliance curves at least for a time range up to 300 hours. Furthermore, significant differences in the creep tendency of the annealed material state compared to the thermally untreated condition revealed the distinct influence of the thermal history on the resulting creep behavior.

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Creep behavior and modeling of high-density polyethylene (HDPE)

Polymer Testing ◽

10.1016/j.polymertesting.2020.107031 ◽

2021 ◽

Vol 94 ◽

pp. 107031

Author(s):

Mohammad Amjadi ◽

Ali Fatemi

Keyword(s):

Creep Behavior ◽

High Density Polyethylene ◽

High Density

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Creep behavior of high density polyethylene under a constant true stress

Polymer Testing ◽

10.1016/j.polymertesting.2009.09.005 ◽

2010 ◽

Vol 29 (1) ◽

pp. 60-65 ◽

Cited By ~ 20

Author(s):

Koh-hei Nitta ◽

Hirohito Maeda

Keyword(s):

Creep Behavior ◽

High Density Polyethylene ◽

True Stress ◽

High Density

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Flexural Creep Behavior of High-Density Polyethylene Lumber and Wood Plastic Composite Lumber Made from Thermally Modified Wood

Polymers ◽

10.3390/polym12020262 ◽

2020 ◽

Vol 12 (2) ◽

pp. 262 ◽

Cited By ~ 2

Author(s):

Murtada Abass A. Alrubaie ◽

Roberto A. Lopez-Anido ◽

Douglas J. Gardner

Keyword(s):

Creep Behavior ◽

Creep Deformation ◽

High Density Polyethylene ◽

Creep Compliance ◽

High Density ◽

Wood Plastic Composite ◽

Creep Stress ◽

Plastic Composite ◽

Thermally Modified Wood ◽

Modified Wood

The use of wood plastic composite lumber as a structural member material in marine applications is challenging due to the tendency of wood plastic composites (WPCs) to creep and absorb water. A novel patent-pending WPC formulation that combines a thermally modified wood flour (as a cellulosic material) and a high strength styrenic copolymer (high impact polystyrene and styrene maleic anhydride) have been developed with advantageous viscoelastic properties (low initial creep compliance and creep rate) compared with the conventional WPCs. In this study, the creep behavior of the WPC and high-density polyethylene (HDPE) lumber in flexure was characterized and compared. Three sample groupings of WPC and HDPE lumber were subjected to three levels of creep stress; 7.5, 15, and 30% of the ultimate flexural strength (Fb) for a duration of 180 days. Because of the relatively low initial creep compliance of the WPC specimens (five times less) compared with the initial creep compliance of HDPE specimens, the creep deformation of HDPE specimens was six times higher than the creep deformation of WPC specimens at the 30% creep stress level. A Power Law model predicted that the strain (3%) to failure in the HDPE lumber would occur in 1.5 years at 30% Fb flexural stress while the predicted strain (1%) failure for the WPC lumber would occur in 150 years. The findings of this study suggest using the WPC lumber in structural application to replace the HDPE lumber in flexure attributable to the low time-dependent deformation when the applied stress value is withing the linear region of the stress-strain relationship.

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Investigation of Tensile Creep Behavior for High-Density Polyethylene (HDPE) via Experiments and Mathematical Model

Materials ◽

10.3390/ma14206188 ◽

2021 ◽

Vol 14 (20) ◽

pp. 6188

Author(s):

Qiang Mao ◽

Buyun Su ◽

Ruiqiang Ma ◽

Zhiqiang Li

Keyword(s):

Creep Behavior ◽

High Density Polyethylene ◽

Strain Curve ◽

Reference Value ◽

High Density ◽

Tensile Creep ◽

Uniaxial Tensile ◽

Form Model ◽

Short Time ◽

Parameter Values

Temperatures of −25 °C, +5 °C, and +35 °C were selected to study the creep behavior of high-density polyethylene (HDPE). The ultimate tensile strength of HDPE materials was obtained through uniaxial tensile experiments and the time–strain curves were obtained through creep experiments. When the loaded stress levels were lower than 60% of the ultimate strength, the specimens could maintain a longer time in the stable creep stage and were not prone to necking. In contrast, the specimens necked in a short time. Then, the time hardening form model was applied to simulate the time–strain curve and the parameter values were solved. The parameter values changed exponentially with the stresses, thereby expanding and transforming the time hardening model. The expanded model can easily and accurately predict creep behaviors of the initial and stable creep stages as well as the long-term deformations of HDPE materials. This study would provide a theoretical basis and reference value for engineering applications of HDPE.

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