A viscoelastoplastic constitutive model of semi-crystalline polymers under dynamic compressive loading: Application to PE and PA66

Xiang

Polymers for Advanced Techs

et al. 2022

This paper investigated the effects of printing directions (path of nozzle movement) and strain rates on the performances of short carbon and glass fibers filled polyamide-based composites prepared by fused deposition modeling (FDM). Cylindrical specimens printed in three different printing directions were compressed at a wide range of strain rate. The results showed that, for short fiber reinforced polyamide, the compressive properties of cylindrical specimens were affected by printing directions closely associated with the fiber orientation. The highest elastic modulus and yield strength of short fiber reinforced specimens were obtained when the printing direction was parallel to the applied loading direction, because the orientation of short fibers was preferred to the printing direction. However, at large deformation, the orientation of fibers in specimens changed, accompanied by a decrease in stress. With increasing strain rates, the short fiber reinforced polyamide with different fiber orientations showed different failure modes. However, the compressive behaviors of pure polyamide were similar, although they were printed in different printing directions.

Section: Mechanical Properties Of Printed Compositessupporting

confidence: 85%

Effects of printing direction on quasi‐static and dynamic compressive behavior of 3D printed short fiber reinforced polyamide‐based composites

Xiang

Polymers for Advanced Techs

et al. 2022

“…In previous study [ 14 ], a one-dimensional constitutive model was proposed to characterize dynamic properties of semi-crystalline polymers. Figure 1 displays a structure of the model, which consists of a viscoelastic and a viscoplastic phase.…”

Section: Description Of the Constitutive Modelmentioning

confidence: 99%

“…Previous numerous studies provide sufficient help in understanding the mechanical properties of semi-crystalline polymers. A one-dimensional constitutive model has been proposed to predict the mechanical behaviour of semi-crystalline polymers by our team [ 14 ]. The purpose of this paper is to convert the one-dimensional model into three-dimensional constitutive model, to demonstrate the accuracy of the three-dimensional model and to realize application of the constitutive model in LS-DYNA software.…”

Section: Introductionmentioning

confidence: 99%

Semi-Crystalline Polymers Applied to Taylor Impact Test: Constitutive, Experimental and FEM Analysis

Cheng

et al. 2020

Polymers

Self Cite

Based on mechanical properties of Polyamide 66 (PA66) under complex loading conditions, a Drucker–Prager yield criterion was employed to characterize its yield behavior. Then, a one-dimensional model, which contains a viscoelastic regime and a viscoplastic regime, was introduced and converted into a three-dimensional constitutive model. The three-dimensional model was implemented into a LS-DYNA software, which was used to predict the dynamic response of PA66 under Taylor impact conditions, whose corresponding tests were conducted by gas gun and recorded by high-speed camera. By contrasting the simulation results and these of the corresponding tests, the deformed shapes including the residual length, the maximum diameter and the shape of the mushroom head of the PA66 bars were found to be similar to these obtained from the tests, which verified the accuracy of the three-dimensional constitutive model, and proved that the model was able to be applied to high-rate impact loading conditions.

“…PE100 pipes have been widely used in water and gas supply networks [ 1 , 2 , 3 ]. It is well recognized that HDPE exhibits viscoelastic–plastic behavior at room temperature, and its stress–strain response is strongly affected by the loading rate [ 4 , 5 , 6 ]. The yield stress and strain hardening modulus are reported to increase linearly with increasing logarithmic value of the strain rate [ 7 ].…”

Section: Introductionmentioning

confidence: 99%

“…In engineering practice, the tensile properties of the pipe material are measured in accordance with the ISO 527 standard at various test speeds ranging from 0.125 mm/min to 500 mm/min, depending on the test specimen size and test material type, and used to check the failure of the pipe accordingly. Numerous studies have shown that the strength of polymers, including HDPE, decreases with decreasing strain rate and with increasing temperature [ 4 , 11 , 12 ]; for instance, El-Bagory et al [ 13 ] demonstrated that the room-temperature yield stress of an HDPE standard specimen with a gage length of 50 mm is 27.24 MPa when the loading speed is set to be 500 mm/min, while it decreases to 19.58 MPa under a loading speed of 5 mm/min. Thus, it is not conservative to directly use the strength tested under the laboratory loading rate, which is much higher than the creep rate in the real pipe case under a constant internal pressure, to evaluate the long-term strength of the pipe material.…”

Section: Introductionmentioning

confidence: 99%

Strain Rate-Dependent Hyperbolic Constitutive Model for Tensile Behavior of PE100 Pipe Material

Luo

et al. 2022

Polymers

It is not conservative to directly use the strength tested under the laboratory loading rates to evaluate the long-term creep strength of polymers. A suitable strain rate-dependent constitutive model is crucial for accurately predicting the long-term strength and mechanical behavior of polymer pressure pipes. In this study, the Kondner hyperbolic constitutive model is considered the base model in deriving the rate-dependent constitutive model for PE100 pipe material, and the yield stress and initial tangent modulus are the two rate-dependent parameters of the model. Uniaxial tension tests are carried out under five specified strain rates ranging from 10−5 s−1 to 5 × 10−2 s−1 to obtain these two parameters. It is demonstrated that the strain rate dependence of the yield stress and the initial tangent modulus can be described by either a power or a logarithm law. The predictions from the two models are in good agreement with the experiments. In contrast, the power-law rate-dependent Kondner model is more suitable for describing the rate-dependent tensile behavior of PE100 pipe material than the logarithm-law rate-dependent Kondner model, especially for the cases of very low strain rates which relate to the polymer pressure pipe applications.