Polymers

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13 pages, 4035 KiB

Open AccessArticle

Numerical Simulation of the Pouring Process in Deep-Water Flexible Pipe End Fittings

by Hongxia Li, Chenwei He, Tao Zhang, Qingzhen Lu and Jun Yan

Polymers 2023, 15(6), 1397; https://doi.org/10.3390/polym15061397 - 10 Mar 2023

Viewed by 1394

The pouring quality of epoxy resin in the resin cavity of deep-water composite flexible pipe end fittings has a decisive effect on the performance of the end fitting, and accurate investigation of the resin flow during the pouring process can provide a reference [...] Read more.

The pouring quality of epoxy resin in the resin cavity of deep-water composite flexible pipe end fittings has a decisive effect on the performance of the end fitting, and accurate investigation of the resin flow during the pouring process can provide a reference for optimization of the pouring process so that the pouring quality can be improved. In this paper, numerical methods were employed to investigate the pouring process of the resin cavity. The distribution and evolution of defects were studied, and the influence of pouring rate and fluid viscosity on pouring quality was analyzed. In addition, based on the simulation results obtained, some local pouring simulations were conducted for the armor steel wire, the key characteristic structure of the end fitting resin cavity that has a significant influence on the pouring quality, to investigate the influence of the geometrical characteristics of the armor steel wire on the pouring quality. Based on these results, the existing end fitting resin cavity structure and pouring process were optimized, and better pouring quality was obtained. Full article

(This article belongs to the Special Issue Advances in Polymer Processing and Molding)

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17 pages, 4226 KiB

Open AccessArticle

Study on the Influence of Microinjection Molding Processing Parameters on Replication Quality of Polylactic Acid Microneedle Array Product

by Wenqian Yu, Junfeng Gu, Zheng Li, Shilun Ruan, Biaosong Chen, Changyu Shen, Ly James Lee and Xinyu Wang

Polymers 2023, 15(5), 1199; https://doi.org/10.3390/polym15051199 - 27 Feb 2023

Cited by 7 | Viewed by 2044

Abstract

Biodegradable microneedles with a drug delivery channel have enormous potential for consumers, including use in chronic disease, vaccines, and beauty applications, due to being painless and scarless. This study designed a microinjection mold to fabricate a biodegradable polylactic acid (PLA) in-plane microneedle array [...] Read more.

Biodegradable microneedles with a drug delivery channel have enormous potential for consumers, including use in chronic disease, vaccines, and beauty applications, due to being painless and scarless. This study designed a microinjection mold to fabricate a biodegradable polylactic acid (PLA) in-plane microneedle array product. In order to ensure that the microcavities could be well filled before production, the influences of the processing parameters on the filling fraction were investigated. The results indicated that the PLA microneedle can be filled under fast filling, higher melt temperature, higher mold temperature, and higher packing pressure, although the dimensions of the microcavities were much smaller than the base portion. We also observed that the side microcavities filled better than the central ones under certain processing parameters. However, this does not mean that the side microcavities filled better than the central ones. The central microcavity was filled when the side microcavities were not, under certain conditions in this study. The final filling fraction was determined by the combination of all parameters, according to the analysis of a 16 orthogonal latin hypercube sampling analysis. This analysis also showed the distribution in any two-parameter space as to whether the product was filled entirely or not. Finally, the microneedle array product was fabricated according to the investigation in this study. Full article

(This article belongs to the Special Issue Advances in Polymer Processing and Molding)

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11 pages, 6321 KiB

Open AccessArticle

An Injecting Molding Method for Forming the HFRP/PA6 Composite Parts

by Bin Xu, Meng-Yang Wei, Xiao-Yu Wu, Jian-Guo Lei, Zhi-Wen Zhou, Lian-Yu Fu and Li-Kuan Zhu

Polymers 2022, 14(23), 5085; https://doi.org/10.3390/polym14235085 - 23 Nov 2022

Cited by 2 | Viewed by 1823

Abstract

Carbon/glass fiber-reinforced polymer hybrid composite (HFRP) has the advantages of a light weight and high strength. For the lightweight design of automobile parts, composite parts made of HFRP and polymer materials are increasingly in demand. The method of the injection molding is usually [...] Read more.

Carbon/glass fiber-reinforced polymer hybrid composite (HFRP) has the advantages of a light weight and high strength. For the lightweight design of automobile parts, composite parts made of HFRP and polymer materials are increasingly in demand. The method of the injection molding is usually adopted to fabricate composite part with HFRP and polymer materials. The connecting strength between the two materials has an important influence on the service life of the composite part. In this paper, HFRP and polyamide-6 (PA6) were used to fabricate a composite part by the injection molding method. In order to improve the connecting strength between HFRP and PA6, a kind of micro-grooves was fabricated on the HFRP surface. The micro-grooves on the surface of the HFRP provided sufficient adhesion and infiltrating space of molten PA6 material into the mold. In addition, the glass fiber in HFRP can also be used as nucleating agent to facilitate the rapid crystallization of PA6. The micro-grooves on the surface of HFRP were embedded into PA6 like nails, which could improve the connecting strength at the interface effectively. The paper investigated the effects of mold temperature, injection pressure, holding pressure and holding time on the injection quality and connecting strength of composite parts in detail. With a mold temperature of 240 °C, an injection pressure of 8 MPa, a holding pressure of 8 MPa and a holding time of 3 s, the maximum tensile strength of 10.68 MPa was obtained for the composite part. At the effect of micro-grooves, the tensile strength of the composite part could be increased by 126.27%. Full article

(This article belongs to the Special Issue Advances in Polymer Processing and Molding)

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17 pages, 50676 KiB

Open AccessArticle

Study on the Extrusion Molding Process of Polylactic Acid Micro Tubes for Biodegradable Vascular Stents

by Yunbo Wei, Jiangeng Bai, Haitao Zhao, Rui Wang and Hongxia Li

Polymers 2022, 14(22), 4790; https://doi.org/10.3390/polym14224790 - 8 Nov 2022

Cited by 4 | Viewed by 1837

Abstract

Polylactic acid (PLA) has been widely used in the field of medical devices. However, few studies have been conducted on the extrusion molding of PLA micro tubes for the preparation of biodegradable vascular stents. In this paper, the extrusion die for PLA single-cavity [...] Read more.

Polylactic acid (PLA) has been widely used in the field of medical devices. However, few studies have been conducted on the extrusion molding of PLA micro tubes for the preparation of biodegradable vascular stents. In this paper, the extrusion die for PLA single-cavity micro tubes was designed and manufactured by micro-extrusion theory. Taking the outer diameter, wall thickness, wall thickness uniformity and ovality of micro tubes as the evaluation index, the influence of the main extrusion process parameters on the evaluation index was studied. The experimental results show that the outer diameter and wall thickness are significantly affected by screw speed, pulling speed and gas flow rate; extrusion process parameters have little influence on wall thickness uniformity and ovality within a certain range, which mainly depends on the processing accuracy and assembly accuracy of the extrusion die. However, excessively high screw speed and low gas flow rate have significant effects on ovality. Finally, according to the influence of extrusion process parameters on the evaluation index, a series of micro tubes that meet the design requirements are extruded and carved into vascular stent structures. Full article

(This article belongs to the Special Issue Advances in Polymer Processing and Molding)

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18 pages, 4215 KiB

Open AccessArticle

A Multiscale Simulation of Polymer Melt Injection Molding Filling Flow Using SPH Method with Slip-Link Model

by Mengke Ren, Junfeng Gu, Zheng Li, Shilun Ruan and Changyu Shen

Polymers 2022, 14(20), 4334; https://doi.org/10.3390/polym14204334 - 14 Oct 2022

Cited by 2 | Viewed by 2049

Abstract

In this article, a multiscale simulation method of polymer melt injection molding filling flow is established by combining an improved smoothed particle hydrodynamics method and clustered fixed slip-link model. The proposed method is first applied to the simulation of HDPE melt in a [...] Read more.

In this article, a multiscale simulation method of polymer melt injection molding filling flow is established by combining an improved smoothed particle hydrodynamics method and clustered fixed slip-link model. The proposed method is first applied to the simulation of HDPE melt in a classic Poiseuille flow case, and then two high-speed and high-viscosity injection molding flow cases in two simple long 2D rectangular cavities with and without a circular obstacle, respectively, are analyzed. For each case, the macro velocity results, and the micro average number of entanglements Z_ave and orientation degree S results are demonstrated and discussed, and the changing trends of Z_ave and S are analyzed. The results of the two injection molding cases are compared, and the influence of the obstacle on the injection flow at both the macro and micro levels is analyzed. Furthermore, based on the multiscale results, reason of some structural features and defects in injection molded products are analyzed. Full article

(This article belongs to the Special Issue Advances in Polymer Processing and Molding)

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20 pages, 9626 KiB

Open AccessArticle

Experimental and Numerical Investigation of 3D Printing PLA Origami Tubes under Quasi-Static Uniaxial Compression

by Weidong Chen, Chengjie Guo, Xiubin Zuo, Jian Zhao, Yang Peng and Yixiao Wang

Polymers 2022, 14(19), 4135; https://doi.org/10.3390/polym14194135 - 2 Oct 2022

Cited by 6 | Viewed by 2713

Abstract

The investigation aims to study the effects of temperature and damage constitutive model on the energy absorption performance of polymeric origami tubes under quasi-static impact. The uniaxial tensile responses of 3D-printed polylactic acid (PLA) samples following standard ASTM-D412 have been studied to characterize [...] Read more.

The investigation aims to study the effects of temperature and damage constitutive model on the energy absorption performance of polymeric origami tubes under quasi-static impact. The uniaxial tensile responses of 3D-printed polylactic acid (PLA) samples following standard ASTM-D412 have been studied to characterize the mechanical properties at three temperatures: 30 °C, 40 °C, and 50 °C. The damage constitutive model is used to accurately characterize the stress-strain relations of the PLA. Quasi-static compressive experiments are performed on polymetric tubes with different temperatures. The 3D-printed technique is used to ensure the integrated formation of these polymeric origami tubes. The user-defined material subroutine VUMAT for ABAQUS/Explicit has been developed for the damage model. Compared with the results, the observed deformation processes are well captured by the numerical simulations, and the influence of temperature on the axial compression is also analyzed in detail. Full article

(This article belongs to the Special Issue Advances in Polymer Processing and Molding)

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15 pages, 8438 KiB

Open AccessArticle

Geometry Optimization of the Runner Insert for Improving the Appearance Quality of the Injection Molded Auto Part

by Zhiguo Ma, Zheng Li, Ming Huang, Chuntai Liu, Changyu Shen and Xinyu Wang

Polymers 2022, 14(19), 4085; https://doi.org/10.3390/polym14194085 - 29 Sep 2022

Cited by 2 | Viewed by 1589

Abstract

Appearance quality is one of the most important indexes for many injection-molded products, like optical parts, automotive parts etc., especially at the area near the injection gate. Different from the work that focused on designing the dimensions of the runner, this work proposed [...] Read more.

Appearance quality is one of the most important indexes for many injection-molded products, like optical parts, automotive parts etc., especially at the area near the injection gate. Different from the work that focused on designing the dimensions of the runner, this work proposed a method which is based on the insert technology to improve the appearance quality of a standard automotive part. An insert was introduced into the runner system which located before the gate. Three different shapes of this insert (circular, rectangular and diamond) were used to study the effect of geometrical factors on the appearance quality in this paper. All inserts were parameterized to describe their location and dimensions. Based on the geometrical design parameters, expected improvement optimization problem about the appearance quality were solved by using sequential approximate optimization method. The appearance qualities of three cases are improved by 13.77%, 21.56%, 14.37% respectively. Results showed that the best geometrical design scheme of the insert is rectangular with the optimal geometrical location and dimensions. The reasons were discussed by investigating the flow and thermal history in detail. Compared with the design case without any insert, the heat was absorbed and the velocity field was changed by the insert before the polymer melts ran into the cavity. It changed the complicated thermo-mechanical history inside the material during the entire processing history, which improved the final appearance quality of this auto part. Full article

(This article belongs to the Special Issue Advances in Polymer Processing and Molding)

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18 pages, 4476 KiB

Open AccessArticle

Influence of Loading Rate and Temperature on the Energy Absorption of 3D-Printed Polymeric Origami Tubes under Quasi-Static Loading

by Xiubin Zuo, Chengjie Guo, Weidong Chen, Yixiao Wang, Jian Zhao and Huanlin Lv

Polymers 2022, 14(18), 3859; https://doi.org/10.3390/polym14183859 - 15 Sep 2022

Cited by 2 | Viewed by 1905

Abstract

Owing to deformation in the form of the diamond mode with high-energy absorption capacity, origami thin-walled tubes have attracted considerable attention in recent years. Stamping and welding are mainly employed to produce different types of origami thin-walled tubes. The processing defects and geometric [...] Read more.

Owing to deformation in the form of the diamond mode with high-energy absorption capacity, origami thin-walled tubes have attracted considerable attention in recent years. Stamping and welding are mainly employed to produce different types of origami thin-walled tubes. The processing defects and geometric asymmetry may be caused by the manufacturing process, which changes the collapsed mode and decreases the energy-absorbing capacity. In this study, fused filament fabrication (FFF) 3D printing is used to fabricate the origami-ending tube (OET) by integrated formation. Experiments and numerical simulations were conducted to study the influence of loading rate and temperature on the energy absorption of polymeric origami tubes under quasi-static loading. The experiments showed that different constitutive models are needed to capture the complex true stress–strain behavior of 3D printing polylactic acid (PLA) material at different temperatures. The damage model is established and then applied to the numerical simulations, which could predict the collapsed mode and the damage behavior of the OET tubes under different loading rates at 30 °C, 40 °C, and 50 °C. Based on the experiments and the validated numerical model, the influence of loading rate and temperature on the crashworthiness performance of the OET tubes is analyzed. Full article

(This article belongs to the Special Issue Advances in Polymer Processing and Molding)

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