Research

13 pages, 8751 KiB

Open AccessArticle

Fibre-Reinforced Polymers and Steel for the Reinforcement of Wooden Elements—Experimental and Numerical Analysis

by Agnieszka Wdowiak-Postulak, Marek Wieruszewski, František Bahleda, Jozef Prokop and Janusz Brol

Polymers 2023, 15(9), 2062; https://0-doi-org.brum.beds.ac.uk/10.3390/polym15092062 - 26 Apr 2023

Cited by 4 | Viewed by 1364

These elements are innovative and of interest to many researchers for the reinforcement of wooden elements. For the reinforced beam elements, the effect of the reinforcement factor, FRP and steel elastic modulus or FRP and steel arrangement of the reinforcement on the performance [...] Read more.

These elements are innovative and of interest to many researchers for the reinforcement of wooden elements. For the reinforced beam elements, the effect of the reinforcement factor, FRP and steel elastic modulus or FRP and steel arrangement of the reinforcement on the performance of the flexural elements was determined, followed by reading the load-displacement diagram of the reinforced beam elements. The finite element model was then developed and verified with the experimental results, which was mainly related to the fact that the general theory took into account the typical tensile failure mode, which can be used to predict the flexural strength of reinforced timber beams. From the tests, it was determined that reinforced timber beam elements had relatively ductile flexural strengths up to brittle tension for unreinforced elements. As for the reinforcements of FRP, the highest increase in load-bearing capacity was for carbon mats at 52.47%, with a reinforcement grade of 0.43%, while the lowest was for glass mats at 16.62% with a reinforcement grade of 0.22%. Basalt bars achieved the highest stiffness, followed by glass mats. Taking into account all the reinforcements used, the highest stiffness was demonstrated by the tests of the effectiveness of the reinforcement using 3 mm thick steel plates. For this configuration with a reinforcement percentage of 10%, this increase in load capacity was 79.48% and stiffness was 31.08%. The difference between the experimental and numerical results was within 3.62–27.36%, respectively. Full article

(This article belongs to the Special Issue Multifunctional Polymer (Nano)Composites: Structure-Property Relationships)

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17 pages, 3208 KiB

Open AccessArticle

Mechanical and Thermo-Mechanical Performance of Natural Fiber-Based Single-Ply and 2-Ply Woven Prepregs

by Hafsa Jamshaid, Rajesh Kumar Mishra, Vijay Chandan, Shabnam Nazari, Muhammad Shoaib, Laurent Bizet, Tatiana Alexiou Ivanova, Miroslav Muller and Petr Valasek

Polymers 2023, 15(4), 994; https://0-doi-org.brum.beds.ac.uk/10.3390/polym15040994 - 16 Feb 2023

Cited by 4 | Viewed by 1701

Abstract

This paper presents a study conducted on prepregs manufactured by a novel method for the impregnation of a thermoplastic matrix. Different composite prepregs based on polypropylene and reinforced with natural fibers (e.g., basalt and jute fibers) were developed. The mechanical and dynamic mechanical [...] Read more.

This paper presents a study conducted on prepregs manufactured by a novel method for the impregnation of a thermoplastic matrix. Different composite prepregs based on polypropylene and reinforced with natural fibers (e.g., basalt and jute fibers) were developed. The mechanical and dynamic mechanical properties were investigated. DMA tests were conducted at 1 Hz frequency and properties such as storage modulus and damping (tan δ) were evaluated. The overall mechanical properties of the basalt fiber composites were found to be superior to that of the jute fiber-based samples. Thermo-gravimetric analysis (TG/DTG) of the composite samples showed that the thermal degradation temperatures of the basalt-based composites shifted to higher temperature regions compared to the PP or jute fiber composites. The addition of basalt fiber considerably improved the thermal stability of the composite samples. Microscopic images of the tensile fractured composite samples illustrated better fiber–matrix interfacial interaction due to the novel technology of prepregs. Single-ply and 2-ply prepregs showed significantly superior mechanical, thermal, and thermo-dynamical performance compared to the control sample (pure PP). 2-Ply composites demonstrated higher modulus, tensile strength, and storage modulus due to the higher fiber volume fraction. Basalt-based samples showed a minimum weight loss of about 57% up to 700 °C in contrast to 96.05% weight loss in the jute-based samples and 98.4% in the case of pure PP. The heat resistance index (T_HRI) is more than twice for basalt compared to jute and PP. Furthermore, the superior thermal stability of basalt is reflected in its DSC curves, showing the highest endothermic peak. The technique of using the resin in the form of thermoplastic yarns offers cost effective and efficient alternatives for composite manufacturing. Full article

(This article belongs to the Special Issue Multifunctional Polymer (Nano)Composites: Structure-Property Relationships)

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23 pages, 9070 KiB

Open AccessArticle

Structural, Mechanical, and Tribological Properties of Oriented Ultra-High Molecular Weight Polyethylene/Graphene Nanoplates/Polyaniline Films

by Tarek Dayyoub, Aleksey Maksimkin, Leonid K. Olifirov, Dilus Chukov, Evgeniy Kolesnikov, Sergey D. Kaloshkin and Dmitry V. Telyshev

Polymers 2023, 15(3), 758; https://0-doi-org.brum.beds.ac.uk/10.3390/polym15030758 - 02 Feb 2023

Cited by 3 | Viewed by 2316

Abstract

Preparing high-strength polymeric materials using an orientation drawing process is considered one of the most urgent topics in the modern world. Graphene nanoplates/polyaniline (GNP/PANI) were added to the commercial grade UHMWPE (GUR 4120) matrix as a filler with antifriction properties. The effect of [...] Read more.

Preparing high-strength polymeric materials using an orientation drawing process is considered one of the most urgent topics in the modern world. Graphene nanoplates/polyaniline (GNP/PANI) were added to the commercial grade UHMWPE (GUR 4120) matrix as a filler with antifriction properties. The effect of GNP/PANI addition on the structure, the orientation process, the void formation (cavitation), the mechanical, and tribological properties was studied using differential scanning calorimetry (DSC), dynamical mechanical analysis (DMA), and scanning electron microscopy (SEM). The paper’s findings indicated an increase in the cavitation effect of 120–320% after the addition of GNP/PANI to the UHMWPE polymer matrix. This increase, during the process of the oriented films’ thermal orientation hardening, led, in turn, to a decrease in the tensile strength during the process of the oriented films’ thermal orientation hardening. Furthermore, the decrease in the coefficient of friction in the best samples of oriented UHMWPE films was two times greater, and the increase in wear resistance was more than an order of magnitude. This process was part of the orientation hardening process for the UHMWPE films containing PE-wax as an intermolecular lubricant, as well as the presence of GNP/PANI in the material, which have a high resistance to abrasive wear. Full article

(This article belongs to the Special Issue Multifunctional Polymer (Nano)Composites: Structure-Property Relationships)

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14 pages, 3137 KiB

Open AccessArticle

A Scalable Heat Pump Film with Zero Energy Consumption

by Zhenghua Meng, Boyu Cao, Wei Guo, Yetao Zhong, Bin Li, Changhao Chen, Hengren Hu, Shigang Wu and Zhilin Xia

Polymers 2023, 15(1), 159; https://0-doi-org.brum.beds.ac.uk/10.3390/polym15010159 - 29 Dec 2022

Viewed by 1586

Abstract

Radiative cooling is an effective technology with zero energy consumption to alleviate climate warming and combat the urban heat island effect. At present, researchers often use foam boxes to isolate non-radiant heat exchange between the cooler and the environment through experiments, so as [...] Read more.

Radiative cooling is an effective technology with zero energy consumption to alleviate climate warming and combat the urban heat island effect. At present, researchers often use foam boxes to isolate non-radiant heat exchange between the cooler and the environment through experiments, so as to achieve maximum cooling power. In practice, however, there are challenges in setting up foam boxes on a large scale, resulting in coolers that can be cooled below ambient only under low convection conditions. Based on polymer materials and nano-zinc oxide (nano-ZnO, refractive index > 2, the peak equivalent spherical diameter 500 nm), the manufacturing process of heat pump film (HPF) was proposed. The HPF (4.1 mm thick) consists of polyethylene (PE) bubble film (heat transfer coefficient 0.04 W/m/K, 4 mm thick) and Ethylene-1-octene copolymer (POE) cured nano-ZnO (solar reflectance ≈94% at 0.075 mm thick). Covering with HPF, the object achieves 7.15 °C decreasing in normal natural environment and 3.68 °C even under certain circumstances with high surface convective heat transfer (56.9 W/m²/K). HPF has advantages of cooling the covered object, certain strength (1.45 Mpa), scalable manufacturing with low cost, hydrophobic characteristics (the water contact angle, 150.6°), and meeting the basic requirements of various application scenarios. Full article

(This article belongs to the Special Issue Multifunctional Polymer (Nano)Composites: Structure-Property Relationships)

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15 pages, 3693 KiB

Open AccessArticle

Castor Oil-Based Polyurethane/S2 Glass/Aramid Hybrid Composites Manufactured by Vacuum Infusion

by Joziel Aparecido da Cruz, Eduardo Fischer Kerche, Otávio Bianchi, Andrea Manes and Sandro Campos Amico

Polymers 2022, 14(23), 5150; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14235150 - 26 Nov 2022

Cited by 4 | Viewed by 1385

Abstract

This study evaluates the hybridization effect of S2-glass/aramid on polyurethane (PU) composites produced by vacuum infusion. Different laminates were produced with similar thickness (around 2.5 mm), using, as reinforcement, only aramid fabrics (five layers, named as K₅) or only S2-glass fabrics [...] Read more.

This study evaluates the hybridization effect of S2-glass/aramid on polyurethane (PU) composites produced by vacuum infusion. Different laminates were produced with similar thickness (around 2.5 mm), using, as reinforcement, only aramid fabrics (five layers, named as K₅) or only S2-glass fabrics (eight layers, named as G₈). Furthermore, hybridization was obtained by manufacturing symmetrical hybrid inter-ply laminates, with four S2-glass layers and two of aramid, (G₂K)_S and (KG₂)_S. The mechanical response of the laminates was evaluated in tensile, interlaminar shear strength, dynamical mechanical analysis and quasi-static indentation tests, and related to their morphological characteristics. The main results show that the pure glass composites presented less voids, but a higher density as well as higher tensile stiffness and strength. The aramid laminates showed a high capability for absorbing impact energy (ca. 30% higher than the pure glass laminates), and the hybrid laminates had intermediate properties. More importantly, this work shows the possibility of using a polyurethane matrix for vacuum infusion processing, effective even for aramid/S2-glass hybrid composites with thermoset polyurethane resin. This study is therefore promising for impact absorption in applications such as protective armor. The studied hybrid laminate may display a suitable set of properties and greater energy absorption capability and penetration resistance for impact applications. Full article

(This article belongs to the Special Issue Multifunctional Polymer (Nano)Composites: Structure-Property Relationships)

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16 pages, 2748 KiB

Open AccessArticle

Impact of Particle and Crystallite Size of Ba_0.6Sr_0.4TiO₃ on the Dielectric Properties of BST/P(VDF-TrFE) Composites in Fully Printed Varactors

by Tim P. Mach, Yingfang Ding and Joachim R. Binder

Polymers 2022, 14(22), 5027; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14225027 - 19 Nov 2022

Cited by 3 | Viewed by 1734

Abstract

In the field of printed electronics, electronic components such as varactors are of special interest. As ferroelectric materials, Ba_0.6Sr_0.4TiO₃ (BST) and poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) are promising compounds to be used in functional inks for the fabrication [...] Read more.

In the field of printed electronics, electronic components such as varactors are of special interest. As ferroelectric materials, Ba_0.6Sr_0.4TiO₃ (BST) and poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) are promising compounds to be used in functional inks for the fabrication of fully inkjet-printed dielectric layers. In BST/P(VDF-TrFE) composite inks, the influence of the particle and crystallite size is investigated by using different grinding media sizes and thermal treatments at varying temperatures. It was found that with an increasing particle and crystallite size, both the relative permittivity and tunability increase as well. However, the thermal treatment which impacts both the particle and crystallite size has a greater effect on the dielectric properties. An additional approach is the reduction in the dielectric layer thickness, which has a significant effect on the maximal tunability. Here, with a thickness of 0.9 µm, a tunability of 29.6% could be achieved in an external electric field of 34 V µm⁻¹. Full article

(This article belongs to the Special Issue Multifunctional Polymer (Nano)Composites: Structure-Property Relationships)

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15 pages, 6267 KiB

Open AccessArticle

Experimental Investigation on the Mechanical and Physical Properties of Glass/Jute Hybrid Laminates

by Thaís da Costa Dias, Amanda Albertin Xavier da Silva, Maikson Luiz Passaia Tonatto and Sandro Campos Amico

Polymers 2022, 14(21), 4742; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14214742 - 05 Nov 2022

Cited by 2 | Viewed by 1722

Abstract

Natural fibres have been partly substituting synthetic fibres in polymer composites due to their renewable character and many other advantages, and sometimes, they can be hybridized into a single composite for a better combination of properties. This work aims to study the effect [...] Read more.

Natural fibres have been partly substituting synthetic fibres in polymer composites due to their renewable character and many other advantages, and sometimes, they can be hybridized into a single composite for a better combination of properties. This work aims to study the effect of hybridization and stacking sequence on the mechanical and physical properties of the glass/jute laminates. For that, pure jute, pure glass and glass/jute hybrids were manufactured by vacuum infusion process using orthophthalic polyester resin. The composites were characterized via C-scan analysis, density, volume fraction of constituents and optical microscopy analyses. Mechanical properties were obtained from tensile, compression and shear tests. The longitudinal properties were higher than transverse properties for all laminates. The hybrids presented intermediate density and mechanical properties compared to pure glass and pure jute laminates. The hybrids produced similar density and tensile modulus, but with small differences in tensile strength and compressive strength which were justified based on variations in resin and void content due to the influence of the stacking sequence (glass/jute interlayer regions). In addition, the pure glass and the hybrid laminates displayed acceptable failure morphology in the in-plane shear test, but not the pure jute laminate. Full article

(This article belongs to the Special Issue Multifunctional Polymer (Nano)Composites: Structure-Property Relationships)

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23 pages, 7426 KiB

Open AccessArticle

Influence of CNT Length on Dispersion, Localization, and Electrical Percolation in a Styrene-Butadiene-Based Star Block Copolymer

by Ulrike Staudinger, Andreas Janke, Christine Steinbach, Uta Reuter, Martin Ganß and Oliver Voigt

Polymers 2022, 14(13), 2715; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14132715 - 02 Jul 2022

Cited by 5 | Viewed by 1922

Abstract

This study followed the approach of dispersing and localizing carbon nanotubes (CNTs) in nanostructured domains of block copolymers (BCPs) by shortening the CNTs via ball milling. The aim was to selectively tune the electrical and mechanical properties of the resulting nanocomposites, e.g., for [...] Read more.

This study followed the approach of dispersing and localizing carbon nanotubes (CNTs) in nanostructured domains of block copolymers (BCPs) by shortening the CNTs via ball milling. The aim was to selectively tune the electrical and mechanical properties of the resulting nanocomposites, e.g., for use as sensor materials. Multiwalled carbon nanotubes (MWCNTs) were ground into different size fractions. The MWCNT length distribution was evaluated via transmission electron microscopy and dynamic light scattering. The nanostructure of the BCPs and the glass transition temperatures of the PB-rich and PS phases were not strongly affected by the addition of CNTs up to 2 wt%. However, AFM and TEM investigations indicated a partial localization of the shortened CNTs in the soft PB-rich phase or at the interface of the PB-rich and PS phase, respectively. The stress-strain behavior of the solution-mixed composites differed little from the mechanical property profile of the neat BCP and was largely independent of CNT amount and CNT size fraction. Significant changes could only be observed for Young’s modulus and strain at break and may be attributed to CNT localization and small changes in morphology. For nanocomposites with unmilled CNTs, the electrical percolation threshold was less than 0.1 wt%. As the CNTs were shortened, the resistivity increased and the percolation threshold shifted to higher CNT contents. Composites with CNTs ground for 7.5 h and 13.5 h showed no bulk conductivity but significantly decreased surface resistivity on the bottom side of the films, which could be attributed to a sedimentation process of the grind and thereby highly compressed CNT agglomerates during evaporation. Full article

(This article belongs to the Special Issue Multifunctional Polymer (Nano)Composites: Structure-Property Relationships)

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14 pages, 2757 KiB

Open AccessArticle

Investigation of Mechanical Behaviors of Functionally Graded CNT-Reinforced Composite Plates

by Jin-Rae Cho and Young-Ju Ahn

Polymers 2022, 14(13), 2664; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14132664 - 29 Jun 2022

Cited by 8 | Viewed by 1527

Abstract

In this paper, the mechanical behavior of a functionally graded carbon nanotube-reinforced composite (FG-CNTRC) plate is numerically investigated. According to the concept of a hierarchical model, the displacement is decomposed into the in-field functions and the assumed thickness-wise monomial. The former is defined [...] Read more.

In this paper, the mechanical behavior of a functionally graded carbon nanotube-reinforced composite (FG-CNTRC) plate is numerically investigated. According to the concept of a hierarchical model, the displacement is decomposed into the in-field functions and the assumed thickness-wise monomial. The former is defined on the plate midsurface and is approximated by the 2-D meshfree natural element method (NEM). The FG-CNTRC plate is modeled as a homogenized orthotropic body, and its effective elastic properties are determined by referring to MD simulation and the linear rule of mixtures. Regarding the thickness-wise distribution of CNTs, one uniform and three functionally gradient distributions are taken. Through comparative numerical experiments, the reliability of the numerical method is justified with the maximum relative difference of 6.12%. The effects of the volume fraction and vertical distribution of CNTs, the plate width-thickness and aspect ratios, and the boundary conditions on the bending, free vibration, and buckling behaviors of FG-CNTRC plates are examined. It is found that the mechanical behavior of FG-CNTRC plates is significantly dependent of these major parameters. Full article

(This article belongs to the Special Issue Multifunctional Polymer (Nano)Composites: Structure-Property Relationships)

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