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17 pages, 5344 KiB

Open AccessArticle

Tribological, Mechanical and Thermal Properties of Fluorinated Ethylene Propylene Filled with Al-Cu-Cr Quasicrystals, Polytetrafluoroethylene, Synthetic Graphite and Carbon Black

by Leonid K. Olifirov, Andrey A. Stepashkin, Galal Sherif and Victor V. Tcherdyntsev

Polymers 2021, 13(5), 781; https://doi.org/10.3390/polym13050781 - 4 Mar 2021

Cited by 12 | Viewed by 3261

Abstract

Antifriction hybrid fluorinated ethylene propylene-based composites filled with quasicrystalline Al₇₃Cu₁₁Cr₁₆ powder, polytetrafluoroethylene, synthetic graphite and carbon black were elaborated and investigated. Composite samples were formed by high-energy ball milling of initial powders mixture with subsequent consolidation by injection [...] Read more.

Antifriction hybrid fluorinated ethylene propylene-based composites filled with quasicrystalline Al₇₃Cu₁₁Cr₁₆ powder, polytetrafluoroethylene, synthetic graphite and carbon black were elaborated and investigated. Composite samples were formed by high-energy ball milling of initial powders mixture with subsequent consolidation by injection molding. Thermal, mechanical, and tribological properties of the obtained composites were studied. It was found that composite containing 5 wt.% of Al₇₃Cu₁₁Cr₁₆ quasicrystals and 2 wt.% of nanosized polytetrafluoroethylene has 50 times better wear resistance and a 1.5 times lower coefficient of dry friction comparing with unfilled fluorinated ethylene propylene. Addition of 15 wt.% of synthetic graphite to the above mentioned composition allows to achieve an increase in thermal conductivity in 2.5 times comparing with unfilled fluorinated ethylene propylene, at that this composite kept excellent tribological properties. Full article

(This article belongs to the Special Issue Reinforced Polymer Composites II)

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16 pages, 21632 KiB

Open AccessArticle

Utilization of Bracing Arms as Additional Reinforcement in Pultruded Glass Fiber-Reinforced Polymer Composite Cross-Arms: Creep Experimental and Numerical Analyses

by Muhammad Rizal Muhammad Asyraf, Mohamad Ridzwan Ishak, Salit Mohd Sapuan and Noorfaizal Yidris

Polymers 2021, 13(4), 620; https://doi.org/10.3390/polym13040620 - 19 Feb 2021

Cited by 44 | Viewed by 3721

Abstract

The application of pultruded glass fiber-reinforced polymer composites (PGFRPCs) as a replacement for conventional wooden cross-arms in transmission towers is relatively new. Although numerous studies have conducted creep tests on coupon-scale PGFRPC cross-arms, none had performed creep analyses on full-scale PGFRPC cross-arms under [...] Read more.

The application of pultruded glass fiber-reinforced polymer composites (PGFRPCs) as a replacement for conventional wooden cross-arms in transmission towers is relatively new. Although numerous studies have conducted creep tests on coupon-scale PGFRPC cross-arms, none had performed creep analyses on full-scale PGFRPC cross-arms under actual working load conditions. Thus, this work proposed to study the influence of an additional bracing system on the creep responses of PGFRPC cross-arms in a 132 kV transmission tower. The creep behaviors and responses of the main members in current and braced PGFRPC cross-arm designs were compared and evaluated in a transmission tower under actual working conditions. These PGFRPC cross-arms were subjected to actual working loads mimicking the actual weight of electrical cables and insulators for a duration of 1000 h. The cross-arms were installed on a custom test rig in an open area to simulate the actual environment of tropical climate conditions. Further creep analysis was performed by using Findley and Burger models on the basis of experimental data to link instantaneous and extended (transient and viscoelastic) creep strains. The addition of braced arms to the structure reduced the total strain of a cross-arm’s main member beams and improved elastic and viscous moduli. The addition of bracing arms improved the structural integrity and stiffness of the cross-arm structure. The findings of this study suggested that the use of a bracing system in cross-arm structures could prolong the structures’ service life and subsequently reduce maintenance effort and cost for long-term applications in transmission towers. Full article

(This article belongs to the Special Issue Reinforced Polymer Composites II)

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17 pages, 5453 KiB

Open AccessArticle

Effects of Nanoclay on Mechanical and Dynamic Mechanical Properties of Bamboo/Kenaf Reinforced Epoxy Hybrid Composites

by Siew Sand Chee, Mohammad Jawaid, Othman Y. Alothman and Hassan Fouad

Polymers 2021, 13(3), 395; https://doi.org/10.3390/polym13030395 - 27 Jan 2021

Cited by 54 | Viewed by 3505

Abstract

Current work aims to study the mechanical and dynamical mechanical properties of non-woven bamboo (B)/woven kenaf (K)/epoxy (E) hybrid composites filled with nanoclay. The nanoclay-filled BK/E hybrid composites were prepared by dispersing 1 wt.% nanoclay (organically-modified montmorillonite (MMT; OMMT), montmorillonite (MMT), and halloysite [...] Read more.

Current work aims to study the mechanical and dynamical mechanical properties of non-woven bamboo (B)/woven kenaf (K)/epoxy (E) hybrid composites filled with nanoclay. The nanoclay-filled BK/E hybrid composites were prepared by dispersing 1 wt.% nanoclay (organically-modified montmorillonite (MMT; OMMT), montmorillonite (MMT), and halloysite nanotube (HNT)) with high shear speed homogenizer followed by hand lay-up fabrication technique. The effect of adding nanoclay on the tensile, flexural, and impact properties of the hybrid nanocomposites were studied. Fractography of tensile-fractured sample of hybrid composites was studied by field emission scanning electron microscope. The dynamic mechanical analyzer was used to study the viscoelastic properties of the hybrid nanocomposites. BK/E-OMMT exhibit enhanced mechanical properties compared to the other hybrid nanocomposites, with tensile, flexural, and impact strength values of 55.82 MPa, 105 MPa, and 65.68 J/m, respectively. Statistical analysis and grouping information were performed by one-way ANOVA (analysis of variance) and Tukey method, and it corroborates that the mechanical properties of the nanoclay-filled hybrid nanocomposites are statistically significant. The storage modulus of the hybrid nanocomposites was improved by 98.4%, 41.5%, and 21.7% with the addition of OMMT, MMT, and HNT, respectively. Morphology of the tensile fracture BK/E-OMMT composites shows that lesser voids, microcracks and fibers pull out due to strong fiber–matrix adhesion compared to other hybrid composites. Hence, the OMMT-filled BK/E hybrid nanocomposites can be utilized for load-bearing structure applications, such as floor panels and seatbacks, whereby lightweight and high strength are the main requirements. Full article

(This article belongs to the Special Issue Reinforced Polymer Composites II)

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15 pages, 1783 KiB

Open AccessArticle

Dynamic Characteristics of Woven Flax/Epoxy Laminated Composite Plate

by Venkatachalam Gopalan, Vimalanand Suthenthiraveerappa, A. Raja Annamalai, Santhanakrishnan Manivannan, Vignesh Pragasam, Panidvelan Chinnaiyan, Giriraj Mannayee and Chun-Ping Jen

Polymers 2021, 13(2), 209; https://doi.org/10.3390/polym13020209 - 8 Jan 2021

Cited by 16 | Viewed by 2894

Abstract

Due to the growing environmental awareness, the development of sustainable green composites is in high demand in composite industries, mainly in the automotive, aircraft, construction and marine applications. This work was an attempt to experimentally and numerically investigate the dynamic characteristics of Woven [...] Read more.

Due to the growing environmental awareness, the development of sustainable green composites is in high demand in composite industries, mainly in the automotive, aircraft, construction and marine applications. This work was an attempt to experimentally and numerically investigate the dynamic characteristics of Woven Flax/Bio epoxy laminated composite plates. In addition, the optimisation study on the dynamic behaviours of the Woven Flax/Bio epoxy composite plate is carried out using the response surface methodology (RSM) by consideration of the various parameters like ply orientation, boundary condition and aspect ratio. The elastic constants of the Woven Flax/Bio epoxy composite lamina needed for the numerical simulation are determined experimentally using two methods, i.e., the usual mechanical tests as well as through the impulse excitation of vibration-based approach and made a comparison between them. The numerical analysis on the free vibration characteristics of the composite was carried out using ANSYS, a finite element analysis (FEA) software. The confirmation of the FE model was accomplished by comparing the numerical results with its experimental counterpart. Finally, a comparison was made between the results obtained through the regression equation and finite element analysis. Full article

(This article belongs to the Special Issue Reinforced Polymer Composites II)

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17 pages, 8934 KiB

Open AccessArticle

Enhanced Thermal Conductivity of Epoxy Composites Filled with Al₂O₃/Boron Nitride Hybrids for Underfill Encapsulation Materials

by William Anderson Lee Sanchez, Chen-Yang Huang, Jian-Xun Chen, Yu-Chian Soong, Ying-Nan Chan, Kuo-Chan Chiou, Tzong-Ming Lee, Chih-Chia Cheng and Chih-Wei Chiu

Polymers 2021, 13(1), 147; https://doi.org/10.3390/polym13010147 - 1 Jan 2021

Cited by 53 | Viewed by 7841

Abstract

In this study, a thermal conductivity of 0.22 W·m⁻¹·K⁻¹ was obtained for pristine epoxy (EP), and the impact of a hybrid filler composed of two-dimensional (2D) flake-like boron nitride (BN) and zero-dimensional (0D) spherical micro-sized aluminum oxide (Al₂O [...] Read more.

In this study, a thermal conductivity of 0.22 W·m⁻¹·K⁻¹ was obtained for pristine epoxy (EP), and the impact of a hybrid filler composed of two-dimensional (2D) flake-like boron nitride (BN) and zero-dimensional (0D) spherical micro-sized aluminum oxide (Al₂O₃) on the thermal conductivity of epoxy resin was investigated. With 80 wt.% hybrid Al₂O₃–BN filler contents, the thermal conductivity of the EP composite reached 1.72 W·m⁻¹·K⁻¹, increasing approximately 7.8-fold with respect to the pure epoxy matrix. Furthermore, different important properties for the application were analyzed, such as Fourier-transform infrared (FTIR) spectra, viscosity, morphology, coefficient of thermal expansion (CTE), glass transition temperature (T_g), decomposition temperature (T_d), dielectric properties, and thermal infrared images. The obtained thermal performance is suitable for specific electronic applications such as flip-chip underfill packaging. Full article

(This article belongs to the Special Issue Reinforced Polymer Composites II)

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12 pages, 529 KiB

Open AccessArticle

Influence of Mechanical Couplings on the Dynamical Behavior and Energy Harvesting of a Composite Structure

by Marek Borowiec, Jaroslaw Gawryluk and Marcin Bochenski

Polymers 2021, 13(1), 66; https://doi.org/10.3390/polym13010066 - 26 Dec 2020

Cited by 5 | Viewed by 2477

Abstract

In this paper, the dynamical behavior of composite material is analyzed, including the energy harvesting effect. The composite is modeled by the Finite Element Method (FEM) and is made of pre-impregnate with a matrix of thermosetting epoxy resin reinforced with high-strength R-type glass [...] Read more.

In this paper, the dynamical behavior of composite material is analyzed, including the energy harvesting effect. The composite is modeled by the Finite Element Method (FEM) and is made of pre-impregnate with a matrix of thermosetting epoxy resin reinforced with high-strength R-type glass fibers, and it is designed as a beam structure that is exposed to mechanical vibrations. The structure assumed the form of a beam with a substantially rectangular cross section. The couplings of motion occurring between mode shapes at properly selected fiber orientations are investigated. The beams with determined sets of composite layers and a coupling effect are used to recover electricity from the mechanical vibrations in the vicinity of the first resonance zone. The composite with a certain number of fiber glass layers has assumed an orientation relative to the beam axis. The new values found in this paper are the intensity of the coupling between the bending in the stiff and flexible directions of the beam for a chosen fiber layer stacking sequence. Additionally, the influence of layer configuration on the energy harvesting efficiency of the Macro-Fiber Composite (MFC) piezoelectric element is assessed. Full article

(This article belongs to the Special Issue Reinforced Polymer Composites II)

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8 pages, 2144 KiB

Open AccessArticle

Two-Dimensional Piezoresistive Response and Measurement of Sensitivity Factor of Polymer-Matrix Carbon Fiber Mat

by Min Wu, Li Huang, Xiaoyu Zhang, Jianzhong Chen and Yong Lv

Polymers 2020, 12(12), 3072; https://doi.org/10.3390/polym12123072 - 21 Dec 2020

Cited by 1 | Viewed by 2205

Abstract

Based on the piezoresistive effect, the piezoresistive constitutive relation of a carbon fiber mat under orthogonal strain was deduced. Considering the Poisson effect, the piezoresistive responses and measurement of the sensitivity factor of a polymer-matrix carbon fiber mat under bidirectional strain were studied [...] Read more.

Based on the piezoresistive effect, the piezoresistive constitutive relation of a carbon fiber mat under orthogonal strain was deduced. Considering the Poisson effect, the piezoresistive responses and measurement of the sensitivity factor of a polymer-matrix carbon fiber mat under bidirectional strain were studied by a two-times uniaxial tension loading method in different directions, which was pasted in the center area of a cruciform aluminum substrate. The relations between the resistance change rate and the orthogonal strains were established, the reasonability of which was confirmed by comparison with the experimental results. The results show that the longitudinal piezoresistive sensitivity factor C₁₁ is 21.55, and the lateral piezoresistive sensitivity factor C₁₂ is 24.15. Using these factors, the resistance change rate of another polymer-matrix carbon mat was predicted, which was made by the same technique, and the error between the predicted and the experimental results was 1.3% in the longitudinal direction and 6.1% in the lateral direction. Full article

(This article belongs to the Special Issue Reinforced Polymer Composites II)

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17 pages, 6624 KiB

Open AccessArticle

Numerical Analysis of the Contact Behavior of a Polymer-Based Waterproof Membrane for Tunnel Lining

by Kicheol Lee, Dongwook Kim, Soon-Wook Choi, Soo-Ho Chang, Tae-Ho Kang and Chulho Lee

Polymers 2020, 12(11), 2704; https://doi.org/10.3390/polym12112704 - 16 Nov 2020

Cited by 8 | Viewed by 3209

Abstract

Waterproof membranes have higher initial strength, faster construction, and better waterproofing than conventional sheet membranes. In addition, their polymer constituents have much higher interfacial adhesion and tensile strength than those of conventional materials. However, despite their advantages, waterproof membranes are not widely used [...] Read more.

Waterproof membranes have higher initial strength, faster construction, and better waterproofing than conventional sheet membranes. In addition, their polymer constituents have much higher interfacial adhesion and tensile strength than those of conventional materials. However, despite their advantages, waterproof membranes are not widely used in civil construction. This study evaluates the material properties and interface parameters of a waterproof membrane by considering the results of laboratory experiments and numerical analysis. Since the contact behavior of a membrane at its interface with shotcrete is important for understanding the mechanism of the support it offers known as a shotcrete tunnel lining, modeling should adopt appropriate contact conditions. The numerical analysis identifies the suitability and contact conditions of the waterproof membrane in various conditions. Full article

(This article belongs to the Special Issue Reinforced Polymer Composites II)

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15 pages, 7041 KiB

Open AccessArticle

Low-Temperature Carbonized Elastomer-Based Composites Filled with Silicon Carbide

by Andrey A. Stepashkin, Semen D. Ignatyev, Dilyus I. Chukov, Victor V. Tcherdyntsev, Sergey D. Kaloshkin and Elena V. Medvedeva

Polymers 2020, 12(11), 2669; https://doi.org/10.3390/polym12112669 - 12 Nov 2020

Cited by 2 | Viewed by 4061

Abstract

Thermally stable composites obtained by the low-temperature carbonization of an elastomeric matrix filled with hard dispersed silicon carbide particles were obtained and investigated. Evolution of the microstructure and of mechanical and thermal characteristics of composites during thermal degradation and carbonization processes in a [...] Read more.

Thermally stable composites obtained by the low-temperature carbonization of an elastomeric matrix filled with hard dispersed silicon carbide particles were obtained and investigated. Evolution of the microstructure and of mechanical and thermal characteristics of composites during thermal degradation and carbonization processes in a wide range of filling from 0 to 450 parts per hundred rubber was studied. For highly filled composites, the compressive strength values were found to be more than 200 MPa; Young’s modulus was more than 15 GPa. The thermal conductivity coefficient of composites was up to 1.6 W/(m·K), and this magnitude varied slightly in the temperature range of 25–300 °C. Coupled with the high thermal stability of the composites, the observed properties make it possible to consider using such composites as strained friction units instead of reinforced polymers. Full article

(This article belongs to the Special Issue Reinforced Polymer Composites II)

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16 pages, 6027 KiB

Open AccessArticle

Analysis of Viscoelastic Behavior of Polypropylene/Carbon Nanotube Nanocomposites by Instrumented Indentation

by Felicia Stan, Adriana-Madalina Turcanu (Constantinescu) and Catalin Fetecau

Polymers 2020, 12(11), 2535; https://doi.org/10.3390/polym12112535 - 29 Oct 2020

Cited by 8 | Viewed by 2771

Abstract

In this work, the viscoelastic behavior of polypropylene (PP)/multi-walled carbon nanotube (MWCNT) nanocomposites was investigated by indentation testing and phenomenological modeling. Firstly, indentation tests including two-cycle indentation were carried out on PP/MWCNT nanocomposite with three MWCNT loadings (1, 3 and 5 wt %). [...] Read more.

In this work, the viscoelastic behavior of polypropylene (PP)/multi-walled carbon nanotube (MWCNT) nanocomposites was investigated by indentation testing and phenomenological modeling. Firstly, indentation tests including two-cycle indentation were carried out on PP/MWCNT nanocomposite with three MWCNT loadings (1, 3 and 5 wt %). Next, the Maxwell–Voigt–Kelvin model coupled with two-cycle indentation tests was used to predict the shear creep compliance function and the equivalent indentation modulus. The indentation hardness and elastic modulus of the PP/MWCNT nanocomposites extracted based on the Oliver and Pharr method were compared with the equivalent indentation modulus predicted based on the Maxwell–Voigt–Kelvin mode. The experimental results indicated that the addition of nanotubes into the polypropylene has a positive effect on the micro-mechanical properties of PP/MWCNT nanocomposites. Indentation hardness and elastic modulus increased significantly with increasing MWCNT loading. The creep resistance at the micro-scale of the PP/MWCNT nanocomposites improved with the addition of MWCNTs, with creep displacement reduced by up to 20% by increasing the carbon nanotube loading from 1 to 5 wt %. The Maxwell–Voigt–Kelvin model with three and five Voigt–Kelvin units accurately predicted the shear creep function and its change with increasing MWCNT loading. However, the equivalent indentation modulus was found to be sensitive to the number of Voigt–Kelvin units: the more Voigt–Kelvin units, the better the model predicts the equivalent indentation modulus. Full article

(This article belongs to the Special Issue Reinforced Polymer Composites II)

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13 pages, 6130 KiB

Open AccessEditor’s ChoiceArticle

Fatigue Behavior of 3D Braided Composites Containing an Open-Hole

by Shuangqiang Liang, Qihong Zhou, Haiyang Mei, Ge Chen and Frank Ko

Polymers 2020, 12(9), 2147; https://doi.org/10.3390/polym12092147 - 21 Sep 2020

Cited by 4 | Viewed by 3220

Abstract

The static and dynamic mechanical performances of notched and un-notched 3D braided composites were studied. The effect of longitudinal laid-in yarn was investigated in comparison with low braiding angle composites. The specimens were fatigue tested for up to millions of cycles, and the [...] Read more.

The static and dynamic mechanical performances of notched and un-notched 3D braided composites were studied. The effect of longitudinal laid-in yarn was investigated in comparison with low braiding angle composites. The specimens were fatigue tested for up to millions of cycles, and the residual strength of the samples that survived millions of cycles was tested. The cross-section of the 3D braided specimens was observed after fatigue loading. It was found that the static and fatigue properties of low angle 3D braided behaved better than longitudinally reinforced 3D braided composites. For failure behavior, pure braids contain damage better and show less damage area than the braids with longitudinal yarns under fatigue loading. More cracks occurred in the 3D braided specimen with axial yarn cross-section along the longitudinal and transverse direction. Full article

(This article belongs to the Special Issue Reinforced Polymer Composites II)

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22 pages, 3111 KiB

Open AccessArticle

End-of-Life Recycling Options of (Nano)Enhanced CFRP Composite Prototypes Waste—A Life Cycle Perspective

by Fotini Petrakli, Anastasia Gkika, Alexandra Bonou, Panagiotis Karayannis, Elias P. Koumoulos, Dionisis Semitekolos, Aikaterini-Flora Trompeta, Nuno Rocha, Raquel M. Santos, Guy Simmonds, Glen Monaghan, Giorgio Valota, Guan Gong and Costas A. Charitidis

Polymers 2020, 12(9), 2129; https://doi.org/10.3390/polym12092129 - 18 Sep 2020

Cited by 26 | Viewed by 7152

Abstract

Life cycle assessment is a methodology to assess environmental impacts associated with a product or system/process by accounting resource requirements and emissions over its life cycle. The life cycle consists of four stages: material production, manufacturing, use, and end-of-life. This study highlights the [...] Read more.

Life cycle assessment is a methodology to assess environmental impacts associated with a product or system/process by accounting resource requirements and emissions over its life cycle. The life cycle consists of four stages: material production, manufacturing, use, and end-of-life. This study highlights the need to conduct life cycle assessment (LCA) early in the new product development process, as a means to assess and evaluate the environmental impacts of (nano)enhanced carbon fibre-reinforced polymer (CFRP) prototypes over their entire life cycle. These prototypes, namely SleekFast sailing boat and handbrake lever, were manufactured by functionalized carbon fibre fabric and modified epoxy resin with multi-walled carbon nanotubes (MWCNTs). The environmental impacts of both have been assessed via LCA with a functional unit of ‘1 product piece’. Climate change has been selected as the key impact indicator for hotspot identification (kg CO₂ eq). Significant focus has been given to the end-of-life phase by assessing different recycling scenarios. In addition, the respective life cycle inventories (LCIs) are provided, enabling the identification of resource hot spots and quantifying the environmental benefits of end-of-life options. Full article

(This article belongs to the Special Issue Reinforced Polymer Composites II)

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15 pages, 3764 KiB

Open AccessArticle

Leather Waste to Enhance Mechanical Performance of High-Density Polyethylene

by Eylem Kiliç, Quim Tarrés, Marc Delgado-Aguilar, Xavier Espinach, Pere Fullana-i-Palmer and Rita Puig

Polymers 2020, 12(9), 2016; https://doi.org/10.3390/polym12092016 - 3 Sep 2020

Cited by 19 | Viewed by 4973

Abstract

Leather buffing dust (BF) is a waste from tannery which is usually disposed on landfills. The interest in using wastes as fillers or reinforcements for composites has raised recently due to environmental concerns. This study investigates the potential use of BF waste as [...] Read more.

Leather buffing dust (BF) is a waste from tannery which is usually disposed on landfills. The interest in using wastes as fillers or reinforcements for composites has raised recently due to environmental concerns. This study investigates the potential use of BF waste as filler for a high density polyethylene matrix (HDPE). A series of HDPE-BF composites, containing filler concentrations ranging from 20 to 50wt%, were formulated, injection molded and tested. The effect of filler contents on the mechanical properties of the composites were evaluated and discussed. Composites with BF contents up to 30wt% improved the tensile strength and Young’s modulus of the matrix, achieving similar mechanical properties to polypropylene (PP). In the case of flexural strength, it was found to be proportionally enhanced by increasing reinforcement content, maintaining high impact strength. These composites present great opportunities for PP application areas that require higher impact resistance. The materials were submitted to a series of closed-loop recycling cycles in order to assess their recyclability, being able to maintain better tensile strength than virgin HDPE after 5 cycles. The study develops new low-cost and sustainable composites by using a waste as composite filler. Full article

(This article belongs to the Special Issue Reinforced Polymer Composites II)

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16 pages, 3710 KiB

Open AccessArticle

Viscoelastic Behavior of Glass-Fiber-Reinforced Silicone Composites Exposed to Cyclic Loading

by Julia Beter, Bernd Schrittesser, Bernhard Lechner, Mohammad Reza Mansouri, Claudia Marano, Peter Filipp Fuchs and Gerald Pinter

Polymers 2020, 12(9), 1862; https://doi.org/10.3390/polym12091862 - 19 Aug 2020

Cited by 21 | Viewed by 4395

Abstract

The aim of this work was to analyze the influence of fibers on the mechanical behavior of fiber-reinforced elastomers under cyclic loading. Thus, the focus was on the characterization of structure–property interactions, in particular the dynamic mechanical and viscoelastic behavior. Endless twill-woven glass [...] Read more.

The aim of this work was to analyze the influence of fibers on the mechanical behavior of fiber-reinforced elastomers under cyclic loading. Thus, the focus was on the characterization of structure–property interactions, in particular the dynamic mechanical and viscoelastic behavior. Endless twill-woven glass fibers were chosen as the reinforcement, along with silicone as the matrix material. For the characterization of the flexible composites, a novel testing device was developed. Apart from the conventional dynamic mechanical analysis, in which the effect of the fiber orientation was also considered, modified step cycle tests were conducted under tensile loading. The material viscoelastic behavior was studied, evaluating both the stress relaxation response and the capability of the material to dissipate energy under straining. The effects of the displacement rate of the strain level, the amplitude of the strain applied in the loading–unloading step cycle test, and the number of the applied cycles were evaluated. The results revealed that an optimized fiber orientation leads to 30-fold enhanced stiffness, along with 10 times higher bearable stress. The findings demonstrated that tailored reinforced elastomers with endless fibers have a strong influence on the mechanical performance, affecting the structural properties significantly. Full article

(This article belongs to the Special Issue Reinforced Polymer Composites II)

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13 pages, 10076 KiB

Open AccessArticle

Analysis of Three-Phase Structure of Epoxy Resin/CNT/Graphene by Molecular Simulation

by Shun Naito, Jun Koyanagi, Takuji Komukai and Toshikazu Uno

Polymers 2020, 12(8), 1821; https://doi.org/10.3390/polym12081821 - 13 Aug 2020

Cited by 3 | Viewed by 3413

Abstract

In this study, the three-phase structure consisting of epoxy resin, carbon nanotubes (CNTs), and graphene, which is assumed to be the surface of carbon fiber, was simulated using molecular dynamics. Models in which the CNT number and initial position of CNT are varied [...] Read more.

In this study, the three-phase structure consisting of epoxy resin, carbon nanotubes (CNTs), and graphene, which is assumed to be the surface of carbon fiber, was simulated using molecular dynamics. Models in which the CNT number and initial position of CNT are varied were prepared in this study. Relaxation calculation for each three-phase model was implemented, and the movement of molecules was investigated. When CNTs are located between the graphene and epoxy at initial, how the epoxy approaches to graphene was discussed. Besides, interaction energies between CNT/graphene, CNT/epoxy, and graphene/epoxy were evaluated after relaxations. The value of the interaction energy between two individual molecules (epoxy resin and graphene, CNTs and graphene, epoxy resin and CNTs) among three-phase structure were obtained, respectively, and those mechanisms were discussed in this study. Full article

(This article belongs to the Special Issue Reinforced Polymer Composites II)

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13 pages, 5480 KiB

Open AccessArticle

Tribo-Mechanical Characterization of Carbon Fiber-Reinforced Cyanate Ester Resins Modified With Fillers

by Ankur Bajpai, Prateek Saxena and Klaus Kunze

Polymers 2020, 12(8), 1725; https://doi.org/10.3390/polym12081725 - 31 Jul 2020

Cited by 22 | Viewed by 4417

Abstract

High-performance polymer composites are being increasingly favored for structural applications. For this purpose, efforts are being focused on exploring the potential of high-performance thermoplastics and thermosets. Cyanate ester (CE) resin is a special thermoset that can be used at up to 400 °C [...] Read more.

High-performance polymer composites are being increasingly favored for structural applications. For this purpose, efforts are being focused on exploring the potential of high-performance thermoplastics and thermosets. Cyanate ester (CE) resin is a special thermoset that can be used at up to 400 °C without any considerable degradation; however, its tribological properties are not at the adequate level. Hence, it is needed to use this polymer in composite form with the fibrous/particulate reinforcement to impart better tribological properties and mechanical strength via a strong fiber–matrix interface. Carbon fiber/fabrics are at the forefront as reinforcement for specialty polymers. The tribological and tensile properties of cyanate ester (CE) composites-filled graphite, polytetrafluoroethylene (PTFE), and MoS₂ micron-sized fillers reinforced with carbon fibers (CF) are investigated experimentally in a block-on-ring setup at 100 N, for 10 h, and with a sliding distance of approximately 10,000 m, against a hardened polished 100Cr6 steel shaft and diamond-like-coated (DLC) 100Cr6 steel shaft. The tribological properties of the composites including the coefficient of friction and specific wear rate are enhanced especially with the incorporation of graphite fillers. The friction coefficient and wear rate of the graphite-based composite was decreased significantly at 5 wt.% of graphite concentration. Further, at the same concentration, the graphite-based composite showed superior tensile properties as compared to the reference system owing to better dispersion and adhesion between the fibers and matrix. Tensile tests are performed to characterize the fiber–matrix interfacial adhesion and other strength properties. Full article

(This article belongs to the Special Issue Reinforced Polymer Composites II)

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15 pages, 4980 KiB

Open AccessArticle

Experimental and Numerical Research on Open-Hole Strength and Damage Mechanism of Regularly Arrayed Short Fiber Reinforced Polymer Composite

by Junfeng Hu, Xutong Zhang, Zhou Chen, Wenkang Guo, Hang Li and Xi Deng

Polymers 2020, 12(7), 1622; https://doi.org/10.3390/polym12071622 - 21 Jul 2020

Cited by 10 | Viewed by 3190

Abstract

Laminates with unidirectionally arrayed chopped strands (UACS) are one of the advanced short fiber reinforced polymer composites (SFRP) with significant application prospect, which greatly improves mechanical properties compared to the traditional SFRP, meanwhile ensuring excellent flowability. In practice, composite laminate with an open [...] Read more.

Laminates with unidirectionally arrayed chopped strands (UACS) are one of the advanced short fiber reinforced polymer composites (SFRP) with significant application prospect, which greatly improves mechanical properties compared to the traditional SFRP, meanwhile ensuring excellent flowability. In practice, composite laminate with an open hole is one of the typical connective components, and it is necessary to clarify the allowable load and damage tolerance performance of notched structures. In the present study, UACS laminates were fabricated using the continuous carbon fiber reinforced polymer (CFRP) prepreg, on which regularly arrayed bi-angled slits were introduced by a commercial numerical control cutter. The tensile strength and strain distribution around the open hole of the notched UACS laminate were experimentally investigated, while the damage progression near the open hole of the notched UACS laminate was analyzed by the finite element method (FEM). The tensile strength of the notched UACS laminate was measured at 298 MPa, which is about 60% of the strength of the unnotched UACS laminate. The simulation results match well with the experimental results, although there is a little overestimate on strength, by about 5% and 7%, for unnotched and notched UACS laminates, respectively. The final critical failure mode for the notched UACS laminate is mainly dominated by the delamination instead of the fiber breakage in the unnotched UACS laminate. Full article

(This article belongs to the Special Issue Reinforced Polymer Composites II)

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20 pages, 5239 KiB

Open AccessArticle

Study of Compaction Properties and Permeability Prediction of Multilayered Quadriaxial Non-Crimp Fabric in Liquid Composite Molding Process

by Yi Geng, Jinhua Jiang, Fangbing Lin, Huiqi Shao, Chenglong Zhang and Nanliang Chen

Polymers 2020, 12(7), 1525; https://doi.org/10.3390/polym12071525 - 9 Jul 2020

Cited by 3 | Viewed by 3472

Abstract

A systematic experimental study was performed to detect the compaction and permeability properties of multilayered biaxial and quadriaxial preforms under vacuum pressure. Compression response on ply level showed that the degree of nesting between quadriaxial NCF was more pronounced and the nesting deformation [...] Read more.

A systematic experimental study was performed to detect the compaction and permeability properties of multilayered biaxial and quadriaxial preforms under vacuum pressure. Compression response on ply level showed that the degree of nesting between quadriaxial NCF was more pronounced and the nesting deformation mechanism was affected by the interaction with stitch yarns. Owing to the meso-channels in the fibrous structure and the nesting between layers, the in-plane permeability of quadriaxial NCF did not follow an inverse proportion relationship with the fiber volume fraction. To predict the in-plane permeability of multilayered quadriaxial NCFs, unit cell models at a high level of geometrical details were built, including local variations in yarn cross-sections and the nesting deformation between layers. Numerical methods were implemented, and the prediction results were in very good agreement with the experimental data. Besides, the major contributing parameters to the enhancement of the in-plane permeabilities were identified by investigating the correlation between permeability and structural parameters of quadriaxial NCF. The modeling methodology and the principles established can be applied to the design of the quadriaxial NCF fabrics, where the permeability enhancement was evidenced. Full article

(This article belongs to the Special Issue Reinforced Polymer Composites II)

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12 pages, 8333 KiB

Open AccessArticle

Preparation and Characterization of Furan–Matrix Composites Blended with Modified Hollow Glass Microsphere

by Yizhe Ma, Ying Du, Jin Zhao, Xubo Yuan and Xin Hou

Polymers 2020, 12(7), 1480; https://doi.org/10.3390/polym12071480 - 1 Jul 2020

Cited by 14 | Viewed by 3405

Abstract

In this study, a new class of thermal insulation composites was prepared by blending a modified hollow glass microsphere (HGM) with furan resin. The particle dispersion between the microparticles and resin matrix was improved using 3-methacryloxypropyltrimethoxy silane (KH-570). Furthermore, the structure and morphology [...] Read more.

In this study, a new class of thermal insulation composites was prepared by blending a modified hollow glass microsphere (HGM) with furan resin. The particle dispersion between the microparticles and resin matrix was improved using 3-methacryloxypropyltrimethoxy silane (KH-570). Furthermore, the structure and morphology of the modified HGM were characterised by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). In addition, the effects of the modified HGM on the thermal insulation, flame retardancy, and thermal properties of the composites were investigated. The thermal conductivity of the composites was lower than that of the native furan resin. The minimum thermal conductivity of the composites was 0.0274 W/m·K; the flame retardancy of the composites improved, and the limiting oxygen index become a maximum of 31.6%, reaching the refractory material level. Furthermore, the thermal analysis of the composites demonstrated enhanced thermal stability. This study demonstrates that the composite material exhibited good thermal insulation performance and flame retardancy and that it can be applied in the field of thermal insulation. Full article

(This article belongs to the Special Issue Reinforced Polymer Composites II)

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10 pages, 1729 KiB

Open AccessArticle

Tensile Properties of Composite Reinforced with Three-Dimensional Printed Fibers

by Komal Agarwal, Rahul Sahay and Avinash Baji

Polymers 2020, 12(5), 1089; https://doi.org/10.3390/polym12051089 - 10 May 2020

Cited by 10 | Viewed by 4231

Abstract

This study used melt-electrospinning writing to fabricate three-dimensional fiber constructs by embedding them in a polyvinyl alcohol (PVA) matrix to obtain thin composite films. Fourier transform infrared spectroscopy (FTIR) and dynamic scanning calorimetry (DSC) were used to demonstrate an interaction between the polycaprolactone [...] Read more.

This study used melt-electrospinning writing to fabricate three-dimensional fiber constructs by embedding them in a polyvinyl alcohol (PVA) matrix to obtain thin composite films. Fourier transform infrared spectroscopy (FTIR) and dynamic scanning calorimetry (DSC) were used to demonstrate an interaction between the polycaprolactone (PCL) fibrous phase and the PVA matrix phase. Following this, the mechanical deformation behavior of the composite was investigated, and the effect of reinforcement with three-dimensional fibrous constructs was illustrated. The specific strength of the composite was found to be five times higher than the specific strength of the neat PVA matrix. Additionally, the specific toughness of the composite was determined to be roughly four times higher than the specific toughness determined for the neat PVA matrix. These results demonstrate the potential of using melt-electrospinning writing for producing three-dimensional fibrous constructs for composite reinforcement purposes. Full article

(This article belongs to the Special Issue Reinforced Polymer Composites II)

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Review

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48 pages, 4163 KiB

Open AccessReview

Mechanical Joining of Fibre Reinforced Polymer Composites to Metals—A Review. Part I: Bolted Joining

by Anna Galińska

Polymers 2020, 12(10), 2252; https://doi.org/10.3390/polym12102252 - 30 Sep 2020

Cited by 83 | Viewed by 12828

Abstract

As the fibre reinforced plastic composites gain larger and larger share in industry, the problem of joining them with metal elements becomes significant. The current paper is the first part of the literature review, which gathers and evaluates knowledge about methods suitable for [...] Read more.

As the fibre reinforced plastic composites gain larger and larger share in industry, the problem of joining them with metal elements becomes significant. The current paper is the first part of the literature review, which gathers and evaluates knowledge about methods suitable for mechanical joining of composite and metal elements. This paper concerns bolted joining, because this method of mechanical joining is widely used for joining composite materials. The paper describes failure modes of bolted joints in composite materials, the influence of the bolt clamping torque, the clearance between the bolt and the hole and aging on the performance of the joint, drilling techniques used in composite materials in order to minimize damages, different fastener types, inspection techniques, and finally, the techniques that have been developed in order to improve the strength of the bolted joints in composites. Since the hole drilled in a composite material in order to perform bolted joining is a weak point of the structure, those techniques: bonded inserts, titanium foil internal inserts, fibre steering, additional reinforcement, and moulded holes, mainly aim to improve the strength of the hole in the composite. The techniques have been discussed in details and compared with each other in the summary section. Full article

(This article belongs to the Special Issue Reinforced Polymer Composites II)

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40 pages, 8757 KiB

Open AccessReview

Mechanical Joining of Fibre Reinforced Polymer Composites to Metals—A Review. Part II: Riveting, Clinching, Non-Adhesive Form-Locked Joints, Pin and Loop Joining

by Anna Galińska and Cezary Galiński

Polymers 2020, 12(8), 1681; https://doi.org/10.3390/polym12081681 - 28 Jul 2020

Cited by 71 | Viewed by 12196

Abstract

As fiber reinforced plastic composites gain an increasingly larger share in aerospace structures, the problem of joining them with metal elements becomes significant. The current paper is the second part of the literature review, which gathers and evaluates knowledge about methods suitable for [...] Read more.

As fiber reinforced plastic composites gain an increasingly larger share in aerospace structures, the problem of joining them with metal elements becomes significant. The current paper is the second part of the literature review, which gathers and evaluates knowledge about methods suitable for the mechanical joining of composite and metal elements. This paper reviews the joining methods other than bolted joining, which are discussed in the first part of the review, namely self-piercing riveting, friction riveting, clinching, non-adhesive form-locked joints, pin joints, and loop joints. Some of those methods are full-fledged and employed in commercial applications, whereas others are merely ideas tested at the level of specimens. The current review describes the ideas and the qualities of the joining methods as well as the experimental work carried out so far. The summary section of this paper contains a comparison of those methods with the reference to their qualities, which is important from the point of view of a composite structure designer: possibility of the joint disassembly, damages induced in composite, complication level, weight penalty, range of possible materials to be joined, and the joint strength. Full article

(This article belongs to the Special Issue Reinforced Polymer Composites II)

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24 pages, 2557 KiB

Open AccessReview

Strength Degradation in Curved Fiber-reinforced Polymer (FRP) Bars Used as Concrete Reinforcement

by Thanongsak Imjai, Reyes Garcia, Maurizio Guadagnini and Kypros Pilakoutas

Polymers 2020, 12(8), 1653; https://doi.org/10.3390/polym12081653 - 24 Jul 2020

Cited by 27 | Viewed by 7016

Abstract

Steel reinforcements in concrete tend to corrode and this process can lead to structural damage. Fiber-reinforced polymer (FRP) reinforcements represent a viable alternative for structures exposed to aggressive environments and have many possible applications where superior corrosion resistance properties are required. The use [...] Read more.

Steel reinforcements in concrete tend to corrode and this process can lead to structural damage. Fiber-reinforced polymer (FRP) reinforcements represent a viable alternative for structures exposed to aggressive environments and have many possible applications where superior corrosion resistance properties are required. The use of FRP rebars as internal reinforcements for concrete, however, is limited to specific structural elements and does not yet extend to the whole structure. The reason for this relates to the limited availability of curved or shaped reinforcing FRP elements on the market, as well as their reduced structural performance. This article presents a state-of-the art review on the strength degradation of curved FRP composites, and also assesses the performance of existing predictive models for the bend capacity of FRP reinforcements. Previous research has shown that the mechanical performance of bent portions of FRP bars significantly reduces under a multiaxial combination of stresses. Indeed, the tensile strength of bent FRP bars can be as low as 25% of the maximum tensile strength developed in a straight counterpart. In a significant number of cases, the current design recommendations for concrete structures reinforced with FRP were found to overestimate the bend capacity of FRP bars. A more accurate and practical predictive model based on the Tsai–Hill failure criteria is also discussed. This review article also identifies potential challenges and future directions of research for exploring the use of curved/shaped FRP composites in civil engineering applications. Full article

(This article belongs to the Special Issue Reinforced Polymer Composites II)

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