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Polymers
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Fiber and Polymer Composites: Processing, Simulation, Properties and Applications II
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Fiber and Polymer Composites: Processing, Simulation, Properties and Applications II

A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Polymer Fibers".

Deadline for manuscript submissions: closed (25 January 2024) | Viewed by 20133

Special Issue Editor

Dr. Zina Vuluga

E-Mail Website1 Website2
Guest Editor
Polymers Department, Nanocomposite Group, National Institute for Research and Development in Chemistry and Petrochemistry, ICECHIM, Bucharest, Romania
Interests: synthetic/natural nanofillers; synthetic/natural polymer (nano)composites; bio-based thermoplastics; melt processing; polymer masterbatches; automotive/packaging/biomedicine applications
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Polymer composites reinforced with fibers are a promising alternative to metal parts and the solution for light construction materials. Due to their exceptional properties (flexibility, functionality and formability in complicated design parts), fiber-reinforced polymer composites have found applications in many industrial fields (construction, automobile, aerospace), biomedicine, marine and others. The performance of the polymeric composite material mainly depends on the nature of the components, the degree of interaction between the components and the processing technology.

The purpose of this Special Issue is to highlight the latest original results in the development of composite materials based on synthetic and/or natural polymers and synthetic and/or natural fibers, with improved properties imposed by various applications.

Dr. Zina Vuluga
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Polymers is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • synthetic and/or natural fibers
  • synthetic and/or natural polymers
  • polymer composites
  • processing technology
  • modelling, simulation and optimization
  • properties
  • applications

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Published Papers (16 papers)

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Research

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21 pages, 9016 KiB  
Article
New Composites Derived from the Natural Fiber Polymers of Discarded Date Palm Surface and Pineapple Leaf Fibers for Thermal Insulation and Sound Absorption
by Mohamed Ali, Zeyad Al-Suhaibani, Redhwan Almuzaiqer, Ali Albahbooh, Khaled Al-Salem and Abdullah Nuhait
Polymers 2024, 16(7), 1002; https://doi.org/10.3390/polym16071002 - 06 Apr 2024
Viewed by 396
Abstract
New composites made of natural fiber polymers such as wasted date palm surface fiber (DPSF) and pineapple leaf fibers (PALFs) are developed in an attempt to lower the environmental impact worldwide and, at the same time, produce eco-friendly insulation materials. Composite samples of [...] Read more.
New composites made of natural fiber polymers such as wasted date palm surface fiber (DPSF) and pineapple leaf fibers (PALFs) are developed in an attempt to lower the environmental impact worldwide and, at the same time, produce eco-friendly insulation materials. Composite samples of different compositions are obtained using wood adhesive as a binder. Seven samples are prepared: two for the loose natural polymers of PALF and DPSF, two for the composites bound by single materials of PALF and DPSF using wood adhesive as a binder, and three composites of both materials and the binder with different compositions. Sound absorption coefficients (SACs) are obtained for bound and hybrid composite samples for a wide range of frequencies. Flexural moment tests are determined for these composites. A thermogravimetric analysis test (TGA) and the moisture content are obtained for the natural polymers and composites. The results show that the average range of thermal conductivity coefficient is 0.042–0.06 W/(m K), 0.052–0.075 W/(m K), and 0.054–0.07 W/(m K) for the loose fiber polymers, bound composites, and hybrid composites, respectively. The bound composites of DPSF have a very good sound absorption coefficient (>0.5) for almost all frequencies greater than 300 Hz, followed by the hybrid composite ones for frequencies greater than 1000 Hz (SAC > 0.5). The loose fiber polymers of PALF are thermally stable up to 218 °C. Most bound and hybrid composites have a good flexure modulus (6.47–64.16 MPa) and flexure stress (0.43–1.67 Mpa). The loose fiber polymers and bound and hybrid composites have a low moisture content below 4%. These characteristics of the newly developed sustainable and biodegradable fiber polymers and their composites are considered promising thermal insulation and sound absorption materials in replacing synthetic and petrochemical insulation materials in buildings and other engineering applications. Full article
(This article belongs to the Special Issue Fiber and Polymer Composites: Processing, Simulation, Properties and Applications II)
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17 pages, 12429 KiB  
Article
Artificial Neural Network Approach for Assessing Mechanical Properties and Impact Performance of Natural-Fiber Composites Exposed to UV Radiation
by Khaled Nasri and Lotfi Toubal
Polymers 2024, 16(4), 538; https://doi.org/10.3390/polym16040538 - 17 Feb 2024
Viewed by 508
Abstract
Amidst escalating environmental concerns, short natural-fiber thermoplastic (SNFT) biocomposites have emerged as sustainable materials for the eco-friendly production of mechanical components. However, their limited durability has prompted research into the experimental evaluation of the deterioration of the mechanical characteristics of SNFT biocomposites, particularly [...] Read more.
Amidst escalating environmental concerns, short natural-fiber thermoplastic (SNFT) biocomposites have emerged as sustainable materials for the eco-friendly production of mechanical components. However, their limited durability has prompted research into the experimental evaluation of the deterioration of the mechanical characteristics of SNFT biocomposites, particularly under the influence of ultraviolet rays. However, conducting tests to evaluate the mechanical properties can be time-consuming and expensive. In this study, an artificial neural network (ANN) model was employed to predict the mechanical properties (tensile strength) and the impact performance (resistance and absorbed energy) of polypropylene reinforced with 30 wt.% short flax or wood pine fibers (referred to as PP30-F or PP30-P, respectively). Eight parameters were collected from experimental studies. The ANN input parameters comprised nondestructive test results, including mass, hardness, roughness, and natural frequencies, while the output parameters were the tensile strength, the maximum impact load, and absorbed energy. The model was developed using the ANN toolbox in MATLAB. The linear coefficient of correlation and mean squared error were selected as the metrics for evaluating the performance function and accuracy of the ANN model. They calculate the relationship and the average squared difference between the predicted and actual values. The data analysis conducted by the models demonstrated exceptional predictive capability, achieving an accuracy rate exceeding 96%, which was deemed satisfactory. For both the PP30-F and PP30-P biocomposites, the ANN predictions deviated from the experimental data by 3, 5, and 6% with regard to the impact load, absorbed energy, and tensile strength, respectively. Full article
(This article belongs to the Special Issue Fiber and Polymer Composites: Processing, Simulation, Properties and Applications II)
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14 pages, 8014 KiB  
Article
Three-Dimensional Bioprinting of Strontium-Modified Controlled Assembly of Collagen Polylactic Acid Composite Scaffold for Bone Repair
by Weiwei Sun, Wenyu Xie, Kun Hu, Zongwen Yang, Lu Han, Luhai Li, Yuansheng Qi and Yen Wei
Polymers 2024, 16(4), 498; https://doi.org/10.3390/polym16040498 - 11 Feb 2024
Viewed by 774
Abstract
In recent years, the incidence of bone defects has been increasing year by year. Bone transplantation has become the most needed surgery after a blood transfusion and shows a rising trend. Three-dimensional-printed implants can be arbitrarily shaped according to the defects of tissues [...] Read more.
In recent years, the incidence of bone defects has been increasing year by year. Bone transplantation has become the most needed surgery after a blood transfusion and shows a rising trend. Three-dimensional-printed implants can be arbitrarily shaped according to the defects of tissues and organs to achieve perfect morphological repair, opening a new way for non-traumatic repair and functional reconstruction. In this paper, strontium-doped mineralized collagen was first prepared by an in vitro biomimetic mineralization method and then polylactic acid was homogeneously blended with the mineralized collagen to produce a comprehensive bone repair scaffold by a gas extrusion 3D printing method. Characterization through scanning electron microscopy, X-ray diffraction, and mechanical testing revealed that the strontium-functionalized composite scaffold exhibits an inorganic composition and nanostructure akin to those of human bone tissue. The scaffold possesses uniformly distributed and interconnected pores, with a compressive strength reaching 21.04 MPa. The strontium doping in the mineralized collagen improved the biocompatibility of the scaffold and inhibited the differentiation of osteoclasts to promote bone regeneration. This innovative composite scaffold holds significant promise in the field of bone tissue engineering, providing a forward-thinking solution for prospective bone injury repair. Full article
(This article belongs to the Special Issue Fiber and Polymer Composites: Processing, Simulation, Properties and Applications II)
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13 pages, 2415 KiB  
Article
Estimation of Digital Porosity of Electrospun Veils by Image Analysis
by Guadalupe Cuahuizo-Huitzil, Octavio Olivares-Xometl, Paulina Arellanes-Lozada, José Oscar Laguna Cortés, Janette Arriola Morales, Claudia Santacruz-Vázquez and Verónica Santacruz-Vázquez
Polymers 2024, 16(2), 300; https://doi.org/10.3390/polym16020300 - 22 Jan 2024
Viewed by 672
Abstract
The present work reports on an empirical mathematical expression for predicting the digital porosity (DP) of electrospun nanofiber veils, employing emulsions of poly(vinyl alcohol) (PVOH) and olive and orange oils. The electrospun nanofibers were analyzed by scanning electron microscopy (SEM), observing orientation and [...] Read more.
The present work reports on an empirical mathematical expression for predicting the digital porosity (DP) of electrospun nanofiber veils, employing emulsions of poly(vinyl alcohol) (PVOH) and olive and orange oils. The electrospun nanofibers were analyzed by scanning electron microscopy (SEM), observing orientation and digital porosity (DP) in the electrospun veils. To determine the DP of the veils, the SEM micrographs were transformed into a binary system, and then the threshold was established, and the nanofiber solid surfaces were emphasized. The relationship between the experimental results and those obtained with the empirical mathematical expression displayed a correlation coefficient (R2) of 0.97 by employing threshold II. The mathematical expression took into account experimental variables such as the nanofiber humidity and emulsion conductivity prior to electrospinning, in addition to the corresponding operation conditions. The results produced with the proposed expression showed that the prediction of the DP of the electrospun veils was feasible with the considered thresholds. Full article
(This article belongs to the Special Issue Fiber and Polymer Composites: Processing, Simulation, Properties and Applications II)
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15 pages, 8447 KiB  
Article
Effects of Process Parameters in Thermoforming of Unidirectional Fibre-Reinforced Thermoplastics
by Johannes Winhard, Daisy Nestler and Lothar Kroll
Polymers 2024, 16(2), 221; https://doi.org/10.3390/polym16020221 - 12 Jan 2024
Viewed by 701
Abstract
Process-induced defects during thermoforming are widespread problems in laminate manufacturing. The aim of this study is to describe the effects of holding time and pressure on several properties of the manufactured laminate. A design of experiments is performed, followed by an analysis of [...] Read more.
Process-induced defects during thermoforming are widespread problems in laminate manufacturing. The aim of this study is to describe the effects of holding time and pressure on several properties of the manufactured laminate. A design of experiments is performed, followed by an analysis of variance to examine significant effects. Subsequently, a regression model is created to predict the laminate’s properties, which is also validated. A significant interaction between holding time and pressure is determined for the resulting tensile strength and elongation at break with a p-value of 1.52·10−16 and 0.02, respectively. The highest values of tensile strength and elongation at break are found for low settings of holding time and pressure. The fibre volume fraction is not affected by the process parameters. As holding time and pressure increase, significant fibre misalignment takes place, leading to a decrease of the mechanical properties. The regression model corresponds well with the validation and a tensile strength of 1049 MPa with an elongation at break of 2.3% is reached. Full article
(This article belongs to the Special Issue Fiber and Polymer Composites: Processing, Simulation, Properties and Applications II)
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12 pages, 4607 KiB  
Article
One-Step Preparation of Fiber-Based Chlorzoxazone Solid Dispersion by Centrifugal Spinning
by Enikő Bitay, Attila Levente Gergely and Zoltán-István Szabó
Polymers 2024, 16(1), 123; https://doi.org/10.3390/polym16010123 - 29 Dec 2023
Viewed by 721
Abstract
An amorphous fiber-based solid dispersion of chlorzoxazone was prepared for the first time by employing centrifugal spinning, using polyvinylpyrrolidone as the fiber-forming polymer. After optimization of the spinning parameters, the obtained fibers were characterized using a set of analytical techniques, both in a [...] Read more.
An amorphous fiber-based solid dispersion of chlorzoxazone was prepared for the first time by employing centrifugal spinning, using polyvinylpyrrolidone as the fiber-forming polymer. After optimization of the spinning parameters, the obtained fibers were characterized using a set of analytical techniques, both in a solid- and solution-state. Morphological characterization revealed a slightly aligned, defect-free fibrous structure with an average fiber diameter of d = 3.07 ± 1.32 μm. The differential scanning calorimetric results indicated a crystalline-to-amorphous transition of the active substance during the centrifugal spinning process, while gas chromatographic determinations revealed a residual ethanol content of 0.42 ± 0.04%. UV spectroscopy indicated the incorporation of chlorzoxazone in the fibrous structures, with an average active substance content of 15.91 ± 0.36 w/w%. During small-volume dissolution studies, the prepared fiber mats presented immediate disintegration upon contact with the dissolution media, followed by rapid dissolution of the active substance, with 84.8% dissolved at 1 min and 93.7% at 3 min, outperforming the micronized, pure chlorzoxazone. The obtained results indicate that centrifugal spinning is a low-cost, high-yield, viable alternative to the currently used methods to prepare fiber-based amorphous solid dispersions of poorly soluble drugs. The prepared chlorzoxazone-loaded microfibers could be used as a buccal dosage form for the systematic delivery of chlorzoxazone and could potentially lead to a rapid onset of action and longer efficacy of the muscle relaxant drug. Full article
(This article belongs to the Special Issue Fiber and Polymer Composites: Processing, Simulation, Properties and Applications II)
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21 pages, 6432 KiB  
Article
Polymer Composite Thermoforming: Ultrasonic-Assisted Optimization for Enhanced Adhesive Performance in Automotive Interior Components
by Liufei Yue, Weiguo Yao, Fei Teng, Yanchao Zhu, Zengxia Zhao, Ce Liang and Lijuan Zhu
Polymers 2024, 16(1), 52; https://doi.org/10.3390/polym16010052 - 22 Dec 2023
Viewed by 742
Abstract
Dual-component epoxy resins are widely used for bonding different materials in automotive interior processing. However, due to the complexity and variability of automotive interior parts, uneven temperature distribution on curved surfaces during the thermoforming process can lead to uneven thermal stress distribution, damaging [...] Read more.
Dual-component epoxy resins are widely used for bonding different materials in automotive interior processing. However, due to the complexity and variability of automotive interior parts, uneven temperature distribution on curved surfaces during the thermoforming process can lead to uneven thermal stress distribution, damaging the interior components. This study focuses on addressing the damage issues caused by uneven thermal stress distribution during the thermoforming of automotive interior components. By monitoring the temperature and strain on the adhesive surface of the interior components during processing, using sensors and combining the readings with a finite element simulation, damage to the adhesive during processing was simulated. Based on this, a segmented thermoforming method for the model surface was employed, but it was found that this method did not significantly reduce the level of damage to the adhesive during application. Building upon the segmented simulation, significant results were achieved by applying temperature modulation at a certain frequency to adjust the damage of the interior components during processing. The techniques used in this study successfully reduced the unevenness of the adhesive surface temperature, improved the performance of the adhesive during application through segmented optimization and the application of ultrasound-assisted techniques, and markedly reduced the manufacturing process’s energy consumption. Full article
(This article belongs to the Special Issue Fiber and Polymer Composites: Processing, Simulation, Properties and Applications II)
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18 pages, 13305 KiB  
Article
Upcycling of HDPE Milk Bottles into High-Stiffness, High-HDT Composites with Pineapple Leaf Waste Materials
by Taweechai Amornsakchai and Sorn Duangsuwan
Polymers 2023, 15(24), 4697; https://doi.org/10.3390/polym15244697 - 13 Dec 2023
Cited by 1 | Viewed by 1903
Abstract
In the pursuit of sustainability and reduced dependence on new plastic materials, this study explores the upcycling potential of high-density polyethylene (HDPE) milk bottles into high-stiffness, high-heat-distortion-temperature (HDT) composites. Recycled high-density polyethylene (rHDPE) sourced from used milk bottles serves as the composite matrix, [...] Read more.
In the pursuit of sustainability and reduced dependence on new plastic materials, this study explores the upcycling potential of high-density polyethylene (HDPE) milk bottles into high-stiffness, high-heat-distortion-temperature (HDT) composites. Recycled high-density polyethylene (rHDPE) sourced from used milk bottles serves as the composite matrix, while reinforcing fillers are derived from dried pineapple leaves, comprising fibers (PALF) and non-fibrous materials (NFM). A two-roll mixer is employed to prepare rHDPE/NFM and rHDPE/PALF mixtures, facilitating filler alignment in the resulting prepreg. The prepreg is subsequently stacked and pressed into composite sheets. The introduction of PALF as a reinforcing filler significantly enhances the flexural strength and modulus of the rHDPE composite. A 20 wt.% PALF content yields a remarkable 162% increase in flexural strength and a 204% increase in modulus compared to neat rHDPE. The rHDPE/NFM composite also shows improved mechanical properties, albeit to a lesser degree than fiber reinforcement. Both composites exhibit a slight reduction in impact resistance. Notably, the addition of NFM or PALF substantially elevates HDT, raising the HDT values of the composites to approximately 84 °C and 108 °C, respectively, in contrast to the 71 °C HDT of neat rHDPE. Furthermore, the overall properties of both the composites are further enhanced by improving their compatibility through maleic anhydride-modified polyethylene (MAPE) use. Impact fracture surfaces of both composites reveal higher compatibility and clear alignment of NFM and PALF fillers, underscoring the enhanced performance and environmental friendliness of composites produced from recycled plastics reinforced with pineapple leaf waste fillers. Full article
(This article belongs to the Special Issue Fiber and Polymer Composites: Processing, Simulation, Properties and Applications II)
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18 pages, 14235 KiB  
Article
Effect of Fiber Sizing Levels on the Mechanical Properties of Carbon Fiber-Reinforced Thermoset Composites
by Albraa A. Jaber, Sara A. Abbas, Abdiaziz A. Farah, Karina K. Kopeć, Yahya M. Alsalik, Mohammed A. Tayeb and Nikhil Verghese
Polymers 2023, 15(24), 4678; https://doi.org/10.3390/polym15244678 - 11 Dec 2023
Cited by 1 | Viewed by 1429
Abstract
Fiber sizing is one of the most important components in manufacturing composites by affecting mechanical properties, including strength and stiffness. The sizing of manmade fibers offers many advantages, such as improving fiber/matrix adhesion and bonding properties, protecting fiber surfaces from damage during the [...] Read more.
Fiber sizing is one of the most important components in manufacturing composites by affecting mechanical properties, including strength and stiffness. The sizing of manmade fibers offers many advantages, such as improving fiber/matrix adhesion and bonding properties, protecting fiber surfaces from damage during the processing and weaving stages, and enhancing the surface wettability of polymer matrices. In this work, the influence of fiber sizing levels on carbon fibers’ (CFs) mechanical properties is reported at room temperature using single fiber tensile testing (Favimat+), single fiber pullout testing (SFPO), and interfacial elemental analysis by X-ray photoelectron spectroscopy (XPS). Standard modulus CFs (7 ± 0.2 μm in diameter) were sized using two commercially available Michelman sizing formulations. The average solid content for each sizing formulation was 26.3 ± 0.2% and 34.1 ± 0.2%, respectively. HEXION RIMR 135 with curing agent RIMH 137 was used as a model thermoset epoxy matrix during SFPO measurements. A predictive engineering fiber sizing methodology was also developed. Sizing amounts of 0.5, 1, and 2 wt.% on the fiber surface were achieved for both sizing formulations. For each fiber size level, 50 single-fiber tensile testing experiments and 20 single-fiber pull-out tests were conducted. The ultimate tensile strength (σult) of the carbon fibers and the interfacial shear strength (τapp) of the single fiber composite were analyzed. The sizing levels’ effect on interfacial shear stress and the O/C (Oxygen/Carbon) surface composition ratio was investigated. Based on our experimental findings, an increase of 6% in fiber performance was recorded for ultimate tensile and interfacial shear strengths. As a result, generalized fiber sizing and characterization methods were established. These developed methods can be used to characterize the strength and interfacial shear strength of manmade fibers with different sizing formulations and solid contents irrespective of the matrix, i.e., thermoset or thermoplastic. Full article
(This article belongs to the Special Issue Fiber and Polymer Composites: Processing, Simulation, Properties and Applications II)
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7 pages, 795 KiB  
Communication
Shear Strength Range of GF/Polyester Composites Controlled by Plasma Nanotechnology
by Veronika Sirjovova, Milan Zvonek, Michal Jurko and Vladimir Cech
Polymers 2023, 15(16), 3331; https://doi.org/10.3390/polym15163331 - 08 Aug 2023
Viewed by 733
Abstract
Unsized single-end rovings are oxygen plasma pretreated and organosilicon plasma coated using plasma nanotechnology to optimize the interphase in glass-fiber-reinforced polyester composites and to determine the achievable range of their shear strength for potential applications. This surface modification of the fibers allows us [...] Read more.
Unsized single-end rovings are oxygen plasma pretreated and organosilicon plasma coated using plasma nanotechnology to optimize the interphase in glass-fiber-reinforced polyester composites and to determine the achievable range of their shear strength for potential applications. This surface modification of the fibers allows us to vary the shear strength of the composite in the range of 23.1 to 45.2 MPa at reduced financial costs of the process, while the commercial sizing corresponds to 39.2 MPa. The shear strength variability is controlled by the adhesion of the interlayer (plasma nanocoating) due to the variable density of chemical bonds at the interlayer/glass interface. The optimized technological conditions can be used for continuous surface modification of rovings in commercial online fiber-processing systems. Full article
(This article belongs to the Special Issue Fiber and Polymer Composites: Processing, Simulation, Properties and Applications II)
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18 pages, 6204 KiB  
Article
Mechanical Performances Analysis and Prediction of Short Plant Fiber-Reinforced PLA Composites
by Wenlong Mu, Xianglin Chen, Shijie Li, Yufeng Sun, Qingpeng Wang and Jingxin Na
Polymers 2023, 15(15), 3222; https://doi.org/10.3390/polym15153222 - 28 Jul 2023
Cited by 3 | Viewed by 1079
Abstract
Plant fiber-reinforced polylactic acid (PLA) exhibits excellent mechanical properties and environmental friendliness and, therefore, has a wide range of applications. This study investigated the mechanical properties of three short plant fiber-reinforced PLA composites (flax, jute, and ramie) using mechanical testing and material characterization [...] Read more.
Plant fiber-reinforced polylactic acid (PLA) exhibits excellent mechanical properties and environmental friendliness and, therefore, has a wide range of applications. This study investigated the mechanical properties of three short plant fiber-reinforced PLA composites (flax, jute, and ramie) using mechanical testing and material characterization techniques (SEM, FTIR, and DSC). Additionally, we propose a methodology for predicting the mechanical properties of high-content short plant fiber-reinforced composite materials. Results indicate that flax fibers provide the optimal reinforcement effect due to differences in fiber composition and microstructure. Surface pretreatment of the fibers using alkali and silane coupling agents increases the fiber–matrix interface contact area, improves interface performance, and effectively enhances the mechanical properties of the composite. The mechanical properties of the composites increase with increasing fiber content, reaching the highest value at 40%, which is 38.79% higher than pure PLA. However, further increases in content lead to fiber agglomeration and decreased composite properties. When the content is relatively low (10%), the mechanical properties are degraded because of internal defects in the material, which is 40.42% lower than pure PLA. Through Micro-CT technology, the fiber was reconstructed, and it was found that the fiber was distributed mainly along the direction of injection molding, and the twin-screw process changes the shape and length of the fiber. By introducing the fiber agglomeration factor function and correcting the Halpin-Tsai criterion, the mechanical properties of composite materials with different contents were successfully predicted. Considering the complex stress state of composite materials in actual service processes, a numerical simulation method was established based on transversely isotropic material using the finite element method combined with theoretical analysis. The mechanical properties of high-content short plant fiber-reinforced composite materials were successfully predicted, and the simulation results showed strong agreement with the experimental results. Full article
(This article belongs to the Special Issue Fiber and Polymer Composites: Processing, Simulation, Properties and Applications II)
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21 pages, 11910 KiB  
Article
Ballistic Response of a Glass Fiber Composite for Two Levels of Threat
by George Ghiocel Ojoc, Larisa Chiper Titire, Cristian Munteniță, Cătălin Pîrvu, Simona Sandu and Lorena Deleanu
Polymers 2023, 15(4), 1039; https://doi.org/10.3390/polym15041039 - 19 Feb 2023
Cited by 2 | Viewed by 1679
Abstract
This paper presents the behavior of composite panels based on glass fiber unidirectional fabrics and a bi-component epoxy resin under ballistic impacts that characterize two threat levels: FB2 and FB3, according to EN 1523:2004. The tested panels had characteristics kept in narrow ranges: [...] Read more.
This paper presents the behavior of composite panels based on glass fiber unidirectional fabrics and a bi-component epoxy resin under ballistic impacts that characterize two threat levels: FB2 and FB3, according to EN 1523:2004. The tested panels had characteristics kept in narrow ranges: thickness 18.26 ± 0.22 mm, mass ratio fabrics/panel 0.788 ± 0.015, surface density 27.51 ± 0.26 kg/m2. After testing the panels, the failure mechanisms of the panel were evidenced by scanning electron microscopy and photographs. Here the authors present a finite-element model at meso scale that was used for evaluating if the composite, initially tested at level FB2 (9 mm FMJ, v0 = 375 m/s), could withstand the higher level of impact, FB3 (projectile type 0.357 Magnum and impact velocity of v0 = 433 m/s). Simulation was performed in Explicit Dynamics (Ansys), keeping the same target but changing the projectile for the two different levels of threat. The results of the simulation were encouraging for making tests at level FB3, indicating the importance of alternating actual tests with simulations in order to achieve better protection with reduced surface weight. The simulation illustrated differences in impact duration and number of layers broken on the panel for each level. Validation of the model was based on the number of broken layers and the dimension of the delamination zone between the last two layers. Scanning electron microscopy was used for identifying failure mechanisms at the micro and meso scale. We found that damage to the composite was intensively dependent on impact velocity, this being quantitatively evaluated using the number of layers broken, the effect of delamination on separating layers and the deformation of the last layer. Full article
(This article belongs to the Special Issue Fiber and Polymer Composites: Processing, Simulation, Properties and Applications II)
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19 pages, 8342 KiB  
Article
Complex Effects of Hemp Fibers and Impact Modifiers in Multiphase Polypropylene Systems
by Denis Mihaela Panaitescu, Zina Vuluga, Adriana Nicoleta Frone, Augusta Raluca Gabor, Cristian-Andi Nicolae and Cătălina-Diana Uşurelu
Polymers 2023, 15(2), 409; https://doi.org/10.3390/polym15020409 - 12 Jan 2023
Cited by 3 | Viewed by 1445
Abstract
Natural fibers-reinforced polymer composites have progressed rapidly due to their undeniable advantages. Most of the commercial polypropylene (PP)-based materials are characterized by either high impact toughness or high stiffness, while the manufacture of PP composites with both good toughness and stiffness is challenging [...] Read more.
Natural fibers-reinforced polymer composites have progressed rapidly due to their undeniable advantages. Most of the commercial polypropylene (PP)-based materials are characterized by either high impact toughness or high stiffness, while the manufacture of PP composites with both good toughness and stiffness is challenging at present. In this work, poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS) and poly(styrene-b-butadiene-b-styrene) (SBS) copolymers were used in different amounts as modifiers in PP/hemp fibers (HF) composites, with the aim to use them for electrical vehicle parts. The interface in these multiphase systems was controlled by the addition of maleated polypropylene (MAPP). SEBS and SBS showed different effects on the elongation at break of the blends and the corresponding composites due to the HF that stiffened the multiphase systems. Similarly, a different action of MAPP was observed in the composites containing SEBS or SBS: higher Young’s and storage moduli were obtained for the composite containing SBS, while greater elongation at break and impact strength values were recorded for the SEBS-containing system. In addition, a remarkable dispersion in the MAPP-containing composite and two times smaller average particle size were revealed by the SEM analysis for the SEBS particles compared to the SBS ones. The higher affinity of SEBS for PP compared to that for SBS and the different morphological characteristics of the systems containing SEBS and SBS may explain the different effects of these impact modifiers on the mechanical properties of the composites. The composites developed in this work were designed as substitutes for the fully synthetic polymeric materials or metal components used in the manufacturing of automotive parts. Full article
(This article belongs to the Special Issue Fiber and Polymer Composites: Processing, Simulation, Properties and Applications II)
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15 pages, 4209 KiB  
Article
Development of a Novel Biobased Polyurethane Resin System for Structural Composites
by Oihane Echeverria-Altuna, Olatz Ollo, Izaskun Larraza, Cristina Elizetxea, Isabel Harismendy and Arantxa Eceiza
Polymers 2022, 14(21), 4553; https://doi.org/10.3390/polym14214553 - 27 Oct 2022
Cited by 6 | Viewed by 1757
Abstract
Polyurethanes are gaining increasing interest for their use as structural components subjected to cyclic loads, such as leaf springs. Thermoset polyurethane (PUR) based technology offers some advantages, such as fatigue resistance, low viscosity, and fast curing. However, current PUR formulations present two major [...] Read more.
Polyurethanes are gaining increasing interest for their use as structural components subjected to cyclic loads, such as leaf springs. Thermoset polyurethane (PUR) based technology offers some advantages, such as fatigue resistance, low viscosity, and fast curing. However, current PUR formulations present two major drawbacks: their petrochemical origin and high reactivity. The aim of this work was to develop a novel biobased PUR (BIO-PUR) with the required mechanical properties and processability for manufacturing structural composites by resin transfer moulding (RTM). For this purpose, a high functionality and high hydroxyl index castor-oil-based polyol was used combined with a biobased glycerol (BIO-Gly) to increase the crosslinking density and improve the final properties of the BIO-PUR. The viscosity and reactivity of the different systems were studied by means of rheology tests and differential scanning calorimetry (DSC). Thermal and mechanical properties were studied by dynamic mechanical analysis (DMA) and flexural tests. Furthermore, the RTM process of a representative part was simulated and validated through the manufacturing and testing of plates. The properties of the BIO-PUR resin systems were strongly influenced by the addition of biobased glycerol and its effect on the crosslinking density. The combination of a high functionality and hydroxyl index biobased polyol with the biobased glycerol resulted in a high-performance BIO-PUR with the required reactivity and final properties for structural applications. Full article
(This article belongs to the Special Issue Fiber and Polymer Composites: Processing, Simulation, Properties and Applications II)
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11 pages, 2833 KiB  
Article
The In-Situ Mechanical Properties of Carbon Fiber/Epoxy Composite under the Electric-Current Loading
by Runtian Zhu, Xiaolu Li, Cankun Wu, Longji Du and Xusheng Du
Polymers 2022, 14(20), 4452; https://doi.org/10.3390/polym14204452 - 21 Oct 2022
Cited by 1 | Viewed by 1236
Abstract
The Joule heating behavior of the carbon fiber/epoxy composite (CF/EP) was studied in this work, as well as their influence on the in-situ mechanical properties of the composites and their de-icing performance. The equilibrium temperature of the CF/EP composite could be conveniently adjusted [...] Read more.
The Joule heating behavior of the carbon fiber/epoxy composite (CF/EP) was studied in this work, as well as their influence on the in-situ mechanical properties of the composites and their de-icing performance. The equilibrium temperature of the CF/EP composite could be conveniently adjusted by tuning the current according to the Joule’s law. Dynamic mechanical analysis (DMA) tests indicated that the rigidity and stiffness of the fiber-reinforced composite decreased with increasing temperature, and the glass transition temperature (Tg) of the composites was around 104 °C. It was found that the flexural properties of the composites in situ, measured under the electric-current loading, depended on the current value in the range of room temperature to Tg. With increasing the loading current, either the flexural modulus or strength of CF/EP decreased gradually. Such results could be explained that the higher current loading, the larger Joule heat, led to the higher operating temperature of the composite samples and the evolution of their mechanical properties accordingly. Vickers hardness tests indicated that the micro-hardness of the composite decreased with the increase of the operating temperature, which coincided with the evolution of its flexural properties with the electric-current loading. The dependence of the failure behaviors of the CF/EP on the loading current was revealed by the analysis of their fractured surface, where micro-buckling, kinking, fiber pull-out and breakage were involved. A preliminary study indicated that less energy was consumed for the deicing of the same amount of the ice with the CF/EP composite in the case of less electric-current loading. The research on the Joule heating effect of CF/EP and their corresponding mechanical properties benefits the design and direct application of the composites under the electric-current loading. Full article
(This article belongs to the Special Issue Fiber and Polymer Composites: Processing, Simulation, Properties and Applications II)
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Review

Jump to: Research

50 pages, 7061 KiB  
Review
Fresh Properties, Strength, and Durability of Fiber-Reinforced Geopolymer and Conventional Concrete: A Review
by Osama Mohamed and Haya Zuaiter
Polymers 2024, 16(1), 141; https://doi.org/10.3390/polym16010141 - 01 Jan 2024
Cited by 3 | Viewed by 2643
Abstract
Reducing the environmental footprint of the construction industry in general and concrete in particular is essential. The addition of synthetic and natural fibers to concrete mixes at appropriate dosages enhances durability and strength and extends the lifespan of concrete infrastructures. This study reviews [...] Read more.
Reducing the environmental footprint of the construction industry in general and concrete in particular is essential. The addition of synthetic and natural fibers to concrete mixes at appropriate dosages enhances durability and strength and extends the lifespan of concrete infrastructures. This study reviews the geometric and mechanical properties of selected fibers such as steel, basalt, polypropylene, polyvinyl alcohol, polyethylene, glass, carbon, and natural fibers and their impact on concrete fresh, mechanical, and durability properties when combined in different configurations. The study focuses on the effect of blending fibers with concrete mixes that use alkali-activated binders based on recycled industrial byproducts such as slag and fly ash and thereby contribute to reduction of CO2 contribution through complete or partial replacement of Ordinary Portland cement (OPC). As a result, the effect of binder content, binder composition, alkaline activator concentration, and water-to-binder (w/b) ratio on fresh properties, mechanical strength, and durability of concrete with blended fibers is also evaluated in this study. The properties of fiber-reinforced concrete with alkali-activated binder and conventional OPC binders are compared. Fiber-reinforced concrete with alkali-activated binders that are based on industrial byproducts may represent sustainable alternatives to conventional concrete and offers competitive fresh and mechanical properties when fiber properties, fiber content, w/b ratio, binder type, and dosage are carefully considered in concrete mix design. Full article
(This article belongs to the Special Issue Fiber and Polymer Composites: Processing, Simulation, Properties and Applications II)
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