Research

19 pages, 7842 KiB

Open AccessArticle

Influence of the Fibre Content, Exposure Time, and Compaction Pressure on the Mechanical Properties of Ultraviolet-Cured Composites

by Natalia G. Pérez-de-Eulate, Ane Aranburu Iztueta, Koldo Gondra and Francisco Javier Vallejo

J. Compos. Sci. 2020, 4(1), 30; https://doi.org/10.3390/jcs4010030 - 20 Mar 2020

Cited by 5 | Viewed by 2776

Abstract

A new process for the impregnation, consolidation, and curing of glass-fibre-reinforced polyester composites was developed to reduce manufacturing costs and secure end properties that compete with other traditional materials. This new process, based on the ultraviolet (UV) curing of prepregs, could be a [...] Read more.

A new process for the impregnation, consolidation, and curing of glass-fibre-reinforced polyester composites was developed to reduce manufacturing costs and secure end properties that compete with other traditional materials. This new process, based on the ultraviolet (UV) curing of prepregs, could be a viable alternative to infusion and other processes. In this paper, we showed that glass fibre composites 3 mm thick could be easily formed using suitable photoinitiating systems. We achieved improved mechanical properties through the application of favourable parameters to traditional manufacturing processes such as hand lay-up and infusion. The prepreg polymerization was monitored by dielectric analysis (DEA), and we evaluated the relationship between the UV radiation exposure time and curing degree. Both the exposure time and compaction pressure affected the fibre content of composites and interlaminar shear strength. Experimental results showed that compaction pressures higher than 4 bar are necessary to increase the mechanical properties of the UV-cured composites. Finally, the properties of the composites manufactured by this new process were compared to the properties of composites manufactured using traditional processes such as hand lay-up and infusion. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2019)

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14 pages, 2116 KiB

Open AccessArticle

Moisture Absorption of Carbon/Epoxy Nanocomposites

by Gorkem E. Guloglu and M. Cengiz Altan

J. Compos. Sci. 2020, 4(1), 21; https://doi.org/10.3390/jcs4010021 - 20 Feb 2020

Cited by 22 | Viewed by 3231

Abstract

Moisture absorption of composites with nanoscale carbon additives such as carbon nanotubes, carbon nanofibers, graphite nanoplatelets, and carbon black is investigated using thermogravimetric data and a non-Fickian hindered diffusion (Langmuir-type) model. The moisture absorption parameters are determined using this model for six different [...] Read more.

Moisture absorption of composites with nanoscale carbon additives such as carbon nanotubes, carbon nanofibers, graphite nanoplatelets, and carbon black is investigated using thermogravimetric data and a non-Fickian hindered diffusion (Langmuir-type) model. The moisture absorption parameters are determined using this model for six different types of carbon/epoxy nanocomposites. The absorption behaviors obtained at different humidity levels and thermal environments are recovered by minimizing the error between the experimental data and model predictions, thus enabling the accurate determination of the moisture equilibrium level. The absorption behavior and the weight gain of all nanocomposites are shown to be accurately represented by this model over the entire absorption period. The presence of carbon nanomaterials is found to induce varying levels of non-Fickian behavior, governed by the nondimensional hindrance coefficient. This behavior is enhanced with the nanomaterial content and separate from the slight non-Fickian behavior of all neat epoxy samples. The molecular bonding during diffusion, as well as the interfacial moisture storage, could be among the reasons for non-Fickian behavior and should be included in the absorption models for accurate characterization of carbon/epoxy nanocomposites. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2019)

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20 pages, 3431 KiB

Open AccessArticle

Preparation of Multicomponent Biocomposites and Characterization of Their Physicochemical and Mechanical Properties

by Yuriy A. Anisimov, Duncan E. Cree and Lee D. Wilson

J. Compos. Sci. 2020, 4(1), 18; https://doi.org/10.3390/jcs4010018 - 06 Feb 2020

Cited by 9 | Viewed by 2656

Abstract

This work focused on a mutual comparison and characterization of the physicochemical properties of three-component polymer composites. Binary polyaniline–chitosan (PANI–CHT) composites were synthesized by in situ polymerization of PANI onto CHT. Ternary composites were prepared by blending with a third component, polyvinyl alcohol [...] Read more.

This work focused on a mutual comparison and characterization of the physicochemical properties of three-component polymer composites. Binary polyaniline–chitosan (PANI–CHT) composites were synthesized by in situ polymerization of PANI onto CHT. Ternary composites were prepared by blending with a third component, polyvinyl alcohol (PVA). Composites with variable PANI:CHT (25:75, 50:50 and 75:25) weight ratios were prepared whilst fixing the composition of PVA. The structure and physicochemical properties of the composites were evaluated using thermal analysis (thermogravimetric analysis (TGA), differential scanning calorimetry (DSC)) and spectroscopic methods (infrared (IR), nuclear magnetic resonance (NMR)). The equilibrium and dynamic adsorption properties of composites were evaluated by solvent swelling in water, water vapour adsorption and dye adsorption isotherms. The electrical conductivity was estimated using current–voltage curves. The mechanical properties of the samples were evaluated using dynamic mechanical analysis (DMA) and correlated with the structural parameters of the composites. The adsorption and swelling properties paralleled the change in the electrical and mechanical properties of the materials. In most cases, samples with higher content of chitosan exhibit higher adsorption and mechanical properties, and lower conductivity. Acid-doped samples showed much higher adsorption, swelling, and electrical conductivity than their undoped analogues. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2019)

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14 pages, 3118 KiB

Open AccessEditor’s ChoiceCommunication

Application of Chitosan-Clay Biocomposite Beads for Removal of Heavy Metal and Dye from Industrial Effluent

by Shanta Biswas, Taslim Ur Rashid, Tonmoy Debnath, Papia Haque and Mohammed Mizanur Rahman

J. Compos. Sci. 2020, 4(1), 16; https://doi.org/10.3390/jcs4010016 - 01 Feb 2020

Cited by 64 | Viewed by 8061

Abstract

In recent years, there has been increasing interest in developing green biocomposite for industrial wastewater treatment. In this study, prawn-shell-derived chitosan (CHT) and kaolinite rich modified clay (MC) were used to fabricate biocomposite beads with different compositions. Prepared composite beads were characterized by [...] Read more.

In recent years, there has been increasing interest in developing green biocomposite for industrial wastewater treatment. In this study, prawn-shell-derived chitosan (CHT) and kaolinite rich modified clay (MC) were used to fabricate biocomposite beads with different compositions. Prepared composite beads were characterized by FTIR, and XRD, and SEM. The possible application of the beads was evaluated primarily by measuring the adsorption efficiency in standard models of lead (II) and methylene blue (MB) dye solution, and the results show a promising removal efficiency. In addition, the composites were used to remove Cr (VI), Pb (II), and MB from real industrial effluents. From tannery effluent, 50.90% of chromium and 39.50% of lead ions were removed by composites rich in chitosan and 31.50% of MB was removed from textile effluent by a composite rich in clay. Moreover, the composite beads were found to be activated in both acidic and basic media depending on their composition, which gives a scope to their universal application in dye and heavy metal removal from wastewater from various industries. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2019)

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11 pages, 2403 KiB

Open AccessFeature PaperArticle

Animal Biopolymer-Plant Biomass Composites: Synergism and Improved Sorption Efficiency

by Mohamed H. Mohamed, Inimfon A. Udoetok and Lee D. Wilson

J. Compos. Sci. 2020, 4(1), 15; https://doi.org/10.3390/jcs4010015 - 01 Feb 2020

Cited by 13 | Viewed by 2236

Abstract

Pelletized biomaterial composites that contain chitosan (C) and torrefied wheat straw (S) at variable weight composition (C:S) were prepared using a facile blending process. The fractional content of the wheat straw was studied to elucidate the role of biomass on the pelletized product [...] Read more.

Pelletized biomaterial composites that contain chitosan (C) and torrefied wheat straw (S) at variable weight composition (C:S) were prepared using a facile blending process. The fractional content of the wheat straw was studied to elucidate the role of biomass on the pelletized product and effects of S-content on the physicochemical properties relevant to adsorption phenomena. Chitosan pellets (with and without S) were characterized by spectroscopic (FT-IR and ¹³C NMR) and thermal (TGA and DSC) techniques to provide support for their respective C:S composition. Confocal microscopy using fluorescein (FL) as a dye probe revealed the presence and an increase in the accessibility of the active sites for the composite pellets according to the S-content (wt %). Equilibrium and kinetic sorption studies using FL and reactive black (RB) dyes revealed an incremental adsorption affinity of the pellets with anionic dyes in variable charge states (FL and RB). The trend for dye adsorption parallels the incremental S-content (wt %) in the composite pellets. This study reports a first-example of a low-cost, facile, and sustainable approach for the valorization of straw and chitosan suitable for sorption-based applications in aqueous media. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2019)

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16 pages, 2025 KiB

Open AccessArticle

A Dimensionless Characteristic Number for Process Selection and Mold Design in Composites Manufacturing: Part I—Theory

by Claudio Di Fratta, Yixun Sun, Philippe Causse and François Trochu

J. Compos. Sci. 2020, 4(1), 11; https://doi.org/10.3390/jcs4010011 - 18 Jan 2020

Cited by 5 | Viewed by 2958

Abstract

The present article introduces a dimensionless number devised to assist composite engineers in the fabrication of continuous fiber composites by Liquid Composite Molding (LCM), i.e., by injecting a liquid polymer resin through a fibrous reinforcement contained in a closed mold. This dimensionless number [...] Read more.

The present article introduces a dimensionless number devised to assist composite engineers in the fabrication of continuous fiber composites by Liquid Composite Molding (LCM), i.e., by injecting a liquid polymer resin through a fibrous reinforcement contained in a closed mold. This dimensionless number is calculated by integrating the ratio of the injection pressure to the liquid viscosity over the cavity filling time. It is hereby called the “injectability number” and provides an evaluation of the difficulty to inject a liquid into a porous material for a given part geometry, permeability distribution, and position of the inlet gate. The theoretical aspects behind this new concept are analyzed in Part I of the article, which demonstrates the invariance of the injectability number with respect to process parameters like constant and varying injection pressure or flow rate. Part I also details how process engineers can use the injectability number to address challenges in composite fabrication, such as process selection, mold design, and parameter optimization. Thanks to the injectability number, the optimal position of the inlet gate can be assessed and injection parameters scaled to speed up mold design. Part II of the article completes the demonstration of the novel concept by applying it to a series of LCM process examples of increasing complexity. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2019)

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17 pages, 10547 KiB

Open AccessArticle

A Dimensionless Characteristic Number for Process Selection and Mold Design in Composites Manufacturing: Part II—Applications

by Claudio Di Fratta, Yixun Sun, Philippe Causse and François Trochu

J. Compos. Sci. 2020, 4(1), 10; https://doi.org/10.3390/jcs4010010 - 18 Jan 2020

Cited by 3 | Viewed by 2724

Abstract

The dimensionless “injectability number” was devised to assist composite engineers in the fabrication of continuous fiber composites by Liquid Composite Molding (LCM), i.e., by injecting a liquid polymer resin through a fibrous reinforcement contained in a mold cavity. Part I of [...] Read more.

The dimensionless “injectability number” was devised to assist composite engineers in the fabrication of continuous fiber composites by Liquid Composite Molding (LCM), i.e., by injecting a liquid polymer resin through a fibrous reinforcement contained in a mold cavity. Part I of this article introduced the injectability number as the integral of the ratio of the injection pressure to the resin viscosity over the cavity filling time and analyzed the theoretical aspects behind this new concept. For a given mold configuration and reinforcement material characteristics, the invariance of the injectability number with regard to process parameters was demonstrated, and an initial verification in unidirectional injection cases was conducted. Part II completes the analysis by evaluating the injectability number in more complex application cases, confirming its invariance properties. The investigation, which was carried out using numerical simulations of different LCM processes and injection strategies, examined the fabrication of various composite parts: a rectangular laminate, a hood for automotive applications, a reservoir box and a fuselage section for the aerospace industry. The results indicate that more efficient injection strategies lead to lower values of the injectability number, thus enabling the use of this dimensionless number as a tool to assess the difficulty to manufacture a given part by LCM as well as to guide process selection and compare different mold configurations. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2019)

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12 pages, 4974 KiB

Open AccessArticle

Micro Flowers of SrS/Bi₂S₃ Nanocomposite and Its Field Emission Properties

by Aarti R. Gunjal, Ujjwala P. Chothe, Yogesh A. Sethi, Rajendra P. Panmand, Jalinder D. Ambekar, Milind V. Kulkarni, Mahendra A. More and Bharat B. Kale

J. Compos. Sci. 2019, 3(4), 105; https://doi.org/10.3390/jcs3040105 - 03 Dec 2019

Cited by 6 | Viewed by 2294

Abstract

The three-dimensional hierarchical SrS/Bi₂S₃ heterostructures were synthesized by a template-free single-step hydrothermal method. The structural and morphological studies revealed the formation of a single crystalline orthorhombic heterostructure with rod-like morphologies possessing a high aspect ratio. The field emission properties of [...] Read more.

The three-dimensional hierarchical SrS/Bi₂S₃ heterostructures were synthesized by a template-free single-step hydrothermal method. The structural and morphological studies revealed the formation of a single crystalline orthorhombic heterostructure with rod-like morphologies possessing a high aspect ratio. The field emission properties of SrS/Bi₂S₃ nanorods were investigated. J–E and the Fowler–Nordheim (F–N) plot, as well as long-term field emission (FE) stability, were studied. SrS/Bi₂S₃ nanoflowers have enhanced the FE properties more than the virgin Bi₂S₃. The observed values of the re-producible turn-on field for SrS/Bi₂S₃ defined to draw an emission current density of ca. 1 µA/cm² were found to be ca. 2.50 V/µm, and of the threshold field to draw a current density of ca. 10 µA/cm² were found to be ca. 3.00 V/µm (without visible light illumination). A maximum emission current density of ca. 527 μA/cm² was drawn without light and a current density of ca. 1078 μA/cm² with light, which is higher than that of pristine Bi₂S₃. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2019)

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30 pages, 15642 KiB

Open AccessArticle

A Family of C⁰ Quadrilateral Plate Elements Based on the Refined Zigzag Theory for the Analysis of Thin and Thick Laminated Composite and Sandwich Plates

by Marco Di Sciuva and Matteo Sorrenti

J. Compos. Sci. 2019, 3(4), 100; https://doi.org/10.3390/jcs3040100 - 16 Nov 2019

Cited by 4 | Viewed by 3399

Abstract

The present work focuses on the formulation and numerical assessment of a family of C⁰ quadrilateral plate elements based on the refined zigzag theory (RZT). Specifically, four quadrilateral plate elements are developed and numerically tested: The classical bi-linear 4-node element (RZT4), the [...] Read more.

The present work focuses on the formulation and numerical assessment of a family of C⁰ quadrilateral plate elements based on the refined zigzag theory (RZT). Specifically, four quadrilateral plate elements are developed and numerically tested: The classical bi-linear 4-node element (RZT4), the serendipity 8-node element (RZT8), the virgin 8-node element (RZT8v), and the 4-node anisoparametric constrained element (RZT4c). To assess the relative merits and drawbacks, numerical tests on bending (maximum deflection and stresses) and free vibration analysis of laminated composite and sandwich plates under different boundary conditions and transverse load distributions are performed. Convergences studies with regular and distorted meshes, transverse shear-locking effect for thin and very thin plates are carried out. It is concluded that the bi-linear 4-node element (RZT4) has performances comparable to the other elements in the range of thin plates when reduced integration is adopted but presents extra zero strain energy modes. The serendipity 8-node element (RZT8), the virgin 8-node element (RZT8v), and the 4-node anisoparametric constrained element (RZT4c) show remarkable performance and predictive capabilities for various problems, and transverse shear-locking is greatly relieved, at least for aspect ratio equal to 5 × 10², without using any reduced integration scheme. Moreover, RZT4c has well-conditioned element stiffness matrix, contrary to RZT4 using reduced integration strategy, and has the same computational cost of the RZT4 element. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2019)

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11 pages, 424 KiB

Open AccessArticle

Boundary Characteristic Bernstein Polynomials Based Solution for Free Vibration of Euler Nanobeams

by Somnath Karmakar and Snehashish Chakraverty

J. Compos. Sci. 2019, 3(4), 99; https://doi.org/10.3390/jcs3040099 - 13 Nov 2019

Viewed by 2225

Abstract

This paper is concerned with the free vibration problem of nanobeams based on Euler–Bernoulli beam theory. The governing equations for the vibration of Euler nanobeams are considered based on Eringen’s nonlocal elasticity theory. In this investigation, computationally efficient Bernstein polynomials have been used [...] Read more.

This paper is concerned with the free vibration problem of nanobeams based on Euler–Bernoulli beam theory. The governing equations for the vibration of Euler nanobeams are considered based on Eringen’s nonlocal elasticity theory. In this investigation, computationally efficient Bernstein polynomials have been used as shape functions in the Rayleigh-Ritz method. It is worth mentioning that Bernstein polynomials make the computation efficient to obtain the frequency parameters. Different classical boundary conditions are considered to address the titled problem. Convergence of frequency parameters is also tested by increasing the number of Bernstein polynomials in the simulation. Further, comparison studies of the results with existing literature are done after fixing the number of polynomials required from the said convergence study. This shows the efficacy and powerfulness of the method. The novelty of using the Bernstein polynomials is addressed in detail and solutions obtained by this method provide a better representation of the vibration behavior of Euler nanobeams. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2019)

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13 pages, 3315 KiB

Open AccessArticle

Composite Electrodes of Activated Carbon and Multiwall Carbon Nanotubes Decorated with Silver Nanoparticles for High Power Energy Storage

by Foivos Markoulidis, Nadia Todorova, Rossana Grilli, Constantina Lekakou and Christos Trapalis

J. Compos. Sci. 2019, 3(4), 97; https://doi.org/10.3390/jcs3040097 - 08 Nov 2019

Cited by 14 | Viewed by 3174

Abstract

Composite materials in electrodes for energy storage devices can combine different materials of high energy density, in terms of high specific surface area and pseudocapacitance, with materials of high power density, in terms of high electrical conductivity and features lowering the contact resistance [...] Read more.

Composite materials in electrodes for energy storage devices can combine different materials of high energy density, in terms of high specific surface area and pseudocapacitance, with materials of high power density, in terms of high electrical conductivity and features lowering the contact resistance between electrode and current collector. The present study investigates composite coatings as electrodes for supercapacitors with organic electrolyte 1.5 M TEABF₄ in acetonitrile. The composite coatings contain high surface area activated carbon (AC) with only 0.15 wt% multiwall carbon nanotubes (MWCNTs) which, dispersed to their percolation limit, offer high conductivity. The focus of the investigations is on the decoration of MWCNTs with silver nanoparticles, where smaller Ag crystallites of 16.7 nm grew on carboxylic group-functionalized MWCNTs, MWCNT–COOH, against 27–32 nm Ag crystallites grown on unfunctionalized MWCNTs. All Ag-decorated MWCNTs eliminate the contact resistance between the composite electrode and the current collector that exists when undecorated MWCNTs are used in the composite electrodes. Ag-decorated MWCNT–COOH tripled the power density and Ag-decorated MWCNT additive doubled the power density and increased the maximum energy density by 6%, due to pseudocapacitance of Ag, compared to composite electrodes with undecorated MWCNTs. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2019)

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20 pages, 2126 KiB

Open AccessFeature PaperArticle

Thermoelastic Stress and Deformation Analyses of Functionally Graded Doubly Curved Shells

by Chih-Ping Wu and Yu-Wen He

J. Compos. Sci. 2019, 3(4), 94; https://doi.org/10.3390/jcs3040094 - 22 Oct 2019

Cited by 3 | Viewed by 2192

Abstract

In this paper, the authors develop Reissner’s mixed variational theorem (RMVT)-based finite layer methods for the three-dimensional (3D) coupled thermoelastic analysis of simply supported, functionally graded, doubly curved (DC) shells with temperature-independent material properties. A two-phase composite material is considered to form the [...] Read more.

In this paper, the authors develop Reissner’s mixed variational theorem (RMVT)-based finite layer methods for the three-dimensional (3D) coupled thermoelastic analysis of simply supported, functionally graded, doubly curved (DC) shells with temperature-independent material properties. A two-phase composite material is considered to form the shell, and its material properties are assumed to obey a power–law distribution of the volume fractions of the constituents through the thickness direction of the shell. The effective material properties are estimated using the Mori–Tanaka scheme. The accuracy and convergence rate of these RMVT-based finite layer methods are validated by comparing their solutions with the quasi 3D and accurate two-dimensional solutions available in the literature. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2019)

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16 pages, 5691 KiB

Open AccessArticle

Effects of Nano Organoclay and Wax on the Machining Temperature and Mechanical Properties of Carbon Fiber Reinforced Plastics (CFRP)

by Khalid El-Ghaoui, Jean-Francois Chatelain, Claudiane Ouellet-Plamondon and Ronan Mathieu

J. Compos. Sci. 2019, 3(3), 85; https://doi.org/10.3390/jcs3030085 - 20 Aug 2019

Cited by 1 | Viewed by 2931

Abstract

Carbon fiber reinforced plastics (CFRP) are appreciated for their high mechanical properties and lightness. Due to their heterogeneous nature, CFRP machining remains delicate. Damages are caused on the material and early tool wear occurs. The present study aims to evaluate the effects of [...] Read more.

Carbon fiber reinforced plastics (CFRP) are appreciated for their high mechanical properties and lightness. Due to their heterogeneous nature, CFRP machining remains delicate. Damages are caused on the material and early tool wear occurs. The present study aims to evaluate the effects of fillers on CFRP machinability and mechanical behavior. CFRP laminates were fabricated by the vacuum assisted resin transfer molding (VARTM) process, using a modified epoxy resin. Three fillers (organoclay, hydrocarbon wax, and wetting agent) were mixed with the resin prior to the laminate infusion. Milling tests were performed with polycrystalline diamond (PCD) tools, equipped with thermocouples on their teeth. Machinability was then studied through the cutting temperatures and forces. Tensile, flexural, and short-beam tests were carried out on all samples to investigate the effects of fillers on mechanical properties. Fillers, especially wax, allowed us to observe an improvement in machinability. The best improvement was observed with 1% wax and 2% organoclay, which allowed a significant decrease in the cutting forces and the temperatures, and no deteriorations were seen on mechanical properties. These results demonstrate that upgrades to CFRP machining through the addition of nanoclays and wax is a path to explore. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2019)

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17 pages, 1663 KiB

Open AccessFeature PaperArticle

Evaluation of Critical Parameters in Tensile Strength Measurement of Single Fibres

by Faisal Islam, Sébastien Joannès and Lucien Laiarinandrasana

J. Compos. Sci. 2019, 3(3), 69; https://doi.org/10.3390/jcs3030069 - 09 Jul 2019

Cited by 19 | Viewed by 6266

Abstract

Mechanical properties of fibre reinforced composites are primarily dependent on those of fibres. Fibre properties are used for estimating the damage and strength behaviour of composite materials and structures. Tensile strength of fibres is commonly determined by single fibre tensile tests, which is [...] Read more.

Mechanical properties of fibre reinforced composites are primarily dependent on those of fibres. Fibre properties are used for estimating the damage and strength behaviour of composite materials and structures. Tensile strength of fibres is commonly determined by single fibre tensile tests, which is challenging and is prone to measurement errors. In this study, different possible sources of errors due to experimental limitations in the fibre testing process were identified. Their effect on fibre tensile strength was analytically modelled. This model was used to evaluate the uncertainty in experimentally determined fibre strength. A sensitivity analysis was conducted to rank the relative significance of input quantities on the calculated fibre strength. Since composite models require fibre properties determined at very small gauge lengths, the results of the sensitivity analysis were extrapolated to determine critical parameters for tests done at those small gauge lengths of a few millimetres. It was shown that, for sufficiently long fibres, their strength depends mainly on the diameter and failure force; however, for shorter gauge lengths, the effects of misalignment become very significant. The knowledge of uncertainty would be useful in estimating the reliability of the predictions made by composite strength models on the damage and failure behaviour of composite materials and structures. Minimising the influence of critical parameters on fibre strength would help in designing improved single fibre testing systems capable of determining fibre strength more accurately. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2019)

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13 pages, 4784 KiB

Open AccessFeature PaperArticle

Effect of Different Types of Block Copolymers on Morphology, Mechanical Properties, and Fracture Mechanisms of Bisphenol-F Based Epoxy System

by Ankur Bajpai and Bernd Wetzel

J. Compos. Sci. 2019, 3(3), 68; https://doi.org/10.3390/jcs3030068 - 04 Jul 2019

Cited by 20 | Viewed by 3435

Abstract

The effect of adding different types of soft block copolymer on the tensile properties, fracture mechanic properties, and thermo-mechanical properties of bisphenol F based epoxy resin were studied. Two different self-assembling block copolymers, (a) constituting of a center block of poly (butyl acrylate) [...] Read more.

The effect of adding different types of soft block copolymer on the tensile properties, fracture mechanic properties, and thermo-mechanical properties of bisphenol F based epoxy resin were studied. Two different self-assembling block copolymers, (a) constituting of a center block of poly (butyl acrylate) and two side blocks of poly (methyl) methacrylate-co-polar co-monomer (BCP 1) and (b) poly(ethylene oxide)-b-poly(butylene oxide) (PEO-PBO) diblock copolymer (BCP 2), were used with an epoxy-hardener system. The maximum fracture toughness and fracture energy were measured as K_Ic = 2.75 MPa·m^1/2 and G_Ic = 2.37 kJ/m² for the 10 wt % of BCP 1 modified system, which were 366% and 2270% higher in comparison to reference epoxy system, and a 63% reduction in tensile strength was also observed. Similarly, for BCP2 modified systems, the maximum value of K_Ic = 1.65 MPa·m^1/2 and G_Ic = 1.10 kJ/m² was obtained for epoxy modified with 12 wt % of BCP2 and a reduction of 32% in tensile strength. The fracture toughness and fracture energy were co-related to the plastic zone size for all the modified systems. Finally, the analysis of the fracture surfaces revealed the toughening micro-mechanisms of the nanocomposites. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2019)

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22 pages, 9630 KiB

Open AccessFeature PaperArticle

Analysis and Evaluation of Fiber Orientation Reconstruction Methods

by Kevin Breuer, Markus Stommel and Wolfgang Korte

J. Compos. Sci. 2019, 3(3), 67; https://doi.org/10.3390/jcs3030067 - 04 Jul 2019

Cited by 29 | Viewed by 4869

Abstract

The calculation of the fiber orientation of short fiber-reinforced plastics with the Fokker–Planck equation requires a considerable numerical effort, which is practically not feasible for injection molding simulations. Therefore, only the fiber orientation tensors are determined, i.e., by the Folgar–Tucker equation, which requires [...] Read more.

The calculation of the fiber orientation of short fiber-reinforced plastics with the Fokker–Planck equation requires a considerable numerical effort, which is practically not feasible for injection molding simulations. Therefore, only the fiber orientation tensors are determined, i.e., by the Folgar–Tucker equation, which requires much less computational effort. However, spatial fiber orientation must be reconstructed from the fiber orientation tensors in advance for structural simulations. In this contribution, two reconstruction methods were investigated and evaluated using generated test scenarios and experimentally measured fiber orientation. The reconstruction methods include spherical harmonics up to the 8th order and the method of maximum entropy, with which a Bingham distribution is reconstructed. It is shown that the quality of the reconstruction depends massively on the original fiber orientation to be reconstructed. If the original distribution can be regarded as a Bingham distribution in good approximation, the method of maximum entropy is superior to spherical harmonics. If there is no Bingham distribution, spherical harmonics is more suitable due to its greater flexibility, but only if sufficiently high orders of the fiber orientation tensor can be determined exactly. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2019)

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15 pages, 7655 KiB

Open AccessFeature PaperArticle

The Role of Multiwalled Carbon Nanotubes in the Mechanical, Thermal, Rheological, and Electrical Properties of PP/PLA/MWCNTs Nanocomposites

by Sohrab Azizi, Morteza Azizi and Maryam Sabetzadeh

J. Compos. Sci. 2019, 3(3), 64; https://doi.org/10.3390/jcs3030064 - 01 Jul 2019

Cited by 29 | Viewed by 4323

Abstract

Polypropylene/polylactic acid (PP/PLA) blend (10–40% of PLA) and PP/PLA/MWCNTs nanocomposites (0.5, 1, and 2 wt% of MWCNTs) were prepared via melt compounding. Scanning electron microscopy revealed a co-continuous PLA phase in the PP/PLA blends with high PLA content. Moreover, the addition of 2 [...] Read more.

Polypropylene/polylactic acid (PP/PLA) blend (10–40% of PLA) and PP/PLA/MWCNTs nanocomposites (0.5, 1, and 2 wt% of MWCNTs) were prepared via melt compounding. Scanning electron microscopy revealed a co-continuous PLA phase in the PP/PLA blends with high PLA content. Moreover, the addition of 2 wt% multi-walled carbon nanotubes (MWCNTs) increased the tensile modulus and tensile strength of the PP/PLA40% by 60% and 95%, respectively. A conductive network was found with the addition of 2 wt% MWCNTs, where the electrical conductivity of the PP/PLA increased by nine orders of magnitude. At 2 wt% MWCNTs, a solid network within the composite was characterized by rheological assessment, where the composite turned from nonterminal to terminal behavior. Soil burial testing of the PP/PLA blend within 30 days in natural humus compost soil featured suitable biodegradation, which indicates the PP/PLA blend is as an appropriate candidate for food packing applications. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2019)

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Review

Jump to: Research, Other

41 pages, 31085 KiB

Open AccessReview

Review of Through-the-Thickness Reinforced z-Pinned Composites

by Vassilis Kostopoulos, Nikolaos Sarantinos and Stavros Tsantzalis

J. Compos. Sci. 2020, 4(1), 31; https://doi.org/10.3390/jcs4010031 - 20 Mar 2020

Cited by 27 | Viewed by 3616

Abstract

This work reviews the effects of z-Pins used in composite laminates as through-the-thickness reinforcement to increase the composite’s properties in the out-of-plane direction. The paper presents the manufacture and microstructure of this reinforcement type while also incorporating the impact of z-Pins on the [...] Read more.

This work reviews the effects of z-Pins used in composite laminates as through-the-thickness reinforcement to increase the composite’s properties in the out-of-plane direction. The paper presents the manufacture and microstructure of this reinforcement type while also incorporating the impact of z-Pins on the mechanical properties of the composite. Mechanical properties include tensile, compression, flexure properties in static, dynamic and fatigue loads. Additionally, mode I and mode II properties in both static and fatigue loading are presented, as well as hygrothermal, impact and compression after impact properties. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2019)

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15 pages, 3084 KiB

Open AccessEditor’s ChoiceReview

Structural Health Monitoring for Advanced Composite Structures: A Review

by Alfredo Güemes, Antonio Fernandez-Lopez, Angel Renato Pozo and Julián Sierra-Pérez

J. Compos. Sci. 2020, 4(1), 13; https://doi.org/10.3390/jcs4010013 - 27 Jan 2020

Cited by 143 | Viewed by 11163

Abstract

Condition-based maintenance refers to the installation of permanent sensors on a structure/system. By means of early fault detection, severe damage can be avoided, allowing efficient timing of maintenance works and avoiding unnecessary inspections at the same time. These are the goals for structural [...] Read more.

Condition-based maintenance refers to the installation of permanent sensors on a structure/system. By means of early fault detection, severe damage can be avoided, allowing efficient timing of maintenance works and avoiding unnecessary inspections at the same time. These are the goals for structural health monitoring (SHM). The changes caused by incipient damage on raw data collected by sensors are quite small, and are usually contaminated by noise and varying environmental factors, so the algorithms used to extract information from sensor data need to focus on sensitive damage features. The developments of SHM techniques over the last 20 years have been more related to algorithm improvements than to sensor progress, which essentially have been maintained without major conceptual changes (with regards to accelerometers, piezoelectric wafers, and fiber optic sensors). The main different SHM systems (vibration methods, strain-based fiber optics methods, guided waves, acoustic emission, and nanoparticle-doped resins) are reviewed, and the main issues to be solved are identified. Reliability is the key question, and can only be demonstrated through a probability of detection (POD) analysis. Attention has only been paid to this issue over the last ten years, but now it is a growing trend. Simulation of the SHM system is needed in order to reduce the number of experiments. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2019)

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37 pages, 3501 KiB

Open AccessReview

A Survey of Scrutinizing Delaminated Composites via Various Categories of Sensing Apparatus

by Khadijeh Askaripour and Arkadiusz Zak

J. Compos. Sci. 2019, 3(4), 95; https://doi.org/10.3390/jcs3040095 - 30 Oct 2019

Cited by 14 | Viewed by 3787

Abstract

Scrutinizing delaminated composites is extensively conducted based on measurements of various types of nondestructive sensing apparatus, classified herein as systems of thermographic inspection, piezoelectric inspection, optical interferometric inspection, electromagnetic testing, ultrasonic testing, and visual testing. The development of the subject has been reviewed [...] Read more.

Scrutinizing delaminated composites is extensively conducted based on measurements of various types of nondestructive sensing apparatus, classified herein as systems of thermographic inspection, piezoelectric inspection, optical interferometric inspection, electromagnetic testing, ultrasonic testing, and visual testing. The development of the subject has been reviewed during 2000–2017. Not only does the substantial corresponding literature strongly indicates numerous increasing industrial demand for composites, including carbon fiber-reinforced polymer, glass fiber-reinforced polymer, and fiber-reinforced metal laminate, but also the significant potential of composites to delaminate when subjected particularly to impact, machining operation or manufacturing imperfections. Conducting a study on the corresponding literature, the subject of delamination inspection within composites is found to be a dynamic, mature field, while lacking a thorough literature review. Therefore, the present study addresses the mentioned gap regarding various sensation systems utilized so as to detect internal anomalies in composites for the review arrangement. To that end, the literature inclusion in terms of citation times is electronically adopted associated with an appropriate combination of keywords. The study may be considered as a comprehensive, up-to-date review covering all delamination inspection techniques founded on sensation systems, thus benefiting the readers with information in an organized configuration. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2019)

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28 pages, 2522 KiB

Open AccessDiscussion

Research and Development in Carbon Fibers and Advanced High-Performance Composites Supply Chain in Europe: A Roadmap for Challenges and the Industrial Uptake

by Elias P. Koumoulos, Aikaterini-Flora Trompeta, Raquel-Miriam Santos, Marta Martins, Cláudio Monterio dos Santos, Vanessa Iglesias, Robert Böhm, Guan Gong, Agustin Chiminelli, Ignaas Verpoest, Paul Kiekens and Costas A. Charitidis

J. Compos. Sci. 2019, 3(3), 86; https://doi.org/10.3390/jcs3030086 - 22 Aug 2019

Cited by 81 | Viewed by 11811

Abstract

Structural materials, typically based on metal, have been gradually substituted by high-performance composites based on carbon fibers, embedded in a polymer matrix, due to their potential to provide lighter, stronger, and more durable solutions. In the last decades, the composites industry has witnessed [...] Read more.

Structural materials, typically based on metal, have been gradually substituted by high-performance composites based on carbon fibers, embedded in a polymer matrix, due to their potential to provide lighter, stronger, and more durable solutions. In the last decades, the composites industry has witnessed a sustained growth, especially due to diffusion of these materials in key markets, such as the construction, wind energy, aeronautics, and automobile sectors. Carbon fibers are, by far, the most widely used fiber in high-performance applications. This important technology has huge potential for the future and it is expected to have a significant impact in the manufacturing industry within Europe and, therefore, coordination and strategic roadmapping actions are required. To lead a further drive to develop the potential of composites into new sectors, it is important to establish strategic roadmapping actions, including the development of business and cost models, supply chains implementation, and development, suitability for high volume markets and addressing technology management. Europe already has a vibrant and competitive composites industry that is supported by several research centers, but for its positioning in a forefront position in this technology, further challenges are still required to be addressed. Full article

(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2019)

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