Journal of Composites Science

Editorial

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2 pages, 195 KiB

Open AccessEditorial

Editorial for the Special Issue on Characterization and Modelling of Composites

by Stelios K. Georgantzinos

J. Compos. Sci. 2021, 5(2), 47; https://doi.org/10.3390/jcs5020047 - 03 Feb 2021

Cited by 3 | Viewed by 1395

Abstract

The papers published in this Special Issue of the Journal of Composites Science will give the composite engineer and scientist insight into what the existing challenges are in the characterization and modelling for the composites field, and how these challenges are being addressed [...] Read more.

The papers published in this Special Issue of the Journal of Composites Science will give the composite engineer and scientist insight into what the existing challenges are in the characterization and modelling for the composites field, and how these challenges are being addressed by the research community [...] Full article

(This article belongs to the Special Issue Characterization and Modelling of Composites)

Research

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27 pages, 13478 KiB

Open AccessArticle

Damage Detection in Glass/Epoxy Laminated Composite Plates Using Modal Curvature for Structural Health Monitoring Applications

by Mahendran Govindasamy, Gopalakrishnan Kamalakannan, Chandrasekaran Kesavan and Ganesh Kumar Meenashisundaram

J. Compos. Sci. 2020, 4(4), 185; https://doi.org/10.3390/jcs4040185 - 14 Dec 2020

Cited by 18 | Viewed by 3528

Abstract

This paper deals with detection of macro-level crack type damage in rectangular E-Glass fiber/Epoxy resin (LY556) laminated composite plates using modal analysis. Composite plate-like structures are widely found in aerospace and automotive structural applications which are susceptible to damages. The formation of cracks [...] Read more.

This paper deals with detection of macro-level crack type damage in rectangular E-Glass fiber/Epoxy resin (LY556) laminated composite plates using modal analysis. Composite plate-like structures are widely found in aerospace and automotive structural applications which are susceptible to damages. The formation of cracks in a structure that undergoes vibration may lead to catastrophic events such as structural failure, thus detection of such occurrences is considered necessary. In this research, a novel technique called as node-releasing technique in Finite Element Analysis (FEA), which was not attempted by the earlier researchers, is used to model the perpendicular cracks (the type of damage mostly considered in all the pioneering research works) and also slant cracks (a new type of damage considered in the present work) of various depths and lengths for Unidirectional Laminate (UDL) (

{[0]}_{S}

and

{[45]}_{S}

) composite layered configurations using commercial FE code Ansys, thus simulating the actual damage scenario. Another novelty of the present work is that the crack is modeled with partial depth along the thickness of the plate, instead of the through the thickness crack which has been of major focus in the literature so far, in order to include the possibility of existence of the crack up to certain layers in the laminated composite structures. The experimental modal analysis is carried out to validate the numerical model. Using central difference approximation method, the modal curvature is determined from the displacement mode shapes which are obtained via finite element analysis. The damage indicators investigated in this paper are Normalized Curvature Damage Factor (NCDF) and modal strain energy-based methods such as Strain Energy Difference (SED) and Damage Index (DI). It is concluded that, all the three damage detection algorithms detect the transverse crack clearly. In addition, the damage indicator NCDF seems to be more effective than the other two, particularly when the detection is for damage inclined to the longitudinal axis of the plate. The proposed method will provide the base data for implementing online structural health monitoring of structures using technologies such as Machine Learning, Artificial Intelligence, etc. Full article

(This article belongs to the Special Issue Characterization and Modelling of Composites)

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12 pages, 10029 KiB

Open AccessArticle

Mechanical Strength of Bamboo Filled PLA Composite Material in Fused Filament Fabrication

by Scott Landes and Todd Letcher

J. Compos. Sci. 2020, 4(4), 159; https://doi.org/10.3390/jcs4040159 - 26 Oct 2020

Cited by 19 | Viewed by 3562

Abstract

Through the past two decades, there has been a continued push for renewable resources and future sustainability of materials and processes. This has prompted more developments of providing environmentally friendly practices and products, both in terms of higher recyclability and greater use of [...] Read more.

Through the past two decades, there has been a continued push for renewable resources and future sustainability of materials and processes. This has prompted more developments of providing environmentally friendly practices and products, both in terms of higher recyclability and greater use of renewable resources. An important area of interest are materials for construction and manufacturing purposes, specifically “green” sustainable reinforcement materials for thermoplastic composite materials. During this time, there has also been an evolution in manufacturing methods. Additive manufacturing (AM) has continued to grow exponentially since its inception for its extensive benefits. This study aims to investigate an additive manufactured composite material that is a greener alternative to other composites that are not reinforced by natural fibers. A bamboo filled polylactic acid (PLA) composite manufactured by fused filament fabrication was evaluated in order to gather mechanical strength characteristics by means of tensile, flexure, compression, impact, and shear tests. In this material, the bamboo reinforcing material and the PLA matrix material can both be sourced from highly renewable resources. In this study, a variety of test samples were manufactured at different manufacturing parameters to be used for mechanical testing. The results were recorded with respect to varying manufacturing parameters (raster angle orientation). It was found that the 0° raster angle orientation performed the best in every category except tensile. Additively manufactured bamboo filled PLA was also seen to have comparable strength to certain traditionally manufactured bamboo fiber reinforced plastics. Full article

(This article belongs to the Special Issue Characterization and Modelling of Composites)

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19 pages, 3472 KiB

Open AccessArticle

Modelling and Experimental Investigation of Hexagonal Nacre-Like Structure Stiffness

by Rami Rouhana and Markus Stommel

J. Compos. Sci. 2020, 4(3), 91; https://doi.org/10.3390/jcs4030091 - 15 Jul 2020

Cited by 2 | Viewed by 3163

Abstract

A highly ordered, hexagonal, nacre-like composite stiffness is investigated using experiments, simulations, and analytical models. Polystyrene and polyurethane are selected as materials for the manufactured specimens using laser cutting and hand lamination. A simulation geometry is made by digital microscope measurements of the [...] Read more.

A highly ordered, hexagonal, nacre-like composite stiffness is investigated using experiments, simulations, and analytical models. Polystyrene and polyurethane are selected as materials for the manufactured specimens using laser cutting and hand lamination. A simulation geometry is made by digital microscope measurements of the specimens, and a simulation is conducted using material data based on component material characterization. Available analytical models are compared to the experimental results, and a more accurate model is derived specifically for highly ordered hexagonal tablets with relatively large in-plane gaps. The influence of hexagonal width, cut width, and interface thickness are analyzed using the hexagonal nacre-like composite stiffness model. The proposed analytical model converges within 1% with the simulation and experimental results. Full article

(This article belongs to the Special Issue Characterization and Modelling of Composites)

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12 pages, 4074 KiB

Open AccessArticle

Developing an Equivalent Solid Material Model for BCC Lattice Cell Structures Involving Vertical and Horizontal Struts

by Tahseen A. Alwattar and Ahsan Mian

J. Compos. Sci. 2020, 4(2), 74; https://doi.org/10.3390/jcs4020074 - 17 Jun 2020

Cited by 17 | Viewed by 3371

Abstract

In this study, a body-centered cubic (BCC) lattice unit cell occupied inside a frame structure to create a so-called “InsideBCC” is considered. The equivalent quasi-isotropic properties required to describe the material behavior of the InsideBCC unit cell are equivalent Young’s modulus [...] Read more.

In this study, a body-centered cubic (BCC) lattice unit cell occupied inside a frame structure to create a so-called “InsideBCC” is considered. The equivalent quasi-isotropic properties required to describe the material behavior of the InsideBCC unit cell are equivalent Young’s modulus

(E_{e})

, equivalent shear modulus

(G_{e})

, and equivalent Poisson’s ratio

(ν_{e})

. The finite element analysis (FEA) based computational approach is used to simulate and calculate the mechanical responses of InsideBCC unit cell, which are the mechanical responses of the equivalent solid. Two separates finite element models are then developed for samples under compression: one with a 6 × 6 × 4 cell InsideBCC lattice cell structure (LCS) and one completely solid with equivalent solid properties obtained from a unit cell model. In addition, 6 × 6 × 4 cell specimens are fabricated on a fused deposition modeling (FDM) uPrint SEplus 3D printer using acrylonitrile butadiene styrene (ABS) material and tested experimentally under quasi-static compression load. Then, the results extracted from the finite element simulation of both the entire lattice and the equivalent solid models are compared with the experimental data. A good agreement between the experimental stress–strain behavior and that obtained from the FEA models is observed within the linear elastic limit. Full article

(This article belongs to the Special Issue Characterization and Modelling of Composites)

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20 pages, 1980 KiB

Open AccessArticle

A Machine Learning Model to Detect Flow Disturbances during Manufacturing of Composites by Liquid Moulding

by Carlos González and Joaquín Fernández-León

J. Compos. Sci. 2020, 4(2), 71; https://doi.org/10.3390/jcs4020071 - 10 Jun 2020

Cited by 16 | Viewed by 3017

Abstract

In this work, a supervised machine learning (ML) model was developed to detect flow disturbances caused by the presence of a dissimilar material region in liquid moulding manufacturing of composites. The machine learning model was designed to predict the position, size and relative [...] Read more.

In this work, a supervised machine learning (ML) model was developed to detect flow disturbances caused by the presence of a dissimilar material region in liquid moulding manufacturing of composites. The machine learning model was designed to predict the position, size and relative permeability of an embedded rectangular dissimilar material region through use of only the signals corresponding to an array of pressure sensors evenly distributed on the mould surface. The burden of experimental tests required to train in an efficient manner such predictive models is so high that favours its substitution with synthetically-generated simulation datasets. A regression model based on the use of convolutional neural networks (CNN) was developed and trained with data generated from mould-filling simulations carried out through use of OpenFoam as numerical solver. The evolution of the pressure sensors through the filling time was stored and used as grey-level images containing information regarding the pressure, the sensor location within the mould and filling time. The trained CNN model was able to recognise the presence of a dissimilar material region from the data used as inputs, meeting accuracy expectation in terms of detection. The purpose of this work was to establish a general framework for fully-synthetic-trained machine learning models to address the occurrence of manufacturing disturbances without placing emphasis on its performance, robustness and optimization. Accuracy and model robustness were also addressed in the paper. The effect of noise signals, pressure sensor network size, presence of different shape dissimilar regions, among others, were analysed in detail. The ability of ML models to examine and overcome complex physical and engineering problems such as defects produced during manufacturing of materials and parts is particularly innovative and highly aligned with Industry 4.0 concepts. Full article

(This article belongs to the Special Issue Characterization and Modelling of Composites)

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23 pages, 5576 KiB

Open AccessArticle

A Study of the Interlaminar Fracture Toughness of Unidirectional Flax/Epoxy Composites

by Yousef Saadati, Jean-Francois Chatelain, Gilbert Lebrun, Yves Beauchamp, Philippe Bocher and Nicolas Vanderesse

J. Compos. Sci. 2020, 4(2), 66; https://doi.org/10.3390/jcs4020066 - 05 Jun 2020

Cited by 13 | Viewed by 5072

Abstract

Having environmental and economic advantages, flax fibers have been recognized as a potential replacement for glass fibers as reinforcement in epoxy composites for various applications. Its widening applications require employing failure criteria and analysis methods for engineering design, analysis, and optimization of this [...] Read more.

Having environmental and economic advantages, flax fibers have been recognized as a potential replacement for glass fibers as reinforcement in epoxy composites for various applications. Its widening applications require employing failure criteria and analysis methods for engineering design, analysis, and optimization of this material. Among different failure modes, delamination is known as one of the earliest ones in laminated composites and needs to be studied in detail. However, the delamination characteristics of unidirectional (UD) flax/epoxy composites in pure Mode I has rarely been addressed, while Mode II and Mixed-mode I/II have never been addressed before. This work studies and evaluates the interlaminar fracture toughness and delamination behavior of UD flax/epoxy composite under Mode I, Mode II, and Mixed-mode I/II loading. The composites were tested following corresponding ASTM standards and fulfilled all the requirements. The interlaminar fracture toughness of the composite were determined and validated based on the specific characteristics of natural fibers. Considering the variation in the composite structure configuration and its effects, the results of interlaminar fracture toughness fit in the range of those reported for similar composites in the literature and provide a basis for the material properties of this composite. Full article

(This article belongs to the Special Issue Characterization and Modelling of Composites)

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13 pages, 5241 KiB

Open AccessArticle

Finite Element Modeling of the Fiber-Matrix Interface in Polymer Composites

by Daljeet K. Singh, Amol Vaidya, Vinoy Thomas, Merlin Theodore, Surbhi Kore and Uday Vaidya

J. Compos. Sci. 2020, 4(2), 58; https://doi.org/10.3390/jcs4020058 - 20 May 2020

Cited by 22 | Viewed by 4829

Abstract

Polymer composites are used in numerous industries due to their high specific strength and high specific stiffness. Composites have markedly different properties than both the reinforcement and the matrix. Of the several factors that govern the final properties of the composite, the interface [...] Read more.

Polymer composites are used in numerous industries due to their high specific strength and high specific stiffness. Composites have markedly different properties than both the reinforcement and the matrix. Of the several factors that govern the final properties of the composite, the interface is an important factor that influences the stress transfer between the fiber and matrix. The present study is an effort to characterize and model the fiber-matrix interface in polymer matrix composites. Finite element models were developed to study the interfacial behavior during pull-out of a single fiber in continuous fiber-reinforced polymer composites. A three-dimensional (3D) unit-cell cohesive damage model (CDM) for the fiber/matrix interface debonding was employed to investigate the effect of interface/sizing coverage on the fiber. Furthermore, a two-dimensional (2D) axisymmetric model was used to (a) analyze the sensitivity of interface stiffness, interface strength, friction coefficient, and fiber length via a parametric study; and (b) study the shear stress distribution across the fiber-interface-matrix zone. It was determined that the force required to debond a single fiber from the matrix is three times higher if there is adequate distribution of the sizing on the fiber. The parametric study indicated that cohesive strength was the most influential factor in debonding. Moreover, the stress distribution model showed the debonding mechanism of the interface. It was observed that the interface debonded first from the matrix and remained in contact with the fiber even when the fiber was completely pulled out. Full article

(This article belongs to the Special Issue Characterization and Modelling of Composites)

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18 pages, 4082 KiB

Open AccessArticle

Freeze-Thaw Performance Characterization and Leachability of Potassium-Based Geopolymer Concrete

by Peiman Azarsa and Rishi Gupta

J. Compos. Sci. 2020, 4(2), 45; https://doi.org/10.3390/jcs4020045 - 27 Apr 2020

Cited by 11 | Viewed by 2719

Abstract

It is well known that concrete is one of the most widely used construction materials in the world, and cement as its key constituent is partly responsible for global Carbon Dioxide (CO₂) emission. Due to these reasons, high strength concrete with [...] Read more.

It is well known that concrete is one of the most widely used construction materials in the world, and cement as its key constituent is partly responsible for global Carbon Dioxide (CO₂) emission. Due to these reasons, high strength concrete with lower CO₂ emission, and concrete with lower reliance on natural resources is increasingly popular. Geopolymer Concrete (GPC), due to its capability to minimize the consumption of natural resources, has attracted the attention of researchers. In cold regions, frost action is one of the primary GPC deterioration mechanisms requiring huge expenditures for repair and maintenance. In this regard, two types of GPC (fly-ash based GPC and bottom-ash based GPC) were exposed to the harsh freeze-thaw conditions using a standard test method. The dynamic elastic modulus of both types of GPC was determined using a Non-Destructive Test (NDT) method called Resonant Frequency Test (RFT). The results of RFT after exposing to 300 freeze-thaw cycles showed that bottom-ash based GPC has better freeze-thaw resistance than fly-ash based GPC. Moreover, in this study, the leachability of bottom-ash based GPC was also investigated to trace the heavy metals (including Si, Al, Na, Cr, Cu, Hg) using Toxicity Characteristic Leaching Procedure (TCLP) test. The results of the TCLP test showed that all of the heavy metals could be effectively immobilized into the geopolymer paste. Full article

(This article belongs to the Special Issue Characterization and Modelling of Composites)

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21 pages, 8497 KiB

Open AccessArticle

Arbitrary-Reconsidered-Double-Inclusion (ARDI) Model to Describe the Anisotropic, Viscoelastic Stiffness and Damping of Short Fiber-Reinforced Thermoplastics

by Alexander Kriwet and Markus Stommel

J. Compos. Sci. 2020, 4(2), 37; https://doi.org/10.3390/jcs4020037 - 09 Apr 2020

Cited by 6 | Viewed by 2327

Abstract

Current state of the art, simulation methods to determine the frequency-, temperature- and humidity-depending stiffness and damping do not show an accurate prediction of the structural dynamics of short-fiber-reinforced thermoplastics. Thus, in the current work the new developed Arbitrary-Reconsidered-Double-Inclusion (ARDI) model has been [...] Read more.

Current state of the art, simulation methods to determine the frequency-, temperature- and humidity-depending stiffness and damping do not show an accurate prediction of the structural dynamics of short-fiber-reinforced thermoplastics. Thus, in the current work the new developed Arbitrary-Reconsidered-Double-Inclusion (ARDI) model has been used to describe the stiffness and damping. Thereby, a homogenization equation has been used to derive the transversal-isotropic stiffness and damping tensors. By rotating and weighting these tensors using orientation distribution functions (ODF), it is possible to create a material database. A validation of the developed ARDI model was performed on bending vibration specimens under variation of the fiber direction, temperature and humidity, to investigate the structural dynamics. In general, the comparison of the results of the simulation and experiments shows a good correlation of the eigenfrequencies and the amplitudes. The main differences in the simulation can be traced back to the used modelling of the damping behavior. Full article

(This article belongs to the Special Issue Characterization and Modelling of Composites)

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Review

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35 pages, 16976 KiB

Open AccessReview

Strain State Detection in Composite Structures: Review and New Challenges

by Maurizio Arena and Massimo Viscardi

J. Compos. Sci. 2020, 4(2), 60; https://doi.org/10.3390/jcs4020060 - 25 May 2020

Cited by 21 | Viewed by 4965

Abstract

Developing an advanced monitoring system for strain measurements on structural components represents a significant task, both in relation to testing of in-service parameters and early identification of structural problems. This paper aims to provide a state-of-the-art review on strain detection techniques in composite [...] Read more.

Developing an advanced monitoring system for strain measurements on structural components represents a significant task, both in relation to testing of in-service parameters and early identification of structural problems. This paper aims to provide a state-of-the-art review on strain detection techniques in composite structures. The review represented a good opportunity for direct comparison of different novel strain measurement techniques. Fibers Bragg grating (FBG) was discussed as well as non-contact techniques together with semiconductor strain gauges (SGs), specifically infrared (IR) thermography and the digital image correlation (DIC) applied in order to detect strain and failure growth during the tests. The challenges of the research community are finally discussed by opening the current scenario to new objectives and industrial applications. Full article

(This article belongs to the Special Issue Characterization and Modelling of Composites)

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