Journal of Composites Science

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16 pages, 5413 KiB

Open AccessArticle

Influence of Glass Microfibers on the Control of Autogenous Shrinkage in Very High Strength Self-Compacting Concretes (VHSSCC)

by Lucas Onghero, Marcelo Tramontin Souza, Daniel Cusson and Wellington Longuini Repette

J. Compos. Sci. 2024, 8(3), 101; https://doi.org/10.3390/jcs8030101 - 12 Mar 2024

Viewed by 1010

Abstract

High-performance concrete (HPC) is widely used in infrastructure for its durability and sustainability benefits. However, it faces challenges like autogenous shrinkage, leading to potential cracking and reduced durability. Fiber reinforcement offers a solution by mitigating shrinkage-induced stresses and enhancing concrete durability. In this [...] Read more.

High-performance concrete (HPC) is widely used in infrastructure for its durability and sustainability benefits. However, it faces challenges like autogenous shrinkage, leading to potential cracking and reduced durability. Fiber reinforcement offers a solution by mitigating shrinkage-induced stresses and enhancing concrete durability. In this sense, this study investigates the use of glass microfibers to mitigate autogenous shrinkage and early-age cracking in high-strength self-compacting concrete. Samples were prepared with two water-to-binder ratios (w/b): 0.25 and 0.32; and three glass microfiber contents: 0.20%, 0.25%, and 0.30 vol.%. The concrete mixtures were characterized in the fresh state for slump flow and in the hardened state for compressive strength, static, and dynamic Young’s modulus. Unrestrained and restrained shrinkage tests were also conducted in the seven days-age. The findings revealed that glass microfibers reduced the workability in mixtures with lower slump flow values (w/b of 0.25), while less viscous mixtures (w/b of 0.32) exhibited a slight improvement. Compressive strength showed a proportional enhancement with increasing fiber contents in concretes with a w/b ratio of 0.32. A contrasting trend emerged in concretes with a w/b ratio of 0.25, wherein strength diminished as fiber additions increased. The modulus of elasticity improved with fiber additions only in the matrix with a w/b ratio of 0.25, showing no correlation with compressive strength results. In shrinkage tests, the addition of glass microfibers up to specific limits (0.20% for a w/b ratio of 0.25 and 0.25% for w/b of 0.32) demonstrated improvements in controlling concrete deformation in unrestrained shrinkage analyses. Concerning cracking reduction in restrained concrete specimens, the mixtures did not exhibit significant improvements in crack prevention. Full article

(This article belongs to the Special Issue Discontinuous Fiber Composites, Volume III)

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14 pages, 1142 KiB

Open AccessArticle

Analysis of Stress Intensity Factor of a Fibre Embedded in a Matrix

by Mostafa Barzegar, Josep Costa, Daniel Trias, Jose M. Guerrero, Claudio Lopes and Carlos Gonzalez

J. Compos. Sci. 2023, 7(1), 22; https://doi.org/10.3390/jcs7010022 - 10 Jan 2023

Viewed by 1351

Abstract

The analytical or numerical determination of the stress intensity factor (SIF) in cracked bodies usually assumes the body to be isolated. However, in fibre-reinforced composites, the fibre, which is the main load-carrying component, is embedded in a matrix. To clarify the effect the [...] Read more.

The analytical or numerical determination of the stress intensity factor (SIF) in cracked bodies usually assumes the body to be isolated. However, in fibre-reinforced composites, the fibre, which is the main load-carrying component, is embedded in a matrix. To clarify the effect the embedding matrix has on the SIF of the fibre, we propose a 3D computational model of an orthotropic fibre embedded in an isotropic matrix, and compute the SIF using the J-integral method. A parametric analysis based on dimensionless variables explores the effect of the fibre–matrix stiffness ratio as well as the effect of the degree of elastic orthotropy of the fibre. The results show that the SIF is strongly influenced by both factors, and that the matrix reduces the SIF by limiting the crack opening. Full article

(This article belongs to the Special Issue Discontinuous Fiber Composites, Volume III)

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22 pages, 6634 KiB

Open AccessArticle

Digital Manufacture of a Continuous Fiber Reinforced Thermoplastic Matrix Truss Core Structural Panel Using Off-the-Tool Consolidation

by Mark E. Bourgeois and Donald W. Radford

J. Compos. Sci. 2022, 6(11), 343; https://doi.org/10.3390/jcs6110343 - 7 Nov 2022

Cited by 1 | Viewed by 1722

Abstract

Sandwich panels are commonly used as structure, based on fiber reinforced composites, with the goal of high flexural stiffness and low mass. It is most common to separate two high performance composite facesheets with a low-density core, generally in the form of a [...] Read more.

Sandwich panels are commonly used as structure, based on fiber reinforced composites, with the goal of high flexural stiffness and low mass. It is most common to separate two high performance composite facesheets with a low-density core, generally in the form of a foam or honeycomb. A recent concept has been to replace these traditional core materials with fiber reinforced truss-like structures, with the goal of further reducing mass. A system is described that can radically reduce the amount of tooling required for truss core sandwich panel manufacture. This system, which is a digital manufacturing platform for the extrusion of continuous fiber reinforced commingled glass fiber/PET tow, was developed to demonstrate the rigidization of composites both on, and off, a tool surface. Navtruss core panels were successfully manufactured using this digital manufacturing platform, without conventional tooling, and the resulting through thickness compression moduli and panel shear moduli were within 14.6% and 23% of the values baseline compression molded specimens. Thus, the results suggest that, with further development, complex truss core structures with performance approaching that of compression molded panels can be manufactured with radically reduced tooling requirements from high volume fraction, continuous fiber reinforced thermoplastic matrix composites. Full article

(This article belongs to the Special Issue Discontinuous Fiber Composites, Volume III)

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10 pages, 1695 KiB

Open AccessArticle

Physico-Chemical Characterization of Alkali-Treated Ethiopian Arabica Coffee Husk Fiber for Composite Materials Production

by Berhanu Tolessa Amena, Holm Altenbach, Getechew Shunki Tibba and Nazia Hossain

J. Compos. Sci. 2022, 6(8), 233; https://doi.org/10.3390/jcs6080233 - 7 Aug 2022

Cited by 3 | Viewed by 1985

Abstract

Chemical treatment is a significant factor in improving the natural fiber quality for composite materials production. In this study, the alkaline treatment of Ethiopian Arabica coffee husk by sodium hydroxide (NaOH) was performed to improve the fiber quality. A total of 10% ( [...] Read more.

Chemical treatment is a significant factor in improving the natural fiber quality for composite materials production. In this study, the alkaline treatment of Ethiopian Arabica coffee husk by sodium hydroxide (NaOH) was performed to improve the fiber quality. A total of 10% (w/w) NaOH has been applied for the alkaline treatment. Comprehensive physicochemical characterizations, such as proximate analysis, cellulosic composition, porosity, and structural analysis of treated and untreated coffee husk, have been conducted and compared. The experimental results showed that lignin and hemicellulose were reduced by 72% and 52%, respectively, thus improving the overall fiber quality. Therefore, this study indicated alkaline treatment of Ethiopian coffee husk is effective for fiber quality enhancement. It can be applied as a potential feedstock for fiber production in the composite production sector. Full article

(This article belongs to the Special Issue Discontinuous Fiber Composites, Volume III)

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13 pages, 3961 KiB

Open AccessArticle

Effect of Fiber Orientation on the Tribological Performance of Abaca-Reinforced Epoxy Composite under Dry Contact Conditions

by Marko Milosevic, Dragan Dzunic, Petr Valasek, Slobodan Mitrovic and Alessandro Ruggiero

J. Compos. Sci. 2022, 6(7), 204; https://doi.org/10.3390/jcs6070204 - 14 Jul 2022

Cited by 11 | Viewed by 1623

Abstract

This paper presents tribological research of an abaca fiber-reinforced epoxy composite material, analyzing fiber orientation and its effect on the tribological performances of the composite. The extremely low viscosity epoxy resin reinforced with NaOH-treated long abaca fibers is investigated under the different operating [...] Read more.

This paper presents tribological research of an abaca fiber-reinforced epoxy composite material, analyzing fiber orientation and its effect on the tribological performances of the composite. The extremely low viscosity epoxy resin reinforced with NaOH-treated long abaca fibers is investigated under the different operating conditions. The unidirectional abaca fibers reinforced the epoxy resin and formed composite specimens with fibers in three directions, parallel (P-O), anti-parallel (AP-O) and normal (N-O), while keeping the sliding direction. The specimens were fabricated using fiber volume fractions of 10 vol%, 20 vol% and 30 vol% using the vacuum infusion technique. The block-on-disc (BOD) apparatus has been used to exhibit the tribological tests. Normal loads of 35 N and 45 N have been used for testing purposes. The experimental results indicated that the presence of abaca fiber significantly improved the wear characteristics of the matrix. An increased coefficient of friction was observed in samples with anti-parallel-oriented fibers at an applied load of 35 N. The conducted research shows that the use of abaca fibers as fillers could improve the tribological characteristics of the epoxy resin-based composite material. Full article

(This article belongs to the Special Issue Discontinuous Fiber Composites, Volume III)

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11 pages, 2796 KiB

Open AccessArticle

Mean Value-Amplitude Method for the Determination of Anisotropic Mechanical Properties of Short Fiber Reinforced Thermoplastics

by Joachim Hausmann, Esha, Stefan Schmidt and Janna Krummenacker

J. Compos. Sci. 2022, 6(6), 179; https://doi.org/10.3390/jcs6060179 - 20 Jun 2022

Cited by 2 | Viewed by 1253

Abstract

Short fiber reinforced thermoplastics show distinct anisotropic behaviors due to their microstructure. The mechanical testing of specimens cut from injection molded plates at different angles to the injection molding direction reveals direction-dependent properties. However, these results are an average value for the tested [...] Read more.

Short fiber reinforced thermoplastics show distinct anisotropic behaviors due to their microstructure. The mechanical testing of specimens cut from injection molded plates at different angles to the injection molding direction reveals direction-dependent properties. However, these results are an average value for the tested cross section, which in more detail has a core-shell microstructure. When analyzing the stresses and deformation of a structural component, the local anisotropy will be very different compared to these tensile specimens. Therefore, a methodology is needed to transfer the properties obtained by mechanical testing to the local properties of an injection molded component. The core-shell microstructure and tests with different specimen thicknesses enable the determination of microstructure-dependent material properties. This paper presents a method using a mean value representing isotropy and an amplitude applied to the mean value to determine orientation-dependent mechanical properties. The amplitude in turn depends on the degree of anisotropy. The method is applied for extracting the anisotropic Young’s modulus of the core and shell layer of short glass fiber reinforced polyamide 46. The results obtained by this method and their reliability are discussed. Full article

(This article belongs to the Special Issue Discontinuous Fiber Composites, Volume III)

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30 pages, 17442 KiB

Open AccessArticle

Experimental and Numerical Analysis of SMC Compression Molding in Confined Regions—A Comparison of Simulation Approaches

by Florian Rothenhäusler, Nils Meyer, Simon Wehler, Martin Hohberg, Maik Gude, Frank Henning and Luise Kärger

J. Compos. Sci. 2022, 6(3), 68; https://doi.org/10.3390/jcs6030068 - 23 Feb 2022

Cited by 7 | Viewed by 3586

Abstract

The compression molding process of sheet molding compound (SMC) is an economical manufacturing process for lightweight parts. However, molding defects, such as fiber matrix separation, and fiber re-orientation, may develop during the molding process in confined regions, such as ribs and bosses. Hence, [...] Read more.

The compression molding process of sheet molding compound (SMC) is an economical manufacturing process for lightweight parts. However, molding defects, such as fiber matrix separation, and fiber re-orientation, may develop during the molding process in confined regions, such as ribs and bosses. Hence, the mechanical properties of the composite depend on the local fiber architecture. Consequently, this work compares the predictive capabilities of tensor-based and directly modeled process simulation approaches regarding compression force, fiber volume content and fiber orientation on the example of honeycomb structures molded from SMC. The results are validated by micro-computed tomography and thermal gravimetric analysis. The fiber orientation in the honeycomb varies between individual samples because a sheet molding compound is macroscopically heterogeneous and thus the fiber architecture is strongly influenced by random events. Tensor-based fiber orientation models can not reliably predict fiber volume content and fiber orientation in the part’s thickness direction if there is a lack of scale separation. Therefore, directly modeled process simulations should be preferred in cases in which fiber length and mold dimensions prohibit scale separation. The prediction of fiber volume content is a difficult task and no simulation can predict the severity of fiber matrix separation precisely in all cases. Full article

(This article belongs to the Special Issue Discontinuous Fiber Composites, Volume III)

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Review

Jump to: Research

43 pages, 13005 KiB

Open AccessReview

Effects of Low-Velocity-Impact on Facesheet-Core Debonding of Natural-Core Composite Sandwich Structures—A Review of Experimental Research

by Michael Ong and Arlindo Silva

J. Compos. Sci. 2024, 8(1), 23; https://doi.org/10.3390/jcs8010023 - 9 Jan 2024

Viewed by 1619

Abstract

Sandwich composites are often used as primary load-bearing structures in various industries like aviation, wind, and marine due to their high strength-to-weight and stiffness-to-weight ratios, but they are vulnerable to damage from Low-velocity-impact (LVI) events like dropped tools, hail, and birdstrikes. This often [...] Read more.

Sandwich composites are often used as primary load-bearing structures in various industries like aviation, wind, and marine due to their high strength-to-weight and stiffness-to-weight ratios, but they are vulnerable to damage from Low-velocity-impact (LVI) events like dropped tools, hail, and birdstrikes. This often manifests in the form of Facesheet-Core-Debonding (FCD) and is often termed Barely-Visible-Impact-Damage (BVID), which is difficult to detect and can considerably reduce mechanical properties. In general, a balsa core sandwich is especially vulnerable to FCD under LVI as it has poorer adhesion than synthetic core materials. A cork core sandwich does show promise in absorbing LVI with low permanent indentation depth. This paper also reviews surface treatment/modification as a means of improving the adhesion of composite core and fiber materials: key concepts involved, a comparison of surface free energies of various materials, and research literature on surface modification of cork, glass, and carbon fibers. Since both balsa and cork have a relatively low surface free energy compared to other materials, this paper concludes that it may be possible to use surface modification techniques to boost adhesion and thus FCD on balsa or cork sandwich composites under LVI, which has not been covered by existing research literature. Full article

(This article belongs to the Special Issue Discontinuous Fiber Composites, Volume III)

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26 pages, 4503 KiB

Open AccessReview

Developments and Industrial Applications of Basalt Fibre Reinforced Composite Materials

by Indraneel R. Chowdhury, Richard Pemberton and John Summerscales

J. Compos. Sci. 2022, 6(12), 367; https://doi.org/10.3390/jcs6120367 - 5 Dec 2022

Cited by 12 | Viewed by 5285

Abstract

Basalt mineral fibre, made directly from basalt rock, has good mechanical behavior, superior thermal stability, better chemical durability, good moisture resistance and can easily be recycled when compared to E-glass fibres (borosilicate glass is called ‘E-glass’ or ‘electric al-grade glass’ because of its [...] Read more.

Basalt mineral fibre, made directly from basalt rock, has good mechanical behavior, superior thermal stability, better chemical durability, good moisture resistance and can easily be recycled when compared to E-glass fibres (borosilicate glass is called ‘E-glass’ or ‘electric al-grade glass’ because of its high electrical resistance) which are traditionally used in structural composites for industrial applications. Industrial adoption of basalt fibre reinforced composites (FRC) is still very low mainly due to inadequate data and lower production volumes leading to higher cost. These reasons constrain the composites industry from seriously considering basalt as a potential alternative to conventional (e.g., E-glass) fibre reinforced composites for different applications. This paper provides a critical review of the state-of-the-art concerning basalt FRC highlighting the increasing trend in research and publications related to basalt composites. The paper also provides information regarding physico-chemical, and mechanical properties of basalt fibres, some initial Life cycle assessment inventory data is also included, and reviews common industrial applications of basalt fibre composites. Full article

(This article belongs to the Special Issue Discontinuous Fiber Composites, Volume III)

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