Materials

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21 pages, 3078 KiB

Open AccessArticle

Application of Gene Expression Programming (GEP) for the Prediction of Compressive Strength of Geopolymer Concrete

by Mohsin Ali Khan, Adeel Zafar, Arslan Akbar, Muhammad Faisal Javed and Amir Mosavi

Materials 2021, 14(5), 1106; https://doi.org/10.3390/ma14051106 - 26 Feb 2021

Cited by 71 | Viewed by 4090

For the production of geopolymer concrete (GPC), fly-ash (FA) like waste material has been effectively utilized by various researchers. In this paper, the soft computing techniques known as gene expression programming (GEP) are executed to deliver an empirical equation to estimate the compressive [...] Read more.

For the production of geopolymer concrete (GPC), fly-ash (FA) like waste material has been effectively utilized by various researchers. In this paper, the soft computing techniques known as gene expression programming (GEP) are executed to deliver an empirical equation to estimate the compressive strength

f_{c}^{'}

of GPC made by employing FA. To build a model, a consistent, extensive and reliable data base is compiled through a detailed review of the published research. The compiled data set is comprised of 298

f_{c}^{'}

experimental results. The utmost dominant parameters are counted as explanatory variables, in other words, the extra water added as percent FA (

% E_{W}

), the percentage of plasticizer (

% P

), the initial curing temperature (

T

), the age of the specimen (

A

), the curing duration (

t

), the fine aggregate to total aggregate ratio (

F / A_{G}

), the percentage of total aggregate by volume (

% A_{G}

), the percent SiO₂ solids to water ratio (

% S / W

) in sodium silicate (Na₂SiO₃) solution, the NaOH solution molarity (

M

), the activator or alkali to FA ratio (

A_{L} / F_{A}

), the sodium oxide (Na₂O) to water ratio (

N / W

) for preparing Na₂SiO₃ solution, and the Na₂SiO₃ to NaOH ratio (

N_{s} / N_{o}

). A GEP empirical equation is proposed to estimate the

f_{c}^{'}

of GPC made with FA. The accuracy, generalization, and prediction capability of the proposed model was evaluated by performing parametric analysis, applying statistical checks, and then compared with non-linear and linear regression equations. Full article

(This article belongs to the Special Issue Advances in Natural Fiber Reinforced Polymer and Geopolymer Composites: Synthesis, Applications and Future Directions)

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11 pages, 3915 KiB

Open AccessArticle

A New Strategy to Produce Hemp Fibers through a Waterglass-Based Ecofriendly Process

by Aurelio Bifulco, Brigida Silvestri, Jessica Passaro, Luca Boccarusso, Valentina Roviello, Francesco Branda and Massimo Durante

Materials 2020, 13(8), 1844; https://doi.org/10.3390/ma13081844 - 14 Apr 2020

Cited by 5 | Viewed by 2877

Abstract

Natural fibers such as kenaf, hemp, flax, jute, and sisal have become the subject of much research as potential green or eco-friendly reinforcement composites, since they assure the reduction of weight, cost, and CO₂ release with less reliance on oil sources. Herein, [...] Read more.

Natural fibers such as kenaf, hemp, flax, jute, and sisal have become the subject of much research as potential green or eco-friendly reinforcement composites, since they assure the reduction of weight, cost, and CO₂ release with less reliance on oil sources. Herein, an inexpensive and eco-friendly waterglass treatment is proposed, allowing the production of silica-coated fibers that can be easily obtained in micro/nano fibrils through a low power mixer. The silica coating has been exploited to improve the chemical compatibility between fibers and the polymer matrix through the reaction of silanol groups with suitable coupling agents. In particular, silica-coated fibers easily functionalized with (3-Aminopropyl) triethoxysilane (APTS) were used as a filler in the manufacturing of epoxy-based composites. Morphological investigation of the composites through Scanning Electron Microscopy (SEM) demonstrated that the filler has a tendency to produce a web-like structure, formed by continuously interconnected fibrils and microfibrils, from which particularly effective mechanical properties may be obtained. Dynamic Mechanical Analysis (DMA) shows that the functionalized fibers, in a concentration of 5 wt%, strongly affect the glass transformation temperature (10 °C increase) and the storage modulus of the pristine resin. Taking into account the large number of organosilicon compounds (in particular the alkoxide ones) available on the market, the new process appears to pave the way for the cleaner and cheaper production of biocomposites with different polymeric matrices and well-tailored interfaces. Full article

(This article belongs to the Special Issue Advances in Natural Fiber Reinforced Polymer and Geopolymer Composites: Synthesis, Applications and Future Directions)

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14 pages, 3190 KiB

Open AccessArticle

Phenolic Resin Foam Composites Reinforced by Acetylated Poplar Fiber with High Mechanical Properties, Low Pulverization Ratio, and Good Thermal Insulation and Flame Retardant Performance

by Jian Liu, Liuliu Wang, Wei Zhang and Yanming Han

Materials 2020, 13(1), 148; https://doi.org/10.3390/ma13010148 - 31 Dec 2019

Cited by 15 | Viewed by 3266

Abstract

Phenolic foam composites (PFs) are of substantial interest due to their uniform closed-cell structure, low thermal conductivity, and good thermal insulation performance. However, their disadvantages of a high pulverization rate and poor mechanical properties restrict their application in building exterior insulation. Therefore, the [...] Read more.

Phenolic foam composites (PFs) are of substantial interest due to their uniform closed-cell structure, low thermal conductivity, and good thermal insulation performance. However, their disadvantages of a high pulverization rate and poor mechanical properties restrict their application in building exterior insulation. Therefore, the toughening of these composites is necessary. In this paper, poplar fiber was treated with an acetylation reagent, and the acetylated fiber was used to prepare modified phenolic foams (FTPFs); this successfully solved the phenomenon of the destruction of the foam structure due to the agglomeration of poplar fiber in the resin substrate. The foam composites were comprehensively evaluated via the characterization of their chemical structures, surface morphologies, mechanical properties, thermal conductivities, and flame retardant properties. It was found that the compressive strength and compressive modulus of FTPF-5% respectively increased by 28.5% and 37.9% as compared with those of PF. The pulverization ratio was reduced by 32.3%, and the thermal insulation performance and flame retardant performance (LOI) were improved. Compared with other toughening methods for phenolic foam composites, the phenolic foam composites modified with surface-compatibilized poplar fiber offer a novel strategy for the value-added utilization of woody fiber, and improve the toughness and industrial viability of phenolic foam. Full article

(This article belongs to the Special Issue Advances in Natural Fiber Reinforced Polymer and Geopolymer Composites: Synthesis, Applications and Future Directions)

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11 pages, 3971 KiB

Open AccessArticle

Effect of Nanosilica on Mechanical Properties and Microstructure of PVA Fiber-Reinforced Geopolymer Composite (PVA-FRGC)

by Hasan Assaedi, Thamer Alomayri, Ayesha Siddika, Faiz Shaikh, Hatem Alamri, Subaer Subaer and It-Meng Low

Materials 2019, 12(21), 3624; https://doi.org/10.3390/ma12213624 - 04 Nov 2019

Cited by 29 | Viewed by 4716

Abstract

This paper presents the effects of various nanosilica (NS) contents on the mechanical properties of polyvinyl alcohol (PVA) fiber-reinforced geopolymer composites (PVA-FRGC). Microstructure analysis with X-ray diffraction (XRD) and scanning electron microscopy (SEM) was used to characterize the geopolymer composites. The results showed [...] Read more.

This paper presents the effects of various nanosilica (NS) contents on the mechanical properties of polyvinyl alcohol (PVA) fiber-reinforced geopolymer composites (PVA-FRGC). Microstructure analysis with X-ray diffraction (XRD) and scanning electron microscopy (SEM) was used to characterize the geopolymer composites. The results showed that the mechanical properties in terms of compressive strength, impact strength, and flexural behavior were improved due to the addition of NS to the PVA-FRGC. The optimum NS content was 1.0 to 2.0 wt%, which exhibited highest improvement in the above mechanical properties. Microstructure analysis showed that the addition of NS up to an optimum level densified the microstructure of the matrix as well as the PVA fiber–geopolymer matrix interface. Full article

(This article belongs to the Special Issue Advances in Natural Fiber Reinforced Polymer and Geopolymer Composites: Synthesis, Applications and Future Directions)

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11 pages, 3847 KiB

Open AccessArticle

Effect of Hygrothermal Aging and Surface Treatment on the Dynamic Mechanical Behavior of Flax Fiber Reinforced Composites

by Xiaomeng Wang and Michal Petrů

Materials 2019, 12(15), 2376; https://doi.org/10.3390/ma12152376 - 25 Jul 2019

Cited by 18 | Viewed by 2900 | Correction

Abstract

The recent developments of FRP (fiber reinforced polymer) are towards the growth and usage of natural FRP in the field of engineering due to both environmental and economic benefits. Flax fiber is one of the most commonly used natural fibers. One of the [...] Read more.

The recent developments of FRP (fiber reinforced polymer) are towards the growth and usage of natural FRP in the field of engineering due to both environmental and economic benefits. Flax fiber is one of the most commonly used natural fibers. One of the critical factors affecting the mechanical behavior of FFRP (flax fiber reinforced polymer) is hygrothermal aging. Some experimental works have been conducted to investigate the effect of hydrothermal aging on static behavior of FFRP. However, fewer efforts have been made to study its damping properties after hydrothermal aging. In this paper, the effect of surface treatment (including alkalization, silanization, acetylation and alkali-silanization) on dynamic mechanical behavior of FFRP under hygrothermal aging is studied. The results show that water resistance and damping properties of FFRP are improved after surface treatment. The acetylation treated FFRP exhibits excellent damping performance among all treated specimens. Full article

(This article belongs to the Special Issue Advances in Natural Fiber Reinforced Polymer and Geopolymer Composites: Synthesis, Applications and Future Directions)

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9 pages, 1973 KiB

Open AccessArticle

Effect of CNT Contents on the Microstructure and Properties of CNT/TiMg Composites

by Xiaomin Yuan, Haonan Zhu, Huiling Ji and Yiwei Zhang

Materials 2019, 12(10), 1620; https://doi.org/10.3390/ma12101620 - 17 May 2019

Cited by 5 | Viewed by 2797

Abstract

Carbon nanotubes (CNTs), dispersed in absolute ethanol, were evenly mixed into Ti/MgH₂ powders by wet milling. Then, we applied the vacuum hot-pressed sinteringmethod to the CNTs/TiMg composite materials. An optical microscope (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive [...] Read more.

Carbon nanotubes (CNTs), dispersed in absolute ethanol, were evenly mixed into Ti/MgH₂ powders by wet milling. Then, we applied the vacuum hot-pressed sinteringmethod to the CNTs/TiMg composite materials. An optical microscope (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and a field emission scanning electron microscope (FESEM) were used for the microstructure observation and phase analysis of samples. The mechanical properties were measured via the micro-vickers hardness. The results show that the main phases in the composites were Ti, Mg and C. Meanwhile, a small amount of Ti-Mg solid solution phase was also found. The cross-section morphology of the composites shows that the melted magnesium fills the grain interface during extrusion and that the composites have a better compactness.The microstructures of the composites have been greatly refined as the CNT contents increased. The structure of the composites was further refined when 0.5 wt.% CNTs were added. The fracture surface is obviously a ductile fracture. The microhardness increases obviously with the CNT content increasing. When the content of the CNTs is 1.0 wt.%, the microhardness of the composites reaches 232 HV, which is 24% higher than that of the matrix. Full article

(This article belongs to the Special Issue Advances in Natural Fiber Reinforced Polymer and Geopolymer Composites: Synthesis, Applications and Future Directions)

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13 pages, 1618 KiB

Open AccessArticle

Comparison of Self-Etching Ceramic Primer and Conventional Silanization to Bond Strength in Cementation of Fiber Reinforced Composite Post

by Nan-Sim Pang, Bock-Young Jung, Byoung-Duck Roh and Yooseok Shin

Materials 2019, 12(10), 1585; https://doi.org/10.3390/ma12101585 - 15 May 2019

Cited by 4 | Viewed by 3203

Abstract

Various mechanical and chemical surface treatments have been proposed to improve the retention of fiber-reinforced composite post (FRCP), but the results are still controversial. The bond strength and durability of a self-etching ceramic primer, which was recently released as an alternative to etching [...] Read more.

Various mechanical and chemical surface treatments have been proposed to improve the retention of fiber-reinforced composite post (FRCP), but the results are still controversial. The bond strength and durability of a self-etching ceramic primer, which was recently released as an alternative to etching and silane, are not yet known. This study aimed to compare and evaluate the push-out bond strength of different surface treatments of FRCPs after an artificial aging procedure. Four groups (n = 10) were established to evaluated FRCP surface treatments (dentin adhesive bonding; silane and adhesive bonding; hydrofluoric acid, silane and adhesive bonding; and a self-etching ceramic primer). They were bonded with dual-curing rein cement (Multilink N) and stored in distilled water at 37 °C for 30 days, then thermal cycled for 7500 cycles. After being sectioned into 1 mm thickness, each coronal and apical part was evaluated for its the push-out bond strength by a universal testing machine. Each debonded specimen was observed by an optical microscope and divided according to the failure modes. The results showed that silane treatment significantly improved push-out bond strength, but the self-etching ceramic primer did not do so. Additional hydrofluoric acid treatment or the adhesive bonding agent alone did not significantly improve the retention of FRCPs. Cohesive failure of the luting material was found most frequently in all groups. Full article

(This article belongs to the Special Issue Advances in Natural Fiber Reinforced Polymer and Geopolymer Composites: Synthesis, Applications and Future Directions)

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14 pages, 6259 KiB

Open AccessArticle

Influence of Nano Silica Particles on Durability of Flax Fabric Reinforced Geopolymer Composites

by Hasan Assaedi, Thamer Alomayri, Faiz Shaikh and It-Meng Low

Materials 2019, 12(9), 1459; https://doi.org/10.3390/ma12091459 - 06 May 2019

Cited by 42 | Viewed by 3476

Abstract

The durability of natural fibres as reinforcement in geopolymer composites continues to be a matter of concern due to the alkalinity of activators of geopolymer matrices. The alkaline environment is the main reason for natural fibres degradation in cementitious matrices. This paper presents [...] Read more.

The durability of natural fibres as reinforcement in geopolymer composites continues to be a matter of concern due to the alkalinity of activators of geopolymer matrices. The alkaline environment is the main reason for natural fibres degradation in cementitious matrices. This paper presents the influence of nano silica (NS) on the durability and mechanical performance of geopolymer composites that are reinforced with flax fabric (FF). The durability investigations were conducted after the storage of samples at ambient temperature for 32 weeks. The study revealed that the addition of nano silica has a positive influence on the physical and mechanical properties of these composites. The presence of NS accelerated the geopolymeric reaction and lowered the alkalinity of the system, thus reducing the degradation of flax fibres. Full article

(This article belongs to the Special Issue Advances in Natural Fiber Reinforced Polymer and Geopolymer Composites: Synthesis, Applications and Future Directions)

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