Exploring the impact performance of functionally-graded preplaced aggregate concrete incorporating steel and polypropylene fibres

AbstractThe characteristics of fibres and paste of ordinary Portland cement transition zone are analysed and correlated to the mechanical properties of the produced composites. The water-cement ratio of the matrix varies from 0.30 to 0.46 and the age of the specimens varies from 7 to 180 days. Composites of vegetable fibres (coir, sisal and malva) are compared with those of chrysotile asbestos and polypropylene fibres. The analysis is made by backscattered electron image (BSEI) and energy dispersive spectroscopy (EDS). Mechanical tests evaluate the composite tensile strength and ductility.Mainly for vegetable fibre composites the transition zone is porous, cracked and rich in calcium hydroxide macrocrystals. These results are directly associated with the fibre-matrix bonding and with the composite mechanical performance. Further studies considering the impact performance of the composites compare the porosity of the transition zone with the toughness of the composites.

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Experimental Study on the Mechanical Properties and Compression Size Effect of Recycled Aggregate Concrete

Materials ◽

10.3390/ma14092323 ◽

2021 ◽

Vol 14 (9) ◽

pp. 2323

Author(s):

Yubing Du ◽

Zhiqing Zhao ◽

Qiang Xiao ◽

Feiting Shi ◽

Jianming Yang ◽

...

Keyword(s):

Mechanical Properties ◽

Size Effect ◽

Compressive Stress ◽

Failure Modes ◽

Recycled Concrete ◽

Recycled Aggregate Concrete ◽

Recycled Aggregate ◽

Aggregate Concrete ◽

Substitution Ratio ◽

The Impact

To explore the basic mechanical properties and size effects of recycled aggregate concrete (RAC) with different substitution ratios of coarse recycled concrete aggregates (CRCAs) to replace natural coarse aggregates (NCA), the failure modes and mechanical parameters of RAC under different loading conditions including compression, splitting tensile resistance and direct shear were compared and analyzed. The conclusions drawn are as follows: the failure mechanisms of concrete with different substitution ratios of CRCAs are similar; with the increase in substitution ratio, the peak compressive stress and peak tensile stress of RAC decrease gradually, the splitting limit displacement decreases, and the splitting tensile modulus slightly increases; with the increase in the concrete cube’s side length, the peak compressive stress of RAC declines gradually, but the integrity after compression is gradually improved; and the increase in the substitution ratio of the recycled aggregate reduces the impact of the size effect on the peak compressive stress of RAC. Furthermore, an influence equation of the coupling effect of the substitution ratio and size effect on the peak compressive stress of RAC was quantitatively established. The research results are of great significance for the engineering application of RAC and the strength selection of RAC structure design.

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Axial Stress-Strain Performance of Recycled Aggregate Concrete Reinforced with Macro-Polypropylene Fibres

Sustainability ◽

10.3390/su13105741 ◽

2021 ◽

Vol 13 (10) ◽

pp. 5741

Author(s):

Muhammad Junaid Munir ◽

Syed Minhaj Saleem Kazmi ◽

Yu-Fei Wu ◽

Xiaoshan Lin ◽

Muhammad Riaz Ahmad

Keyword(s):

Axial Stress ◽

Peak Stress ◽

Polypropylene Fibre ◽

Recycled Aggregate Concrete ◽

Recycled Aggregate ◽

Recycled Aggregates ◽

Peak Strain ◽

Stress Strain ◽

Polypropylene Fibres ◽

Aggregate Concrete

The addition of macro-polypropylene fibres improves the stress-strain performance of natural aggregate concrete (NAC). However, limited studies focus on the stress-strain performance of macro-polypropylene fibre-reinforced recycled aggregate concrete (RAC). Considering the variability of coarse recycled aggregates (CRA), more studies are needed to investigate the stress-strain performance of macro-polypropylene fibre-reinforced RAC. In this study, a new type of 48 mm long BarChip macro-polypropylene fibre with a continuously embossed surface texture is used to produce BarChip fibre-reinforced NAC (BFNAC) and RAC (BFRAC). The stress-strain performance of BFNAC and BFRAC is studied for varying dosages of BarChip fibres. Results show that the increase in energy dissipation capacity (i.e., area under the curve), peak stress, and peak strain of samples is observed with an increase in fibre dosage, indicating the positive effect of fibre addition on the stress-strain performance of concrete. The strength enhancement due to the addition of fibres is higher for BFRAC samples than BFNAC samples. The reduction in peak stress, ultimate strain, toughness and specific toughness of concrete samples due to the utilisation of CRA also reduces with the addition of fibres. Hence, the negative effect of CRA on the properties of concrete samples can be minimised by adding BarChip macro-polypropylene fibres. The applicability of the stress-strain model previously developed for macro-synthetic and steel fibre-reinforced NAC and RAC to BFNAC and BFRAC is also examined.

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Impact Resistance of Epoxy Composites Reinforced with Amazon Guaruman Fiber: A Brief Report

Polymers ◽

10.3390/polym13142264 ◽

2021 ◽

Vol 13 (14) ◽

pp. 2264

Author(s):

Raphael H. M. Reis ◽

Fabio C. Garcia Filho ◽

Larissa F. Nunes ◽

Veronica S. Candido ◽

Alisson C. R. Silva ◽

...

Keyword(s):

Fiber Composite ◽

Impact Resistance ◽

Fiber Composites ◽

Epoxy Composites ◽

Impact Performance ◽

Electron Microscopy Analysis ◽

Ballistic Properties ◽

Microscopy Analysis ◽

Izod Impact ◽

The Impact

Fibers extracted from Amazonian plants that have traditionally been used by local communities to produce simple items such as ropes, nets, and rugs, are now recognized as promising composite reinforcements. This is the case for guaruman (Ischinosiphon körn) fiber, which was recently found to present potential mechanical and ballistic properties as 30 vol% reinforcement of epoxy composites. To complement these properties, Izod impact tests are now communicated in this brief report for similar composites with up to 30 vol% of guaruman fibers. A substantial increase in impact resistance, with over than 20 times the absorbed energy for the 30 vol% guaruman fiber composite, was obtained in comparison to neat epoxy. These results were statistically validated by Weibull analysis, ANOVA, and Tukey’s test. Scanning electron microscopy analysis disclosed the mechanisms responsible for the impact performance of the guaruman fiber composites.

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Ultrahigh Ballistic Resistance of Twisted Bilayer Graphene

Crystals ◽

10.3390/cryst11020206 ◽

2021 ◽

Vol 11 (2) ◽

pp. 206

Author(s):

Qing Peng ◽

Sheng Peng ◽

Qiang Cao

Keyword(s):

Weight Ratio ◽

High Strength ◽

Bilayer Graphene ◽

Energy Propagation ◽

Dynamic Simulations ◽

Protective Material ◽

Impact Performance ◽

Ballistic Resistance ◽

Twisted Bilayer Graphene ◽

The Impact

Graphene is a good candidate for protective material owing to its extremely high stiffness and high strength-to-weight ratio. However, the impact performance of twisted bilayer graphene is still obscure. Herein we have investigated the ballistic resistance capacity of twisted bilayer graphene compared to that of AA-stacked bilayer graphene using molecular dynamic simulations. The energy propagation processes are identical, while the ballistic resistance capacity of the twisted bilayer graphene is almost two times larger than the AA-bilayer graphene. The enhanced capacity of the twisted bilayer graphene is assumed to be caused by the mismatch between the two sheets of graphene, which results in earlier fracture of the first graphene layer and reduces the possibility of penetration.

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A Refined Theory for Bending Vibratory Analysis of Thick Functionally Graded Beams

Mathematics ◽

10.3390/math9121422 ◽

2021 ◽

Vol 9 (12) ◽

pp. 1422

Author(s):

Youssef Boutahar ◽

Nadhir Lebaal ◽

David Bassir

Keyword(s):

Beam Theory ◽

Functionally Graded ◽

Effective Characteristics ◽

Hyperbolic Function ◽

Transverse Displacement ◽

Refined Theory ◽

Distribution Law ◽

Fg Beam ◽

The Impact ◽

Beam Theories

A refined beam theory that takes the thickness-stretching into account is presented in this study for the bending vibratory behavior analysis of thick functionally graded (FG) beams. In this theory, the number of unknowns is reduced to four instead of five in the other approaches. Transverse displacement is expressed through a hyperbolic function and subdivided into bending, shear, and thickness-stretching components. The number of unknowns is reduced, which involves a decrease in the number of the governing equation. The boundary conditions at the top and bottom FG beam faces are satisfied without any shear correction factor. According to a distribution law, effective characteristics of FG beam material change continuously in the thickness direction depending on the constituent’s volume proportion. Equations of motion are obtained from Hamilton’s principle and are solved by assuming the Navier’s solution type, for the case of a supported FG beam that is transversely loaded. The numerical results obtained are exposed and analyzed in detail to verify the validity of the current theory and prove the influence of the material composition, geometry, and shear deformation on the vibratory responses of FG beams, showing the impact of normal deformation on these responses which is neglected in most of the beam theories. The obtained results are compared with those predicted by other beam theories. It can be concluded that the present theory is not only accurate but also simple in predicting the bending and free vibration responses of FG beams.

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Improvement of the Impact Properties of Composite Laminates by Means of Nano-Modification of the Matrix—A Review

Applied Sciences ◽

10.3390/app8122406 ◽

2018 ◽

Vol 8 (12) ◽

pp. 2406 ◽

Cited By ~ 20

Author(s):

Hamed Saghafi ◽

Mohamad Fotouhi ◽

Giangiacomo Minak

Keyword(s):

Composite Laminates ◽

Cost Effective ◽

Careful Consideration ◽

Impact Performance ◽

Compression After Impact ◽

The Matrix ◽

The Right ◽

2D And 3D ◽

The Impact ◽

Selection Of

This paper reviews recent works on the application of nanofibers and nanoparticle reinforcements to enhance the interlaminar fracture toughness, to reduce the impact induced damage and to improve the compression after impact performance of fiber reinforced composites with brittle thermosetting resins. The nanofibers have been mainly used as mats embedded between plies of laminated composites, whereas the nanoparticles have been used in 0D, 1D, 2D, and 3D dimensional patterns to reinforce the matrix and consequently the composite. The reinforcement mechanisms are presented, and a comparison is done between the different papers in the literature. This review shows that in order to have an efficient reinforcement effect, careful consideration is required in the manufacturing, materials selection and reinforcement content and percentage. The selection of the right parameters can provide a tough and impact resistant composite with cost effective reinforcements.

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Cost efficient internet of things based smart farm system for rural farmers: Leveraging design thinking approach

Heritage and Sustainable Development, ISSN 2712-0554 ◽

10.37868/hsd.v3i2.64 ◽

2021 ◽

Vol 3 (2) ◽

pp. 111-120

Author(s):

Segun Adebayo ◽

Ozichi Emuoyibofarhe ◽

Tolulope Awofolaju

Keyword(s):

Design Thinking ◽

Agricultural Sector ◽

Cost Benefit ◽

Design Development ◽

Impact Performance ◽

Farm Productivity ◽

Cost Benefit Ratio ◽

Cost Efficient ◽

The Cost ◽

The Impact

Farmers are faced with challenges of producing enough food and the use of traditional methods seems not to keep pace with the ever-growing demand of the populace thus creating increased concern in food scarcity. Although it has been identified that smart tools will enhance the production pace needed in the Agricultural sector, unfortunately, most of these tools are designed for farmers without their inputs, thus creating tools that are not meeting demands. This study focused on a farmer-centered design, development, and deployment approach to improving farm productivity. The design thinking approach was used to identify the specific need of the farmers in selected areas, ideas were created using brainstorming sessions involving experts in the field, and prototypes were developed and deployed to evaluate the impact performance. The result shows that the proposed system improved the cost-benefit ratio of crop farming from 2.14 to 2.26. This is a 12% productivity increase.

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The theoretical approaches for calculation of the vertical effective pressure of drop impact of artificial rain on soil and hard surface

10.35688/2413-8452-2016-01-004 ◽

2016 ◽

Vol 1 ◽

pp. 16-20

Author(s):

Bryl S.V. ◽

Zverkov M.S.

Keyword(s):

Solid Surface ◽

Land Reclamation ◽

Effective Pressure ◽

Pressure Drops ◽

Impact Performance ◽

Theoretical Approaches ◽

Rain Drops ◽

Artificial Rain ◽

Newton’S Laws ◽

The Impact

The article considers the problem of calculating the vertical effective pressure drops of artificial rain on soil and hard surfaces. It is noted that the problem of determining the effective vertical pressure p of rain drops on soil although it is difficult, however, has a solution using Newton’s laws. This issue V.V. Slastenin, G. and A.P. Isaev, V.M. Moskovkin and V.F. gahs, etc., and N scientists. Erowyn S. , M.B. Lebedev, V.I., Gorodnichev, etc. proposed different approaches for determining the pressure p in terms of land reclamation (artificial irrigation). These issues dealt with and foreign researchers. Selected according to, according to the authors, the most suitable for the study of impact of the drops of artificial rain with the help of the patented device, and also to compare the obtained results with those of researchers dealing with the drip of erosion and determining the impact performance characteristics of droplets on a solid surface.

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