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Keywords = nominal bonding stress

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18 pages, 5907 KiB  
Article
Improvement of Bending Stiffness of Timber Beams with Ultra-High-Modulus-Carbon-Fibre-Reinforced Polymer Sheets
by Michał Marcin Bakalarz and Paweł Grzegorz Kossakowski
Materials 2025, 18(1), 71; https://doi.org/10.3390/ma18010071 - 27 Dec 2024
Cited by 1 | Viewed by 791
Abstract
The bending stiffness of beams represents a pivotal parameter influencing both the dimensions of the elements during their design and their subsequent utilisation. It is evident that excessive deflections can cause discomfort to users and contribute to further structural degradation. The objective of [...] Read more.
The bending stiffness of beams represents a pivotal parameter influencing both the dimensions of the elements during their design and their subsequent utilisation. It is evident that excessive deflections can cause discomfort to users and contribute to further structural degradation. The objective of this study was to enhance the bending stiffness of timber beams by bonding a composite sheet to their external surfaces. A carbon sheet exhibiting an ultra-high modulus of elasticity and low elongation at rupture was employed. Two variables of analysis can be distinguished including whether the reinforcement was applied or not and the number of reinforcement layers. The beams, with nominal dimensions of 80 × 80 × 1600 mm, were subjected to a four-point bending test in order to ascertain their mechanical properties. In total, 15 beams were tested (5 unreinforced and 10 reinforced). The reinforcement had no appreciable impact on the increase in flexural load capacity, with the maximum average increase recorded at 9%. Nevertheless, an increase in stiffness of 34% was observed. Additionally, significant increases were observed in ductility up to 248%. However, the ductile behaviour of the beam occurred after the rupture of the reinforcement. In all instances, the failure was attributed to the fracturing of the wooden components or the UHM CFRP (ultra-high-modulus-carbon-fibre-reinforced polymer) sheet. The numerical analysis proved to be a valuable tool for predicting the stiffness of the wood–composite system, with a relatively low error margin of a few percentage points. The modified approach, based on the equivalent cross-section method, permits the determination of a bilinear load deflection relationship for reinforced beams. The aforementioned curve is indicative of the actual behaviour. Given the propensity for the sudden rupture of reinforcement, the described method of reinforcement is recommended for beams subjected to lower levels of stress. Full article
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18 pages, 3725 KiB  
Article
Research on the Distributive Relationship between Bond Force and Bearing Pressure for Anchorage Force by Headed Bars
by Tianming Miao, Jian Yang, Ying Zhou, Meiqiu Zhan, Lirong Sha and Wenzhong Zheng
Buildings 2023, 13(10), 2463; https://doi.org/10.3390/buildings13102463 - 28 Sep 2023
Viewed by 1137
Abstract
Anchorage force comprises bond force and bearing pressure when headed bars are used. Pull-out tests were conducted on 120 concrete specimens to derive a method for calculating the bond force for reinforcement in straight anchor sections at the yield moment. The parameters include [...] Read more.
Anchorage force comprises bond force and bearing pressure when headed bars are used. Pull-out tests were conducted on 120 concrete specimens to derive a method for calculating the bond force for reinforcement in straight anchor sections at the yield moment. The parameters include the diameter d, embedded length lae, and yield strength fy of the reinforcement, as well as the strength grade of the concrete fcg. The experimental results indicated that the specimens underwent three failure modes depending primarily on the embedded length lae. The nominal average bond stress τu concept was proposed and the difference between τu and the actual average bond stress τ caused by the headed bars was observed. To reduce the difference between the τu and τ values, the correction coefficient γ was proposed. Analysis indicated that γ increased with an increase in the lae/d (on average, 146% higher than the initial value) and decreased with an increase in the fy/ft (on average, 33% less than the initial value). A formula was developed to calculate γ, and the bond force in the straight anchor sections at the yield moment for the reinforcement was determined. Thus, a distributive relationship was established for the anchorage force, the bond force, and the bearing pressure. Full article
(This article belongs to the Section Building Structures)
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18 pages, 7447 KiB  
Article
An Experimental and Numerical Study on Glass Frit Wafer-to-Wafer Bonding
by Seyed Amir Fouad Farshchi Yazdi, Matteo Garavaglia, Aldo Ghisi and Alberto Corigliano
Micromachines 2023, 14(1), 165; https://doi.org/10.3390/mi14010165 - 8 Jan 2023
Cited by 2 | Viewed by 2615
Abstract
A thermo-mechanical wafer-to-wafer bonding process is studied through experiments on the glass frit material and thermo-mechanical numerical simulations to evaluate the effect of the residual stresses on the wafer warpage. To experimentally characterize the material, confocal laser profilometry and scanning electron microscopy for [...] Read more.
A thermo-mechanical wafer-to-wafer bonding process is studied through experiments on the glass frit material and thermo-mechanical numerical simulations to evaluate the effect of the residual stresses on the wafer warpage. To experimentally characterize the material, confocal laser profilometry and scanning electron microscopy for surface observation, energy dispersive X-ray spectroscopy for microstructural investigation, and nanoindentation and die shear tests for the evaluation of mechanical properties are used. An average effective Young’s modulus of 86.5 ± 9.5 GPa, a Poisson’s ratio of 0.19 ± 0.02, and a hardness of 5.26 ± 0.8 GPa were measured through nanoindentation for the glass frit material. The lowest nominal shear strength ranged 1.13 ÷ 1.58 MPa in the strain rate interval to 0.33 ÷ 4.99 × 103 s1. To validate the thermo-mechanical model, numerical results are compared with experimental measurements of the out-of-plane displacements at the wafer surface (i.e., warpage), showing acceptable agreement. Full article
(This article belongs to the Special Issue MEMS in Italy)
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15 pages, 2249 KiB  
Article
Numerical Performance Analysis of Concrete-Filled Hollow GFRP Beams including Inner Surface Bearing Stresses at the Interface
by Tuna Ülger and Ahmad Shayan Sharifi
Buildings 2022, 12(9), 1340; https://doi.org/10.3390/buildings12091340 - 31 Aug 2022
Cited by 1 | Viewed by 1659
Abstract
GFRP sections with filler concrete material form promising structural components for structures; therefore, the structural performance of them has been investigated with increasing popularity. However, the performance of these composites degrades when fully composite action cannot be developed at the interface in where [...] Read more.
GFRP sections with filler concrete material form promising structural components for structures; therefore, the structural performance of them has been investigated with increasing popularity. However, the performance of these composites degrades when fully composite action cannot be developed at the interface in where the literature hosts limited knowledge. Different techniques, such as abraded and sand-bonded surface treatments, were investigated experimentally to improve the bond-slip behavior between GFRP and concrete; however, there is a need to define shear mechanism at the interface of the numerical models. In this study, first, the average frictional bearing strengths were extracted for the treated and untreated inner surfaces using experimental results; then, the coulomb friction model was utilized to transfer the shear stresses between two dissimilar materials. Numerical models were verified by the experimental results, and different parametric studies were investigated by varying the amount and shape of GFRP in the cross section, compressive strength of concrete including the non-linear material behavior and interface frictional contact models. The findings showed that the interface strength can improve the flexural capacity of the concrete-filled GFRP beams by about 15.4%. Square GFRP box sections can be suggested for the construction of hybrid beams instead of rectangular sections, whereas the 10% areal ratio in a square cross section reached 103% load capacity improvement. The increased nominal compressive strength of concrete in hybrid beams can increase the hollow GFRP beams’ nominal load capacities and elastic stiffness of the hybrid beams in between; however, the relative gain is reduced due to increased compressive strength of concrete. Full article
(This article belongs to the Special Issue Finite Element Analysis and Design of Hybrid Structures)
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12 pages, 2698 KiB  
Article
A Study on the Bond–Slip Relationship of the CFRP–Steel Interface of CFRP Strengthened Steel
by Xinyan Guo, Zuodong Wu, Yi Yang, Jiahao Bai and Qianziyang Zhou
Materials 2022, 15(12), 4187; https://doi.org/10.3390/ma15124187 - 13 Jun 2022
Cited by 11 | Viewed by 2179
Abstract
The bonding interface between the CFRP and the steel plate is the weak link of CFRP-strengthened steel structures. This paper studies the bond–slip relationship of the CFRP–steel interface by experiments and numerical tests. First, a series of double-strap experiments on a CFRP-strengthened steel [...] Read more.
The bonding interface between the CFRP and the steel plate is the weak link of CFRP-strengthened steel structures. This paper studies the bond–slip relationship of the CFRP–steel interface by experiments and numerical tests. First, a series of double-strap experiments on a CFRP-strengthened steel plate are carried out. The results show that the maximum shear stress of the bonding interface of the Q345B specimen is larger than that of the X100 specimen. The initial slip and maximum slip become larger as the thickness of the bonding interface becomes larger. Finite element analysis of the above tests is carried out; we introduce the maximum stress criterion to simulate the bonding interface, which assumes that when the nominal stress of the material reaches the maximum nominal stress of damage, the material begins to damage. The FE model established has proved very effective for analyzing the bond characteristics of CFRP-strengthened steel plates. Finally, a verification test was carried out, using an FE analysis to verify the accuracy of the modified equations; the results prove that the results of the modified equations are in good agreement with the numerical results and experiment results, which verifies the effectiveness of the equations. Full article
(This article belongs to the Topic Composites in Aerospace and Mechanical Engineering)
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20 pages, 7589 KiB  
Article
Effect of Wet-Dry Cycles on the Bond Behavior of Fiber-Reinforced Inorganic-Matrix Systems Bonded to Masonry Substrates
by Karrar Al-Lami, Angelo Savio Calabrese, Pierluigi Colombi and Tommaso D’Antino
Materials 2021, 14(20), 6171; https://doi.org/10.3390/ma14206171 - 18 Oct 2021
Cited by 12 | Viewed by 2259
Abstract
In recent years, inorganic-matrix reinforcement systems, such as fiber-reinforced cementitious matrix (FRCM), composite-reinforced mortars (CRM), and steel-reinforced grout (SRG), have been increasingly used to retrofit and strengthen existing masonry and concrete structures. Despite their good short-term properties, limited information is available on their [...] Read more.
In recent years, inorganic-matrix reinforcement systems, such as fiber-reinforced cementitious matrix (FRCM), composite-reinforced mortars (CRM), and steel-reinforced grout (SRG), have been increasingly used to retrofit and strengthen existing masonry and concrete structures. Despite their good short-term properties, limited information is available on their long-term behavior. In this paper, the long-term bond behavior of some FRCM, CRM, and SRG systems bonded to masonry substrates is investigated. Namely, the results of single-lap direct shear tests of FRCM-, CRM-, and SRG-masonry joints subjected to wet-dry cycles are provided and discussed. First, FRCM composites comprising carbon, polyparaphenylene benzobisoxazole (PBO), and alkali-resistant (AR) glass textiles embedded within cement-based matrices, are considered. Then, CRM and SRG systems made of an AR glass composite grid embedded with natural hydraulic lime (NHL) and of unidirectional steel cords embedded within the same lime matrix, respectively, are studied. For each type of composite, six specimens are exposed to 50 wet–dry cycles prior to testing. The results are compared with those of nominally equal unconditioned specimens previously tested by the authors. This comparison shows a shifting of the failure mode for some composites from debonding at the matrix–fiber interface to debonding at the matrix-substrate interface. Furthermore, the average peak stress of all systems decreases except for the carbon FRCM and the CRM, for which it remains unaltered or increases. Full article
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16 pages, 4534 KiB  
Article
Study and Verification of a New Method to Test the Bonding Ability between Basalt Fiber and Asphalt Mortar
by Xing Wu, Zhengguang Wu, Aihong Kang, Peng Xiao and Bangwei Wu
Appl. Sci. 2021, 11(1), 235; https://doi.org/10.3390/app11010235 - 29 Dec 2020
Cited by 7 | Viewed by 2207
Abstract
The bonding ability between basalt fiber bundle and asphalt mortar has a great influence on the properties of basalt fiber reinforced asphalt mixtures, yet the studies about the bonding between them is very limited. In this paper, a new test instrument called fiber-asphalt [...] Read more.
The bonding ability between basalt fiber bundle and asphalt mortar has a great influence on the properties of basalt fiber reinforced asphalt mixtures, yet the studies about the bonding between them is very limited. In this paper, a new test instrument called fiber-asphalt pulling machine and a new index called the nominal bonding stress (NBS) were designed and adopted to test and reveal the bonding between basalt fiber bundle and asphalt mortar. The procedures and rationality analysis of this new experiment was specified in this paper. In order to verify the reliability of the NBS index, the NBS values derived from this new test method and the rheological property indexes values of asphalt mortar under different powder–cement ratios were adopted to analyze the correlation between them. Two kinds of basalt fibers produced by two different manufacturers were adopted to conduct the parallel experiment. The results show that the nominal bonding stress between basalt fiber and asphalt mortar derived from this new test has a great correlation with the rheological properties of asphalt mortar, which also proves the credibility of this new test method and the NBS index. Full article
(This article belongs to the Section Civil Engineering)
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14 pages, 6202 KiB  
Article
Shear Deformation Behavior of a Double-Layer Asphalt Mixture Based on the Virtual Simulation of a Uniaxial Penetration Test
by Changjiang Kou, Xiaohui Pan, Peng Xiao, Aihong Kang and Zhengguang Wu
Materials 2020, 13(17), 3700; https://doi.org/10.3390/ma13173700 - 21 Aug 2020
Cited by 5 | Viewed by 2225
Abstract
This paper aims to clarify the shear deformation behavior of double-layer asphalt mixtures using the virtual uniaxial penetration test (UPT) with a discrete element method. For this purpose, asphalt mixtures with two different nominal maximum aggregate sizes were designed for the preparation of [...] Read more.
This paper aims to clarify the shear deformation behavior of double-layer asphalt mixtures using the virtual uniaxial penetration test (UPT) with a discrete element method. For this purpose, asphalt mixtures with two different nominal maximum aggregate sizes were designed for the preparation of double-layer wheel tracking test specimens. Then, the cylindrical cores were prepared from the specimens and were cut for capturing the longitudinal profile images. These images were used to reconstruct a two-dimensional discrete element model (DEM) of the uniaxial penetration test specimen. The results indicate that the shear deformation behavior of the asphalt mixtures showed corresponding changes under the virtual loading. The tensile and compressive stress were distributed unevenly within the upper layer after the test, and both coarse aggregates and asphalt mortars bore a greater shear stress. Therefore, cracks were more likely to occur in the upper layer, leading to the failure of the specimens. This process enhanced the bonding between the asphalt mortars and the mineral aggregates. The aggregate particles in the upper layer moved more vertically, while those in the lower layer generally moved more laterally under the virtual loading. This behavior reveals the rutting mechanism of asphalt pavement. Full article
(This article belongs to the Section Construction and Building Materials)
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11 pages, 2696 KiB  
Article
Waste Utilization: Insulation Panel from Recycled Polyurethane Particles and Wheat Husks
by Štěpán Hýsek, Pavel Neuberger, Adam Sikora, Ondřej Schönfelder and Gianluca Ditommaso
Materials 2019, 12(19), 3075; https://doi.org/10.3390/ma12193075 - 20 Sep 2019
Cited by 19 | Viewed by 3698
Abstract
This study provides a solution for the utilization of two waste materials, namely the residues of soft polyurethane foam from the production of mattresses and winter wheat husks. Thermal insulation panels with a nominal density of 50–150 kg/m3, bonded one-component moisture [...] Read more.
This study provides a solution for the utilization of two waste materials, namely the residues of soft polyurethane foam from the production of mattresses and winter wheat husks. Thermal insulation panels with a nominal density of 50–150 kg/m3, bonded one-component moisture curing polyurethane adhesive, were developed, and the effect of the ratio between recycled polyurethane foam and winter wheat husk on internal bond strength, compressive stress at 10% strain, water uptake, coefficient of thermal conductivity, and volumetric heat capacity was observed. The developed composite materials make use of the very good thermal insulation properties of the two input waste materials, and the coefficient of thermal conductivity of the resulting boards achieves excellent values, namely 0.0418–0.0574 W/(m.K). The developed boards can be used as thermal insulation in the structures of environmentally friendly buildings. Full article
(This article belongs to the Special Issue Sustainability in Construction and Building Materials)
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21 pages, 5462 KiB  
Article
The Influence of Manufacturing Parameters on the Mechanical Behaviour of PLA and ABS Pieces Manufactured by FDM: A Comparative Analysis
by Adrián Rodríguez-Panes, Juan Claver and Ana María Camacho
Materials 2018, 11(8), 1333; https://doi.org/10.3390/ma11081333 - 1 Aug 2018
Cited by 360 | Viewed by 18567
Abstract
This paper presents a comparative study of the tensile mechanical behaviour of pieces produced using the Fused Deposition Modelling (FDM) additive manufacturing technique with respect to the two types of thermoplastic material most widely used in this technique: polylactide (PLA) and acrylonitrile butadiene [...] Read more.
This paper presents a comparative study of the tensile mechanical behaviour of pieces produced using the Fused Deposition Modelling (FDM) additive manufacturing technique with respect to the two types of thermoplastic material most widely used in this technique: polylactide (PLA) and acrylonitrile butadiene styrene (ABS). The aim of this study is to compare the effect of layer height, infill density, and layer orientation on the mechanical performance of PLA and ABS test specimens. The variables under study here are tensile yield stress, tensile strength, nominal strain at break, and modulus of elasticity. The results obtained with ABS show a lower variability than those obtained with PLA. In general, the infill percentage is the manufacturing parameter of greatest influence on the results, although the effect is more noticeable in PLA than in ABS. The test specimens manufactured using PLA perform more rigidly and they are found to have greater tensile strength than ABS. The bond between layers in PLA turns out to be extremely strong and is, therefore, highly suitable for use in additive technologies. The methodology proposed is a reference of interest in studies involving the determination of mechanical properties of polymer materials manufactured using these technologies. Full article
(This article belongs to the Special Issue Special Issue of the Manufacturing Engineering Society (MES))
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