Compressive Properties Research Articles

Dynamic Progressive Failure Analysis of 3D Five-directional Braided Composites under Transverse Compression Based on Macro-scale Heterogeneous Model

At present, there are few systematic researches on macro-scale heterogeneous modeling and numerical simulation of dynamic mechanical properties of 3-D braided composites. In this paper, the parametric virtual simulation model of 3D five-directional braided composites is realized in the way of “point-line-solid” based on the integrated design idea of process-structure-performance. And the impact compression numerical simulation of the material is carried out by using multi-scale analysis method. The effects of strain rate and braiding angle on transverse impact compression properties and fracture characteristics of composites is studies and verified by comparing the test results with the numerical simulation results systematically. The dynamic failure mechanism of the matrix and fiber bundles during the impact compression process is revealed. The results show that the macro-scale heterogeneous simulation model of 3D five-directional braided composites established is effective, and the numerical simulation results agree well with the test results. The matrix fracture and shear failure of fiber bundles are presented simultaneously under transverse impact compression. The failure of fiber bundles and matrix mainly concentrates on two main fracture shear planes. And the included angle between the fracture shear planes and the vertical direction is consistent with the corresponding internal braiding angle of specimens.

Application of Computer-Aided Design Software to the Simulation and Analysis of Composite Material Properties in Housing Engineering Structures

Reinforced polymer composites are widely used in engineering applications due to their excellent mechanical properties, and this paper combines experiments and numerical simulations to fully examine the properties of the composites. The article takes the reinforced concrete structure of civil engineering as the basis for experimental testing on the basic properties of carbon fiber composites in its application. Subsequently, the intrinsic model of reinforced concrete and carbon fiber composites was constructed, and each finite element unit of the member was selected to simulate and finite element analysis the performance of the composites through ABAQUS computer-aided design software. The results show that increasing the diameter of carbon fibers will reduce the number of carbon fibers at the same time, which will reduce the toughness of the composite material, random and chaotic distribution of carbon fibers for the improvement of the compressive properties of concrete can achieve a relatively balanced effect, and the high elastic modulus carbon fibers for the improvement of uniaxial and cyclic compressive properties of concrete play a dominant role. In addition, the oriented elliptical fibers in the long-axis direction have a significant increase in the modulus of elasticity and strength of the material, and this phenomenon will become more and more obvious with the increase of the length-to-diameter ratio. The reasonable structural design may help to improve the performance of composites and enhance their adaptability for engineering applications.

Bending and compressive properties of ultralight carbon fiber honeycomb sandwich beams via stretching process

Due to excellent thermal stability and high specific strength, there are high requirements for all-carbon fiber composite honeycomb sandwich structure (ACFH) in the field of space observation, especially as the support of space telescope and satellite antenna. However, there are few studies on the mechanical properties of ultra-low density ACFH (ρ < 50 kg/m3). Based on the stretching process, the ultra-low density curved-wall ACFH is prepared, and its three-point bending performance and in-plane compression performance are deeply studied by means of theoretical and experimental methods. The interaction and competition mechanism of various failure modes were primarily revealed based on the failure mechanism map. In addition, the mechanical properties of specimens prepared through stretching process were tested and analyzed. The research results shows that the theoretical prediction and experimental testing agree very well in terms of failure modes and ultimate loads. Finally, some suggestions for improving the mechanical properties of ultra-low density ACFH are given, which lays the solid foundation for its application in advanced engineering fields.

A high toughness hydrogel with Dy3+ enhanced fluorescence properties: For visual Zn2+ detection

Rapid, portable, and sensitive detection of Zn2+ is crucial for human health. In this study, SA/PEG/Ln fluorescent hydrogels were synthesized via in situ polymerization with lanthanide metals (Tb3+/Dy3+) and PAM. The results demonstrated a significant improvement in mechanical properties (132.8 % increase in compressive properties) after rare earth doping. The addition of Dy3+ enhanced the fluorescence properties of the singly doped Tb3+ fluorescent hydrogel (maximum luminous intensity increased by 1900 cd). Monitoring changes in fluorescence intensity enabled the realization of Zn2+ detection, allowing for quick and accurate determination of zinc ion presence. Visual monitoring of Zn2+ was achieved with the assistance of a portable ultraviolet lamp.

Enhancing Thermal and Mechanical Properties of Rigid Polyurethane Foam with Eco-friendly Silane-modified Cellulose Nanocrystals

Cellulose nanocrystals (CNC) are promising candidates for strengthening polymeric matrices, offering unique features like biodegradability, renewability, and exceptional mechanical properties. However, efficiently dispersing CNC in these matrices and finely adjusting their interfacial characteristics are critical for harnessing their full potential in novel nanomaterial development. Herein, we developed novel eco-friendly and effective method to modify the surface of the CNC with three types of silane coupling agents – (3-Aminopropyl trimethoxysilane (APTMS), N-ethyl-2,2-dimethoxy-4-methyl-1-aza-2-silacyclopentane (ASCP1), and N-(2-aminoethyl)-2,2,4-trimethyl-1-aza-2-silacyclopentane (ASCP2) by using chemical vapor deposition (CVD). The sustainable rigid polyurethane foams (RPUFs) were then prepared by incorporating three modified CNCs (CNC-APTMS, CNC-ASCP1, and CNC-ASCP2) from 0.5 to 5wt.%. Afterward, the influence of these three modified CNCs with increasing content on the morphology, thermal, and compressive properties of RPUFs was examined. It was observed that the RPUFs containing 0.5wt.% and 1wt.% of CNC-ASCP2 exhibited a lower thermal conductivity (0.043 ± 0.002 and 0.045 ± 0.001W/m·K, respectively) compared to standard RPUF sample (0.049 ± 0.005W/m·K). Furthermore, these foams also showed enhanced compressive strength (1.96 ± 0.08 and 2.03 ± 0.5MPa) in comparison to the standard RPUF sample (1.25 ± 0.09MPa). This improvement in thermal and compressive properties is attributed to the better compatibility of CNC-ASCP2 with polyol and foam components, promoting efficient nucleation of cells and uniform dispersion within the foam.

Microstructure and energy release properties of W-Zr-Al energetic structural material fabricated by explosive consolidation

Multi-element intermetallic energetic structural materials (ESMs) as a new typical ESMs characterized by their high heat release properties and strength, which could be applied as reactive fragment, reactive shell and reactive shaped charge. Al-based ESMs had been extensively studied due to their excellent mechanical properties and high energy release characteristics. But, the low density of Al-based ESMs hindered its application. However, the need for higher density and energy release persists. In this work, the nearly fully dense W-Zr-Al ESMs with a molar ratio of 1.9:1:1 was fabricated successfully by explosive consolidation. The density reached 10.12 g/cm3 (97.5 % of the theoretical maximum density). Microstructure of the specimen was characterized by X-ray diffractometer (XRD), optical microscopy (OM), scanning electron microscope (SEM), energy dispersive spectrometry (EDS) and transmission electron microscope (TEM). The heat treatment was used to further improve the performance of the specimen and the mechanical properties of quasi-static compression was investigated before and after heat treatment. The reaction activity and process of W-Zr-Al ESMs was discussed by differential scanning calorimetry (DSC). Besides, the impact-induced energy release tests were carried out to evaluate the reactive characteristics of the W-Zr-Al ESMs. The results indicated that high-density, good-strength and high energy release unreacted W-Zr-Al energetic materials were fabricated successfully by explosive consolidation.

Enhancing Concrete Properties with Banana Stem Juice Additive: A Study on Workability and Compressive Strength

Additives are integral components of modern concrete mixing materials. This study aimed to evaluate the workability and compressive strength of concrete incorporating banana stem juice as a natural additive (BSJA). A laboratory experiment was conducted to assess the impact of BSJA on concrete properties. Concrete mixtures with a ratio of 1:2:4 were prepared both with and without BSJA. A total of 36 cube specimens were created with varying percentages of banana stem juice, and their compressive strengths were measured. The results indicated that the inclusion of banana stem juice affected the concrete properties. On the 21st day, the compressive strength of the concrete without BSJA was 27.67 N/mm², compared to 29.67 N/mm² for 5% BSJA, 16.33 N/mm² for 10% BSJA, and 8.00 N/mm² for 15% BSJA. The slump values recorded were 15 mm for 0% BSJA, 20 mm for 5% BSJA, 45 mm for 10% BSJA, and 65 mm for 15% BSJA. The average compressive strengths of concrete specimens with 5% BSJA at 14 days (23.3 N/mm²) and 21 days (29.2 N/mm²) were higher than those of specimens without BSJA. Over the 14 and 21-day periods, specimens with BSJA consistently showed higher compressive strengths compared to those without. These results suggest that 5% BSJA enhances the compressive strength properties of concrete.

Unveiling the tunable electronic, optoelectronic, and strain-sensitive gas sensing properties of Janus ZrBrCl: Insights from DFT study

Janus monolayers materials exhibit extraordinary physical and chemical properties because of crystal field changes caused by their asymmetric structures. Here, we investigate the electronic, switching, optoelectronic, and strain-sensitive gas-sensing properties of a Janus ZrBrCl monolayer via density-functional theory and the nonequilibrium Green’s function methods. The electronic properties can be tuned by applying biaxial strain and electric fields. In particular, the band gap can be changed from indirect to direct via applied a + 8 % biaxial tensile strain. It can be transformed from a semiconductor to a metal with an applied −14 % biaxial compressive strain, with a 1011 switching ratio. In addition, a biaxial strain and an electric field can modulate visible light absorption and photocurrents. Under a −12 % biaxial compressive strain, the absorption coefficient increased to 5.26 × 105 cm−1 from the intrinsic 4.08 × 105 cm−1. Across biaxial strains from −4% to + 4 %, the photocurrent density peak displayed red and blue shifts, respectively, with increasing tensile and compressive strains. NH3, NO2, and NO physically adsorb on the Br side of the ZrBrCl monolayer. Maximum gas sensitivity values of a ZrBrCl sensor are 52 % in the zigzag direction and 21 % in the armchair direction. After application of the −14 % biaxial strain, the maximum values respectively increased to 76 % and 179 %. The biaxial compressive strain-sensitive gas-sensing properties are driven by changes in the electrostatic potential difference between the Br and Cl surfaces. These findings indicate promising candidate materials for high-performance switching and optoelectronic devices, and also provide a strategy for improved gas sensors.

Mechanical properties investigation on recycled rubber desert sand concrete

The mechanical properties of recycled rubber desert sand concrete were studied to determine the effect of the replacement rate of recycled rubber and desert sand. The replacement rates of recycled rubber aggregates were set to 0 %, 5 %, 10 %, and 15 %, respectively, and for dessert sand aggregates were set to 0 %, 10 %, 20 %, and 30 %, respectively, during concrete preparation. The concrete's compressive, tensile, and freeze-thaw mechanical properties were tested at each replacement rate. The experimental results show that when the replacement rate of desert sand increases from 0 % to 30 %, the replacement rate of recycled rubber is 15 %, and the splitting tensile strength of concrete shows a pattern of first increasing and then decreasing. When the replacement rate for desert sand is 30 %, the replacement rate for recycled rubber rises from 0 % to 15 %, and the splitting tensile strength shows a pattern of first decreasing. With replacement rates of 10 percent for recycled rubber aggregate and 20 percent for desert sand aggregate, the damage to the concrete from external forces is relatively ideal. The compressive strength values are the highest, and the split tensile strength is the best, demonstrating good compressive and tensile strength. The results of CO2 emission analysis show that as the amount of recycled rubber increases, the CO2 emissions per unit volume of concrete also increase. The interface of the micro-optical structure in the concrete is straightforward, the pores are few, and it exhibits good mechanical properties. The concrete undergoes freeze-thaw cycles with relatively stable changes in compressive strength and split tensile strength, demonstrating a solid freeze-thaw resistive mechanical property.

Experimental investigation on mechanical properties of the sandwich structure with orthogonal corrugated core reinforced by polyurethane foam

AbstractThe aim of this paper is to explore the effect of polyurethane foam filler on the out‐of‐plane compressive property and low‐velocity impact resistance of the orthogonal corrugated sandwich panel by experimental method. The results show that foam filling increases the energy absorption and specific energy absorption of the orthogonal corrugated sandwich panel by 64.75% and 38.22% under compressive load, respectively. Furthermore, during compression, the filled foam causes the core strut undergo pure buckling failure and gradually folds rather than brittle fracture. Under low‐velocity impact, the strengthening effect of foam filling on the first peak load of the load–displacement of the orthogonal corrugated sandwich panel decreases with the increase of impact energy, while the inhibition effect on the impactor drop increases with the increase of impact energy. The results can provide a reference for the design and optimization of foam‐filled hybrid sandwich structures.Highlights The compressive property and low‐velocity impact resistance of the foam‐filled orthogonal corrugated sandwich panel are tested. The effect of foam filling on the mechanical properties of the orthogonal corrugated sandwich panel is obtained by comparing the out‐of‐plane compressive response and low‐velocity impact response of the empty and foam‐filled orthogonal corrugated sandwich panel and foam sandwich panel. Foam filling can improve the load‐bearing property and energy‐absorbing capacity of the orthogonal corrugated sandwich panel and make it more stable progressive damage.

Effects of recycled sand and shell sand as sand replacement on the dynamic properties of seawater sea-sand recycled aggregate concrete

This study utilizes recycled sand and shell sand to replace sea-sand in seawater sea-sand recycled aggregate concrete (SSRAC) and explores their dynamic compressive properties. A total of 28 sets of specimens were designed, and their stress-strain curves under different strain rates were analyzed. The findings indicated that the dynamic increasing factor (DIF) of peak stress in SSRAC reached its peak at a 50% replacement ratio of recycled sand, exhibiting a 3.9% to 7.7% increase compared to a 0% replacement ratio. Conversely, there was an overall decreasing trend in the DIF when the replacement ratio of shell sand increased. Using recycled sand resulted in an average reduction of approximately 45% in the elastic modulus of the interfacial transition zone (ITZ), while the introduction of shell sand slightly increased that of it. Finally, considering strain rate effects, a dynamic compressive prediction model for SSRAC with different types of fine aggregates was established.

Compressive Properties and Fracture Behaviours of Ti/Al Interpenetrating Phase Composites with Additive-Manufactured Triply Periodic Minimal Surface Porous Structures

Compressive Properties and Fracture Behaviours of Ti/Al Interpenetrating Phase Composites with Additive-Manufactured Triply Periodic Minimal Surface Porous Structures

Enhancement of the compressive performances of additive manufactured Corrax maraging stainless steel lattice by heat treatment

The objective of this study was to investigate the influences of integrated solution and aging treatment (SAT) on the compressive properties of laser powder bed fusion (LPBF) Corrax maraging stainless steel lattices. Cubic and face-centered cubic with Z-axis strut (FCCZ) lattices were produced and used to formulate two types of functionally-graded material (FGM) lattices. The lattices with FGM directions parallel and vertical to the stress were designated as FGM-P and FGM-V lattices, respectively. The compressive performances and fracture mechanisms were identified experimentally by digital image correction and theoretically by finite element analysis.The results show that SAT can significantly increase the specific strengths of these lattices by 34–42 %. The compressive performances and fracture mode of the FGM-V sample principally corresponded to the rule of mixture. However, the FGM-P sample did not follow the rule of mixture because its deformation concentrated only in the cubic-dominated regions. Moreover, the SEAs of the cubic and FGM-P samples were respectively improved by 30 % and 19 % by SAT, given their higher compressive strength and stable stress–strain curve. SAT can be applied to further extend the future application of these materials as cost-effective, high-performance lightweight structural materials.

Statistical-Based Optimization of Modified Mangifera indica Fruit Starch as Substituent for Pharmaceutical Tableting Excipient.

This study aimed to optimize modified starch from Mangifera indica (mango) fruit using acid hydrolysis and pre-gelatinization via computer-assisted techniques as a substituent for pharmaceutical tableting excipients. The hydrolysis and microwave-assisted pre-gelatinization time and temperature were optimized using a three-level factorial design. The modified starches were characterized for flowability, compressibility, and swelling properties. It was found that all parameters fit a quadratic model, which can be used to predict the properties of the modified starch. The optimized hydrolysis reaction was 3.8 h at 56.4 °C, while the pre-gelatinization reaction was 3 min at 150 °C. Structural changes were found, ascertaining that starch modification was successful. The optimized hydrolyzed starch showed superior properties in relative to unmodified M. indica fruit starch and comparable characteristics to conventional excipients. The optimized pre-gelatinized starch presented an excellent enhancement in the flow and compression properties, with %swelling greatly augmented 3.95-fold and 1.24-fold compared to unmodified starch and SSG, respectively. Additionally, the pre-gelatinized starch presented comparable binding effect, while the hydrolyzed powder had reduced binding capacity due to shorter chains. The findings revealed that the use of software-assisted design of experiment facilitated a data-driven approach to optimize the modifications. The optimized modified mango starch demonstrated potential as a multifunctional excipient, capable of functioning as binder, disintegrant, and diluent.

Improving flexural response of rubberized RC beams with multi-dimensional sustainable approaches

This research presents a sustainable solution to waste tire disposal and raw material depletion by incorporating recycled rubber into concrete mixtures. To mitigate the reduction in mechanical properties, a novel slag pretreatment of rubber particles with controlled temperature is proposed. The study also investigates the effects of pouring concrete in layers with rubberized concrete (RuC) in tension side and normal concrete in compression side, as well as evaluating the use of GFRP compared to conventional steel, thereby introducing multiple innovative dimensions to enhance structural performance. The experimental study included a total of 27 specimens, consisting of normal concrete, untreated rubberized concrete, and treated rubberized concrete mixtures with 15 % rubber content. The study investigated both compression and tension mechanical properties of the concrete mixtures and assessed the flexural response of reinforced concrete (RC) beams. Parameters explored included rubber treatment, utilization of steel and GFRP as tensile reinforcement, and layered concrete pouring. Subsequently, a numerical study was conducted to address the impact of reinforcement ratio and layer depth on the behavior of slag-treated rubberized RC beams. The findings reveal a significant recovery of concrete compressive strength by 23 %, along with a 28 % enhancement in toughness and a 17 % increase in splitting tensile strength attributed to the application of slag treatment to rubberized concrete. The effect of rubber treatment was more pronounced in GFRP RC beams, as they showed similar load capacity as normal concrete. Furthermore, utilizing layered concrete beams with a 67 % depth of slag-treated RuC showed a comparable load capacity to normal RC beams, demonstrating only a 1 % reduction for steel-reinforced beams and a 2.4 % improvement for GFRP-reinforced beams. Notably, the numerical model emphasized this outcome and suggested that increasing the layer depth to 72 % of slag-treated depth displayed better performance.

Compressive and flexural properties and damage modes of aluminum foam/epoxy resin interpenetrating phase composites reinforced by silica powder

AbstractInterpenetrating phase composites (IPCs) can combine the advantages of each component and have a good application prospect. IPCs were prepared by combining open‐cell aluminum foam (AF) and epoxy resin (EP) in three‐dimensional space in this study. Different contents of silica powder (SP, 80, 100, 120, and 140 wt%) were added to EP to improve the compressive and three‐point bending properties of IPCs. In the bending test, acoustic emission (AE) was applied to track the bending deformation of the samples, and k‐means clustering algorithm was applied to identify the damage modes. The compressive and bending properties of IPCs increased first and then decreased with the increase of SP content, and reached the maximum when the SP content was 100 wt%, with a compressive yield strength of 74.6 MPa and a bending peak load of 1.96 kN. The performance degradation was mainly attributed to the AF/EP debonding due to SP distribution at the interface. The X‐type shear band and EP/AF debonding appeared in compression failures of AF and IPCs, respectively. The AE clustering results showed that under bending load, plastic deformation of matrix (60–200 kHz) and fracture failure (230–340 kHz) modes appeared in AF, while EP/AF debonding (60–120 kHz), EP failure (120–230 kHz) and plastic deformation of foam matrix (230–250 kHz) modes appeared in IPCs.Highlights Silica powder was added to improve compressive and bending properties of IPCs. Acoustic emission was used to monitor bending of foam and IPCs firstly. k‐means clustering was used to identify and classify bending damage patterns.

The preparation and axial compressive properties of 3D-printed polymer lattice-reinforced cementitious composite columns

Research on the mechanical properties of 3D-printed lattice-reinforced cementitious materials is becoming increasingly widespread. The bending and compression performances of such materials have been studied from the perspectives of the lattice preparation materials, structural forms, gradient design, and cement-based material types. The extant research has primarily focused on the bending performance of lattice-reinforced specimens, while little research has been conducted on the compressive properties. In addition, the reinforcing effect of the lattice on cementitious materials under lateral constraints has not been considered. This article investigates the compressive performance of cement mortar reinforced by 3D-printed spiral lattices or skin structures with different volume reinforcement ratios (different grid constraint layers). Multi Jet Fusion (MJF) technology was used to print four types of spiral lattices, and six specimens, including a control group, were prepared. The experiment considered the performance differences of polymer-reinforced mortars with different volume reinforcement ratios, bonding performance, and skin reinforcement. The load, displacement, stress, strain and other data of the specimen were measured, and combined with the full field strain measured by DIC technology, the strength, energy absorption performance, ductility, elastic modulus, constraint effect, deformation mechanism, and failure mode of the specimen were comprehensively analyzed. The experimental results indicate that 3D-printed spiral or skin lattices can improve the ductility and energy absorption capacity of cementitious materials. However, the elastic modulus of the raw materials used to reinforce the structure is lower than that of cementitious materials, which will reduce the compressive strength and elastic modulus. In addition, the lateral deformation constraint effect of the lattice or skin structure on the cement mortar under axial compression is not significant. All cementitious specimens were found to exhibit the shear failure of the inclined section under axial compression. This article reveals that 3D printed spiral lattices can improve the deformation ability of cementitious composite materials under compression, providing new ideas for the ideal replacement of stirrups and the development of building energy conservation and emission reduction.

An explainable machine learning approach to predict the compressive strength of graphene oxide-based concrete

Graphene oxide (GO) has shown promise in improving concrete strength. Despite its frequent use in cement composites, its effect on concrete properties is less explored. The influence of GO on concrete remains unclear due to various interactions among constituents such as GO type and percentage, Superplasticiser (SP) type and percentage, dispersion technique, and curing age. Therefore, making prediction of compressive strength using simple mathematical formation is challenging. This study represents the first-ever attempt at developing a comprehensively validated machine learning model to predict GO-concrete's compressive strength characteristics by considering all key variable parameters. A comprehensive laboratory experiment program was conducted to collect the data required for training the machine learning (ML) models. Once the ML models were trained, they were used to predict the relationship of each of those input variables towards the compressive strength properties. Four machine learning models—(a) multiple linear regression (MLR), (b) k-nearest neighbour (KNN), (c) random forest (RF) and (d) extreme gradient boost (XGB)—were utilised to model the relationship between input parameters and compressive strength. Also, explainable machine learning (XML) methods were employed to elucidate the impact of mixed constituents on the compressive strength of GO concrete. The results from test predictions showcase that the XGB has attained a coefficient of determination (R2) of 0.981, coefficient of correlation (R) of 0.99, mean square error (MSE) of 0.9, mean normalised bias (MNB) of 0.004, scatter index (SI) of 0.2 with mean absolute error (MAE) of 0.8 MPa for the predictions, outperforming the remaining models. XML highlighted the true impact of GO and the remaining variables, emphasising that the presence of GO significantly improves compressive strength. The optimum GO content and optimum superplasticiser content observed from the experimental work agreed with results obtained from the XML analysis, showing the consistency of the explanation with the experimental results. This implies the superiority of using XML methods in concrete mix design applications in industry.

EXPERIMENTAL STUDY ON COMPRESSIVE STRENGTH AND SHEAR STRENGTH OF MASONRY UNIT WITH FIBER GLASS AND POLYPROPYLENE FIBER PAINT COATING

In this study, the effects of fiber layers on the compressive and shear strength properties of masonry are investigated. The aim is to improve the mechanical properties of masonry walls that are prone to earthquakes The experimental investigations provide information on the mechanical properties of Indonesian masonry blocks under two conditions: without and with fiber coating. Two different types of fibers were used in this study: Fibreglass and Polypropylene fiber. The fiber content is 8% for 1 kg of paint with 5% water. The thickness of the coating applied to the masonry ranges from 1 mm to 3 mm. The compressive strength of the samples with a layer of polypropylene fibers with a thickness of 1 mm and 3 mm is 30.32 kg/cm², 31.16 kg/cm² and 47.16 kg/cm², respectively. The compressive strength of the samples with a layer of glass fiber paint with a thickness of 1 mm, 2 mm, and 3 mm is 30.1 kg/cm², 31.22 kg/cm², 53.31 kg/cm² and the value of the control sample is 25.89 kg/cm². The shear strength of masonry with polypropylene-coated fiber with a layer thickness of 1 mm, 2 mm, and 3 mm is 3.93 kg/cm², 4.64 kg/cm², and 5.89 kg/cm². The bricks reinforced with glass fiber paint with a layer thickness of 1 mm, 2 mm, and 3 mm have 3.77 kg/cm², 5.31 kg/cm², and 5.05 kg/cm².

Experimental study and model evaluation on BFRP tube-confined RAC cylinders under monotonic axial compression

Using concrete waste as recycled aggregate (RA) in engineering structures can generate great ecological and economic benefits. To enhance the compressive properties of RA concrete (RAC), basalt fiber reinforced polymer (BFRP) tubes were used to provide lateral confinement in this study. Monotonic axial compressive tests were carried out on BFRP tube-confined RAC using 36 cylindrical specimens. Detailed test results were presented, including the failure mode, stress-strain curve, compressive strength, axial strain, and dilation property. The influences of the RA replacement ratio and the number of BFRP layers were analyzed. The test results indicated that BFRP tube-confined specimens exhibited strain hardening behavior in all of their stress-strain curves even if only a single layer of BFRP was used, and the failure was due to BFRP rupture along the hoop direction. The ultimate strength and deformability of RAC were significantly enhanced using BFRP confinement, with the confinement effect becoming more pronounced with increasing RA replacement ratios and BFRP layers. Compared to the unconfined specimens, the maximum enhancements in the ultimate strength and axial strain reached 2.8 times and 18.1 times, respectively, after BFRP confinement. Three typical theoretical models of FRP-confined concrete were employed to predict the ultimate conditions and axial stress-strain curves of the specimens. Finally, an improved model was formulated based on the test data to predict the ultimate conditions of BFRP tube-confined RAC cylinders. The proposed model was proven to predict the axial stress-strain curves, ultimate strength, ultimate axial strain with reasonable accuracy.