Flexural Tests Research Articles

Experimental study on the behavior of polypropylene fiber-reinforced concrete beams

This research aimed to analyze the behavior of concrete beams reinforced with polypropylene fibers. This type of reinforcement has been increasingly used in construction to improve the tensile properties of concrete, mitigate the propagation of microcracks due to shrinkage, enhance impact capacity, and extend the durability of concrete structures. An experimental study was conducted on twelve concrete beams with dimensions of 150 x 150 x 600 mm, reinforced with polypropylene fibers, divided into four groups: 0.35%, 0.45%, and 0.55% fibers/m³ of concrete, along with a reference group without fibers. Four-point flexural tests were performed following the recommendations of the NBR 12142 (ABNT, 2010) to evaluate the influence of the fibers on the contribution to tensile strength in flexure. The results showed that the beams reinforced with 0.35% fibers/m³ exhibited the best performance, with a significant increase in strength compared to the other groups, with and without fiber reinforcement. All fiber-reinforced groups showed a shift from brittle to ductile behavior. Additionally, the beams with 0.55% fiber content demonstrated greater ductility but less contribution to tensile strength.

Upcycling Post-Consumer Paint Pail Plastic Waste.

The need for ending plastic waste and creating a circular economy has prompted significant interest in developing a new family of composite materials through recycling and recovery of waste resources (including bio-sourced materials). In this work, a family of natural fiber-reinforced plastic composites has been developed from paint pail waste recycled polypropylene (rPP) and waste wool fibers of different diameter and aspect ratio. Composites were fabricated by melt processing using polypropylene-graft-maleic anhydride as a compatibilizer. The internal morphology, interfacial and thermal characteristics, viscoelastic behavior, water sorption/wettability, and mechanical properties of composites were studied using electron microscopy, high-resolution synchrotron Fourier transform infrared microspectroscopy, thermal analysis, rheology, immersion test, contact angle measurement, tensile test and flexural test. The composite matrix exhibited an internal morphology of coalescent micro-droplets due to the presence of polyethylene and dry paint in the rPP phase. In general, the rheological and mechanical properties of the composites comprising higher-aspect-ratio (lower diameter) fibers exhibited relatively superior performance. About an 18% increase in tensile strength and a 39% increase in flexural strength were measured for composites with an optimal fiber loading of 10 wt.%. Interfacial debonding and fiber pull-out were observed as the main failure mechanism of the composites. The developed composites have potential for applications in automotive, decking, and building industries.

Direct tensile tests on steel fiber reinforced concrete with focus on wall effect and fiber orientation

Adding steel fibers to concrete essentially improves its post-crack tensile properties. To determine this experimentally, indirect methods, such as flexural tensile tests, are generally used, which allow only indirect conclusions about the material´s tensile properties. In contrast, direct tensile tests provide the desired result immediately, but are difficult to realize. A key parameter affecting the performance of the SRFC is the orientation of the fibers, which is mainly influenced by the manufacturing process. Typically, when the concrete is cast, the steel fibers align with the edges of the formwork. This is commonly called the wall effect. We address these issues, presenting the setup and results of direct tensile tests on bone shaped specimens with three different steel fiber contents. For each content, a series of specimens with a three-sided formwork (i.e. three-sided wall effect and strong influence on the fiber orientation) and a series with cut-out bones (i.e. one-sided wall effect and less influence on fiber orientation) were fabricated and tested. After these tests, the fiber orientation was determined using an opto-analytical method to quantify the influence of the manufacturing methods on the fiber orientation. Comparing the stress-crack-opening relationships shows that the cut specimens at 0.5 mm crack openings have only about 80% of the tensile strength of three-sided formwork specimens. This effect decreases with larger crack openings and vanishes at about 3 mm crack opening. Finally, a new fiber reinforcement index is defined to correlate observed stress in direct tensile tests to fiber content and orientation in direct tensile tests.

Effect of High Fiber Content on Properties and Performance of CFRTP Composites

Continuously reinforced thermoplastic composites are widely used in structural applications due to their toughness, light weight, and shorter process cycle. Moreover, they provide flexibility in design and material selection. Unlike thermoset composites, continuous fiber content to maximize mechanical properties in thermoplastic composites has not been well investigated. In this paper, three thermoplastic systems are investigated to study the optimum content of continuous fiber reinforcement. These systems include carbon fiber/polyphenylene sulfide (PPS), glass fiber/PPS, and glass fiber/high-density polyethylene (HDPE). Tapes were made at several fiber contents, and samples were compression molded and tested using thermo-gravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), tensile, 3-point flexure, and short-beam shear tests. Results revealed that higher fiber content led to an increase in the glass transition and melt transition temperatures of the polymer. Some mechanical properties increased with fiber content and then began to decrease upon further addition of fibers, while other properties, such as ductility and interfacial bond strength, decreased with more reinforcement. Furthermore, the optimum fiber contents to maximize mechanical properties are different for different properties and different materials.

Mechanical Properties of Permeable Concrete Reinforced with Polypropylene Fibers for Different Water–Cement Ratios

Permeable concrete is a material that allows water filtration, reduces surface runoff, and maintains the natural water cycle. Previous studies have shown that its mechanical properties, particularly its compressive and flexural tensile strengths, are generally lower than those of conventional concrete, with significant variability observed among similar tests. This study investigates the compressive strength, flexural strength, and permeability of polypropylene fiber-reinforced permeable concrete specimens at two water–cement ratios (0.30 and 0.35). The mix design was conducted using the ACI 522R-10 method. Forty-eight cylinders measuring 200 mm × 100 mm were fabricated for permeability and compression tests. Additionally, 12 beams measuring 100 mm × 100 mm × 350 mm were produced and subjected to simple flexural testing in accordance with ASTM C78 guidelines. Compressive strength versus permeability and load versus deflection graphs were plotted, and the fracture energy was calculated for various deflections. The results indicate that the addition of fibers increased permeability and tensile strength but decreased compressive strength. Furthermore, an increase in the water–cement ratio led to higher compressive and flexural tensile strengths.

Study of the Effect of Cedar Sawdust Content on Physical and Mechanical Properties of Cement Boards.

The growing demand for sustainable building materials, amid escalating costs, has spurred interest in alternative solutions such as wood cement composites. This study explores the feasibility of producing wood cement boards (WCBs) using locally sourced cedar sawdust as a reinforcing agent. Boards with a thickness of 10 mm and a target density of 1200 kg/m3 were manufactured under pressures ranging from 2 to 6 MPa for 24 h. Cedar sawdust, used as raw and untreated material, was incorporated into the mixture as a partial substitute for cement in varying proportions, ranging from 10% to 25% (by weight). The WCBs were cured for 28 days under ambient conditions. Physical properties including density, water absorption (WA), and thickness swelling (TS) were assessed, along with mechanical properties through flexural tests. The results showed that increasing cedar sawdust content decreased both density and mechanical performance while increasing WA and TS. Microstructural analysis (SEM and EDS) revealed significant porosity at higher sawdust contents, while lower contents had better matrix-reinforcement cohesion. Additionally, substantial levels of calcium and silicon were detected on the sawdust surface, indicating stabilized cement hydration products. These findings, supported by thermal (TGA and DSC) and FTIR analyses, clearly demonstrate that cement boards with 10% cedar sawdust exhibit favorable properties for non-structural applications, such as wall and partition cladding.

Novel bio-based propylene-derived phthalonitrile compounds: Synthesis, curing behavior and thermal properties

Bio-based bisphenol compounds were prepared using eugenol from biomass as the initial raw material. A reaction of nucleophilic substitution takes place with 4-nitrophthalonitrile in an environmentally friendly solvent to produce bio-based propenyl-derived phthalonitrile monomers. The effective preparation of compounds was proven using hydrogen and carbon nuclear magnetic resonance and fourier transform infrared spectroscopy (FT-IR). By employing the process of free radical catalysis, it is possible to directly cure the novel phthalonitrile monomers without the need for a specific small molecule curing agent. The cured resin was reported to have high glass transition temperature, good thermal stability, and processing properties by FT-IR, differential scanning calorimetry, thermogravimetric analyzer, dynamic mechanical analyzer, and rheometer techniques. The flexural test and scanning electron microscopy results show that both resins have a consistent, flawless structure and improved mechanical properties. Eugenol is derived from sustainable biomass, offering an environmentally friendly approach to utilizing biological monophenols effectively. It provides the benefits of carbon reduction and renewability, making it a valuable and eco-conscious resource.

Boosting mortar performance: use of recycled brick sand for enhanced mechanical properties

The construction industry is constantly seeking ways to become more sustainable. One area of exploration is mortar technology, where researchers are looking at replacing traditional components with alternative materials and adding a superplasticizer to improve mechanical strength and reduce the use of natural resources. The present study focuses on substituting brick waste sand in mortar at different replacement ratios of 0%, 10%, 30%, and 50%. The main objective is to investigate the effect of this substitution material on the properties of the mortar. The researchers have conducted compression and flexural tensile tests on prismatic specimens (4 x 4 x 16 cm³) at various curing periods (2, 7, and 28 days). The results showed that replacing 50% of sand with brick wastes significantly improved mortar properties. However, replacing more than 50% of the sand hurt the workability of the mortar. This study highlights the potential of using brick waste sand as an alternative to sand in mortar production, promoting resource conservation and sustainable construction. The findings suggest that while a 50% replacement ratio is beneficial, it is essential to carefully consider the mix design to maintain workability and overall performance.

Avaliação tecnológica de argamassa de revestimento produzida com vermiculita expandida

The construction industry is associated with a high consumption of non-renewable resources, such as sand, in addition to the energy demand involved in the construction processes and the use of buildings. In the search for new technologies for traditional building materials, cement mortars have been modified by replacing sand with lightweight aggregates, such as expanded vermiculite. The aim of the present study is, therefore, to analyze the flexural tensile strength of rendering mortars produced with a 1:1:6 mix ratio by volume, with 10% and 20% substitution of natural aggregate by expanded vermiculite, comparing them with a reference mixture. The experimental phase consisted of the characterization of aggregates, preparation of mortars, tests in the fresh state, and flexural tensile strength tests. Overall, the replacement of sand with expanded vermiculite increased the flexural tensile strength, enhanced the fresh-state bulk density, and reduced the consistency index. Known for contributing to improvements in thermal and acoustic insulation, reducing structural weight, among other effects, the use of vermiculite in mortars demonstrated potential based on the results, as it did not significantly impair the mechanical behavior of the mixtures.

Improved creep resistance of short carbon fiber reinforced polyetherimide composite by solution mixing method

Creep resistance is critical for ensuring the dimensional stability and safe operation of composite components. However, the creep resistance of short fiber reinforced thermoplastic composites has been rarely reported and that of the composites manufactured by conventional extrusion compounding combined with injection molding is kind of low. In this work, in order to address this issue, two short carbon fiber-reinforced polyetherimide (SCF/PEI) composites named respectively as SCF/PEIE and SCF/PEIS are prepared by both conventional extrusion compounding and our newly developed solution mixing method combined with injection molding. The solution mixing method involves the dispersion and mixing of carbon fibers within a PEI solution and allows for the retention of longer fiber lengths. Experimentally, the creep behaviors of the SCF/PEI composites were examined through tensile and flexural creep testing at various stress levels in a wide temperature range. Theoretically, the creep behaviors were characterized by employing the Schapery model and the time–temperature superposition principle (TTSP), and the impact of fiber length retention on creep resistance was quantitatively analyzed using the Fu-Lauke model. The results demonstrate that compared to the SCF/PEIE composite, the SCF/PEIS composite exhibits a higher creep fracture stress level (175 MPa) and a more extensive linear viscoelastic region (0–85 MPa) at room temperature. Furthermore, the SCF/PEIS composite was observed to have a significantly longer secondary creep stage at an elevated temperature of 210 °C. Overall, the creep resistance of the newly manufactured SCF/PEIS is significantly superior to that of the SCF/PEIE, which effectively extends the service life and operational capacity of injection-molded SCF/PEI composites.

An analysis of diffusion mechanism and mechanical properties of jute, JUCO, and banana fiber composites in three different mediums

Natural fiber-reinforced polymer composites (NFRPC) are the most desirable for their low-cost, eco-friendly, and high-durability properties. Scientists are facing numerous challenges with this type of composite in a wet or high-humid environment. High water absorption and reduced mechanical properties are the main concerns for this type of composite. A new kind of fiber mat called JUCO, which is a mixture of jute and cotton, is introduced here. Banana fiber and jute yarn were used to fabricate unidirectional mats, which were made using a custom-designed handloom. The composite fabrication was done by hand layup with the cold press method. The tensile and flexural strengths decreased after immersion in three mediums (pH 3, pH 7, and pH 8) for 150 days due to the water aging effect. Minimum strength was found when the samples were immersed in pH 3 mediums. Tensile and flexural test results were also evaluated by the finite elemental method (FEM) to validate the experimental results. The main objectives of this study are to investigate the mechanical properties and degradation due to the aging of newly developed JUCO fiber-based composites.

Experimental and Numerical Characterization of the In-Plane Shear Behavior of a Load-Bearing Hollow Clay Brick Masonry System with High Thermal Performance

Modern masonry systems are generally built with hollow clay bricks with high thermal insulating properties, fulfilling the latest sustainability and environmental criteria for constructions. Despite the growing use of sustainable masonries in seismic-prone countries, there is a notable lack of experimental and numerical data on their structural behavior under lateral in-plane loads. The present study investigates the in-plane shear behavior of load-bearing masonry walls with thin bed joints and thermal insulating hollow clay blocks. Shear-compression tests were performed on three specimens to obtain information about their shear strength, displacement capacity and failure modes. The experimental characterization was supplemented by three shear tests on triplets, along with flexural and compression tests on the mortar for the thin joints. Furthermore, two Finite Element (FE) models were built to simulate the shear-compression tests, considering different constitutive laws and brick-to-brick contact types. The numerical simulations were able to describe both the shear failure modes and the shear strength values. The results showed that the experimental shear strength was 53% higher than the one obtained through Eurocode 6. The maximum shear load was found to be up to 75% greater compared to similar masonry specimens from the literature. These findings contribute to a better understanding of the potential structural applications of sustainable hollow clay block masonry in earthquake-prone areas.

Experimental investigation on the mechanical characteristics of ultra-high-molecular-weight polyethylene (UHMWPE) based fiber-reinforced concrete

This study investigates the static and dynamic mechanical properties of ultra-high-molecular-weight polyethylene (UHMWPE) fiber-reinforced concrete (FRC). The properties were assessed by conducting compressive strength, flexural strength, split tensile strength, and impact resistance. The pneumatic dispersion method was used for the UHMWPE fiber pretreatment. The concrete mix was prepared with a water-to-cement ratio of 0.6 and an aggregate fineness modulus of 5.39. UHMWPE fibers, measuring 6 mm and 12 mm in length and incorporated at addition rates of 5 wt‰, 10 wt‰, 15 wt‰, and 20 wt‰ of the fiber-to-cement weight ratio, were added to the concrete specimens for testing. The results showed that the FRC with 12 mm UHMWPE fiber and 15 wt‰ fiber-to-cement weight ratio achieved the best performance in the compressive strength test, and it increase 51.92 % compared with benchmark specimen. For the flexural test results, the 6 mm UHMWPR fiber performed best at a 15 wt‰ addition ratio, and it increase 18.77 % compared with benchmark specimen. Moreover, the FRC with 12 mm UHMWPR fiber excelled at a 20 wt‰ addition ratio in split tensile strength test, and it increase 92.14 % compared with benchmark specimen. The drop weight test indicated that a 15 wt‰ addition ratio with 12 mm UHMWPE fiber significantly enhanced performance, with an average impact number improvement of 5527 % under a 50 Joule impact energy, compared to the benchmark specimens. The study concludes that incorporating UHMWPE fiber into concrete significantly boosts its static and dynamic performance.

Material Performance Evaluation for Customized Orthoses: Compression, Flexural, and Tensile Tests Combined with Finite Element Analysis.

Orthoses are commonly used for treating injuries to improve the quality of life of patients, with customized orthoses offering significant benefits. Additive manufacturing, especially fused deposition modelling, enhances these benefits by providing faster, more precise, and more comfortable orthoses. The present study evaluates nine polymeric materials printed in horizontal and vertical directions by assessing their performance through compressive, flexural, and tensile tests. Among all materials, polycarbonate, polylactic acid, and ULTEMTM 1010 showed the most promising results, not only because they had the highest mechanical values, but also due to their minimal or no difference in performance between printing directions, making them advantageous in orthoses fabrication. Based on this, a finite element model of an ankle-foot orthosis was developed to simulate the deformation, strain, and stress fields under static conditions. The findings aim to optimize material selection for orthotic fabrication, where ULTEMTM 1010 is presented as the material with improved performance and durability.

Optimal content of bio-fibers in structural ice

The use of ice as structural material has two main concerns: the low strength and the brittle failure of the structures. With the aim of finding a solution to these problems, an experimental campaign, performed on fiber-reinforced ice (FRI) samples, made with plain water and bio-fibers, is presented in this paper. In total, 12 ice prisms were cast at − 18 °C with a different content of fibers, and then tested in three-point bending and uniaxial compression. Test results indicate that the presence of a reinforcement increases both flexural and compressive strength with respect to plain ice. Moreover, FRI is a tougher material, as multiple cracking and deflection hardening behavior can be observed in the flexural tests. However, the mechanical performances of plain ice are not always enhanced by the fiber-reinforcement. Therefore, an empirical model, capable of predicting the optimal content of bio-fibers, is also proposed.

EXPERIMENTAL STUDY ON OPTIMIZING THE FUSED DEPOSITION MODELING PARAMETERS FOR POLYETHYLENE TEREPHTHALATE GLYCOL MATERIAL USING TAGUCHI METHOD

In many different manufacturing techniques, additive manufacturing technologies have proven to be quite useful for developing a prototype model in wide range of applications. In that technique, Fused Deposition Modeling (FDM) is one of the concern favorite methods used in industries, because it can create complex structures at a low cost. FDM uses the polymer ingredients that are melted, extruded, and layered on top of one another to create the desired product, independent of design intricacy. This examination analyzes the effects of several process variables on the flexural and impact characteristics of parts produced of polyethylene terephthalate glycol (PETG)material, including infill structure, layer thinness, infill multi-layering, and infill concentration. The L9 orthogonal array was developed by the Taguchi method to be employed in this design of experiment. Through the analysis of variance (ANOVA), the study elucidated the relative substance and percentage effort of each process parametric quantity to the desired outcomes. The results obtained through the Taguchi method revealed optimal parameters for both impact strength and flexural tests. For impact strength, the optimum factor was determined as a layer thinness of 0.12-millimeter, quarter cubic infill structure, 30% infill denseness (density), and a multi-layering of 3. Conversely, for the flexural test, the optimal factor was found to be a layer thinness of 0.12-millimeter, cross 3D infill structure, 60% infill denseness, and a multi-layering of 4 respectively.

Thermo-mechanical coupling failure modeling of 3D four-directional braided composite I-beam under four-point flexure at room temperature, −50°C and 85°C

This paper aims to experimentally and numerically probe thermo-mechanical coupling behaviors of 3D4D (three-dimensional four-directional) braided composite I-beam under four-point flexure. An improved algorithm based on thermo-mechanical coupling constitution model, and mixed failure criterion are devised for modeling thermo-mechanical coupling failure process of 3D4D braided composite I-beam under four-point flexure. Quasi-static four-point flexure tests are, respectively, performed on 3D4D braided composite I-beam at RT (room temperature), −50 ° C and 85 ° C , and mechanical behaviors and failure mechanisms are analyzed and discussed from experiment results. To validate the aforementioned model and algorithm, novel global-local FE (finite element) model is generated and integrated with new algorithm for modeling failure process of 3D4D braided composite I-beam under four-point flexure at three temperatures, and numerical predictions agree well with experimental findings, demonstrating the effective and rational use of the proposed model in the paper.

Lateral stiffness of modular steel joint with semi-rigid bolted intra-module connection

In contrast to the beam-column joints found in traditional assembled steel structures, modular steel structures feature inter-module and intra-module connections within their joints. While existing research has largely focused on the mechanical properties of inter-module connections, the impact of intra-module connection stiffness on the performance of modular steel joints remains unclear. This study introduces a novel corner-fitting-reinforced fully bolted joint specifically designed for modular steel structures. A series of experiments were conducted, including a flexural test on bolted intra-module connection to determine its initial rotational stiffness, and four groups of lateral static tests on full-scale modular steel joints with varying intra-module connection stiffnesses. These tests aimed to characterize mechanical properties such as load-carrying capacity, lateral stiffness, strain development, and ductility. The study elucidates the influence of intra-module connection stiffness on the lateral stiffness of modular steel joints. Furthermore, a refined finite-element (FE) model of the corner-fitting-reinforced fully bolted joint was developed. Simulation results showed good agreement with experimental findings., with an average error of less than 10 % for ultimate load-carrying capacity prediction. The FE model also, analyzed the stress-strain development of the corner fitting throughout the process. The study establishes a theoretical analysis model for the corner-fitting-reinforced fully bolted joint and derives a theoretical formula for the initial lateral stiffness of the modular steel joint, considering semi-rigid intra-module connections. This formula aligns well with both experimental and FE results, with a maximum error of 15 %. Finally, the study delves into the force-transfer mechanism of the corner-fitting-reinforced fully bolted joint, providing valuable insights for its design.

MECHANICAL BEHAVIOUR OF ISTLE FIBRE COMPOSITE REINFORCED WITH EPOXY AND E-GLASS AT DIFFERENT FIBRE ORIENTATIONS

This paper was aimed to study the mechanical properties of Istle fibre composites. The process of fabrication was done by hand layup technique at three different fibre orientations i.e., unidirectional, bidirectional and 45 degrees inclined, and also its effect on tensile and flexural property that was studied in the Instron Testing Machine. The fibre volume ratio was kept uniform for the entire specimen as 50:50. The treatment of istle fibre was done with sodium hydroxide to increase the fibre matrix bonding. The effect of E-glass reinforcement has also been studied in both bending tests and flexural tests. The maximum tensile and bending modulus recorded were from unidirectional fibre specimen.

Investigating mechanical properties of SIFCONs produced with waste PET fibers

It is known that slurry infiltrated fibers concrete (SIFCON) is a type of concrete that possesses superior properties. To reduce the initial cost of fibers and to overcome the detrimental effect of waste plastic this study has been attempted to use polyethylene terephthalate (PET) waste fibers to produce SIFCON mixtures and investigate their properties. Six SIFCON mixtures were produced in which three volumetric proportions of fibers (3 %, 5 %, and 7 %) and two aspect ratios (36.8 and 24.57) were used. Behavior of these mixtures was compared with a normal concrete mixture containing no fibers and having approximately the same compressive strength. Flexural testing was conducted for small prismatic specimens and also on large reinforced concrete beams. The behavior was evaluated in terms of flexural strength, toughness and ductility. The results showed better flexural strength in case of SIFCON mixtures compared to normal concrete mixtures for both investigated aspect ratios. In addition, toughness and ductility were significantly improved as PET fiber content increase. Moreover, enhancement in toughness and ductility is more obvious in case of first aspect ratio. SIFCON reinforced beams showed a ductile behavior and sustained more damage. The use of PET fibers can be considered a promising option to produce sustainable SIFCON mixtures with improved properties.