Fiber-reinforced Composite Materials Research Articles

Evaluation of new nano-cutting fluids for the processing of carbon fiber-reinforced composite materials

Carbon fiber-reinforced composites (CFRP), known for its impressive specific strength and modulus, finds extensive applications in defense, aerospace, automotive, and various other industries. Nevertheless, the widespread application of dry cutting in machining Carbon Fiber Reinforced Polymer (CFRP) presents significant challenges, including dust pollution, fiber layer delamination, and uneven surface quality. These issues make the machining of CFRP a formidable task. In the present investigation, a novel nanohybrid cutting fluid was successfully prepared by adding molybdenum disulfide (MoS2)/silicon carbide (SiC) nanoparticles to a base-cutting fluid synthesize from ethanol, polyethylene glycol, and sodium dodecyl sulfate. Moreover, employing minimal lubrication techniques, the nano-cutting fluid was applied to the milling process of CFRP. The feasibility of applying the cutting fluid to CFRP machining was demonstrated through short beam shear tests. Horizontal comparative milling tests were executed on CFRP, varying operational parameters and cooling-lubrication scenarios. The cooling-lubrication mechanisms of the nanofluid were analyzed, providing further validation of the effectiveness of the cutting fluid in CFRP machining. The results suggest that the nanofluid has a negligible impact on the interlaminar shear strength of CFRP, with only a 3.85% reduction. In comparison to other cooling-lubrication conditions, milling CFRP with the novel nanofluid resulted in a reduction of milling forces by 4.78%–24.84%, a decrease in milling temperatures by 15.38%–69.37%, a lowering of surface roughness by 10.78%–35.93%, and a reduction in tool tip wear by 6.25%–53.81%. Observable phenomena such as fiber pull-out and fracture were significantly reduced.

A multi-stable deployable quadrifilar helix antenna with radiation reconfigurability for disaster-prone areas

In disaster-prone areas, damaged infrastructure requires impromptu communications leveraging lightweight and adaptive antennas. Accordingly, we introduce a bi-stable deployable quadrifilar helix antenna that passively reconfigures its radiation characteristics in terms of pattern and polarization. The proposed structure is composed of counter-rotating helical strips, connected by rotational joints to allow a simultaneous change in the helix height and radius. Each helical strip is composed of a fiber-reinforced composite material to achieve two stable deployed states that are self-locking. The reconfiguration between an almost omnidirectional pattern and a circularly polarized directive pattern enables the antenna to be suitable for both terrestrial and satellite communication within the L-band. More specifically, the presented design in infrastructure-less areas achieves satellite localization with directive circularly polarized waves and point-to-point terrestrial connectivity with an almost omnidirectional state. Hence, we present a portable, agile, and passively reconfigured antenna solution for low-infrastructure areas.

A novel methodology to measure the transverse Poisson’s ratio in the elastic and plastic regions for composite materials

A new methodology to measure the transverse Poisson’s ratios in fibre-reinforced composite materials was developed. Transverse tensile and transverse compressive standardised tests were instrumented using digital image correlation equipment to measure the lateral strain field of the specimens. A thermoplastic-based composite material was used to describe the proposed methodology. The elastic transverse Poisson’s ratio exhibits a different behaviour in tension than in compression, its value being greater in compression than in tension. Assuming no plastic strain in the longitudinal direction, the plastic transverse Poisson’s ratio in compression suggests no volumetric plastic strains for small axial plastic strains, however, plastic dilatancy was observed when the amount of compressive plastic axial strain increases.

An enhanced constitutive model to predict plastic deformation and multiple failure mechanisms in fibre-reinforced polymer composite materials

Spurious damage modes in continuum damage mechanics models for fiber-reinforced polymer composite materials based on the effective stress tensor can be generated when large strains occur. A methodology to prevent this spurious phenomenon is developed in the present work. The longitudinal damage activation functions are based on the effective stress tensor, however, nominal stresses are used on the transverse damage activation functions. The proposed method can be straightforwardly implemented on previously-developed constitutive models which use the effective stress tensor, an explicit implementation of the proposed constitutive model is presented. The enhancement of the predicted failure mechanisms obtained from the present constitutive model, with respect to the models which use the effective stress tensor, is demonstrated. The proposed constitutive model presents a good agreement of the predicted failure pattern obtained from open-hole compressive experimental tests, as well as on the predicted failure strength.

Evaluation of microhardness of short fiber-reinforced composites inside the root canal after different light curing methods – An in vitro study

ObjectivesShort fiber-reinforced composite (SFRC) materials make it possible to reinforce root canal treated teeth with individualized, directly layered intraradicular posts (the Bioblock technique). The question arises, however, as to whether the photopolymerization of the material is sufficient deep within the root canal space and if it can be improved through different light-conducting options. Our study aimed to investigate the hardness of intraradicular SFRC material applied using the Bioblock technique and cured with various illumination methods, as measured through nanoindentation. Materials and methodsFor this investigation, thirty plastic artificial teeth that had undergone root canal treatment were selected. These teeth were randomly divided into six study groups (Group 1–6; each group consisting of 5 teeth). The restoration procedures involved the use of SFRC or conventional composite materials, placed 6 mm apically from the root canal orifice. In Group 1 and 2, a conventional composite was used, whereas in Group 3–6, SFRC was employed for interradicular reinforcement (with a layered technique in Group 3 and 4 and a bulk-fill technique in Group 5 and 6). A modified light source was utilized for photopolymerization in Group 2, 4, and 6, whereas in Group 3 and 5, the polymerization light was directed through a prefabricated glass fiber posts. The control group (Group 1) utilized conventional composite material with a standard light-curing method. Following embedding and sectioning, the hardness of the composite materials was measured at 2 mm intervals within the root canal (1st, 2nd, 3rd measurements, in the coronal to apical direction). ResultsDuring the 1st measurement, light curing conducted through the glass fiber posts (Group 3 and 5) led to markedly higher hardness levels compared to the groups restored with conventional composite (control group with p = 0.002, p = 0.001, and Group 2 with p = 0.043, p = 0.034, respectively). In the 2nd measurement, only Group 5 demonstrated significantly greater hardness in comparison to the control group (p = 0.003) and Group 2 (p = 0.015). However, in the 3rd measurement, no statistically significant differences were observed among the groups. Conclusionlight curing through the glass fiber post provides outstanding hardness for the SFRC material in the apical layer in the root canal.

Scalable and passive carbon nanotube thin-film sensor for detecting micro-strains and potential impact damage in fiber-reinforced composite materials

Structural health monitoring (SHM) of brittle structures will require versatile sensing instrumentation that can transmitting transient loadings into rapid electrical responses. This research investigated the sensing performance of CNT Buckypaper (CNT-BP) thin-films on stressed fiber-reinforced composites, which are integral materials to various industries of the infrastructure. Three-point bending experiments revealed an extraordinary gauge factor (∼40) and impressive response linearity. Electrical responses were instantaneous; moreover, low force impacts were detectable, the sensors provided clear indications of spatial recognition. Most importantly, the manufacturing methods are scalable and cost effective compared to commercialized strain gauges. This study examined micro-strain measurements (<1%) of carbon fiber composites, in which bending strain of 0.002% could be detected. In addition, damage progressions of glass fiber composites were recorded in response to low-impact energies. Less than 20 J of impact energy was detectable by the sensor, and the severity could be assessed from drastic changes in the sensing behavior.

Damage assessment during ultrasonic fatigue testing of a CF-PEKK composite using self-heating phenomenon

The knowledge and experience with the very high cycle fatigue (VHCF) behavior are limited compared to the low cycle and high cycle fatigue behavior of fiber-reinforced composite materials. Accelerated cyclic loading using an ultrasonic fatigue testing system is one potential solution to evaluate the longevity of composite materials within a reasonable time. Insufficient sampling rates and the inherent inaccuracies of non-contact measurement devices pose critical challenges in the adaptation of accelerated fatigue experiments. This study aims to overcome these challenges by combining the temperature response of the composite specimen and the input parameters for the dynamic response of the in-house developed ultrasonic fatigue testing system to detect damage before failure. Increasing- and constant-amplitude fatigue experiments were conducted on a carbon fiber satin fabric-reinforced poly-ether-ketone-ketone (CF-PEKK) composite material. These experiments were carried out under three-point bending loading conditions at a cyclic frequency of about 20 kHz. Various parameters, such as the surface temperature, the cyclic displacement, and the input resonance parameters of the ultrasonic generator, were recorded during these experiments. The VHCF behavior of the CF-PEKK material system was characterized based on these results and through digital light optical microscopy.

A removable use of FRP for the confinement of heritage masonry columns

For masonry structures in historical heritage with architecturally valuable features, such as frescoed surfaces, the application of structural reinforcement techniques appears to be very complex due to the requirements of removability and limited invasiveness. This is valid with reference to both traditional techniques and modern techniques, such as the external reinforcement with fibre-reinforced composite materials. In this scenario, the use of fibersreinforcedpolymers (FRPs) is drastically forbidden due to the use of epoxy-based matrix, which does not allow the removal of the intervention without damage of the substrate, even if the mechanical effectiveness of this system has been largely tested and proved. In fact, the reversibility is one of the most relevant aspects in the field of Heritage engineering. Thus, many efforts need to be spent in order to meet possible solutions, able to mitigate the risk, especially against seismic forces and other natural risks, while ensuring the conservation of the built heritage. This experimental research, which follows a first study on a smaller scale, aims to answer the question: how could a masonry column with frescoes and valuable surfaces be strengthened or repaired in a completely reversible manner?. Two strengthening methods were studied and are proposed herein by assuring the removability of the FRP-confinement of masonry columns. The first technique consists of a liquid adhesion inhibitor applied by brush before the hand lay-up installation of the FRP. The second is set by the interposition of a Mylar™ layer between the substrate and the FRP jacket. Uniaxial compression tests were performed in order to demonstrate the efficacy of the new strengthening techniques in increasing the axial strength (+ 39% and + 27% on average for the tuff- and limestone-based masonry, respectively) and displacement capacity (+ 32% and + 171% on average for the tuff- and limestone-based masonry, respectively) with respect to un-confined columns. Masonry columns FRP-confined with traditional wet lay-up were also tested for direct comparison. At a later moment, the FRP-jacket was removed to observe the substrate, which has been found effectively preserved from the adhesive, without any discoloration. The experimental results are extensively shown and discussed in the paper.

An experimental study of the penetration resistance of UHMWPE laminates with limited thickness

Ultra-high molecular weight polyethylene (UHMWPE) laminates represent the most weight-efficient industrial fiber-reinforced resin-based composite material for ballistic protection. To comprehensively understand the anti-penetration mechanism and quantify the anti-penetration performance of UHMWPE laminates, theoretical, experimental, and equation-fitting methods are employed to study and test the ballistic response characteristics of UHMWPE laminates. The results reveal that UHMWPE fibers possess a theoretically determined longitudinal wave velocity that exceeds 10 km/s and exhibit an extremely strong stress diffusion capacity. The anti-penetration mechanism and performance of UHMWPE laminates are significantly influenced by the laminate thicknesses, projectile velocities, and temperatures. As the laminate thickness increases, the ballistic limits of UHMWPE laminates increase almost linearly. Large area delamination and back face deformation play a crucial role in the energy dissipation of UHMWPE laminates. With the increase of projectile velocities, there exists an energy limit representing the maximum energy absorption capacity of the UHMWPE laminates that is worthy of reasonable utilization in spacing ballistic-proof armors. Additionally, the ballistic performance of UHMWPE laminates generally decreases with increasing temperatures, and this trend becomes more pronounced after 80 ℃. Based on data-driven analysis, this paper proposes an equation for calculating the ballistic limit of UHMWPE laminates that takes into account the temperatures and projectile shapes, with a prediction error basically within 5 %. The research results can offer valuable guidance for the ballistic-proof design of UHMWPE laminates.

Enhanced Dynamic Impact Resistance of 3D-Printed Continuous Optical Fiber-Reinforced Helicoidal Polylactic Acid Composites.

Characterized by light weight and high strength, composites are widely used as protective materials in dynamic impact loading under extreme conditions, such as high strain rates. Therefore, based on the excellent tensile properties of continuous fiber and the good flexibility and toughness of the bionic spiral structure, this study uses a multi-material 3D printer to incorporate continuous fiber, and then modifies the G-CODE file to control the printing path to achieve the production of a continuous fiber-reinforced Polylactic Acid composite helicoidal (spiral angle 60°) structure (COF-HP). Dynamic behavior under high-strain-rate impact experiments have been conducted using the Split Hopkinson Pressure Bar (SHPB). Stress-strain curves, impact energy curves and high-speed camera photographs with different strain rates at 680 s-1 and 890 s-1 have been analyzed to explore the dynamic process and illustrate the damage evolution. In addition, some detailed simulation models considering the incorporation of continuous optical fiber (COF) and different strain rates have been established and verified for deeper investigations. The results show that the COF does enhance the impact resistance of the laminates. When the porosity is reduced, the maximum stress of the continuous fiber-reinforced composite material is 4~7% higher than that of the pure PLA material. Our findings here expand the application of COF and provide a new method for designing protective materials, which have broad application prospects in the aerospace and automotive industries.

Experimental study on the damage characteristics of the stepped repaired fiber reinforced composites

Stepped repair, scarf patch repair, and patch repair are important in terms of repair techniques. The composite plate repair process starts after damage zone determination either by the unaided eye or nondestructive testing (NDT) techniques. This study investigates design cases for the stepped repairs of damaged fiber-reinforced composite materials. Before preparing steps for repair, the material around the damage zone is removed. In the stepped repair, it needs extra care to ensure that the repair plies overlap each other properly in the cut. Different cases are performed considering different step sizes. 5, 10, and 15 mm step sizes are used. The damages are given to the produced fiber-reinforced composite laminates using the Quasi-static indentation (QSI) method. Using QSI high-velocity impact simulation can be done. To get damage characteristics well-known damage test method is issued. Different span-to-punch diameter ratio (SPR) values were also used to compare different damage sizes. As a result, High ratio strength recovery was obtained using the longer step size. Maximum penetration force was reduced by nearly % 6-7 and maximum stress reduction was obtained by nearly % 8-9 for the 15 mm step size repaired composites. Among the all cases, case-1 has the highest strength recovery and case-5 has the lowest. For SPR 2, The average ultimate force value of specimens repaired with case-1 was maintained at nearly 94%. For SPR 4, repairs carried out using case-1 maintain more than 95% of damage resistance.

Orientation optimization via topological derivatives in combination with multi-material topology optimization based on extended level set method

This paper provides an orientation angle optimization method for the design of fiber-reinforced composite materials using topology optimization. The orientation angle optimization is based on a topological derivative, which measures the sensitivity of an objective function with respect to a topological change of anisotropic materials. The sensitivity is incorporated into a new gradient-based optimization algorithm. This method improves our ability to obtain better optimal candidates. We provide some numerical examples and verify the effectiveness of the proposed method.

Dynamic properties of steel fiber-reinforced potassium magnesium phosphate cement-based materials after high-temperature treatment

Potassium magnesium phosphate cement (MKPC) demonstrates remarkably high-temperature resistance and exhibits ceramic-like characteristics above 1000 °C. When micro steel fibers (MSF) are introduced, the resulting micro steel fiber-reinforced potassium magnesium phosphate cement-based (MSF-MKPC) material displays superior impact resistance even at high temperatures. Besides that, it is non-toxic and environmentally friendly. To investigate the impact resistance of MSF-MKPC at high temperatures, the split Hopkinson pressure bar test was conducted to analyze its dynamic mechanical properties under varying conditions, including MSF content, temperature, and strain rate. Mechanism analyses were carried out using scanning electron microscopy, mercury intrusion porosimetry, and X-ray diffraction testing. The experimental findings revealed the following key points: (1) MSF content has a more significant impact on enhancing the dynamic compressive strength of MSF-MKPC after high-temperature exposure compared to room temperature. Additionally, as the temperature increases, the residual dynamic compressive strength of MSF-MKPC initially decreases and then rises. (2) In contrast to room temperature conditions, the overall dynamic toughness index of MSF-MKPC shows an upward trend with increasing MSF content after high-temperature exposure. As the strain rate increases, the overall dynamic toughness index of MSF-MKPC also increases. (3) A dynamic impact constitutive regression equation is proposed for MSF-MKPC after high temperature, and the predicted results align well with the experimental findings. The analysis of the dynamic performance of MSF-MKPC after high temperatures can serve as a theoretical basis for the design of MSF-MKPC in future engineering applications, as well as for advancing the environmental sustainability and mechanical properties of fiber-reinforced cement-based composite materials.

Enhancement of in-plane shear performance in masonry walls strengthened with high-performance fiber-reinforced cementitious composites

This study aims to design a high-performance fiber-reinforced cementitious composite (HPFRCC) material for reinforcing masonry walls and assess its impact on in-plane shear performance. Different specimens were compared, including an unreinforced one, a conventional mortar-reinforced one, and HPFRCC-reinforced specimens of varying thicknesses ranging from 10 mm to 20 mm. Aspects such as failure modes, shear stress–strain curves, pseudo-ductility, and energy dissipation were evaluated. Test results indicated that the unreinforced and mortar-reinforced masonry walls demonstrated brittle failure with wide cracks on both sides, whereas HPFRCC-reinforced walls exhibited ductile failure with controlled crack propagation owing to the excellent mechanical properties of HPFRCC, such as an average tensile strength of 7.32 MPa and a tensile strain capacity of 4.60 %. The HPFRCC significantly enhanced the shear strength and modulus of the masonry walls. The wall reinforced with 20 mm-thick HPFRCC showed a remarkable 26-fold increase in the energy dissipation capacity compared to the unreinforced one, and the 10-mm-thick and 15 mm-thick strengthening demonstrated 4.0- and 5.7-times improvement, respectively. The ideal HPFRCC overlay thickness was found to be between 15 mm and 20 mm. Beyond this thickness, gravitational flow and stiffness asymmetry negatively impacted shear performance.

Structural optimization of composite corrugated cores with variable stiffness

Outstanding progress in manufacturing technology of fiber-reinforced composite materials, allows designers to go beyond classical design rules. Composites with variable stiffness are an innovative division of composite materials that provide more efficient designs for engineers due to their diverse design parameters. In this study, a straightforward methodology is presented for the design of sandwich panels with corrugated variable stiffness core. Based on the homogenization method, a unit-cell of the sandwich panel is used as a representative volume element for the sandwich panel with corrugated core. Due to multiple design variables, conventional numerical and analytical methods cannot be applied to variable stiffness composites, thus PYTHON/ABAQUS framework is developed to determine the extensional and bending behavior of unit-cells. Details of this framework including PYTHON scripting and ABAQUS finite element solver are given along with their corresponding functions. Furthermore, the elitist genetic algorithm is incorporated into a framework for the optimum design of variable stiffness cores. Two optimization problems, namely composites with variable thickness and variable angle are considered for unit-cells, and associated constraints, boundary conditions, and fitness functions are discussed in detail. In addition to the benefits of the proposed framework, the obtained results reveal notable enhancement in the extensional and bending behavior of unit-cell. Results reveal that corresponding displacements are significantly improved (up to 80%) when using the optimum variable thickness case. For variable angle cases, the improvement of displacements is up to about 28%.

Compressive and Shear Strength of Kevlar based Nano Composites

The Fibre Reinforced Composite (FRC) material consists of building materials in macroscopic level by having fibres and resin as reinforcement and matrix material respectively. It has different physical and chemical properties that were bonded together in order to get new material with different required characteristics from individual components. The properties of the composites are largely depending on the matrix and reinforcement materials. The matrix strengthening process by introduction of fine nano particles in composite laminate was done in this work. In order to study the effect of nano particles, the composite consists of Kevlar- 49 (K49) fibre in woven form with epoxy resin as matrix was considered. All the test specimens have been prepared with 12 layers of K49 to build 3mm thickness using vacuum bag moulding method. The K49 fibre in form of plain-woven type were chosen as reinforcement material. The nano fillers such as Titanium dioxide (TiO2), Calcium Carbonate (CaCO3) and Graphite powder (Gr) were used as nanomaterial added in the matrix and was compared with pure K49 reinforced composites for better performance. The TiO2, CaCO3 and GR nano fillers were constituted on various weight ratios in FRC. The structural properties like compression and shear strengths were determined as per ASTM standards. The fracture behaviour for all the categories of laminate has been detailed and reported using scanning electron microscope.

Damage evolution model and failure mechanism of continuous carbon fiber-reinforced thermoplastic resin matrix composite materials

As a new composite material with high strength, toughness, and heat resistance, the continuous fiber-reinforced polyaryl ether sulfone ketone (PPESK) thermoplastic resin matrix composite (CFRP) has a wide temperature range, which is attributed to the complex temperature sensitivity of the matrix. The failure evolution characteristics under different conditions are not clear yet, which significantly limits its development and application to high-precision equipment. In this work, in order to deeply explore the full three-dimensional (3D) multi-scale multi-physics damage evolution mechanism of the CFRP over a wide temperature range, macroscale cross-temperature stretching/bending experiments, computer tomography (CT) scanning, and microscale scanning electron microscopy (SEM) are performed to effectively capture the overall damage morphology and local fiber/matrix damage failure characteristics of the material. The results show that the reinforcement with continuous fibers increases the tensile strength of the CFRP by 14–45 times and its bending strength by 2–6 times compared to those of the PPESK matrix in the cross-temperature domain. Moreover, the main failure mechanism of the CFRP in the cross-temperature domain is matrix crushing and fiber fracture at room temperature and fiber fretting slip and matrix viscous flow at high temperatures. This further explains the deformation mechanism of the CFRP, which can maintain its stability at high temperatures (low elongation at break: 1%–1.2%). The unique trans-temperature regional energy evolution and continuous fiber reinforcement of the material matrix resin PPESK lay the synergic stability of the high temperature performance and damage morphology of the CFRP. In particular, a cell model is constructed to further reveal the damage evolution characteristics of the matrix, fiber, and interface of the CFRP at the micro-scale. Combined with the failure mode theory and the performance degradation mechanism of composite materials, the temperature influence factor is introduced to formulate a multi-scale full 3D temperature-dependent damage evolution constitutive model of the CFRP over a wide temperature range. The constitutive model of the CFRP is incorporated in finite element software, and the simulation results are compared with the experimental ones for validation. The results show that the model developed in this work can effectively characterize the complex mechanical damage morphology and progressive failure characteristics of the CFRP over a wide temperature range.

Hygrothermal analysis of a semi-infinite cylinder: an integral transform approach

PurposeThe purpose of this paper is to examine the impact of moisture and temperature changes on the behavior of a semi-infinite solid cylinder made of T300/5208 composite material. This study aims to provide analytical solutions for temperature, moisture and thermal stress through the de-coupling technique and the method of integral transforms. Both coupled and uncoupled cases are considered.Design/methodology/approachThis study investigates the hygrothermo-elastic response of a semi-infinite solid circular cylinder using an integral transform technique that includes Hankel and Fourier transforms. The cylinder is subjected to prescribed sources, and a numerical algorithm is developed for the numerical computation of the results. The goal is to understand how the cylinder responds to changes in temperature and moisture.FindingsThe paper presents an analytical solution for temperature, moisture and thermal stress in a semi-infinite solid cylinder obtained through the use of an integral transform technique. The study focuses on a graphite fiber-reinforced epoxy matrix composite material (T300/5208) and discusses the coupled and uncoupled effects of temperature, moisture and thermal stress on the material. The results of the transient response hygrothermo-elastic field are presented graphically to provide a visual representation of the findings.Research limitations/implicationsThe research presented in this article is primarily hypothetical and focused on the analysis of mathematical models.Originality/valueTo the authors' best knowledge, this study is the first to investigate the hygrothermal effect in a semi-infinite circular cylinder. Additionally, the material properties used in the analysis are both homogenous and isotropic and independent of both temperature and moisture. These unique aspects of the study make it a novel contribution to the field.

Folding, stowage, and deployment of composite thin-walled lenticular tubes

Composite thin-walled lenticular tube (CTLT) is a lightweight foldable and deployable structural material that enables large-scale deployable mechanisms for various space missions. A key step toward the structural design of CTLT is to understand its folding, stowage, and deployment behaviors. This work presents an integrated experimental and numerical investigation of the dynamic deployment behavior of CTLT that wraps around a central hub, with emphasis on the effect of long-term storage. A two-meter-long CTLT prototype was manufactured, and a gravity compensation system was designed and built for the on-ground dynamic deployment experiments. The deployment experiments were performed on the CTLT prototype both before and after it had been stowed for extended storage periods. The results indicate that after being stowed for 6 and 10.5 months the CTLT is deployed slower and the deployment time increases by 8.2% and 15.0%, respectively. Furthermore, a high-fidelity numerical model was constructed using the explicit dynamic finite element method, where the CTLT was modeled as a deformable part and the folding/deployment mechanisms were modeled as rigid bodies to perform the folding, stowage, and deployment simulations. The long-term storage effect was accounted for in the numerical analyses with the use of a viscoelastic fiber-reinforced composite material model, and a good agreement has been achieved between the experimental and numerical results.

Effect of polyvinyl alcohol fiber on the mechanical properties and embodied carbon of engineered cementitious composites

Engineered cementitious composite (ECC) is a fiber-reinforced cementitious composite material that has garnered considerable attention from the building and scientific sectors. However, ECCs offer improved mechanical and durability characteristics compared to regular concrete. Fibers serve a crucial function in producing ultrahigh tensile ductility and autogenous fracture width control inside the micromechanical reinforcing system of ECC. This research discusses the various proportions of polyvinyl alcohol fibers (PVA) as reinforcing materials by total volume fraction in ECC in terms of mechanical properties performance, environmental consequences, and economic effects. A total of 60 ECC samples were cast to achieve the targeted compressive strength of 45 MPa of ECC mixture reinforced with 1%, 1.5%, and 2% of PVA fiber by the volume fraction. Though, the best compressive of ECC is calculated by 62.60 MPa at 1% of PVA fiber at 28 days. Besides, the tensile and flexural strengths are enhanced by 5.20 MPa, and 11.15 MPa at 1% of PVA fiber in ECC for 28 days respectively. In addition, the density of ECC is reduced with rises in the content of PVA fiber while water absorption is increased as the percentage of PVA fiber growths in the ECC after 28 days respectively. Moreover, the embodied carbon and energy are improved when the PVA fiber by the volume fraction increases in the mixture. It has been observed that the use of 1% PVA fiber by the volume fraction in cementitious composites is offering maximum strength and less embodied carbon and energy, therefore, it has been recommended for structural application.