Fiber Reinforced Polymer Composites Research Articles

Factors affecting flexural and impact strength of natural fiber reinforced polymer composites: a review

The surging demand for energy-efficient products and their environmental implications are important propelling factors contributing to the growing popularity of natural fiber-reinforced polymer composites (NFRPCs) in several domains. NFRP composites diversification significantly influenced the study and their development in recent years. The intrinsic characteristics of natural fibers have posed difficulties in the growth and use of NFRPCs. A significant amount of study has recently been performed to solve these sorts of problems in order to enhance the performance of NFRPCs and their uses. This review article aims to provide a comprehensive overview of the chemical composition of natural fibers, their physical and mechanical characteristics, and factors affecting the flexural and impact strength of NFRPCs, such as type of fiber, weight percentage of fiber, fiber geometry, surface treatments, stacking, hybridization, orientation, fillers, and information accomplished with them. The product life-cycle evaluation and sustainability development of plant-based NFRCs and the growing uses of NFRPCs, focusing on the automobile sector, are also explored. Finally, multiple perceptions were concluded with the expectation that this study may contribute to future improvements in the flexural and impact strength of NFRPCs.

Enhancing fiber/matrix interface adhesion in polymer composites: Mechanical characterization methods and progress in interface modification

The interface between the fiber and polymer matrix is a crucial region that plays a major role in the mechanical performance of fiber reinforced polymer composites (FRPCs) materials. The properties of this zone are recognized to have a significant influence on the fracture and failure of FRPCs. As a result, strong adhesion at the interface is required for effective stress transfer and load distribution within the composite material. In light of this, the aim of this work is to provide an up-to-date review of test methods for assessing fiber/matrix interface adhesion in FRPCs under static and dynamic loadings, along with advancements in interface modification techniques. At the outset, we give an overview of the different modification treatments used thus far, alongside interface testing methods, in order to optimize fiber/matrix compatibility, improve interfacial bonding and scrutinize their impact on interfacial adhesion properties. Particular attention is then focused on the description of the main mechanical characterization techniques used to assess the fiber/matrix interfacial properties. In the final outlook, we highlight the key findings and discuss potential directions for characterization of the fiber/matrix interface.

Higher-order sensitivity analyses to understand the role of FE input parameters on the simulation of composites in progressive fracture tests

With the rise of data-driven engineering methods, such as machine learning, a comprehensive understanding of the underlying data fed into these algorithms is required for effectively applying these methods. This study presents two highly efficient Finite Element (FE) models that operate at different length scales, based on Continuum Damage Mechanics (CDM). The combination with Random Sampling-High Dimensional Model Representation (RS-HDMR) enables the determination of influential FE input parameters and their correlations to simulate Fibre Reinforced Polymer (FRP) composites subjected to a variety of progressive fracture tests in tension and compression. The results indicate that laminate-based models utilise the FE input parameters efficiently where all parameters are found to be influential. On the other hand, only fibre-related properties are relevant in ply-based FE models, with all input parameters related to transverse properties deemed to be non-influential. The findings of this study aid in identifying suitable fracture tests for a meaningful calibration and validation of CDM-based FE models. Moreover, the study lays the foundation for understanding the role of input parameters within data-driven methods, and for developing efficient reduced-order models or surrogates for uncertainty quantification on the damage tolerance of FRP composites.

Research progress on high-temperature properties of carbon fiber reinforced polymer composites for cables

Carbon fiber reinforced polymer composites (CFRP) cable has advantages of lightweight, high strength, and excellent durability, providing a new materials for cables and bringing out potential breakthrough in spanning capacity of structures. At present, CFRP cable has already been applied in some engineering bridges. The fire resistance performance of CFRP cable is critical for ensuring structure safety when suffering accidental fire disaster, and clarifying mechanical performance deterioration and failure mechanism of CFRP cable at elevated temperature is fundamental for research of its fire resistance. This paper summarizes current research progress on high-temperature properties of CFRP cable from two levels, including epoxy resin matrix and CFRP composites. Firstly, at resin matrix level, mechanical properties of epoxy resin and its degradation at elevated temperatures are reviewed and analysed, and potential ways to improve high-temperature performance of epoxy resin are suggested. Secondly, at CFRP composites level, high-temperature properties test methods and mechanical performance of CFRP composites in longitudinal direction and transverse direction at elevated temperatures are summarized and discussed. In addition, research shortage of high-temperature properties of CFRP cable is summarized, and corresponding further research is recommended.

Monitoring of damage evolution in carbon fiber reinforced polymer composites by electrical impedance tomography

Electrical impedance tomography (EIT) has been widely investigated as a nondestructive testing method for carbon fiber reinforced polymer (CFRP) composites. However, the performance of EIT method on the damage process monitoring of the composites is lack of investigation. Herein, quasi-static indentation tests were utilized to introduce damage on CFRP laminates. The damage evolution process was monitored by EIT, while the potential of distinguishing the elastic deformation stage from the plastic stage was analyzed with the aid of acoustic emission. It was found that the changes in conductivity first appeared in the non-central region. With the accumulation of damage, the conductivity changes gradually extended to the center region. The reconstructed damage images were in the crossover shape, which was consist with the micro-CT results that showed the fracture of fibers in ±45° direction. This work further promotes the application of EIT in damage process monitoring of CFRP components.

Tensile Properties of Open Hole and Unhole Sugar Palm ‘Ijuk’ (SPI) Fibre Composite Treated with Sodium Hydroxide (NaOH)

This study evaluates the effects of sodium hydroxide (NaOH) treatment on tensile properties of sugar palm 'ijuk' (SPI) fibre-reinforced polymer (FRP) composites, with and without an open hole that acts as a stress concentrator. The NaOH treatment is aimed to improve the interfacial adhesion between SPI fibres and polymer matrix. Composite specimens were prepared using the hand lay-up method, incorporating SPI fibres in various orientations, and featuring a 6 mm diameter hole. Tensile tests were conducted to evaluate the mechanical performance of SPI FRP composite, including ultimate tensile strength, Young's modulus, and elongation at break. The research also compared the properties of SPI to those of synthetic glass fibre in fibre-reinforced polymer composites. The results showed that NaOH treatment significantly improves the fibre-matrix adhesion with 26% increase in tensile strength, leading to enhanced tensile properties in both samples, regardless of hole presence. The 0° orientation provides the highest strength and stiffness when the load is applied in the direction of the fibres. While for the 90° orientation, strength reduces by 14%. The impact of the hole on stress concentration and the subsequent mechanical behaviour of the open-hole specimens is substantial. The findings of this study offer insightful perspectives on the potential use ofNaOH-treated SPI fibre in structural and other applications, demonstrating its ability to withstand tensile stresses, even with geometric discontinuities like holes.

Effect of Granite Fly Ash on Mechanical Properties of Basalt and Glass Fiber Reinforced Polymer Composite

The granite processing industry generates a substantial volume of residual granite waste daily. This residue is collected through a filtration process during the drying and heating stages of concrete mixture production. Utilizing this residue, known as granite fly ash (GD), offers a promising avenue for mitigating adverse effects due to this waste material. The present study undertakes an experimental investigation into the potential utilization of granite fly ash as a filler to enhance the mechanical properties of basalt/glass composites (BFRC/GFRC). The research focuses on assessing the density and tensile characteristics of the developed fibre-reinforced polymer (FRP) composites. Composite samples were fabricated by incorporating GD at varying loadings, i.e., 1 wt.%, 3 wt.%, and 5 wt.%. The FRP laminates were produced using hand lay-up and vacuum silicon mold curing techniques. The outcomes show a slight increase in density, in which a maximum of 7% increment at 5 wt% of GD in BFRC. Meanwhile, tensile properties displayedsignificant enhancements, especially FRP with 3 wt.% GD content, for both BFRC and GFRC. Notably, the addition of 1 wt.% GD resulted in a 9% increase in tensile strength and a substantial 27% increase in modulus for the BFRC composite. In summary, the study underscores the advantageous influence of GD incorporation, particularly within the 1 wt.%, 3 wt.%, and 5 wt.%, on the mechanical properties of both BFRC and GFRC composites.

Additive manufacturing of continuous fiber-reinforced polymer composites: current trend and future directions

Additive manufacturing of continuous fiber-reinforced polymer composites: current trend and future directions

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.

The effect of nanocellulose and silica filler on the mechanical properties of natural fiber polymer matrix composites

Natural fiber-reinforced polymer matrix composites recently got great attention in biomedical applications due to their inherent characteristics such as biocompatibility, lightweight, and biodegradability. However, natural fiber composites suffer from poor mechanical properties and weak interfacial adhesion. It is well documented that the addition of nanofiller has improved the mechanical properties of different synthetic fibers such as glass and carbon composites. The main objective of this paper is to study nanofillers' effect on the mechanical properties of unidirectional false banana fibers reinforced polymer composites. The filler materials, crystalline nanocellulose fibrils, and crystalline nanosilica particles were extracted from sugarcane bagasse and its byproducts. The composite samples were fabricated by adding the nanofillers in unidirectional natural fibers arranged in four fiber orientations (0°, 0o/90o ±45o, and quasi-isotropic), and their tensile, flexural, compression strength, thermal stability, and void content were measured following ASTM standards. The results revealed that adding nanofillers increased the tensile, flexural, and compressive strengths by 16 % (98.83 Mpa), 11 % (161.60 Mpa), and 23 % (114.62 Mpa), respectively. Similarly, at 0° orientation, the addition of nanoparticles enhances the tensile, bending, and compressive modulus by 30 % (15.43 Gpa), 12 % (13.52 Gpa), and 60 % (42.6 Gpa), respectively. On the other hand, the void content was reduced with the addition of nanofillers. The results also revealed that composites with crystalline nanosilica particle fillers had superior thermal stability compared to crystalline nanocellulose fibril fillers. The overall results of this research give the confidence that nano particle-filled natural fiber composites can be used for bio-based engineering applications, such as prosthetic sockets.

Influence of Fiber Orientation on Mechanical Response of Jute Fiber-Reinforced Polymer Composites.

The influence of fiber orientation on the mechanical behavior of a polymer matrix composite reinforced with natural jute fibers is investigated in this study. Two fiber orientation configurations are examined: the first involves woven fibers aligned in the direction of testing, while the second considers a 45° orientation. The research involves manufacturing composite plates using jute fabric with the mentioned orientations, followed by cutting rectangular specimens for tensile testing to determine which orientation yields superior properties. Displacement fields are measured using a digital image correlation technique, synchronized with load data obtained from a universal testing machine equipped with a load cell to obtain stress-strain curves for each configuration. Results indicate that 0° specimens achieve higher stress but lower strain compared to 45° specimens. This research contributes to understanding the optimal fiber alignment for enhancing the mechanical performance of fiber-reinforced polymer composites.

Revisiting the sequential evolution of sizing agents in CFRP manufacturing to guide cross-scale synergistic optimization of interphase gradient and infiltration

Using sizing agents instead of various nanoparticles to modify carbon fibers is widely recognized as the most practical approach to address processing issues and improve interfacial properties in carbon fiber reinforced polymer composites. However, a limited understanding of sizing agent evolution during composite manufacturing hinders comprehensive theoretical guidance for sizing treatment, thereby limiting further enhancement of composite performance. Here we disentangled the sizing agents into chemical anchoring and physical adsorption components, and elucidated the sequential wetting, diffusion, and crosslinking evolution processes of sizing agents across scales. By manipulating the proportion of chemical anchoring and physical adsorption in the sizing agents, the interfacial modulus gradient and infiltration efficiency were synergistically optimized. Consequently, significant improvements of 26.2 % in interfacial shear strength (IFSS) and 52.9 % in transverse fiber bundle tensile (TFBT) strength were achieved, indicating enhanced interfacial stress transfer and reduced internal defects in the composites. In summary, this work revisited the cross-scale evolution and mechanism of sizing agents during composite manufacturing, and thus provided a new paradigm for optimizing composite performance.

Multiscale modeling of microstructural and hygrothermal effects on vibrations of CNT-enhanced fiber-reinforced polymer composites

This work presents a multi-scale analytical and computational approach designed to predict the hygro-thermo-mechanical vibrational response of laminated composite structures reinforced with multi-walled carbon nanotubes (MWCNTs). Employing the modified Halpin-Tsai model, this study estimates the elastic properties of the MWCNT-enhanced epoxy matrix, incorporating the impacts of MWCNT agglomeration, orientation, waviness, and size-dependent characteristics. Additionally, the Chamis micromechanical model is utilized to ascertain the independent elastic constants of the nanocomposite lamina, considering environmental variables such as temperature and humidity. Subsequent analysis involves the determination of natural frequencies for both pristine and MWCNT-integrated laminated composite structures via the Finite Element Method (FEM), addressing various design-related parameters. This investigation further explores the macroscopic influences of MWCNT incorporation, boundary condition and layup scheme, along with the temperature, moisture content, and the nanoscopic impact of MWCNTs on the natural frequencies of laminated composite plates. The obtained results of the proposed multiscale modeling are compared with experimental and theoretical observations. It has been demonstrated that while the incorporation of carbon nanotubes (CNTs) can enhance the mechanical properties of nanocomposite laminae, the natural frequencies of these nanocomposite plates are adversely affected by variations in temperature and moisture content. Furthermore, the findings indicate that the microstructural characteristics of CNTs play a crucial role in determining the efficacy of the reinforcement phenomenon. The developed multi-scale methodological framework offers significant potential for the design and optimization of MWCNT-based composite structures across diverse industries, including automotive and aerospace sectors.

Influences of various thermoplastic veil interleaves upon carbon fiber-reinforced composites subjected to low-velocity impact

Throughout their service life, composite materials may be subjected to impact loads, which can result in some damage mechanisms that cause degradation in mechanical and dynamic responses. Especially matrix-induced cracks and delamination can have significant effects on the final properties, and cause serious problems if the necessary precautions are not taken. In the current study, Carbon Fiber-Reinforced Polymer (CFRP) composites interleaved with Fine Glass (FG), Polyetherimide (PEI), Polyetheretherketone (PEEK), Polyimide (PI) and Poly-Phenylene Sulphide (PPS) thermoplastic veils were fabricated, and exposed to LVI tests under 25.2 J constant impact energy to determine how veils affect the dynamic properties. The selected veils are commercially available materials and are used for various purposes. In this regard, it was aimed to examine the usability of these commercially available veils as interlayers and to examine the impacts of the veils used as interlayers on the LVI characteristic of CFRP composites. According to the present study, it was found that veil interleaves significantly affect the composite stiffness, and accordingly, relevant LVI responses such as total impulse, bending stiffness, interaction times etc. For instance, approximately 21.2% reduction in the peak displacement and 73.23% increment in the bending stiffness were observed due to FG veil interleaves. On the other hand, when the effects of veil types were examined, the maximum and minimum variations in the LVI responses were observed for the FG and PEI interleaves, respectively, and FG veils were found to be the most effective veil types for the CFRP composites. It was also revealed that veil interleaves strengthen the interlaminar region between plies and delamination resistance, and thereby improved the Delamination Threshold Loads for all configurations.

Extreme temperature influence on low velocity impact damage and residual flexural properties of CFRP

AbstractIn this work, the behavior of carbon fiber reinforced polymer composites (CFRPs) interleaved with electrospun veils under low velocity impact (LVI) conditions and extreme environmental temperatures was investigated. 2/2 twill carbon fiber/epoxy laminates were subjected to LVI at three energy levels (10, 20, and 30 J), and three temperatures (−50°C, room temperature, and 100°C). Two interleaved configurations were explored (six veils placed symmetrically with respect to the middle plane of the laminate and with respect to the external layers of the laminate). Particularly at room temperature and up to 20 J, nanofibrous interlayers effectively reduced localized deformation (by about 13.0%) and delamination (by about 12.2%) when positioned in the outer ply interleaved configuration compared to the reference laminate. At 100°C, this effect is maintained at 10 J, preventing an increase in the delaminated area. At −50°C and 10 J, the promotion of delamination prevented back surface fiber failure. Regarding post‐impact flexural properties, the presence of nanoveils ensured superior mechanical properties compared to the corresponding reference laminate impacted at the same conditions, demonstrating their efficacy in enhancing the damage tolerance of the overall laminate.Highlights Electrospun veils were interleaved in 20 layers of 2/2 twill carbon/epoxy laminate. Three configurations were tested under LVI at 10 J, 20 J, 30 J, and −50°C, RT, and 100°C. Observed damage modes include delamination, indentation, and back surface fiber cracks. Veils symmetrically placed in external layers limit delamination at 20 J (RT) and 10 J (100°C). Electrospun veils enhanced CFRP bending and residual post‐impact properties at RT and 100°C.

Investigation of effects of environmental conditions on wear behaviors of glass fiber reinforced polyester composite materials

AbstractGlass fiber reinforced polymer (GFRP) composites can be subjected to different environmental conditions such as temperature, humidity, ultraviolet radiation, hydrothermal cycle, acidic and alkaline solution in environments where they operate. These environmental conditions cause different damage mechanisms in composites such as pore formation, micro‐cracks, delamination, fiber breakage, fiber/matrix interface separation, plasticization, swelling and surface color change. In this study, wear properties of hybrid glass fiber reinforced polymer composites exposed to various environmental conditions for constant load (60 N), speed (500 rpm) and 2 h were examined comprehensively, depending on material content and environmental conditions. In this experimental study, the service conditions in glass fiber reinforced composites were simulated using different artificial aging environments such as acidic environment, hydrothermal cycle and UV radiation. In addition to the material content, it appears that the environmental conditions to which composites are exposed has a significant effect on friction coefficient. Considering environmental conditions, it is seen that the acid environment and hydrothermal cycle have reduced wear resistance of GFRP composites, while UV radiation improved wear resistance of the composites. In C2 sample, the wear rates under different conditions are 1.87 × 10−14 m3/Nm in non‐treated sample, 6.05 × 10−14 m3/Nm in acid environment, 4.79 × 10−14 m3/Nm in hydrothermal cycle and 0.59 × 10−14 m3/Nm in UV radiation.Highlights Friction coefficient of glass fiber reinforced polyester (GFRP) is higher under aged condition compared to non‐treated. Glass fibers used in correct proportions can reduce friction coefficient in GFRP. GFRP exposed to environmental conditions has an important effect on wear. Acid environment and hydrothermal cycle has reduced wear resistance of GFRP. UV radiation improved wear resistance of GFRP composite.

The role of additive manufacturing in the study of carbon fiber-reinforced polymer composite

The role of additive manufacturing in the study of carbon fiber-reinforced polymer composite

Multi-scale characterization of self-sensing fiber reinforced composites

The piezoresistive properties of fiber-based embedded sensors across tow, fabric, and laminate scales offer opportunities for their efficient application in fiber reinforced polymer composite (FRPC) structures. This study involves the multi-scale characterization of rGO-coated glass fiber tows, fabric, and laminates produced via vacuum assisted resin transfer molding (VARTM). The study demonstrates how fiber type, areal weight, and architecture affect piezoresistivity in rGO-coated glass fiber-based sensors subjected to in-plane tensile loading. In this study, rGO-coated glass fiber tows, with three linear densities (138, 1200, 1232 TEX), were examined. Fabric-level sensors, including plain weave (PW), and quadriaxial (QUAD), with areal densities of 200, 600, and 807 g/m2 were also studied. For comparison, laminates using UD carbon fabrics (300 g/m2) were employed as embedded piezoresistive sensors in the glass fiber-based laminates. It has been shown that rGO-coated sensors with lower areal weights outperformed all other sensor types in terms of their piezoresistive characteristics. This study suggests that piezoresistive sensors offer significant potential for use in load-bearing structural applications which can be further enhanced by investigating their lower scales.

Strengthening of RC Beam with GFRP Composites in Shear N. B. Bhopale

The rehabilitation, repair and strengthening of existing reinforced concrete (RC) structures is essential due to factors such as aging, steel reinforcement corrosion, construction/design defects, increased service loads demand, seismic events, and advancements in design guidelines. Fiber-reinforced polymers (FRP) are now being recognized as a promising material for the rehabilitation of such structures, through strengthening or repairing. In buildings and bridges, RC sections are commonly found in the form of beams and girders. Shear failure of RC beams is particularly due to its sudden occurrence without warning. Therefore, the utilization of externally bonded (EB) FRP composites for shear strengthening of RC beams has gathered popularity as a structural enhancement technique, primarily due to advantages of FRP composites, such as high strength-to- weight ratio and exceptional corrosion resistance. In addition, FRP repair systems give a cost-saving choice to traditional repair methods and materials. A study was performed to analyse the shear characteristics of RC beams enhanced with continuous glass fiber-reinforced polymer (GFRP) sheets. Reinforced concrete beams externally bonded GFRP sheets subjected to failure using a symmetrical two-point concentrated static loading system. The experimental data obtained included load, deflection, and failure modes of each beam, along with the effect of the number of GFRP layers on the beams The failures observed in strengthened beams typically commence with the debonding of the FRP sheets, followed by brittle shear failure. The shear capacities of these beams were higher than that of the control beam.

Sandwich-structured electrospun polyvinylidene difluoride sensor for structural health monitoring of glass fiber reinforced polymer composites

Stress monitoring and interlaminar failure detection attract much attention in glass fiber reinforced polymer (GFRP) structural health monitoring area. However, due to limitations of sensing or electrode materials, existing embedding sensors cannot be designed to have both of the abilities without sacrificing mechanical properties. This work fabricated a sandwich-structured sensor, which is composed of three layers of electrospun polyvinylidene difluoride membranes. The upper and lower electrodes are flexible membranes that ensure stable signal collection in the rigid GFRP material system. The sensor can quantitatively monitor the stress based on piezoelectric effect, and interlaminar crack propagation based on parallel plate capacitors. The voltage and capacitance values have a linear relationship with the stress level and crack length (R-square of the functions is 0.999 and 0.933), respectively. Due to the porous microstructure of electrospun membranes, polymer matric can well infiltrate the polyvinylidene difluoride nanofibers while preparing the sensor embedded GFRP. Thus, the perfect bonding of the sensor within GFRP ensures the effective sensing abilities until sample failure and negligible effect (< -7%) on the mechanical properties of GFRP.