Properties Of Fiber Reinforced Polymer Composites Research Articles

Mechanical Properties and Recyclability of Fiber Reinforced Polyester Composites.

Fiber reinforced polymer composites (FRPs) are valuable construction materials owing to their strength, durability, and design flexibility; however, conventional FRPs utilize petroleum-based polymer matrices with limited recyclability. Furthermore, fiber reinforcements are made from nonrenewable feedstocks, through expensive and energy intensive processes, making recovery and reuse advantageous. Thus, FRPs that use biobased and degradable or reprocessable matrices would enable a more sustainable product, as both components can be recovered and reused. We previously developed a family of degradable and reprocessable cross-linked polyesters from bioderived cyclic esters (l-lactide, δ-valerolactone, and ε-caprolactone) copolymerized with a bis(1,3-dioxolan-4-one) cross-linker. We now incorporate these networks into FRPs and demonstrate degradability of the matrix into tartaric acid and oligomers, enabling recovery and reuse of the fiber reinforcement. Furthermore, the effect of varying comonomer structure, catalyst, reinforcement type, and lay-up method on mechanical properties of the resultant FRPs is explored. The FRPs produced have tensile strengths of up to 202 MPa and Young's moduli up to 25 GPa, promising evidence that sustainable FRPs can rival the mechanical properties of conventional high performance FRPs.

Improving the mechanical properties of fiber-reinforced polymer composites through nanocellulose-modified epoxy matrix

Improving the mechanical properties of fiber-reinforced polymer composites through nanocellulose-modified epoxy matrix

Bilayer coating strategy for glass fiber reinforced polymer composites toward superior fire safety and post-fire mechanical properties

The inherent heat and fire vulnerability from the polymer matrix of fiber-reinforced polymer composites (FRPs) contributes to fire propagation, matrix decomposition and especially loss of structural integrity during fire hazards. Applying surface fire protective coating is a popular approach without sacrificing mechanical properties. In this work, the influence of fire protective coating on the fire safety and post-fire mechanical properties of FRPs with an ingeniously designed coating bilayer composition. The combustion behavior study showed that the bilayer substantially postpones the decomposition of the polymer matrix through the thickness, showing a reduction of 50 % and 65 % for peak heat release rate and total smoke production respectively. Fire insulation tests showed good thermal insulation capabilities with no burn-through. Furthermore, the tensile strength of protected composite coupons was screened and showed a retention of 79 % original tensile strength after suffering 120s of heat/fire attack. This investigation resulted in a proposed protective strategy and mechanism offering a meaningful approach to enhancing the fire safety and fire structural integrity of polymer composites.

FRP-Reinforced/Strengthened Concrete: State-of-the-Art Review on Durability and Mechanical Effects

Fiber-reinforced polymer (FRP) composites have gained increasing recognition and application in the field of civil engineering in recent decades due to their notable mechanical properties and chemical resistance. However, FRP composites may also be affected by harsh environmental conditions (e.g., water, alkaline solutions, saline solutions, elevated temperature) and exhibit mechanical phenomena (e.g., creep rupture, fatigue, shrinkage) that could affect the performance of the FRP reinforced/strengthened concrete (FRP-RSC) elements. This paper presents the current state-of-the-art on the key environmental and mechanical conditions affecting the durability and mechanical properties of the main FRP composites used in reinforced concrete (RC) structures (i.e., Glass/vinyl-ester FRP bars and Carbon/epoxy FRP fabrics for internal and external application, respectively). The most likely sources and their effects on the physical/mechanical properties of FRP composites are highlighted herein. In general, no more than 20% tensile strength was reported in the literature for the different exposures without combined effects. Additionally, some provisions for the serviceability design of FRP-RSC elements (e.g., environmental factors, creep reduction factor) are examined and commented upon to understand the implications of the durability and mechanical properties. Furthermore, the differences in serviceability criteria for FRP and steel RC elements are highlighted. Through familiarity with their behavior and effects on enhancing the long-term performance of RSC elements, it is expected that the results of this study will help in the proper use of FRP materials for concrete structures.

Influence of filler material on properties of fiber-reinforced polymer composites: A review

Abstract The current day target for material scientists and researchers is developing a wholesome material to satisfy the parameters such as durability, manufacturability, low cost, and lightweight. Extensive research studies are ongoing on the possible application of polymer matrix composites in engineering and technology, since these materials have an edge over conventional materials in terms of performance. Hybridization of reinforcements is considered to be a better option to enhance the efficiency and performance of composite materials. Accordingly, research studies focus on the surface treatment of natural fibers and the addition of nanofillers (natural or synthetic) by industry and academia to take the properties and application of composites to the next level. This review purely focuses on the influence of fillers on the properties of composites along with the probable application of filler-based polymer composites.

A review on critical aspects of thermal shocks and thermal cycles in fiber reinforced polymer composites

Fiber reinforced polymer composites (FRPCs) have gained great progress in a wide range of applications from construction and building structures to automobile and vehicle systems. During the operational lifetime, some FRPCs are exposed to various environmental conditions such as thermal cycles and thermal shocks. Fluctuation of the ambient temperature in the forms of thermal shocks or thermal cycles is one of the most important factors that deteriorate the durability and performance of the FRPCs. Compared to ceramic composites, less attention has been paid to the effects of thermal shocks and thermal cycles on the physical/mechanical properties of FRPCs. A comprehensive insight for the future advancements in this field is essential to possibly reduce the failure risks of FRPCs under thermal shocks and thermal cycles. The present work provides a comprehensive review on the physical/mechanical behavior of FRPCs under thermal cycles and thermal shocks. This work also provides a broad review on several factors that determines mechanical behavior of FRPCs, such as polymeric matrix, fiber type, incorporated nanofillers and fiber/polymer interface. Recent studies denoting important aspects and possible problems in mechanical performance of FRPCs under thermal shocks are also summarized.

Test Methods for Characterizing the Properties of Fiber-Reinforced Polymer Composites at Elevated Temperatures.

Recent research trends focus on developing bio-based (derived from agricultural byproducts) fiber-reinforced polymer (FRP) composites for structural applications. Fire resistance is one of the key issues that need to be addressed for the use of these FRP materials in buildings. The thermal and mechanical properties of the constituent materials essentially determine the fire performance (and the fire resistance rating) of a structural member, and these properties vary with temperature. Further, the properties of composite materials such as the FRP are highly influenced by the composition and type of fibers and matrix, and these thermo-mechanical properties also vary significantly with temperature. Due to this variation, the fire resistance of FRP materials (both conventional and bio-based) poses a major concern for use in buildings. Currently, very few standardized test procedures are available for evaluating the high-temperature material properties of FRP composites. In this paper, a review of testing protocols and procedures for undertaking tests on FRP materials at various elevated temperatures for evaluating their properties is carried out. Recommendations are provided on the most suitable test methods, specimen conditions, testing regime, and other issues associated with testing at elevated temperatures. In addition, the applicability of the proposed test methods is illustrated through a case study on conventional FRP specimens. Further, the applicability of the recommended test procedures for measuring high-temperature properties of bio-based FRP composites is highlighted.

Critical investigation on the effect of fiber geometry and orientation on the effective mechanical properties of fiber-reinforced polymer composites

In this study, finite element method is used to investigate the effect of combined geometry and orientation of the fiber on the elastic properties of fiber-reinforced composites. The finite element models were developed using COMSOL Multiphysics. Representative volume elements consisting of circular, square and elliptical cross-section of fibers were used in the case of combined geometry while 0°, 15°, 30°, 45°,60°, 75°, 90° and 135° were angles considered for the fiber orientation. Results from the study show that the combined geometry and fiber orientation angle has significant effect on the performance of fiber reinforced composites.

A Review on the Mechanical Properties of Fiber-Reinforced Polymer Composites and their Application in the Transportation Industry

The application of fiber-reinforced polymer (FRP) composites has achieved significant attention in the industry of transportation, specifically as metal substitutes due to a need for fabricating stable and fuel-efficient airplanes, vehicles, and ships. Excellent strength, resistance to corrosion, lightweight, and suitable fatigue endurance are some of the desirable properties that would encourage the use of FRP composites in the transportation sector. Polymer-based composite materials, combining the favorable properties of both polymer matrix and reinforcing fibers, can contribute to several excellent behaviors of the obtained material. Epoxy, polyethylene, and polypropylene are the primary polymer matrices used in FRP composites. The main reinforcing fibers incorporated in fiber-reinforced composites are made out of glass, carbon, basalt, hemp, or natural resources (e.g., sisal and jute). Due to high cost, low Young's modulus, low durability, and linear stress?strain behavior to failure of the FRP materials, which are used in transportation infrastructure, the objective of this review article is to study the recent aspect of reinforced polymers with a close focus on their mechanical properties in order to evaluate their application in maritime, automotive, and aerospace.

Anisotropic Material Behaviors of Three-Dimensional Printed Carbon-Fiber Polymer Composites With Open-Source Printers

Abstract Composite products are often created using traditional manufacturing methods such as compression or injection molding. Recently, additive manufacturing (three-dimensional (3D) printing) techniques have been used for fabricating composites. 3D printing is the process of producing three-dimensional parts through the successful combination of various layers of material. This layering effect in combination with exposure to ambient (or reduced) temperature and pressure causes the finished products to have inconsistent microstructures. The inconsistent microstructures along with the oriented reinforcing fibers create anisotropic parts with difficulty to predict mechanical properties. In this paper, the mechanical properties of fiber-reinforced polymer composites produced by additive manufacturing technique (3D printing) and by traditional manufacturing technique (compression molding) were investigated. Three open-source 3D printers, i.e., FlashForge Dreamer, Tevo Tornado, and Prusa i3 Mk3, were used to fabricate bending samples from carbon-fiber-reinforced acrylonitrile butadiene styrene (ABS). Results showed that there exist significant discrepancies and anisotropies in mechanical properties of 3D-printed composites. First, the properties vary greatly among parts made from different printers. Second, the mechanical responses of 3D-printed parts strongly depend upon the orientations of the filaments. Parts with the infill oriented along the length of the specimens showed the most favorable mechanical responses such as Young’s modulus, maximum strength, and toughness. Third, all 3D-printed parts exhibit inferior properties to those made by conventional manufacturing. Finally, theoretical modeling has been attempted to predict the mechanical responses of 3D-printed products and can potentially be used to “design” the 3D printing processes to achieve the optimal performance.

The effect of environmental humidity/water absorption on tribo-mechanical performance of polymers and polymer composites – a review

Purpose The mechanical and tribological properties of polymers and polymer composites vary with different environmental conditions. This paper aims to review the influence of humidity/water conditions on various polymers and polymer composites' mechanical properties and tribological behaviors. Design/methodology/approach The influence of humidity and water absorption on mechanical and tribological properties of various polymers, fillers and composites has been discussed in this paper. Tensile strength, modulus, yield strength, impact strength, COF and wear rates of polymer composites are compared for different environmental conditions. The interaction between the water molecules and hydrophobic polymers is also represented. Findings Pure polymer matrices show somewhat mixed behavior in humid environments. Absorbed moisture generally plasticizes the epoxies and polyamides and lowers the tensile strength, yield strength and modulus. Wear rates of PVC generally decrease in humid environments, while for polyamides, it increases. Fillers like graphite and boron-based compounds exhibit low COF, while MoS2 particulate fillers exhibit higher COF at high humidity and water conditions. The mechanical properties of fiber-reinforced polymer composites tend to decrease as the rate of humidity increases while the wear rates of fiber-reinforced polymer composites show somewhat mixed behavior. Particulate fillers like metals and advanced ceramics reinforced polymer composites exhibit low COF and wear rates as the rate of humidity increases. Originality/value The mechanical and tribological properties of polymers and polymer composites vary with the humidity value present in the environment. In dry conditions, wear loss is determined by the hardness of the contacting surfaces, which may not effectively work for high humid environments. The tribological performance of composite constituents, i.e. matrix and fillers in humid environments, defines the overall performance of polymer composite in said environments.

Monitoring of mechanical properties of prestressed glass fiber epoxy composites over 12 months after fabrication

Fiber prestressing during matrix curing can significantly improve the mechanical properties of fiber-reinforced polymer composites. One primary reason behind this improvement is the generated compressive residual stress within the cured matrix, which impedes cracks initiation and propagation. However, the prestressing force might diminish progressively with time due to the creep of the compressed matrix and the relaxation of the tensioned fiber. As a result, the initial compressive residual stress and the acquired improvement in mechanical properties are prone to decline over time. Therefore, it is necessary to evaluate the mechanical properties of the prestressed composites as time proceeds. This study monitors the change in the tensile and flexural properties of unidirectional prestressed glass fiber reinforced epoxy composites over a period of 12 months after manufacturing. The composites were prepared using three different fiber volume fractions 25%, 30%, and 40%. The results of mechanical testing showed that the prestressed composites acquired an initial increase up to 29% in the tensile properties and up to 32% in the flexural properties compared to the non-prestressed counterparts. Throughout the 12 months of study, the initial increase in both tensile and flexural strength showed a progressive reduction. The loss ratio of the initial increase was observed to be inversely proportional to the fiber volume fraction. For the prestressed composites fabricated with 25%, 30%, and 40% fiber volume fraction, the initial increase in tensile and flexural strength dropped by 29%, 25%, and 17%, respectively and by 34%, 26%, and 21%, respectively at the end of the study. Approximately 50% of the total loss took place over the first month after the manufacture, while after the sixth month, the reduction in mechanical properties became insignificant. Tensile modulus started to show a very slight reduction after the fourth/sixth month, while the flexural modulus reduction was observed from the beginning. Although the prestressed composites displayed time-dependent losses, their long-term mechanical properties still outperformed the non-prestressed counterparts.

Comparison of Specimen Geometries for Measuring Through-Thickness Tensile Mechanical Properties of Fibre-Reinforced Polymer Composites

Engineering design of fibre-reinforced polymer (FRP) composite components requires reliable methods for measuring out-of-plane mechanical properties in the through-thickness (T-T) material direction. Within this work, existing indirect and direct test methods and geometries for measuring T-T tensile properties have been evaluated through experimental testing and finite element analysis (FEA). Experimental testing showed variations, particularly in failure properties, for both indirect (failure strengths from 10–94 MPa) and direct (failure strengths from 48–62 MPa) geometries. Results were shown to be in good agreement with FEA, which also confirmed stress concentration factors. A linear relationship between the magnitude of stress concentration factors and experimentally determined T-T tensile failure strengths was observed for all but one of the direct geometries evaluated. Improved knowledge of stress concentration factors from this work should help instil confidence for industry to use T-T tensile properties determined from these methods.

Review of Experimental Studies on Application of FRP for Strengthening of Bridge Structures

In recent years, fiber-reinforced polymer (FRP) composites have been widely used as a new type of high-performance material in concrete structures. FRP composites have the advantages of high strength, light weight, and corrosion resistance. Based on existing studies in the literature, this paper reviews the development and applications of FRP materials for the strengthening and rehabilitation of bridge structures. The types and properties of FRP composites are summarized, and the applications and development of FRP sheets, FRP bars, FRP grids, and prestressed FRP tendons for bridge structures are discussed. Different types of FRP composites result in different failure characteristics and bearing capacities. Moreover, this paper covers the FRP strengthening methods and the response properties of the flexural performance, bonding performance, and ductility. Significant conclusions regarding the strengthening/repair of bridge structures with FRP composites are presented. The review details the current state of knowledge and research on strengthening bridge structures with FRP composites and is helpful for better understanding and establishing design criteria.

Thermal buckling analysis of sandwich plates with soft core and CNT-Reinforced composite face sheets

Previous studies on the thermal buckling of sandwich plates with composite face sheets indicate that only thin skins with high stiffness and low coefficients of thermal expansion (CTE) can lead to the desired buckling temperatures. Thus, carbon nanotubes (CNTs) that can significantly enhance thermo-mechanical properties of fibre-reinforced polymer composites are used in the present study to increase the critical buckling temperature of sandwich plates with soft core and laminated composite face sheets. First, a comprehensive series of experimental tests are conducted to evaluate the effects of nanotubes on thermo-mechanical properties of the face sheets. The experimental results indicate that using only 0.3% CNTs considerably increases the longitudinal and transverse Young’s modulus and shear modulus of the carbon fibre/epoxy composite face sheets. The obtained data also show that CNTs significantly decrease the CTE of composite skins. Subsequently, thermal buckling equations of sandwich plates with CNT-reinforced composite face sheets are derived based on piecewise low-order shear deformation theory (PLSDT). Three analytical, semi analytical, and numerical methods are used to investigate thermal buckling behaviour of the sandwich plates with various boundary conditions. To verify the results, several comparisons are performed, which show that the implemented methods can predict the buckling temperatures of sandwich plates with high accuracy. Finally, a parametric study is conducted to examine the effects of CNTs on the thermal buckling of sandwich plates for different length to thickness ratios, thicknesses of face sheets, stacking sequences of layers, and various types of boundary conditions. The results indicate that CNTs can increase the critical buckling temperature of sandwich plates by 22%–36%, based on the layup, geometrical parameters, and boundary conditions.

Effect of fiber prestressing on mechanical properties of glass fiber epoxy composites manufactured by vacuum-assisted resin transfer molding

The mechanical properties of fiber-reinforced polymer composites depend on several aspects such as the characteristics of constituents, fiber volume fraction, and manufacturing techniques. Fiber prestressing is considered a very attractive manufacturing technique that can be used to produce fiber-reinforced polymer composites with high mechanical properties. This technique has the potential to eliminate or reduce some manufacturing problems like fiber waviness. In the present study, a new approach was used to prepare prestressed fiber-reinforced polymer composites. Unidirectional E-glass fiber-stitched mats were impregnated with epoxy matrix through vacuum-assisted resin transfer molding process. Once the infusion was done, a pre-calculated tensile force was applied to the fiber mats through a hydraulic tensile machine. The impregnated fiber mats were left under tension and vacuum during curing of the epoxy matrix (24 h). Five prestressed samples were prepared by using five different prestressing levels 20, 40, 60, 80, and 100 MPa. In addition, non-prestressed (control) sample was prepared for the purpose of comparison. The influence of fiber prestressing on fiber waviness, fiber volume fraction, and void content was investigated. Flexural, tensile, and compression tests were performed to observe the effect of fiber prestressing on the mechanical properties. The results have shown the success of this new approach in producing prestressed fiber-reinforced polymer composites with high mechanical properties comparing to non-prestressed composites. The microstructure analysis has shown dramatical reduction in fiber waviness for the prestressed samples over control sample. All prestressed samples have shown higher fiber volume fraction and lower void content comparing to the control sample. Also the results have shown as the prestressing level increases, fiber volume fraction increase and void content decreases. Prestressing levels of 40 and 60 MPa were found to be the best candidates, they have led to an increase in tensile strength, compressive strength, and flexural strength by 24.2%, 72.5%, 28% and 28.6%, 100.4%, 26.1%, respectively, comparing to the non-prestressed sample. Ease of implementation and promising results of this new approach would attract the attention toward it. Automotive industry is one potential nominee to apply this approach during manufacturing of fiber-reinforced polymer leaf spring.

Enhancing Longitudinal Compressive Properties of Unidirectional FRP Based on Microbuckling Compression Failure Mechanism

In this study, a new methodology to improve the longitudinal compressive strength and modulus of ultra-high molecular weight polyethylene (UHMWPE) fiber-reinforced epoxy resin matrix is developed. The proposed method involves wrapping a UHMWPE fiber bundle with a poly-p-phenylene benzobisoxazole fiber filament using a winding method, and using these bundles to fabricate unidirectional UHMWPE fabric. UHMWPE/epoxy composites were fabricated using vacuum-assisted resin-transfer molding (VARTM), and the compression properties of the composite were evaluated and compared to investigate the effect of the filament wrapping. Improvements in the compressive modulus were achieved for filaments wound with applied tension, and when increasing the filament-winding spacing; however, the compressive strength decreased with an increase in the filament-winding spacing. Results obtained confirm that fiber microbuckling failure occurred in the composite under longitudinal compression, and that inhibiting the buckling length of the fiber improved compressive properties. These results may be useful when designing the mechanical properties of fiber-reinforced polymer composites.

On the static and dynamic properties of fiber-reinforced polymer composites

This article establishes a reliable constitutive model to describe the behaviors of fiber-reinforced polymer composites under quasi-static and dynamic loading. This model integrates the contributions of all the three phases of a composite: the fiber, the matrix, and the fiber/matrix interphase, which make it capable of capturing the key micromechanical effect of the interphase on the macroscopic mechanical properties of composites. The interphase is taken as a transversely isotropic material together with the fiber. By analyzing glass/epoxy and carbon/epoxy composites, it was found that the model predictions agree well with the experimental data and the model is more effective particularly when the fiber volume fraction is high. The dynamic three-phase model was also established by using the coupling of the elastic and Maxwell elements for the viscoelasticity of the matrix as well as the interphase. The article concludes that the three-phase model with consideration of the interphase influence can precisely characterize the static and dynamic mechanical properties of a FRP composite.

Long-term tensile properties of natural fibre-reinforced polymer composites: Comparison of flax and glass fibres

Abstract Despite of significant research on the mechanical properties of fibre-reinforced polymer composites made of natural fibres, long-term performance of the natural fibre composites against moisture and other environmental conditions is not well-known. In this paper, accelerated durability tests were conducted in order to investigate the long-term performance of flax fibre composites in comparison with glass fibre composites. A total of 490 tensile specimens were prepared and exposed to four different environmental conditions namely dry heat, water (distilled), salt water (3.5% by weight), and alkaline (pH = 12.5) solutions. The temperature of the solutions was controlled at 20, 50, and 60 degrees of Celsius (°C). Tensile tests were performed after 21, 42, 83, and 125 days exposure to the environmental conditions. Overall, the tensile strength of both flax and glass composites significantly decreased with increasing temperature and exposure time, however initial elastic modulus of both materials was not affected. Flax composites showed a bilinear stress–strain behaviour and the secondary slope of the curve become slightly softer after the environmental conditionings, although glass composites almost retained their linear behaviour. In terms of tensile strength retention percentage, flax composites not only were not worse than glass composites but also they had even slightly better strength retention percentage.

Degradation in compressive strength of silica/phenolic composites subjected to thermal and mechanical loading

Reduction to the mechanical properties of fiber-reinforced polymer composites occurs when the material is exposed to radiant heat flux and compressive loading. A thermo-mechanical model was developed to predict the compressive strength and the failure time of silica fiber-reinforced phenolic composites. The coupling heat and mass transfer processes, generation of pyrolysis gases, and their subsequent diffusion process were considered in the model. The thermal softening, thermal decomposition of the matrix material, and phase transition of the reinforced fibers, which reduce the strength of the material, were also taken into account in the formulation of the model. Pyrolysis kinetics of phenolic resin, volume fraction of phase component, temperature profile, compressive strength, and time-to-failure of silica/phenolic composites were predicted using the developed model. The calculated temperature-dependent strength curve was compared with the experimental results measured by a high-temperature compression testing, and the agreement is good. The material fracture morphology was analyzed for silica-phenolic composite specimen after high-temperature compression testing.