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To evaluate the axial compressive performance of the hollow sandwich GFRP-concrete-steel double-skin tubular columns (DSTC), 15 composite column specimens were produced to study the effect of various design variables. And the study presents a rational and accurate finite element (FE) model that provides a detailed working mechanism of the DSTCs, leading to the enrichment of parametric research and the creation of an extensive database. Based upon the unified strength theory of double shear, limit equilibrium theory, and superposition theory, the study evaluates and compares the effectiveness of different bearing capacity calculation models. With each added millimeter in the thickness of the GFRP tube, the ultimate bearing capacity of the DSTC specimen increased by 23.6% and 61.8%, respectively, compared to that of the 1.5 mm thick GFRP tube sample. The lower the hollow ratio of the DSTC section, the higher its ultimate bearing capacity. Specimens with a hollow ratio of 0.3 and 0.43 showed an ultimate bearing capacity 1.4 times and 1.25 times higher, respectively, than those with a hollow ratio of 0.6. The study observes a relatively high level of precision in the results of the ultimate equilibrium theory, with an average error rate of 20%. [ABSTRACT FROM AUTHOR]

This paper introduces a novel combined technique to characterize the elastic modulus gradient for glass/epoxy interphase. The developed procedure is applicable to all fiber-reinforced polymer (FRP) composites. Interphase in FRP composites plays a vital role in the mechanical performance of the material. Scientists almost characterized this region using nanoscale test methods such as atomic force microscopy (AFM) and scratch tests. These local methods characterize the elastic properties at a specific region near the fiber and, usually, are utilized for all regions around the fiber. This paper proposes a combined peridynamic and single-fiber micro tensile test method to characterize the overall elastic modulus gradient at the interphase region. The advantages of peridynamic as a non-local method are used to model the multiscale regions of interphase, fiber, and matrix. Single-fiber micro tensile tests are performed by the authors, and variations of displacements and strains are measured by the digital image correlation method. The obtained displacements are used as target values in the developed peridynamic code, and by performing peridynamic analyses, the elastic modulus variation along the interphase is automatically extracted. Furthermore, the variations of stresses and strains are investigated at the specimens' cross-section using different hypotheses for the interphase region. [ABSTRACT FROM AUTHOR]

Fiber–metal laminates (FMLs) are hybrid materials that provide the advantages of both metal and fiber-reinforced polymer composite (FRP) such as improved damage tolerance and impact strength, particularly in aerospace and automotive applications. However, the production of FMLs remains expensive because the manufacturing process is performed in an autoclave. In addition, delamination failure due to low interfacial adhesive strength between the metal and fiber layer is a problem that must be solved to improve the mechanical properties of FMLs. In this study, simple stitch-assisted carbon fiber-aluminum laminates were developed using vacuum-assisted resin transfer molding (VARTM). The FMLs produced through vacuum-assisted resin transfer molding were stitched with aramid fibers through holes on Al sheets for the resin flow associated with the VARTM. The mechanical properties of the FMLs were investigated by impact and compression after impact tests as well as double cantilever beam and flexural tests. The stitching effectively improved the interfacial strength and toughness owing to the anchoring between the aluminum and carbon fiber layers, thus preventing delamination crack propagation. As a result, the stitched FML with significantly improved interfacial adhesive and toughness was developed by the VARTM process, which will accelerate the application of FML to various lightweight structures. [ABSTRACT FROM AUTHOR]

There is a considerable need for research to fully exploit the application potential of adaptive fiber-reinforced plastics based on functional materials, in particular with regard to industry-specific solutions. Hence, this paper presents the development of a locomotion mechanism based on fiber-elastomer composites with shape memory alloys. In order to attain this goal, shape memory alloys were textile-technically integrated into the reinforcing fabric in the weft direction using flat knitting technology. The functionalized reinforcing fabrics was infused by the vacuum assisted resin infusion with an elastomeric silicone matrix system. Later, an extensive electro-thermal-mechanical characterization of the fiber-elastomer composites by varying electrical power caused by the varying voltage amplitude was completed. The fiber-elastomer composites were then shaped in a cross-country ski as an example of locomotion mechanism. Finally, the forward movement of the cross-country skiers was realized by activating the shape memory alloy in the left and right leg. [ABSTRACT FROM AUTHOR]

Additive manufacturing has the capacity to manufacture functional parts with complicated geometries, fused filament fabrication is a viable additive manufacturing method and an alternative to standard processes for the creation of polymer and fiber-reinforced polymer composites. The influence of process parameters such as layer thickness, infill density, and infill pattern on the interlaminar bonding performance of three-dimensional printed composites was examined in this study. Due to the existence of high porosity and inadequate layer to layer bond, interlaminar shear strength values increase as layer height increases from 0.15mm to 0.2 mm and decrease by 0.3mm. The specimens were also subjected to a wettability test to determine the printed material's adhesive behavior. Scanning electron microscope was used to perform fractography analysis, and fractured specimens were seen. The test findings revealed that carbon fiber reinforced ABS specimens have good interlaminar shear strength and layer adhesive. When comparing carbon fiber reinforced ABS specimens to ABS specimens, the test results demonstrated that interlaminar shear strength and good adhesion between the layers are attained in carbon fiber reinforced ABS specimens. [ABSTRACT FROM AUTHOR]

The fabrication process of Fiber-reinforced polymer (FRP) composite leads to the formation of residual stresses. The effect of these stresses may be insignificant on the monotonous properties like tensile strength etc. However, residual stresses can significantly affect the fatigue performance of the FRP composites. There is lack of rigorous analysis on connecting the evolution of residual stress and the fatigue life of FRPs. A multi-physics analysis was performed to model the evolution of residual stresses in the curing process under different process and material conditions for unidirectional Glass Fiber Reinforced Polymers. The viscoelastic model also accounted for percolation in the matrix and thus gave realistic estimates of residualstress compared to the past elastic models. It was found that the residual-stress varied by over 25% by just changing the cure thermal cycle. The stress prediction results were found to be in-line with the experimental results reported in the literature. A numerical model was developed to obtain a change in the fatigue life (fiber-dominated failure mode in High Cycle fatigue (HCF)) from residual stresses under the simulated circumstances. This numerical model was validated with the experimental fatigue data using two different cure cycles. Fatigue life for HCF was found to be improved by upto 4% under such conditions. Thus, this study gives insight on various processes and material property handles for manipulation of the residual stresses. Accurate numerical prediction of such stresses can be cardinal in composites processing. [ABSTRACT FROM AUTHOR]

Compressive strength is the ability of materials to withstand loads without deformation or cracking. It is one of the most important criteria for evaluating the properties of concrete. The use of Fiber-Reinforced Polymers (FRP) to Strengthen concrete columns and as a supplement to improve some properties of concrete materials has received much attention in recent decades. Therefore, it is important to investigate and determine the compressive strength of confined concrete with FRP sheets. In this study, a comprehensive database containing 1066 specimens of concrete cylinders confined with FRP sheets has been collected. Then, using machine learning methods, the estimation and evaluation of the compressive strength of the mentioned specimens were discussed. The artificial neural network of multilayer perceptron (MLP) and support vector regression (SVR), fuzzy neural inference system (ANFIS), and its combination with particle swarm algorithm (PSO) and kriging interpolation method are the methods used in this study. Subsequently, these methods were compared with the models presented in previous studies. The results of this comparison show that the kriging interpolation method with a correlation coefficient of 0.985 in estimating compressive strength has the lowest error compared to other models. [ABSTRACT FROM AUTHOR]

A micromechanics model to predict the fatigue life of fiber-reinforced polymer matrix composites (FRPC) is developed and used for estimating compressive fatigue failure of unidirectional carbon fiber composite. The micromechanics model utilizes constituent, fiber, and matrix material properties. An experimental procedure to obtain the matrix properties that are needed is also described. The model is implemented using the finite element method (FEM). The FEM simulations can predict the classic kink band failure seen in pre–preg-based and textile composites. In addition, an envelope fatigue loading approach is utilized to model the fatigue cycle. Using the combination of matrix fatigue degradation and the fatigue loading method, it is possible to numerically predict the S-N curve, based on the failure mechanics. [ABSTRACT FROM AUTHOR]

The rapidly rising demand for fiber-reinforced plastics (FRPs) has led to large volumes of manufacturing and end-of-life waste. Recycling fiber-reinforced thermosets is very difficult owing to their complex structure and heterogeneity. Landfill and incineration have become the most commonly used methods for eliminating non-degradable FRP waste, which adversely affects the environment and ecology. The purpose of this review is to evaluate end-of-life FRP recycling technologies in terms of optimizing the reuse/recycling of resources and eliminating waste, thereby improving FRP waste management. The technical progress made in the recycling of thermosetting composites is reviewed, including mechanical, thermal (pyrolysis and fluidized-bed), and chemical (critical fluid and low-temperature solvent) methods. The technical feasibility of each method was compared, and the economic and environmental impacts were considered. The challenges and opportunities facing the establishment of a composite recycling market in the future are examined. Finally, we provide a comprehensive summary of the scope of each recycling method. [ABSTRACT FROM AUTHOR]

Although surface grinding is reported to be capable of precision material removal in carbon fibre reinforced epoxy polymer composites (CFRPs), it is highly limited by deprived cutting temperature dissipation, tool wear and sensitivity to undesired cutting defects. Continuous engagement of abrasive grains and successive accumulation of heat at cutting interface in conventional surface grinding results in severe surface damages. Though the controlled application of cutting fluids exhibited improved surface integrity, entrapment of fluid droplets into the defective zones/cracks of fibre, matrix and its interfaces are shown to be stimulating further defect propagation. Present paper investigates the feasibility of improving cutting fluid application in CFRP grinding, establishing a minimum surface defect condition through eccentric sleeve grinding (ESG). The reduction of post-grinding surface defects through an intermittent-progressive cutting scheme in ESG is demonstrated and the efficacy of cutting fluids in such a grinding scheme is illustrated through the comparison of grinding forces and surface characteristics. [ABSTRACT FROM AUTHOR]

In this study, the stress and deformation rules of the double-row fiber-reinforced plastic sand pipes under the two loading methods of single-pipe and double-pipe loading were discussed. First, the indoor full-scale test was used to analyze the single-tube pipe top loading. The 90° measurement point of the loaded pipe and the 270° measurement point of the adjacent pipe were the most unfavorable positions for the stress of the pipeline. Through investigating the influence of cover soil height, load level, and compaction on the mechanical index of the most unfavorable load-bearing measuring point of the pipeline, the height of the overburden is found to be the most significant factor affecting the double-pipe stress system. Second, the numerical calculation model of the stress of the double-row pipeline was established to analyze the stress and deformation of the pipe culvert when the spacing of the double pipe was changed. The results indicated the critical spacing equivalent to the stress of the single pipe was 2.5D. Finally, the numerical method was also used to optimize the parameter of the geogrid at the top of the pipe in the most unfavorable stress state of the double pipe with 550-mm pipe spacing and double-loaded mode. [ABSTRACT FROM AUTHOR]

The functionalization of fiber-reinforced plastics has been improved continuously in recent years in order to broaden their application potential. By using shape memory alloys in fiber-reinforced plastics, adaptive fiber-reinforced plastics can be developed, which in turn can change their shape depending on the activation of shape memory alloys. In order to ensure the proper force transmission from shape memory alloys to fiber-reinforced plastic, these shape memory alloys need to be integrated into the reinforcing fabric. Hence, this paper presents the application of open reed weaving technology for the development of functionalized preforms for adaptive fiber-reinforced plastics. For an optimized shape memory effect during their thermal induced activation, the shape memory alloys were coated with release agent and then integrated into the woven fabric by open reed weaving technology. The hinged width of functionalized preforms was varied from 50 mm to 150 mm. These preforms were infused by a thermosetting resin matrix system with a modifier. Subsequently, the electro-mechanical testing of adaptive fiber-reinforced plastics was executed. Results show that the maximum deformation of adaptive fiber-reinforced plastics was proportional to their hinged width. [ABSTRACT FROM AUTHOR]

The main purpose of this research is to bolster mechanical properties of the parts, produced by an extrusion-based 3D printer, or fused deposition modeling machine, via increasing the content of continuous fiber yarn to its practical limit. In-melt continuous glass fiber yarn embedding was applied as a reliable and consistent method for simultaneous impregnation to produce continuous fiber-reinforced thermoplastic composites in the fused deposition modeling process. It is well known that the main weakness in the fused deposition modeling 3D printed products is their low strength compared to the manufactured ones by conventional methods such as injection molding and machining processes. This characteristic can be related to both inherent weakness of thermoplastic materials and poor adhesion between the deposited rasters and the layers. Although various attempts have been performed to tackle this issue, it is widely believed that using continuous fibers is the most effective method to serve this purpose if a reliable and consistent method is implemented. Since the mechanical properties of continuous fiber-reinforced composites directly depend on the content of fiber volume, maximizing the fiber content as well as producing an integrated part was assumed as the main objective. In this work, an analysis of various patterns of raster deposition was conducted, followed by the experiments and verification. The effective parameters on the fiber yarn volume, such as fiber yarn diameter, fiber yarn laying pattern, extrusion width, layer height, and flow percentage, were investigated and their optimal values were reported. The attained experimental results showed that, for polylactic acid-glass fiber yarn reinforced composite, with the extrusion width of 0.3 mm, the layer heights of 0.22 mm, flow percentage of 0.43, and the rectangular laying pattern, approximately 50% fiber-volume content can be achieved which resulted in tensile yield strength and modulus of 478 MPa and 29.4 GPa, respectively. There was an excellent agreement between these experimental results and predicted theoretically values by rule of mixture. [ABSTRACT FROM AUTHOR]

In order to process structural materials in additive manufacturing, a three-dimensional printing process with high deposition rate was developed. The process enables new design approaches for structural parts in automotive applications, combining continuous fibre-reinforced thermoplastics with short fibre-reinforced thermoplastics. For the combination of these materials, adhesion and the influence of the process parameters on adhesion is crucial. Within this study the adhesion has been measured in peel tests according to ASTM D, 6862, and the interface was investigated by optical microscopy. The adhesion process was evaluated by thermal imaging. The experiments showed that a good adhesion can be achieved during the printing process, but the continuous fibre-reinforced thermoplastic tape has to be preheated. In addition, an analytical model for the adhesion process has been introduced and validated with experimental results. [ABSTRACT FROM AUTHOR]

For the application of continuous fibre-reinforced thermoplastics in car body structures it has to be ensured that they can pass through the automotive paint shop. There are substantial chemical, hygroscopic and thermal impacts throughout this process that can affect the shape of such components. The aim of this study is to model the deformation behaviour of continuous fibre-reinforced thermoplastics under hygrothermal loading. Relaxation tests were performed to assess temperature-dependent and viscoelastic behaviour. Input parameters for temperature and moisture distribution were determined experimentally and computed using finite difference method. A straightforward approach based on classical laminate theory is presented that comprises anisotropic viscoelasticity as well as hygroscopic, thermal and polymer-chemical effects. The introduced phenomenological model was successfully used to describe the deformation of five different laminate layups both dry and fully saturated with moisture. [ABSTRACT FROM AUTHOR]

Bio-degradability and sustainability have become major objectives in the field of materials engineering. Due to this, the utilisation of natural reinforcement is gaining immense attention among composite researchers. Among the different composites, polymeric composites are used as structural components. In the present day investigations, bio-elements are majorly utilized as reinforcements due to their properties and bio-degradability. Although polymeric components are manufactured in the shape of the final component, they need secondary processing to make it suitable for assembly. Hence, a review on machining and associated investigations on bio-composites would help the composites industries and upcoming researcher to know the scope of research and for selection of apt machining conditions. This review gives a detailed insight on the various machinability factors and their measurement, influence of machining parameters on the machinability and optimum conditions during machining of bio-composites. In addition, this review also presents about the importance of bio-fibre under various situations of machining and untraditional machining methods used for bio-composites. [ABSTRACT FROM AUTHOR]

The present study aims to experimentally validate numerical simulation of fiber orientation distribution performed by molding simulation software Moldex3D in a double-gated injection-molded glass fiber-filled (40 wt%) polypropylene box, by making a detailed comparison of predicted and experimentally measured fiber orientation distribution data. The modeling approach evaluated in this work consists in the implementation of the Folgar–Tucker rotary diffusion model with the invariant-based optimal fitting closure approximation for the fourth-order orientation tensor. The specimen used has a weld line in the center and sharp corners. This investigation characterizes in detail the development of the through-thickness layered structure at distinctive locations of the specimen. The sensitivity of fiber orientation distribution and the layered structure to changes upon injection time and melt temperature is also evaluated. The boxes display the typical layered laminate structure, with fibers aligned in the main flow direction near the walls (shell layer) and less oriented in the middle plane (core layer). The boxes injected at the lowest melt temperature display an additional skin layer. Unfortunately, simulation fails in predicting the five layers structure developed under these latter conditions. The grade of fiber orientation is deemed to be independent of process parameters but not the layered structure. [ABSTRACT FROM AUTHOR]

Many factors can affect the shear capacity of fiber-reinforced polymer in reinforced concrete beams shear-strengthened with externally bonded fiber-reinforced polymer composites. Undoubtedly, the interaction of concrete-stirrup-fiber-reinforced polymer system is one of the key factors. However, most of the existing fiber-reinforced polymer design guidelines do not take account of this important factor on predicting fiber-reinforced polymer shear capacity. This study provides an advanced strengthening model that comprehensively considers the interaction among concrete, stirrup, and fiber-reinforced polymer for calculating the fiber-reinforced polymer effective strain. The advanced strengthening model provides a more accurate prediction for the fiber-reinforced polymer shear contribution compared with existing design guidelines. [ABSTRACT FROM AUTHOR]

This research was undertaken to investigate the influence of the sizing components, principally coupling agents and film formers, of glass fiber on the interface of reinforced polyurethane composites. The contents of film-forming agents and coupling agents were, respectively, checked by acetone extraction and heat treatment. The categories and chemical structures of the film-forming agents, which mainly exist in the extracting solutions, were investigated by nuclear magnetic resonance spectroscopy. The coupling agents, which mainly existed on the extracted glass fiber surfaces, were analyzed by X-ray photoelectron spectroscopy. Then, the interfacial adhesion properties between glass fibers of untreated, extracted and heat-treated and polyurethane resin were measured with micro-droplet test. The results show that the interfacial shear strength of the glass fiber-reinforced polyurethane composite mainly depends on the coupling agents, in which the N-containing groups play a dominant role. The film formers also take some effects, in which the hydroxyl groups have the greatest contribution. [ABSTRACT FROM AUTHOR]

Glass fiber reinforced plastics are used in variety of industrial and constructional applications for their superb mechanical and physical properties. Delamination is one of the most important and prevalent damages in machining of glass fiber reinforced plastics. Diamond core drills have the capability of simultaneously drilling and grinding of fiber reinforced plastics, which results in hole quality improvement. Rotary ultrasonic-assisted drilling is the new machining process to drill holes on fiber reinforced plastics and has attracted increasing attention in recent years. In this paper, thrust force and delamination in rotary ultrasonic-assisted drilling of glass fiber reinforced plastics using diamond core drill have been investigated. A proper ultrasonic system for a core drill in ABAQUS was designed and fabricated. Influence of ultrasonic vibration and then tool grain size, fiber-volume fraction and machining parameters including spindle speed and feed rate on thrust force and delamination was investigated. Higher thrust force induces more delamination. As a result of the study, less delamination was achieved in ultrasonic-assisted mode by using a tool with larger grain size onto lower fiber-volume fraction composites. Additionally, experiments showed that lower spindle speed and higher feed rate induce more delamination. [ABSTRACT FROM AUTHOR]

Machining is an inevitable task after processing a material. Among the different materials, fiber-reinforced plastics are used as structural materials in different industries. Compared to conventional materials, fiber-reinforced plastics are less hard by its nature. Due to this reason, the cutting force required during machining a plastic material is lesser than that of other materials. Although the cutting force is less, the influence of other machining parameters on the ease of machining is to be investigated in order to reduce the machining time and cost. Hence, a review on the machining associated successes and failures will be helpful for the manufacturing sectors and researchers in line with the machinability. This review provides a detailed picture of various issues dealt during machining a plastic material. The influences of manufacturing methods on the machinability and machinability measurement methods are comprehensively addressed. In addition, this review also discusses about the influences of machining parameters and optimum conditions for machining. The review also addresses various statistical methods used, machinability enhancement methods adopted, and unconventional methods used in the various researches. [ABSTRACT FROM AUTHOR]

Premature local failure of web/flange junctions of the majority of unstiffened commercially produced pultruded fiber-reinforced polymer composites profiles is inescapable due to lack of fiber continuity at the resin-dominated junction zones. This paper focuses on evaluating both short- and long-term behavior of such junctions when subjected to axial tensile stresses. In this study, the axial mechanical behavior of web/flange junctions of pultruded bridge deck components before and after hygrothermal aging effect is investigated. In the experimental phase, axial tensile tests were performed on six different types of pultruded web–flange junctions to assess axial characteristics of each web/flange junction type. In order to evaluate the hygrothermal behavior of such junctions, axial tensile tests were conducted on web/flange junction specimens that were exposed to both fresh water and artificial seawater environments at temperatures of 40℃, 60℃, and 80℃. Several controlling parameters affecting both strength and stiffness of pultruded fiber-reinforced polymer junctions were identified and discussed that include: (i) Junction's web and flange thicknesses, (ii) fillet radius, and (iii) variation of hygrothermal exposure environments. Results of this study indicated that the axial tensile capacity of a pultruded profiles is increased as the thickness of both web and flange increases. Also, it was found that the larger fillet radius of the pultruded fiber-reinforced polymer profile may contribute to a larger axial tensile capacity of pultruded profiles. However, due to variable size and geometry of the resin-rich junction zones and the common manufacturing defects in the form of folded fabric and other fibers misalignment effects, it is difficult to generalize the preceding results. Experimental results also showed that the degradation of web/flange junctions axial tensile strength increases when junctions are exposed to higher temperatures. Also, it was found that the axial tensile characteristics for junctions specimens exposed to freshwater environment are slightly different than those that were exposed to artificial seawater environments. [ABSTRACT FROM AUTHOR]

The influence of surface treatment (alkali, potassium permanganate, benzoyl chloride and silane) on the mechanical, dynamic mechanical and free vibration properties of intra-ply hybrid banana/jute woven fabric composite has been analyzed. Intra-ply woven fabrics are fabricated by keeping banana yarn in weft direction and jute yarn in warp direction of a basket-type woven fabric. Results reveal that the enhancement of tensile and flexural strengths of the composite due to the chemical treatment is marginal, except for the benzoyl chloride treatment. However, the chemical treatment results in better impact strength compared to the untreated composite. Tensile, flexural and impact strengths of the benzoyl chloride treatment increase by 10%, 30% and 50%, respectively, compared to untreated composite. It is evident from Fourier Transform-Infrared Spectra that benzoyl chloride treatment effectively removes the hemicellulose and lignin content. It is observed that benzoyl chloride and alkali treatment improves the dynamic mechanical characteristics. Experimental modal analysis carried out on intra-ply fabric composites reveals that benzoyl chloride treatment increases the natural frequency significantly compared to the untreated composite. [ABSTRACT FROM AUTHOR]

This paper presents a comparative study on the energy dissipation capacity of one glass fibre-reinforced polymer frame with bonded sleeve connection and steel frames with bolted endplate connections. Experimentally measured moment-rotation behaviour of a typical bonded sleeve connection was employed to develop the joint model for the glass fibre-reinforced polymer frame. In order to reduce the effect of the different beam size on the overall frame behaviour, the size of the steel profiles was selected to be equal, less than and greater than glass fibre-reinforced polymer profile in terms of the bending stiffness. The moment–rotation response of bolted endplate connection was then theoretically determined through Mohammadi’s design model. The frame models were developed using 3D beam elements and nonlinear spring elements. Comparing the energy dissipation capacity between glass fibre-reinforced polymer and steel frames at connections and floors, it was found that although glass fibre-reinforced polymer members were lack of ductility, the glass fibre-reinforced polymer frame can give satisfactory energy dissipation capacity that is comparable to steel frames. The energy dissipation capacity of glass fibre-reinforced polymer frame can be induced by the yielding of steel endplate from bonded sleeve connection. [ABSTRACT FROM AUTHOR]

Z-pin technology, as a promising through-thickness reinforcement, offers an efficient solution for the weak composite parts joints, especially for large integrated composite structures. This paper presents a two-dimensional finite element model to analyze the enhancing efficiency of Z-pins for composite T-joints. The modeling used a new parameter definition method for delamination growth simulation in Z-pinned joining interface via a regional cohesive zone model. The finite element model was validated by experiments for unpinned and Z-pinned T-joints under web pullout tension. The parametric analysis on the structural configuration shows that shear stress ratio in Z-pins declines with the span ratio increasing and the skin thickness ratio decreasing, which leads to the failure mode change of a single pin from pull-out to shear fracture so that the improvement on the out-of-plane tension declines gradually. Within 1.7–2.1 span ratio (the constant 4 mm skin thickness) or 1.8–2.5 thickness ratio (the 200 mm constant span), the ultimate tension is improved by at least 15%, where Z-pins exhibit the best efficiency. When span ratio is above 2.4 or thickness ratio below 1.2 within the range studied herein, Z-pinned T-joints fail by skin fracture rather than the bonding interface in which cases further increasing of Z-pin reinforcements becomes unfavorable. [ABSTRACT FROM AUTHOR]

Fiber breakage occurs during the processing of fiber-reinforced thermoplastics, thereby resulting in the deterioration of the mechanical properties of the thermoplastic parts. In this paper, the fiber breakage and flow behavior of long glass fiber-reinforced polypropylene containing 30 wt% glass fibers was investigated through a series of conical capillary die at varying shear rates, conical die angles or diameters, and the melt flow index of polypropylene. Moreover, scanning electron microscopy was employed to observe individual fiber cross sections to analyze the mechanism of fiber breakage, of which the conical capillary die geometry dominantly affected the residual fiber length, and the choice of an appropriate geometry most significantly affected improvements in the residual fiber length. The results also indicated an increase in the extent of fiber breakage following an increase in the shear rates. In addition, long glass fiber-reinforced polypropylene also generated a slightly higher average fiber length following an increase in the melt-flow index of polypropylene. Pressure oscillations were observed at the entrance, of which these pressure accumulations and releases affected fiber interactions and breakage at the entrance. [ABSTRACT FROM AUTHOR]

The development and recent applications of reinforced thermoplastic pipes for offshore oil and gas applications are reviewed. The design and materials of reinforced thermoplastic pipes are presented. Reinforced thermoplastic pipes have been increasingly accepted as an important alternative to traditional metallic offshore pipes due to their distinct advantages such as a higher stiffness to weight ratio, improved fatigue resistance and better corrosion resistance. Their potential applications can be extended to deep-water risers. Loading conditions which could be experienced by them for offshore applications are described. Existent studies and analyses of offshore pipes under these loading conditions are discussed. Based on this discussion, this article outlines the limitations of the current studies of reinforced thermoplastic pipes and future work to improve the analysis and design of reinforced thermoplastic pipes is recommended. [ABSTRACT FROM AUTHOR]

Nesting and compression processes of plain woven fabrics are the most important features in the composites manufacture of fiber-reinforced composite components, while their relationships are still not reported. Here, in this work, we clearly reveal nesting and compression characteristics of typical fabrics through systematical compression experiments. We present the theoretical expression of the nesting effects on the initial thickness h and experimentally demonstrate its effectiveness. We find that nesting decreases the h and the minimum h appears in the maximum nesting condition. Meanwhile, we experimentally demonstrate that for plain woven fabrics, nesting has relationships with the thickness in compression t, while it has no effects on the thickness deformation Δ in the whole compression processes. Thus, we reveal the relationships between the nesting and h, t, Δ in the compression processes. Moreover, the applicability of these results for other types of fiber is also illustrated by comprehensive analysis. These obtained results provide the references for thickness evolution rules, volume fraction, and molding process of the fiber-reinforced composite components. [ABSTRACT FROM AUTHOR]

This study examined the bond at the interface of masonry bricks and fiber-reinforced polymer when exposed to five environments. Three fabrics (aramid, carbon, and glass) and one type of epoxy resin were used. A total of 375 brick-fiber-reinforced polymer specimens were made using wet lay-up technic and exposed to chemical solutions at four pH values (2.5, 7, 10, and 12.5) and substitute seawater. The effect of dry heat on the bond at the interface was also investigated. Single-lap shear tests were then carried out on the samples after 2, 4, 6, 8, 10, and 13 weeks of exposure. The experimental results indicated that freshwater and seawater had a considerable effect on the bond strength of brick-aramid fiber reinforced polymer (AFRP) and brick-carbon fiber reinforced polymer (CFRP) samples; however, they did not significantly affect the bond strength of brick-glass fiber reinforced polymer (GFRP). Exposure to the severe environments was detrimental to bond strength. The results showed a significant loss of approximately 60% after 13 weeks of exposure to alkaline and acidic solutions. Dry heat did not significantly affect the bond strength of the tested samples. [ABSTRACT FROM AUTHOR]

This article presents an online statistical life prediction method based on both historical and local residual-stiffness information to reduce the effect of dispersive mechanical properties of fiber-reinforced plastic structures. Normalized residual-stiffness curves obtained from the laboratory are used as a benchmark, and the model parameters are assumed to be independent random variables. According to Bayesian statistical theory, the prior distribution of fatigue life is updated by the residual-stiffness sample information of the in-service structure through online monitoring; then, a more accurate life estimation is obtained. This method precisely captures the essence of stiffness degradation of a composite structure. The individual dispersion effect is largely eliminated through using the local stiffness data. In general, a more accurate life estimation can be obtained if more sample information is available. The test results of glass-fiber-reinforced plastic and carbon-fiber-reinforced plastic laminates show that the fatigue life can be accurately predicted with only the first 20% residual-stiffness data known. [ABSTRACT FROM AUTHOR]

For both environmental and economic consideration, the use of recycled glass fiber-reinforced flame retardant poly(butylene terephthalate) (RGFFRPBT) is of significant importance. In the study, the mechanical, thermal, rheological, and flame retardant properties of RGFFRPBT granulated by different extruders were evaluated. To explore the relationship between the screw structure and the properties of the extruded RGFFRPBT, the carboxyl content (CC), and intrinsic viscosity ([η]) of the processed polymer and the average GF length (L¯) were investigated. Increasing the shear force of the extruder caused both [η] and L¯ to decrease, whereas the CC increase. Variations of these parameters had a different effect on the properties of the RGFFRPBT. Both of mechanical and thermal properties of extruded RGFFRPBT deteriorated with the increase of screw shear force, while the thermal flowability improved. Furthermore, all the extruded products were classified as V-0 with LOI of 32.2%, and passed the glow wire ignition temperature test (GWIT). The results confirmed that the degradation of properties of RGFFRPBT can be controlled by screw-type extrusion. RGFFRPBT granulated by a single screw extruder with 30 mm diameter and length to diameter ratio of 30 was found to produce material with properties meeting the requirements for electronic and electrical applications. [ABSTRACT FROM AUTHOR]

In this study, we experimentally investigated the bond performance of a glass fiber-reinforced polymer hybrid bar with a core section comprising a deformed steel bar and a sand coating. The glass fiber-reinforced polymer and deformed steel hybrid bar (glass fiber-reinforced polymer hybrid bar) can contribute to longer durability and better serviceability of reinforced concrete members because of the increased modulus of elasticity provided by the deformed steel bar. Uniaxial tensile tests in compliance with ASTM D 3916 showed that the modulus of elasticity of the glass fiber-reinforced polymer hybrid bar was enhanced up to three times. For the bond test, a total of 30 specimens with various sand-coating and surface design parameters such as the size of the sand particles (0.6 mm and 0.3 mm), sand-coating type (partially or completely), number of strands of fiber ribs (6 and 10), and pitch space (11.4 mm to 29.1 mm) of the fiber ribs were tested. The completely sand-coated glass fiber-reinforced polymer hybrid bar exhibited a higher bond strength (90.5%) than the deformed steel bar and a reasonable mode of failure in concrete splitting. A modification parameter to the Eligehausen, Popov, and Bertero (BPE) model is suggested based on the representative experimental tests. The bond stress–slip behavior suggested by the modified BPE model in this study was in reasonable agreement with the experimental results. [ABSTRACT FROM AUTHOR]

A critical limitation of fibre reinforced plastic is its large variability on mechanical performance, especially the longitudinal compressive strength. The influence of fibre random packing and waviness on the compressive strength of UD fibre reinforced plastic is studied in this paper. Three-dimensional geometrically non-linear finite element model is constructed to investigate the compressive behaviour, and an improved approach named Latin hypercube sampling based on random sequential expansion is proposed to generate random fibre distribution across the cross-section. Latin hypercube sampling based on random sequential expansion provides high computation efficiency and good distribution characteristics in comparison to previously proposed methods. Fibre waviness defect with different misalignment angles is also incorporated in the finite element model. It is shown that random fibre packing tends to result in a stochastic detriment of fibre reinforced plastic compressive strength in comparison with uniform fibre packing condition, and the stochastic variation of compressive strength tends to follow normal or lognormal distribution. [ABSTRACT FROM AUTHOR]

This paper mainly focuses on flexural behavior of U-shape HFRP profile-concrete composite beams under static and cyclic loading. Four-point-bending experiments of eight pieces of HFRP-RC composite T-shaped beams with shear keys combined with wet-bond interface under both static and cyclic loads were conducted. The fiber-reinforced polymers profiles were produced by using vacuum infusion molding process. Experiment phenomena were detailed, and flexural performance such as failure mode, capacity, stiffness and load–displacement curves was also analyzed. Result shows that the shear keys combined with wet-bond interface is effective. Meanwhile, the flexural performance of the fiber-reinforced polymers-reinforced concrete beams under cyclic load was simulated based on the OpenSees software, in which special constitutive models of different materials were chosen to consider the cyclic loading. The simulation results and the experimental results such as the load–displacement curves, unloading stiffness, residual displacements, etc. were compared. The results show that OpenSees system can simulate the flexural performance of the fiber-reinforced polymers-reinforced concrete beams under both monotonic loads and cyclic loads very well. And then parameters study was conducted by using simulation method, and the influence factors such as concrete strength, steel bar ratio, fiber-reinforced polymers types, tensile stiffness of the longitudinal fiber-reinforced polymers, etc. were analyzed. Meanwhile, the recoverability of the fiber-reinforced polymers-reinforced concrete composite beams was evaluated, and a modified formula for the residual deformation was put forward. Finally, an idealized type of fiber-reinforced polymers-reinforced concrete beams with a medium reinforcement ratio and high post-yield stiffness was proposed, and reasonable values of the secondary stiffness ratio (defined as post-yield tangent stiffness divided by post-crack tangent stiffness) are recommended. [ABSTRACT FROM AUTHOR]

Laboratory compressive tests and acoustic emission analysis have been used to investigate the failure of pultruded fibre reinforced polymer materials after they have been subjected to temperature stress and compressive loading. The acoustic emission approach is then compared with the experimental values of energy released by each sample through the corresponded load-displacement curve. Samples subjected to severe thermal conditions showed more evidence of brittle failure mechanism. This analysis has been conducted in order to confirm the potential capacity of fibre reinforced polymer materials, known currently for their strength and lightweight but often ‘brittle’ physical characteristics, to perform under exaggerated conditions of temperature and compressive stress. [ABSTRACT FROM AUTHOR]

The basalt fiber-reinforced polymer bar is one of the newly evolved materials expected to be used as a structural reinforcement because of its non-corrosive nature and abundant tensile strength properties. The bond stress–slip relationship between fiber-reinforced polymer bars and concrete is necessary to evaluate the load carrying capacity of concrete components or structures reinforced with fiber-reinforced polymer bars. Although the relationship between fiber-reinforced polymer bars and concrete has been studied, the bond stress–slip relationship between concrete and basalt fiber-reinforced polymer bars considering the effect of bar diameter and concrete strength is still lacking. This paper presents an experimental investigation on the bond behavior between basalt fiber-reinforced polymer bars with different diameters (10, 14, and 20 mm) and concrete with two different compressive strengths using a pull-out test. The test results showed that (1) the failure mode between basalt fiber-reinforced polymer bars and concrete was equally contributed from crushing of concrete and failure of basalt fiber-reinforced polymer surface and mainly from delaminated resin-rich surface for the specimens with the concrete compressive strength of 43.6 and 71.8 MPa, respectively; (2) the bond strength between basalt fiber-reinforced polymer bars and concrete decreased with the increase of bar diameter; (3) the slip corresponding to bond strength increased with the increase of diameter of basalt fiber-reinforced polymer bars; (4) the bond strength between the basalt fiber-reinforced polymer bars with diameter of 10 mm and concrete increased by 18.8% when the concrete strength increased by 64.7%; and (5) the formulas for bond stress–slip relationship between basalt fiber-reinforced polymer bars and concrete in consideration of the ratio of concrete cover depth and concrete compressive strength were proposed. The calculation results of the formulas indicated good accuracy with the experimental results. [ABSTRACT FROM AUTHOR]

This paper focuses on the stiffness and recoverability of a new type of composite beam, the Fiber Reinforced Polymers-Reinforced Concrete (FRP-RC) beam, in which steel bars are the main reinforcement. Ten pieces of beams under both static and cyclic bending load were conducted. Fiber-reinforced polymer profile made by the vacuum infusion molding process is used as reinforcement in the composite beams, in which basalt fiber-reinforced polymer sheets were axially laid at the bottom of the beams in order to improve bearing capacity, and hoop-directionally laid at the lateral side of the beams with the advantages of improving the shear resistance. A finite element model is proposed to predict nonlinear deflections and stresses. The flexural stiffness and recoverability index of this new type of composite beam are studied. The results show that the recoverability of the FRP-RC composite beam is better than that of the normal RC beam and it increases along with the fiber-reinforced polymers reinforcement ratio. Stiffness calculation formulas at various stages and residual deformation formulas are proposed. Finally, the calculation results and test results are compared, which shows that the formulas for stiffness and deformation demonstrate good precision. [ABSTRACT FROM AUTHOR]

In this paper, long fiber thermoplastic was prepared by in-line compounding process and premixed powder impregnation process, respectively, and then comolded with unidirectional continuous fiber tapes. The endless fiber reinforced long fiber thermoplastic was obtained. The effect of the endless fiber fraction on the properties was studied through varying the thickness of the unidirectional composite. It is discovered that the unidirectional continuous fiber can improve toughness dramatically, without sacrificing the strength and stiffness. Fiber length and fiber length distribution may be the significant factors that influence the mechanical properties, especially toughness which can be toughened by fiber bundles as well. The rule of hybrid mixture is suitable to estimate the impact strength. [ABSTRACT FROM AUTHOR]

It has been assumed that the fiber-reinforced polymer/concrete interface is subjected to in-plane shear condition when intermediate crack debonding failure occurs. Therefore, the single shear pull-out test results are often used to predict the intermediate crack debonding failure in beams. In this study, the behavior of fiber-reinforced polymer-strengthened concrete beams and single shear pull-out specimens were studied experimentally and numerically. The bond–slip behavior of the fiber-reinforced polymer/concrete interface was obtained by single shear pull-out and beam tests. In all beam specimens, a concrete wedge located at the edge of the notch detached with the fiber-reinforced polymer debonding failure. This phenomenon shows that the initiation of debonding is due to a diagonal crack formation close to the major flexural/shear crack inside the concrete. The diagonal crack formation is due to a local moment at the tip of the notch. This causes the different stress state and slip of the fiber-reinforced polymer/concrete interface of beam specimens from that of the pull-out specimens. It is found that the bond–slip relation obtained from the pull-out test does not represent the bond–slip relation of the fiber-reinforced polymer/concrete interface in the fiber-reinforced polymer-strengthened concrete beams, and it cannot be directly used for predicting the load capacity of the fiber-reinforced polymer-strengthened concrete beams. [ABSTRACT FROM AUTHOR]

This article presents recent developments in long-term behavior of fiber-reinforced polymer composites subjected to moisture, pH, temperature, sustained stress and ultraviolet radiation, as well as response under combined effects of moisture, pH, etc. Although numerous experiments have been conducted to investigate the durability of fiber-reinforced polymers under different environments, at this stage, it is difficult to ascertain the degradation trends and mechanisms of failures of fiber-reinforced polymers because of non-standardization of various conditioning effects and variation in material constituent. Recent findings on the long-term performance of fiber-reinforced polymer composites are synthesized herein. This article critically examined not only the moisture uptake response, mechanical property and failure modes of fiber-reinforced polymers under varying environments, but also the degradation mechanism through physical and chemical reactions. Moreover, based on information in literature, long-term predictive models were described along with the application potential and limitations. The strength reduction factors were proposed from available data to account for the environmental effects on fiber-reinforced polymers. [ABSTRACT FROM AUTHOR]

Fiber-reinforced plastics are a cost efficient solution for many structural applications as they offer sufficient stiffness and a large freedom of shapes provided by injection molding. These materials are increasingly being used for making structural components, which are subjected to complex and repeated mechanical loads. Therefore, the need for a method to predict the mechanical behavior of such materials is important. In this work, a through process modeling methodology suitable for coupling the microstructure and the macroscopic response of composites considering plastic injection molding process for different injection modes is presented. The key tasks discussed in this work are (1) simulation of the whole manufacturing process in order to obtain the fiber orientation distribution at each point of the part; (2) estimation of local effective properties using the orientation tensor obtained by performing a two-step homogenization and (3) prediction of the mechanical response as a function of a local anisotropy using a mean-field homogenization technique which is based on assumed relationships between average values of strain and stress fields in each phase. The scheme suggested allows to analyze the influence of processing conditions on elastic properties of composites. By changing these conditions, for example, the injection mode (central or linear), the cavity thickness, the fiber volume fraction, the microstructure and hence the local elastic properties of the material can be tailored. Thus, for desired structural response of composites, the optimum filling parameters can be chosen even at the stage of design. [ABSTRACT FROM AUTHOR]

This research evaluates the presence of buckling modes in built-up columns made from pultruded fiber reinforced polymer (FRP) profiles when flexural instability is coupled with torsional instability. This phenomenon is already well known in the field of steel construction and is tested and emphasized with the use of thin walled open cross sections of pultruded FRP materials in testing to analyze the effects of local buckling due to FRP’s orthotropy and high deformability. Also through previous tests on columns made by singular “C” shapes that create the built-up columns tested, the study presents the confidence between experimental results for the pultruded FRP built-up columns and the available formulas for calculating the expected buckling interactions. The investigation shows that torsional-flexural buckling is confirmed but is also combined with a local buckling that first influences the buckling interactions. From a practical application point of view, the study examines a comparison between experimental and formulation characterization of buckling analysis with open cross sections assumed as equivalent to the built-up cross sections. The ratio between the different critical loads and their chronology to collapse is described. [ABSTRACT FROM AUTHOR]

The curing behavior of a fiber-reinforced polymer composite part is interesting for both the industrial and scientific community, for it is related to process optimization, quality upgrade, and material characterization. The study at hand focuses on the potential of temperature measurements as a means to monitor curing; kinetic analysis which conventionally is being done for small neat resin samples in a thermally stable environment (laboratory instruments), is in this study implemented for actual scale composite samples in an environment with significant thermal gradients (manufacturing). To ensure the success of this transition, live temperature data and kinetic parameters derived from DSC of composite samples were used as input to the kinetic equations. Process monitoring with thermocouples that was compared with dielectric constant monitoring and conventional kinetic analysis confirmed the validity of the method. An application with infrared thermography determined the impact of heat insulators within the composite (e.g. delaminations) on the superficial curing degree. [ABSTRACT FROM AUTHOR]

In order to study the axial compression behavior of rectangular concrete short columns that have been strengthened with basalt fiber-reinforced polymer sheets, the axial compression test were conducted on 15 groups specimens. The parameters are the cross aspect ratio and the number of basalt fiber-reinforced polymer layers. As the aspect ratio increases, the confined effect of basalt fiber-reinforced polymer decreases. The strength of one ply of basalt fiber-reinforced polymer decreases as the aspect ratio increases, the range is not very obvious, but the two ply of basalt fiber-reinforced polymer has the obvious decreasing tendency. With the increase in aspect ratio, the square and rectangular section columns of basalt fiber-reinforced polymer confined have a certain size effect. When the aspect ratio is 1.0, the values of fcc/fc0 by one ply of basalt fiber-reinforced polymer and two ply of basalt fiber-reinforced polymer are 1.14 and 1.50, respectively. And when the ratio is 2.0, the values of fcc/fc0 are 1.06 and 1.16. The confined effect is best when the aspect ratio is 1.0, while there is no significant effect with the ratio of 2.0. Results of the theoretical analysis compared with the experimental results show good agreement. [ABSTRACT FROM AUTHOR]

Conventional composites are susceptible to impact loading due to their low toughness. Novel annealed steel fibres possess a unique combination of high stiffness and high strain to failure. A range of composite laminates incorporating various steel fibre architectures with thermoplastic and thermoset matrices were produced and the low-velocity penetration impact resistance was characterized by falling weight impact tests, showing the high potential toughness of steel fibre composites. The effect of different parameters was determined. High matrix strain to failure allows a better exploitation of the steel fibre ductility. The higher absorbed energy up to penetration, in case of laminates with lower levels of fibre/matrix adhesion is attributed to fibre debonding, potential for more plastic deformation, and pull-out mechanisms. Thinner fibres are more sensitive to premature failure due to inclusions in the steel fibres. Cross-ply laminates show higher energy absorption, probably due to increased delamination, whereas woven fibre structures lead to more localized damage. A preliminary study shows that layer by layer (‘macro’) hybridization of carbon and steel fabrics leads to penetration impact resistance close to the pure steel fibre composite, in case the steel plies are placed on the outside surfaces, showing a significant positive effect of hybridization. [ABSTRACT FROM PUBLISHER]

Concrete structures retrofitted with externally bonded fiber reinforced polymer (EB-FRP) sheets have been widely introduced and applied for the last several decades. In order to study the coupling effect of concrete strength and bonding length on the bond properties of FRP–concrete system, a series of direct shear bond tests have been conducted. The test results show that not only the failure mode but also the bond capacity are affected significantly by the coupling effect between concrete strength and bonding length. Furthermore, a theoretical model is applied to demonstrate the two-way debonding failure for the specimens with bonding length less than the effective bonding length. Based on the existing bond strength model, an advanced model, which takes into account the coupling effect of concrete strength and bonding length, is then proposed. The advanced model can fairly satisfactorily predicate the bond strength of CFRP–concrete interface under different concrete strengths and bonding lengths. [ABSTRACT FROM AUTHOR]

The gradual replacement of conventional materials with composite materials has become a concern due to their response to adverse environmental conditions, such as ultraviolet radiation, high temperature, and humidity. In this context, composite laminate using ortho-terephthalic polyester resin as matrix, reinforced with two layers of unidirectional woven licuri fiber, was submitted to accelerated environmental aging in order to study the influence of environmental degradation on mechanical properties, morphology, and fracture characteristics. Age-related morphological degradation of composite laminate was studied based on microscopic analysis of the microstructure and mass loss. In general, the licuri fiber reinforced plastics exhibited certain advantages in its responses to environmental aging. These advantages are evident in behavior related to photo-oxidation and microstructure degradation. Losses were recorded in the mechanical properties of the aged laminate when compared to the original condition; however, the structural integrity was little affected. [ABSTRACT FROM AUTHOR]

This work reports on the static mechanical and modal analysis by free vibration response of hybrid natural fiber reinforced polymer composites. Modal analysis may predict the failure of structures prone to dynamic loading conditions. The composites were compression molded using recently identified short Sansevieria cylindrica fibers and coconut sheath mats in a polyester matrix. The study focused on the effect of the stacking sequence and fiber chemical treatment (alkali and silane) on the composite properties. Hybridization of coconut sheath and Sansevieria cylindrica fiber significantly enhanced all properties compared to single-fiber composites. For all composites (pure or hybrid), the increase in mechanical strength and natural frequency was noticed after chemical treatment. The trend in mechanical strength followed: untreated < alkali treated < silane treated. Interestingly, regarding vibrational behavior, coconut sheath/Sansevieria cylindrica/coconut sheath offered superior natural frequency in all three conditions. This highlights that higher modulus composites can be designed by keeping fiber mat as skin and short fiber as core. Morphological investigation revealed that the attraction between fiber–fiber and fiber–matrix is greatly enhanced after silane treatment. [ABSTRACT FROM AUTHOR]

Numerous experimental tests and analytical investigation were carried out on thermal effects on fiber reinforced polymer bars reinforced concrete structures. Nevertheless, the finite element modeling of thermal behavior of fiber reinforced polymer bars embedded in concrete was insufficiently analyzed, particularly, for asymmetric problems. This paper presents a nonlinear numerical study using ADINA finite element software to investigate the effect of the ratio of concrete cover thickness to fiber reinforced polymer bar diameter (c/db) on the distribution of transverse thermal stresses and deformations in fiber reinforced polymer bars and concrete cover for an asymmetric problem using prismatic concrete beams reinforced with fiber reinforced polymer bars submitted to high temperatures up to + 60℃. Also, to predict the thermal loads (ΔTcr) that produce the first radial cracks within concrete and the thermal loads (ΔTsp) which cause the splitting failure of the concrete cover as a function of the ratio of concrete cover thickness to fiber reinforced polymer bar diameter for an asymmetric problem. Nonlinear numerical results in terms of cracking thermal loads, thermal deformations, and thermal stresses are compared to those evaluated from analytical models and experimental tests. [ABSTRACT FROM AUTHOR]

Influence of microarchitectural fiber matrix arrangement in representative volume element is studied to assess the effect of mass diffusion in the fiber-reinforced polymer composites. A novel approach has been proposed to illustrate the quantitative definition of the representative volume element heterogeneity using topological descriptor of clustering. Average fiber center distance from the fixed representative volume element center is described to compute the clustering in different representative volume elements, followed by finite element method simulation to model and visualize two-dimensional microstructures of fiber-reinforced matrix composites with moisture boundary conditions. The suggested topology descriptor shows good correlation with diffusion response in relation to saturation time, whereas a fair degree of correlation was observed for mass accumulation and mass flux characteristics. The results indicate that microstructural heterogeneity has a strong influence on typical moisture diffusion characteristics and hence, an overall diffusion-induced damage. The observations should serve as a clue to design the fiber-reinforced polymer composites with the moisture barrier properties. [ABSTRACT FROM AUTHOR]