Fiber-reinforced Materials Research Articles

A micromechanical approach to effective elastic properties of fiber-reinforced fractured cementitious materials

A micromechanical model is formulated in this work to predict the effective elastic properties of fiber-reinforced fractured cementitious materials. Fractures refer to a region of small thickness, along which mechanical and physical properties of the material are degraded. Unlike cracks, fractures are discontinuities able to transfer stress and, therefore, can be regarded from a mechanical viewpoint as interfaces endowed with a specific behavior under normal and shear loading. The presence of fibers enhances the post-cracking strength of cementitious materials due to the bridging effect of the fibers and improves their ductility. The present work employs a micromechanical approach to formulate the homogenized elastic behavior of fiber-reinforced fractured cementitious materials. In the context of Eshelby’s equivalent inclusion theory, the approach makes use of the Mori-Tanaka scheme to estimate the homogenized elastic moduli. Fractures and fibers are modeled as oblate and prolate spheroids endowed with appropriate elastic properties. Particular emphasis is given to the situation of a cementitious matrix reinforced by aligned or randomly distributed fibers with randomly distributed microfractures.

Research Progress on the Impact Resistance of Basalt Fiber-Reinforced Polymer Composites

Abstract Basalt fibers exhibit excellent properties and have diverse applications. This paper thoroughly investigates the impact resistance of polymer matrix composites reinforced by basalt fibers and analyzes the failure mechanisms during impact, including micro-deformation, delamination, and fiber fracture. Basalt fiber-reinforced resin matrix composites consist of a reinforcement phase, a matrix phase, and an interface phase. To strengthen the material’s resistance to impacts, various approaches have been explored, including optimizing the matrix resin (e.g., selecting vinyl resin and toughening treatments), optimizing the reinforcement phase (e.g., fiber hybridization, morphology optimization, and interlayer hybridization), and improving the interface phase (e.g., coupling agent modification and carbon nanotube grafting). These optimization measures can significantly enhance the impact resistance of basalt fiber-reinforced polymer materials under low-velocity impact loads. Under high-velocity impact loads, increasing the number of laminate layers or employing three-dimensional weaving techniques can significantly improve the material’s impact resistance. These research findings aim to provide a theoretical foundation and practical references for the application of basalt fiber-reinforced polymer materials within the domain of impact resistance.

Research on Interlayer Toughening and Damage Detection of Laser-Induced Graphene and Short Kevlar Fibers Aramid Fiber/Epoxy Resin Composites.

The poor interlaminar fracture toughness is a critical limiting factor for the structural applications of aramid fiber/epoxy resin composites. This study investigates the effects of laser-induced graphene (LIG) and short Kevlar fibers on the interfacial toughness and damage detection of aramid composite materials. Mode II tests and tensile tests were conducted to evaluate mechanical properties and damage detection using the piezoresistive characteristics of LIG. The results indicate that LIG combined with short Kevlar fibers significantly enhances the interfacial toughness of the composites, achieving a 381.60% increase in initial Mode II fracture toughness. Although LIG reduced the tensile strength by 14.02%, the addition of short Kevlar fibers mitigated this effect, preserving the overall mechanical performance. Scanning electron microscopy (SEM) analysis revealed enhanced toughening mechanisms, including increased surface roughness, altered crack propagation paths, and fiber bridging. Additionally, LIG enabled real-time damage monitoring, showing a significant increase in resistance upon delamination or crack propagation and a marked increase in resistance upon the tensile fracture. This research indicates that the synergistic effects of LIG and short Kevlar fibers not only enhance the interlaminar toughness of aramid composites but also provide a novel strategy for effective damage detection in fiber-reinforced materials.

A Study on the Effect of Cutting Temperature on CFRP Hole Wall Damage in Continuous Drilling Process

In the assembly process of aerospace parts, drilling is essential for carbon fiber-reinforced materials. However, due to the extreme thermal sensitivity of these composites, continuous drilling often leads to irreparable defects such as hole wall burns and exit delamination caused by concentrated cutting heat, resulting in the scrapping of parts. To address this issue, this paper explores the impact of temperature characteristics on drilling quality, providing guidance for optimizing the composite drilling process. A simulation model for single and continuous drilling was established to analyze the temperature distribution on the tool surface during drilling. A drilling temperature measurement system based on thin-film thermocouple technology was developed, enabling real-time online temperature monitoring. Continuous drilling experiments were conducted, analyzing the correlation between maximum drilling temperature and hole quality. Results show that temperatures from −25.75 °C to −9.75 °C and from 182 °C to 200.75 °C cause significant exit damage, while optimal hole quality is achieved between −1.25 °C and 168 °C.

Dual-Modal Fusion PRI-SWT Model for Eddy Current Detection of Cracks, Delamination, and Impact Damage in Carbon Fiber-Reinforced Plastic Materials

Carbon fiber-reinforced plastic (CFRP) composites are prone to damage during both manufacturing and operational phases, making the classification and identification of defects critical for maintaining structural integrity. This paper presents a novel dual-modal feature classification approach for the eddy current detection of CFRP defects, utilizing a Parallel Real–Imaginary/Swin Transformer (PRI-SWT) model. Built using the Transformer architecture, the PRI-SWT model effectively integrates the real and imaginary components of sinusoidal voltage signals, demonstrating a significant performance improvement over traditional classification methods such as Support Vector Machine (SVM) and Vision Transformer (ViT). The proposed model achieved a classification accuracy exceeding 95%, highlighting its superior capability in terms of addressing the complexities of defect detection. Furthermore, the influence of key factors—including the real–imaginary fusion layer, the number of layers, the window shift size, and the model’s scale—on the classification performance of the PRI-SWT model was systematically evaluated.

Thermal Stress Analysis of Maxillary Dentures with Different Reinforcement Materials Under Occlusal Load Using Finite Element Method

The purpose of this study was to determine the effect of fiber reinforcement materials on the magnitude of stresses in a critical part of the maxillary denture base under thermal and occlusal load. Thermal stress analyses of the models were carried out using the finite element method. The models consisted of bone, soft tissue, interface gap, and maxillary dentures with and without reinforcements. A concentrated occlusal load of 230 N was applied bilaterally on the molar teeth. A 36 °C reference and 0 °C, 36 °C, and 70 °C variable ambient temperatures were applied to the models. CrCo, unidirectional and woven carbon/epoxy, unidirectional and woven glass/epoxy, and unidirectional and woven Kevlar/epoxy were used as reinforcing materials in the maxillary denture base made of PMMA (polymethyl methacrylate). Stress distributions on the maxillary denture’s midline and lateral line direction were evaluated. Maximum stresses in the incisal notch and the labial frenal notch of the maxillary denture were determined. Failure analysis of reinforcement materials used in maxillary dentures was carried out using the Tsai-Wu index criterion. The results obtained show that the thermal properties of reinforcement materials should be considered as an important criterion in their selection.

Recent Advances in Additive Manufacturing of Fibre-Reinforced Materials: A Comprehensive Review

Additive manufacturing (AM) plays a significant role in the 4th Industrial Revolution due to its flexibility, allowing AM equipment to be connected, monitored, and controlled in real time. In advance, the minimum waste of material, the agility of manufacturing complex geometries, and the ability to use recycled materials can provide an advantage to this manufacturing method. On the other hand, the poor strength and durability of the thermoplastics used in the manufacturing process are the major drawback that keeps AM behind common production methods such as casting and machining. Fibre-reinforced polymers can enhance mechanical properties, advance AM from the commonly used polymers, and make AM competitive against conventional production methods. The main focus of the current review is to examine the work conducted in the field of reinforced additively manufactured technologies in the literature of recent years. More specifically, this review discusses the conducted research in the composite fibre coextrusion (CFC) additive manufacturing techniques developed over the past years and the materials that can be used. In addition, this study includes an up-to-date comprehensive review of the evaluation of fibre-reinforced 3D printing along with its benefits in terms of mechanical response, namely tensile, flexural, compression and energy absorption, anisotropy, and dynamic properties. Finally, this review highlights possible research gaps regarding fibre-reinforced AM and proposes future directions, such as deeper investigations into energy absorption and anisotropy, to position fibre-reinforced AM as a preferred fabrication method for ready-to-use parts in cutting-edge industries, including automotive, aerospace, and biomedical sectors.

Study on Mechanical Properties of Fiber-reinforced Cement-based Materials

Fiber reinforced cement-based materials are used to add various kinds of fibers to ordinary cement-based materials to improve their tensile strength, compressive strength, shear strength, flexural strength, flexural strength and impact resistance. There are many kinds of fiber, including steel fiber, carbon fiber, glass fiber, polypropylene fiber and basalt fiber, etc. The type, shape, content and length-diameter ratio of fiber will affect the performance of cement-based materials. In this paper, the research status of steel fiber, polypropylene fiber and basalt fiber on cement-based materials is reviewed, and the application of fiber reinforced cement-based materials is prospected.

Improving concrete structures with engineered cementitious composites and kevlar sheets: an affordable retrofitting solution for earthquake resistance

Abstract This paper outlines experimental and analytical studies focused on strengthened concrete specimens using Engineered Cementitious Composites and use of Kevlar sheets is highlighted as one of the most effective techniques for achieving the desired structural reinforcement and extending the lifespan of structures. The research examines the mechanical properties of retrofitted concrete and material characterizations of ECC such as Scanning Electron Microscopy and Energy dispersive x-ray analyses were also carried out to corroborate the durability properties of ECC and Kevlar-wrapped specimens, specifically assessing compressive, tensile, and flexural strength. In this study, fiber-reinforced cementitious materials featuring a 2% volume fraction of hybrid fibers comprising hooked-end steel and polyvinyl alcohol fibers were employed to strengthen the concrete structure. This additional layer enhances tensile strength and aids in crack management, necessitating proper curing to ensure strength gain over a specified duration. Kevlar fabric sheets are carefully applied to the ECC surface using resin to create a strong bond between the Kevlar and the underlying material, resulting in a durable retrofitted structure. Preliminary experimental data supported numerical modelling of the specimens using finite element analysis. The numerical results regarding the retrofitted strength of hardened concrete were compared with experimental outcomes. The findings showed that the maximum load of the strengthened samples increased by 6.5%. Additionally, the retrofitted strength prior to complete failure rose by 10.6%. In conclusion, the integration of hybrid fibers for reinforcement and Kevlar for retrofitting proves to be a cost-effective and straightforward approach.

Advancing Circular Economy: Comparative Analysis of Recycled and Virgin Carbon Fiber 3D Printed Composites on Performance and Eco-Efficiency

Carbon fiber-reinforced polymer composites are widely used for their corrosion resistance, high strength, stiffness, and lightweight properties. However, the extensive use of carbon fiber generates significant waste at the end of its lifecycle. Recycling technologies can effectively recover carbon fiber from this waste, making it suitable for reuse in various applications. Recently, there has been a growing trend in using recycled carbon fiber as a reinforcement material in polymer matrices, offering a cost-effective alternative to virgin carbon fiber while maintaining excellent mechanical properties. However, most studies focus on the mechanical strength of parts made from recycled and virgin carbon fibers, with less attention given to the environmental impacts of these materials. The primary objective of this study is the comparative analysis of the specimens manufactured using recycled and virgin carbon fiber-reinforced polyamide-12 material based on the mechanical performance, life cycle cost, and environmental impact. The experimental investigations showed that the mechanical performance of the recycled carbon fiber polyamide-12 (rCFRP12) composites are more efficient than the specimens manufactured using the virgin carbon fiber polyamide-12 (vCFRP12) composites such as three-point bending test results show that parts made from rCFRP12 composites achieved a flexural strength of 56.25 MPa, outperforming those made with vCFRP12 (49.9 MPa). Additionally, the recycled composite specimens also exhibited higher tensile strength than their virgin carbon fiber counterparts. The life cycle analysis revealed that samples made with recycled carbon fiber have a lower environmental impact, reducing global warming, ozone depletion, and carcinogenic effects by 11.98% compared to those made with virgin carbon fiber. Additionally, the production cost of recycled carbon fiber is significantly lower than that of virgin carbon fiber.

A cohesive fracture-enhanced phase-field approach for modeling the damage behavior of steel fiber-reinforced concrete

This study introduces a novel computational framework based on the phase-field fracture/damage model (PFM), providing rapid and accurate predictions of the damage behavior of Steel Fiber Reinforced Concrete (SFRC) material. The framework integrates the interfacial cohesive fracture model with the PFM to depict the interaction between the cementitious matrix and fibers, marking the first demonstration that this model adequately captures both local fracture phenomena between fibers and concrete (such as fiber bridging and interfacial debonding) and mesoscopic stress–strain behavior. Additionally, an enhanced geometric approximation is established based on the spatial distribution density function of fibers and particles, allowing for the transformation of the three-dimensions (3-D) fiber-reinforced material structure into an equivalent two-dimensions (2-D) material. This approach enables the reduction of computational time, a significant limitation of the phase-field method, thereby allowing an in-house code to perform various computations with complex material structures such as SFRC. The effectiveness of the approach is demonstrated through four examples involving variations in the microgeometry and material properties of SFRC structures, ranging from the simplest configurations to real experimental material structures. Extensive Monte Carlo simulations of the model are also employed to provide results closer to reality, which are then compared with recent experimental data and numerical models, demonstrating the efficacy of the proposed computational model.

Optimization of polypropylene high-strength injection molding welding and interface structure analysis

Secondary injection molding is an effective method for joining polymer parts, where the weld interface plays a critical role in the overall performance of the part. This study discusses the influence of injection molding parameters on the interface strength of polypropylene and polypropylene (PP-PP) secondary injection molding and analyzes the welding interface structure. The injection molding parameters for PP-PP were optimized using the Taguchi method and the signal-to-noise ratio (S/N). The optimal injection molding parameters were determined to be a mold temperature of 120°C, injection temperature of 350°C, and injection speed of 100 mm/s. The interface tensile strength was measured at 33.42 MPa, corresponding to 98.1% of the tensile strength of the base material. Among these parameters, mold temperature has the greatest influence on the strength of the welding interface. Secondly, polarizing microscopy, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) were employed to observe and analyze the crystal structure and fracture failure modes at the interface. The results indicate that elevated injection molding parameters promote the formation of crystal nuclei and spherulite growth at the secondary melt interface, with the spherulite size at the interface significantly affecting the interface strength. This study offers valuable reference for the welding of other polymers and fiber-reinforced materials.

Optimizing tensile strength and failure prediction in hemp fiber composites: Coupling effects of microfibril angle and fiber orientation under off-axis loading

In response to environmental concerns associated with synthetic fiber-reinforced materials, plant fiber-reinforced composites are increasingly recognized as a more sustainable alternative. However, predicting the mechanical properties of these composites remains challenging due to the unique microstructure of plant fibers. This study proposes an optimized Tsai-Hill failure criterion that incorporates the microfibril angle (MFA) and fiber orientation to enhance failure predictions. The MFA of hemp fibers was measured using X-ray diffraction (XRD), and the failure mechanisms of unidirectional hemp fiber composites under off-axis tensile stresses were thoroughly analyzed. Experimental results reveal a 10.69 % increase in tensile strength at a 5° off-axis angle compared to the fiber direction. As the off-axis angle increases, the failure mode transitions from fiber fracture and pull-out to matrix tearing and interlayer shear failure. For angles above 10°, the failure stress aligns with both the maximum stress and Tsai-Hill criteria. For angles below 10°, integrating MFA into the Tsai-Hill criterion significantly improves prediction accuracy. These findings offer critical insights for optimizing the tensile performance of hemp fiber composites and predicting their behavior under off-axis loading conditions. Consequently, this study can support the use of hemp fiber composites in a broader range of applications.

Hybrid Fiber-Reinforced Biocomposites for Marine Applications: A Review

Highly efficient fiber-reinforced composites find extensive application in diverse industries. Yet, conventional fiber-reinforced composites have significant environmental impacts during both manufacturing and disposal. Environmentally friendly fiber-reinforced composites have garnered significant attention within the framework of sustainable development. Utilizing natural fibers in place of synthetic fibers and progressively decreasing the use of synthetic fibers are the main approaches to achieving a balance between economic progress and environmental quality. Attention is increasingly being drawn to natural fiber-reinforced biocomposites that exhibit outstanding environmental performance, exceptional physical and mechanical capabilities, and biological features. The lightweight and high-strength characteristics of these biocomposites enable them to significantly decrease the weight of structures, making them increasingly popular in many industries. The objective of this review is to evaluate the effectiveness of hybrid fiber-reinforced biocomposites in marine applications, specifically examining their mechanical characteristics, resistance to seawater, and ability to absorb moisture, all while advocating for sustainable material methodologies. To achieve this objective, the paper delineates the distinction between synthetic and natural fibers, examines the benefits of hybrid fiber-reinforced biocomposite materials, and addresses the obstacles and effective approaches in their production and application in seawater. Considering the review analysis, it can be inferred that the use of fiber-reinforced biocomposites in maritime applications shows significant potential and has abundant untapped growth prospects in the future years.

Bending properties and damage evolution of fiber-reinforced aeolian sand backfill materials

Backfilling is a promising measure for controlling surface subsidence in mined-out areas and disposing solid wastes from the mineral processing, there are increasing demands of enhanced toughness and anti-cracking properties of backfill materials to prolong the service life under the complex loads. In this study, polypropylene (PP) fibers were employed to improve performance of backfills, four-point bending and uniaxial compression tests were conducted to investigate the failure process and damage evolution of fiber-reinforced aeolian-sand backfill materials (FABs) using Digital Image Correlation (DIC) and Acoustic Emission (AE) techniques. The results show that the compressive strength tends to decrease with the increasing fiber volume fractions, while the four-point bending strength shows a tendency to increase initially and then decrease, and the optimum volume fraction of PP fiber is 0.6%. At the optimal fiber volume fraction, PP fibers with lengths of 3 mm and 9 mm resulted in a 65.25% and 81.62% increase in the four-point bending strength of FABs, respectively. As indicated by DIC measurements, PP fibers with a length of 9 mm were more effective in controlling the horizontal and vertical displacements of FABs under four-point bending loads than that of 3 mm, and the cracks developed more slowly at the same deflection. In addition, PP fibers with a length of 9 mm have stronger crack extension delay characteristics due to longer effective anchorage distance, as evidenced by more frequent acoustic emission ringing counts and higher cumulative ringing counts. The results of the study may provide a theoretical basis for the application of FABs materials in backfilling.

ANALYSIS OF SH-WAVES IN ANISOTROPIC FIBER-REINFORCED MEDIUM OVER LINEARLY VARYING INHOMOGENEOUS SUBSTRATE UNDER NON-LOCAL ELASTICITY

An analytical technique employing the variable separable method has been used in an attempt to precisely grasp and assess the impact of the property non-local elasticity upon the wave transmission response of an anisotropic fiber-reinforced material embedded over a semi-infinite, inhomogeneous medium that changes linearly. As depth increases, the stiffness and density of a semi-infinite substrate are believed to alter linearly. Availing the Whittaker function, a relation about dispersion has been acquired to analyze the response of SH waves. The visual representation depicts a significant influence of non-local elasticity on the propagation of SH-wave modes. Special cases have been found assessing the concurrency of the model with the original form equation of Love wave. The effects of non-locality, fiber-reinforcement parameters, and inhomogeneity parameters carry implications in designing and gradation of material characteristics some important parameters on the wave characteristics of the studied model.

Exploring mechanical properties of eco-friendly hybrid epoxy composites reinforced with sisal, hemp, and glass fibers

It is now widely accepted that various subsets of hybrid fiber composites reinforced with combined natural and synthetic fibers can significantly expand the applicability of composite-based materials in design and technology practice. The already existing unnatural circumstances on the planet put natural fibers far ahead of traditions in the field of materials thanks to their biodegradability characteristics, availability and over-term endurance and corrosion resistance. At the same time, composites are rapidly taking their place in many industries and sectors of the economy as metals in as much as it is economically and energetically justified. This study evaluates the mechanical properties of hybrid composites reinforced with glass, hemp, and sisal fibers. Using a hand lay-up method with epoxy resin, composite laminates were fabricated and tested for tensile, flexural, impact strengths and hardness test in accordance with ASTM standards. The experimental results revealed that glass-sisal fiber composites achieved the highest tensile strength of 69.1 MPa, while glass-hemp-sisal fiber composites exhibited superior flexural strength of 15.22 MPa and impact strength of 137.45 kJ/m2 while best hardness value was 24.73 HV for glass-sisal fibre composite. These findings underscore the potential of glass-sisal-hemp fiber-reinforced epoxy composites as viable alternatives to traditional synthetic fiber-reinforced materials in automotive industry where there are no structural loadings i.e. automobile interiors; offering enhanced mechanical performance and sustainability.

Preface: Numerical Modelling of Fibre-Reinforced Materials and Structures

This special issue contains selected papers on “Numerical Modelling of Fibre-reinforced Materials and Structures” presented at ACCM 2021, the Fifth Australasian Conference on Computational Mechanics, which was successfully held in Western Sydney University, Sydney, Australia, in December 2021. The selected papers published in this special issue reported advanced computational methods and modelling technology in the niche area of fibre-reinforced materials and structures. Fibre reinforcement has demonstrated effectiveness in strengthening the high performance and durability of materials and structures. The research and development of high-performance fibre-reinforced materials and structures have been increasing, which has also seen growing interest and adoption in engineering practice with greatly enhanced structure safety and infrastructure resilience. The papers collected in this special issue present advanced theory, algorithm, numerical simulation, and/or novel application of computational techniques to the problems associated with fibre-reinforced materials and structures.

Design of an experimental approach based on the contrast-to-noise ratio measurement for X-ray computed tomography parameters optimization applied to a carbon fiber-reinforced polymer materials scan

This paper proposes a systematic approach for the optimization of scan parameters for industrial X-ray computed tomography (XCT), as regard its specific application as diagnostic tool on carbon fiber-reinforced polymer materials (CFRP). This procedure allows the system operator to overcome suboptimal scan results due to a subjective choice of XCT parameters. In this work, XCT scan quality has been measured in terms of contrast-to-noise ratio (CNR) metric, by calculating it on collected XCT 2D projection images. A four-factor five-level central composite design (CCD) was implemented to perform experiments, and a quadratic polynomial model was chosen to describe the effects of XCT scanning parameters combination on CNR measurement and finally to predict optimal results. Analysis of variance was carried out to evaluate the significance of the model on the response, reporting a R2 of 97.1%, and response surface analyses were also performed for CNR optimization purposes. In order to validate the CCD results, different XCT parameters combinations, coming from the CCD analysis on projection images, were used to run different scans, and, as result, the optimal CNR predicted from the model was also reflected in an optimal CNR measured on the reconstructed XCT images.

Evaluation the Effect of Fiber Reinforcement Materials on Flexural Strength of Heat Cured Denture Based Resin Materials

Evaluation the Effect of Fiber Reinforcement Materials on Flexural Strength of Heat Cured Denture Based Resin Materials