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The present work sets out the evaluation of composite laminates through optimization objective functions. Genetic Algorithms (GA), as well as Simulated Annealing (SA), were performed to determine the optimal ply orientations of a fiber-reinforced polymer laminate for three given load cases: (1) in-plane loads, (2) combined moments, and (3) in-plane loads and combined moments. It searches the optimal orientation layup, which fulfills at the same time both the maximum strain criterion and the Tsai–Wu failure criterion. Construction of an objective function based on the strains and the stresses involves a minimization process to deformations and a maximization of the safety factor. For the first load case, the initial solution is [±45/0/90/±45]s, and the best solution is [(45/135)2/452]s. For the second load case, [–45/45/45/–45/0/90]s is the initial layup sequence, then, the best solution obtained is [(45/–45)2/452]s, where plies at 0° and 90° are not necessary even when axial loads are applied. For the third study case, the original layup sequence is [0/45/–45/45/0/90]s; meanwhile, the best solution calculated is [21/24/145/140/45/49]s. An interesting observation is that each pair of layers has a 5° gap. The simulations show that the qualitative results from the GA are better than the SA, but with a significantly higher computational cost. These computational tools are expected to be used as a reference guide for an optimal fiber configuration concerning the common orientations used when composite laminates are designed for a structural application. [ABSTRACT FROM AUTHOR]

Natural fiber-reinforced composites are composite materials composed of natural fibers, such as plant fibers and synthetic biopolymers. These environmentally friendly composites are biodegradable, renewable, cheap, lightweight, and low-density, attracting attention as eco-friendly alternatives to synthetic fiber-reinforced composites. In this study, natural fiber-reinforced polymer foam core layered composites were produced for the automotive industry. Fabrics woven from goat wool were used as the natural fiber. Polymer foam with expanded polystyrene (EPS) and extruded polystyrene (XPS) structures was used as the core material. During production, fibers were bonded to the upper and lower layers of the core structures using resin. The hand lay-up method was used in production. After resin application, the samples were cured under a heated press for 2 h. After the production was completed, the material was cut according to the standards (10-20-30 Joule), and impact and bending tests were conducted at three different energy levels. The experiments revealed that at 10 J, the material exhibited rebound; at 20 J, it showed resistance to stabbing; and at 30 J, it experienced penetration. While EPS foam demonstrated higher impact resistance in the 10 J test, it was found that XPS foam exhibited better impact resistance and absorption capabilities in the 20 J and 30 J tests. Due to the open and semi-closed cell structure of EPS foams and the closed cell structure of XPS foams, it has been concluded that XPS foams exhibit higher impact resistance and better energy absorption properties [ABSTRACT FROM AUTHOR]

This paper presents a progressive damage model (PDM) based on the 3D Hashin failure criterion within the ABAQUS/ExplicitTM 2021 framework via a VUMAT subroutine, enhancing the characterization of the mechanical performance and damage evolution in the elastic and softening stages of composite materials via the accurate calculation of damage variables and accommodation of non-monotonic loading conditions. In the subsequent multi-level verification, it is found that the model accurately simulates the primary failure modes at the element level and diminishes the influence of element size, ensuring a reliable behavior representation under non-monotonic loading. At the laminate level, it also accurately forecasts the elastic behavior and damage evolution in open-hole lamina and laminates, demonstrating the final crack band at ultimate failure. This paper also emphasizes the importance of correct characteristic length selection and how to minimize mesh size impact by selecting appropriate values. Compared to ABAQUS's built-in 2D model, the 3D VUMAT subroutine shows superior accuracy and effectiveness, proving its value in characterizing the mechanical behavior and damage mechanisms of fiber-reinforced polymer (FRP) materials. The enhanced 3D PDM accurately characterizes the softening processes in composite materials under simple or complex stress states during monotonic or non-monotonic loading, effectively minimizes the mesh dependency, and reasonably captures failure crack bands, making it suitable for future simulations and resolutions of numerical issues in composite material models under complex, three-dimensional stress states. [ABSTRACT FROM AUTHOR]

The need for ending plastic waste and creating a circular economy has prompted significant interest in developing a new family of composite materials through recycling and recovery of waste resources (including bio-sourced materials). In this work, a family of natural fiber-reinforced plastic composites has been developed from paint pail waste recycled polypropylene (rPP) and waste wool fibers of different diameter and aspect ratio. Composites were fabricated by melt processing using polypropylene-graft-maleic anhydride as a compatibilizer. The internal morphology, interfacial and thermal characteristics, viscoelastic behavior, water sorption/wettability, and mechanical properties of composites were studied using electron microscopy, high-resolution synchrotron Fourier transform infrared microspectroscopy, thermal analysis, rheology, immersion test, contact angle measurement, tensile test and flexural test. The composite matrix exhibited an internal morphology of coalescent micro-droplets due to the presence of polyethylene and dry paint in the rPP phase. In general, the rheological and mechanical properties of the composites comprising higher-aspect-ratio (lower diameter) fibers exhibited relatively superior performance. About an 18% increase in tensile strength and a 39% increase in flexural strength were measured for composites with an optimal fiber loading of 10 wt.%. Interfacial debonding and fiber pull-out were observed as the main failure mechanism of the composites. The developed composites have potential for applications in automotive, decking, and building industries. [ABSTRACT FROM AUTHOR]

This study examines the creation and development of composite materials, from conventional techniques to their innovative uses in numerous industries. Composite materials that are robust, versatile, and resilient have advanced significantly, especially with the application of nanotechnology and hybrid fiber reinforcements. Composite materials are difficult to machine due to their anisotropic and non-homogeneous structure, as well as the high abrasiveness of their reinforcing parts. This typically results in the workpiece becoming damaged and the cutting tool wearing down very rapidly. On composite materials, traditional machining methods such as turning, drilling, and milling can be applied with the appropriate tool design and operating parameters. An overview of the various issues related to the conventional machining of the main types of composite materials is given in this work. This article examines novel matrix materials, forms of reinforcement, and production procedures to show how advanced metallic matrix nano composites and fiber-reinforced polymers are replacing traditional composites. Special emphasis is given to the strict manufacturing conditions in addition to the homogenous dispersion of nanoparticles and damage-free machining of fiber composite materials. The essay also discusses how sustainable alternatives, including reinforcements made of natural fibers, affect the ecosystem. This study aims to offer a comprehensive analysis and case studies. [ABSTRACT FROM AUTHOR]

Hole quality in composite materials is gaining interest in aerospace, automotive, and marine industries, especially for structural applications. This paper aims to investigate the quality of holes performed without a backup plate, in thin plates of glass fiber-reinforced polymer (GFRP). The samples were manufactured by two different technologies: vacuum bagging and an innovative method named vacuum mold pressing. Three experiments were designed choosing the control factors that affect the maximum cutting force, delamination factor, and surface roughness of drilled holes in composite materials based on twill fabric layers. Quality analysis of the hole features was performed by microscopy investigations. The effects of the main factors on the targets are investigated using the statistical design of experiments, considering control factors, such as support opening width, weight fraction (wf), feed per tooth, and hole area. The results showed that the feed per tooth and hole area had a more significant influence on the delamination factors and surface roughness (Sa). The best quality of the holes drilled in twill-based GFRP was achieved for a lower feed rate of 0.04 mm/tooth and used a support opening width of 55 mm. [ABSTRACT FROM AUTHOR]

AbstractCarbon fiber-reinforced polymer (CFRP) is prone to machining defects, including burrs and tearing, during milling. These defects are closely associated with interface delamination while milling force plays a crucial role in their occurrence. In this paper, a nonlinear explicit finite element (FE) model is developed to predict the milling force and analyze the delamination damage occurring during the milling of unidirectional CFRP (UD-CFRP). The proposed FE model is validated through numerical comparison with experimental data for milling force. Moreover, a detailed study is conducted to examine the influences of spindle speed, feed rate and depth-of-cut on the side-milling performance and damage response of UD-CFRP. This study provides valuable insights into the effects of machining parameters on milling force and delamination damage in CFRP, thereby supporting the optimization of machining technology for this composite material system. [ABSTRACT FROM AUTHOR]

Fiber composite materials are key components of numerous future technologies. This results in a strongly increased demand and also in increasing amounts of waste in the upcoming years. Thus, recycling of fiber composite materials has become an intensively researched topic. At 95 wt %, glass fiber‐reinforced plastics make up the largest part. This review article will provide an overview of the state of the art of common recycling strategies and technologies, with particular focus on the advantages and challenges of glass fiber‐reinforced polymer recycling. [ABSTRACT FROM AUTHOR]

In the past decade, polymer‐based glass fiber‐reinforced laminate composites have gained significant popularity in various mass transit applications, including marine, aircraft, and automotive industries. However, it is crucial to consider the degradation and potential failure of these materials, especially in mass transit networks. To address this concern, fractographic analysis has emerged as a valuable approach for investigating fracture surfaces, extracting vital information, and facilitating the development of new materials. Furthermore, it sheds light on the underlying physical mechanisms that contribute to composite failure. This paper primarily focuses on examining flaws, failure modes, and performing fractography analysis on fiber‐reinforced polymer (FRP) laminate composites subjected to various loading conditions such as tension, compression, flexure, impact, shear, and fracture. Fractography, as an indispensable method, plays a pivotal role in the comprehensive development of composite structures and has become a reliable tool for composite engineers. The outcomes of this study are expected to serve as a foundation for identifying areas that require further investigation in terms of fracture analysis and failure modes specific to FRP composite materials, particularly those used in marine applications. Highlights: Introduction to FRP laminate composites in marine structures.Concise analysis of failure modes in FRP laminate composites.SEM fractography review of FRP laminate composites under varied loading conditions.Comprehensive study on tensile, flexural, impact, compression, shear, and fracture toughness failure modes.Summarization of identified defects in FRP composites. [ABSTRACT FROM AUTHOR]

The article examines the accuracy of homogenization processes in describing the behavior of materials with microstructure. It discusses how composite materials such as laminates or fiber-reinforced plastics are produced by cleverly combining individual material components at the microscopic level. Homogenization allows for the mathematical prediction of the effective behavior of such composite materials. The article also addresses the homogenization of the wave equation for materials with periodic microstructure. It is shown that classical homogenization is unable to capture the long-term change in waveforms. It is emphasized that homogenization results should be viewed with caution as they may not adequately represent reality. [Extracted from the article]

Arthroplasty is generally used to treat advanced osteoarthritis or other degenerative joint diseases. However, it can also be considered in younger patients with severe joint damage that seriously limits their function and quality of life. Young patients are at risk of aseptic mobilization and bone resorption due to the uneven distribution of stress on the contact surface between the prosthesis and the femur that generates the stress-shielding phenomenon. To overcome this occurrence, it is necessary to use biocompatible materials with a stiffness that is similar to bone. Composite hip prostheses, consisting of continuous fiber-reinforced polymers, play a progressively key role in the development of prosthetic devices. Composite materials can be designed more carefully than monolithic stems (single-phase materials such as metals), allowing for the development of more effective tissue substitutes. Our purpose of this review was to analyze the state of the art in the use of carbon femoral prostheses. In particular, the major mechanical properties of reinforcement (fiber) and matrix were outlined with their applications in the prosthetic field. [ABSTRACT FROM AUTHOR]

Determining the properties of composite materials (knowing the properties of the component phases) is a primary objective in the design phase. Numerous methods have been developed to determine the elastic constants of a composite material. All these methods are laborious and require significant computing time. It is possible to make experimental measurements, but these too are expensive and time-consuming. In order to have a quick estimate of the value of the engineering constants of a new composite material (in our study a polymeric matrix reinforced with carbon fibers), this paper proposes a quick method for determining the homogenized material constants, using the finite element method (FEM). For this, the eigenfrequencies of a beam specimen manufactured by the studied composite material will be computed using FEM. The model will consider both phases of the composite, with the geometry and real size. The mechanical properties of the constituent's material phases are known. With the help of this model, the torsional, longitudinal and transverse vibrations of the beam are studied. Based on the eigenvalues obtained by this calculation, it now is possible to quickly estimate the values of homogenized material constants required in the design. An example for a fiber-reinforced polymer composite material is provided in the paper. [ABSTRACT FROM AUTHOR]

Fiber‐reinforced polymer (FRP) composites are widely used in the aerospace and automotive industries due to their high strength‐to‐weight ratio. However, the manufacturing process of FRP composites is intricate, requiring precise control over multiple parameters, which can be challenging. To ensure top‐notch product quality and bolster confidence in the durability of composite materials, it requires a uniform curing evaluation technique and a predictive strength model. This study presents a rapid nondestructive quality inspection technique for composites, involving three distinct studies that employ machine learning techniques in combination with the frequency‐dependent dielectric response of materials. The first study introduces a nondestructive method for swiftly inspecting the cure state (degree of cure) of composite samples. This technique combines broadband dielectric spectroscopy with supervised machine learning algorithms, particularly support vector machines. The second study employs advanced artificial neural networks like multi‐layer perceptron to predict the tensile strength, a measure of mechanical performance, of composite materials. The results demonstrate an accurate classification of the curing state with 96.7% accuracy and a prediction of tensile strength with 87.5% accuracy. The final study explores the application of machine learning in quality monitoring of prepreg (raw materials for FRP) aging at room temperature. Highlights: Integration of machine learning with frequency‐dependent dielectric measurement offers efficient method for inspecting and monitoring the curing state and mechanical performance of composite materials.Machine learning and frequency‐dependent dielectric response used to accurately assess the curing state of fiber‐reinforced polymer composites with 96.7% accuracy, which saves the time and effort and also reduces the need for destructive testing.Advanced artificial neural networks, specifically multi‐layer perceptron, employed to predict mechanical performance of composite materials with 87.5% accuracy, enhancing confidence in product reliability.Novel dielectric measurement technique integrated with machine learning algorithms enables prepreg age monitoring at room temperature. [ABSTRACT FROM AUTHOR]

Glass fiber-reinforced polymer (GFRP) composite materials are used extensively and increasingly in major industries including aerospace, marine, construction, electrical and automotive. These types of materials have advantages such as low densities, high mechanical properties in certain directions, ease of production and durability. However, its manufacture generates residues and at the end of its life cycle both the fiber and the resin cannot be easily decomposed or recycled. This article explored the influence of recycled GFRPs as reinforcement in limestone calcined clay cements mortar mixes with ratios of 2%,4%,6%, 8% and 10% replacing the fine aggregate weight in the flexural strength, compressive strength, and density. Results demonstrated flexural and compressive strengths in the range of 2.5 MPa-7MPa and 12-28 MPa respectively at the ages of 28 and 56 days. [ABSTRACT FROM AUTHOR]

This paper presents the results of laboratory tests of CFRP (carbon fiber-reinforced polymer) laminates, which allowed the development of numerical material models. The obtained data were used in a further stage to perform numerical simulations of four variants of medical tabletops, differing, among other features, in the shape of the cross-section. Maximum deflections and effort in the composite material were analyzed. The final step was to perform a laboratory test for one of the tabletop versions, the results of which confirmed the correctness of the numerical calculations. This work is aimed at both researchers and designers involved in the practical application of fiber-reinforced polymer matrix composites. [ABSTRACT FROM AUTHOR]

Structural fiber-reinforced polymer (FRP) composite materials consisting of a polymer matrix reinforced with layers of high-strength fibers are used in numerous applications, including but not limited to spacecraft, vehicles, buildings, and bridges. Researchers in the past few decades have suggested the necessary integration of sensors (e.g., fiber optic sensors) in polymer composites to enable health monitoring of composites' performance over their service lives. This work introduces an innovative cognizant composite that can self-sense, compute, and implement decisions based on sensed values. It is a critical step towards smart, resilient infrastructure. We describe a method to fabricate textile sensors with flexible circuitry and a microcontroller within the polymer composite, enabling computational operations to take place in the composite without impacting its integrity. A microstructural investigation of the sensors showed that the amount of oxidative agent and soaking time of the fabric play a major role in the adsorption of polypyrrole (PPy) on fiberglass (FG). XPS results showed that the 10 g ferric chloride solution with 6 h of soaking time had the highest degree of protonation (28%) and, therefore, higher adsorption of PPy on FG. A strain range of 30% was achieved by examining different circuitry and sensor designs for their resistance and strain resolution under mechanical loading. A microcontroller was added to the circuit and then embedded within a composite material. This composite system was tested under flexural loading to demonstrate its self-sensing, computing, and actuation capabilities. The resulting cognizant composite demonstrated the ability to read resistance values and measure strain using the embedded microcontroller and autonomously actuate an LED light when the strain exceeds a predefined limit of 2000 µε. The application of the proposed FRP system would provide in situ monitoring of structural composite components with autonomous response capabilities, as well as reduce manufacturing, production, and maintenance costs. [ABSTRACT FROM AUTHOR]

Background: Interlaminar delamination is a common damage mechanism in composite laminates that can lead to structural failure. Assessment using contemporary numerical modeling techniques requires delamination behavior as a traction–separation response. However, existing experimental characterization approaches are not well suited to support these modeling techniques as specimens were developed to assess single delamination parameters, not a full traction–separation response, or utilize analysis schemes that require knowledge of material properties. Objective: To develop a test specimen and data analysis methodology to directly measure the traction–separation response of Mode I delamination in a laminated fiber-reinforced polymer (FRP) composite, including strength, toughness, and damage response. Methods: The proposed composite Rigid Double Cantilever Beam (cRDCB) specimen is comprised of a [0]_4 unidirectional E-glass/epoxy laminate co-cured to rigid metallic adherends. Traction–separation response was assessed directly from measured force and displacement behavior using a closed-form analysis scheme that does not require a priori knowledge of composite material properties. Standard double cantilever beam (DCB) tests were performed for comparison. Results: The cRDCB specimen captured early damage initiation and progression in greater detail than the DCB, with measured strain energy release rates agreeing well between the two approaches. The cRDCB also captured the effects of large-scale damage mechanisms such as fiber bridging. The measured traction–separation responses are suitable for scenarios where prediction of the initiation and early damage response of delamination is important. Conclusions: Combined with a data processing technique, a single cRDCB test enabled measurement of the full Mode I traction–separation response. In addition, the cRDCB provided high-resolution and could detect early-stage Mode I delamination damage in FRP laminates. The measured traction–separation responses can be directly inputted into cohesive zone models to predict the initiation and progression of Mode I delamination. [ABSTRACT FROM AUTHOR]

Under high temperatures, fiber-reinforced polymers are destroyed, releasing heat, smoke, and harmful volatile substances. Therefore, composite structural elements must have sufficient fire resistance to meet the requirements established by building codes and regulations. Fire resistance of composite materials can be improved by using mineral fillers as flame-retardant additives in resin compositions. This article analyzes the effect of fire-retardant additives on mechanical properties and fire behavior of pultruded composite profiles. Five resin mixtures based on vinyl ester epoxy and on brominated vinyl ester epoxy modified with alumina trihydrate and triphenyl phosphate were prepared for pultrusion of strip profiles of 150 mm × 3.5 mm. A series of tests have been conducted to determine mechanical properties (tensile, flexural, compression, and interlaminar shear) and fire behavior (ignitability, flammability, combustibility, toxicity, smoke generation, and flame spread) of composites. It was found that additives impair mechanical properties of materials, as they the take place of reinforcing fibers and reduce the volume fraction of reinforcing fibers. Profiles based on non-brominated vinyl ester epoxy have higher tensile, compressive, and flexural properties than those based on brominated vinyl ester epoxy by 7%, 30%, and 36%, respectively. Profiles based on non-brominated epoxy resin emit less smoke compared to those based on brominated epoxy resin. Brominated epoxy-based profiles have a flue gas temperature which is seven times lower compared to those based on the non-brominated epoxy. Mineral fillers retard the spread of flame over the composite material surface by as much as 4 times and reduce smoke generation by 30%. [ABSTRACT FROM AUTHOR]

Carbon fiber-reinforced plastic (CFRP) has been widely investigated as a reinforcement material to address the corrosion and durability issues of reinforced concrete (RC). To improve the strain of FRP grids, we investigated the effect of single-fiber types, hybrid ratios, and stacking patterns on the strain of the composite materials. Blended fabrics in which different fibers are woven were used to further improve the strain of carbon fibers (CFs). In the blended fabrics, CFs with high tensile strength were mixed with high-strain glass fibers (GFs) or aramid fibers (AFs). Fibers with different mechanical properties were mixed to improve the strain without reducing the tensile strength of the composite materials. The fiber arrangement direction was controlled by CF/GF blended fabric. CFs are arranged in the direction parallel to the tensile load direction with no strength degradation, and GFs are arranged in the direction perpendicular to the increase in strain. Compared to the mechanical properties of the single CF composites, the fabrics obtained via an FRP mixing method proposed in this study showed an increase in the tensile strength by 7% from 568.17 to 608.34 MPa with no strength degradation and an increase in strain by 34% from 0.97% to 1.30%. [ABSTRACT FROM AUTHOR]

This study focuses on the mechanical behavior of natural fiber-reinforced polymer composites (NFRPs), which are gaining prominence as sustainable materials due to their biodegradability and eco-friendliness. In this study, we aimed to gain a profound understanding of the mechanical behavior of selected NFRPs. Static structural analysis was conducted to simulate tensile effects, while vibrational analysis was performed to predict natural frequencies. The results indicated that all fibers exhibited minimum stress at the 67.5° angle and maximum stress at the 22.5° angle during tensile testing. Additionally, minimum deformation occurred at the 0° angle, whereas maximum deformation was observed at the 67.5° angle. Interestingly, the NFRPs exhibited similar natural frequencies for the lower modes (1st and 2nd), with negligible alterations due to fiber angles. The core aim of this study is to showcase the practicality and viability of the investigated NFRPs by employing sophisticated finite element analysis to anticipate their material behavior beforehand, allowing for a comprehensive comparison of the natural frequencies, stresses, and deformations with traditional Carbon Fiber Reinforced Polymer (CFRP) composites, thereby exploring the potential of NFRPs as feasible alternatives. [ABSTRACT FROM AUTHOR]

This article examines the mechanical properties and compatibility of selected composite materials produced with RP technology and the FFF—fused filament fabrication process. The article scales sophisticated modern materials based on PLA—polylactic acid—plastic and its composite variants. The research is carried out on the 3D FFF printer Felix 3.1 with a dual extruder, which works on the "open-source" principle. In this research, elements of the paradigm and methodology of the processing technology for RP were applied; they were implemented according to EN ISO 527 and ISO 2602 standards. The aim of this study was to investigate the impact of 3D-printing strategy on the mechanical properties of 5 types of PLA composites. The results of this research solve the material compatibility problem, primarily through experimental testing of different combinations of filaments in different printing directions. Analysis of the experimental data showed correlations between the choice of printing strategy and mechanical properties, mainly tensile strength of the selected filaments. The research results show the influence of the printing orientation on mechanical properties of 3D printed samples: parts extruded in length orientation showed higher values of tensile strength compared to parts made in width and height. The CarbonPLA material exhibited 10 times higher tensile strength when printed in length compared to samples. [ABSTRACT FROM AUTHOR]

The prediction of damage and failure to fiber-reinforced polymer composites in extreme environments, particularly when subjected to impact loading, is a crucial issue for the application and design of protective structures. In this paper, based on the prototype microelastic brittle (PMB) model and the LaRC05 composite materials failure model, we proposed a bond-based peridynamic (BB-PD) model with the introduction of plastic hardening of the resin matrix for fiber-reinforced polymer composites. The PD constitutive relationships of the matrix bond and interlayer bond under compressive loading are considered to include two stages of linear elasticity and plastic hardening, according to the stress–strain relationship of the resin matrix in the LaRC05 failure model. The proposed PD model is employed to simulate the damage behaviors of laminated composites subjected to impact loading. The corresponding ballistic impact tests of composite laminates were carried out to observe their damage behaviors. The PD prediction results are in good agreement with the ballistic experimental results, which can verify the correctness and accuracy of the PD model developed in this study in describing the impact damage behaviors of composite materials. In addition, the characteristics and degree of damage in composite laminates are analyzed and discussed based on this PD model. The difference in the impact resistance of composite laminates with different stacking sequences is also studied using the numerical simulation results. [ABSTRACT FROM AUTHOR]

It is well known that the installation loads during offshore pipeline installation are usually higher than the operation loads. Fibre-reinforced plastic (FRP) materials for offshore pipeline applications seem to be very promising due to their high strength, light weight and excellent corrosion and fatigue resistance. However, during S-lay installation, high bending stresses that may cause material failure or buckling take place. Due to the anisotropic nature of multi-layered FRP pipelines, the permissible bending curvature is difficult to estimate. Few published works have proposed a framework for bending stress calculations and those that have provide complex equations that are not convenient for use. In this study, an open numerical code in Mathematica is offered for the first time. Numerical results for S-lay installation of representative pipelines are provided and commended. [ABSTRACT FROM AUTHOR]

A Whipple shield is a double-plate structure commonly used to protect spacecraft from space fragments. The space fragments hit the outer plate and break into a debris cloud with dispersed energy and momentum, which reduces their risk of penetrating the bulkhead. With the development of high-performance materials, for example, high-performance fiber composites, traditional Whipple shields have evolved into advanced complex shields. Using the finite element and smoothed-particle hydrodynamics adaptive method and mesoscopic modeling technology, this study aims to establish a numerical model for fiber-reinforced composite shields under hypervelocity impact. Several mesoscale models for fiber-reinforced composites for problems under hypervelocity impact have been established. These models can be meshed with high-quality elements that satisfy aerospace engineering requirements (identify hazardous fragments in the debris cloud) while retaining the main structural features of materials. We established a numerical model by combining the finite element and smoothed-particle hydrodynamics adaptive method and existent mesoscale models. Using laminates, 2D woven fiber-reinforced plastics, and 3D woven fiber-reinforced composites as examples, numerical simulations of the debris cloud generated by an aluminum ball under hypervelocity impact were conducted. The simulation results, which are highly consistent with the experimental results of the debris cloud shape, accurately reflect the failure features of laminates, that is, fiber fracture and delamination. Simulation results show that the fiber-reinforced composite has better protection than the aluminum plate at the same areal density. By comparing the debris clouds generated by the hypervelocity impact on different fiber-reinforced composite shields, it can be argued that composite knit modes strongly affect the protective effect of fiber-reinforced composites. This work shows that the simulation method combining the finite element and smoothed-particle hydrodynamics adaptive method and mesoscopic modeling is a powerful tool for simulating the Whipple shield with a fiber-reinforced composite. More importantly, this method can also be applied to other Whipple shields with complex structures and advanced materials, for example, other composite materials, metal foam materials, and multilayer board protective structures. • A method combining mesoscopic model and FE-SPH adaptive method is proposed to simulate fiber-reinforced composite under HVI. • A mesoscopic modeling technique for fiber-reinforced composites suitable for HVI problems is provided. • The fiber knit mode of the plate strongly influences the characteristics of the formed debris cloud. • The debris cloud from a projectile hypervelocity impacting a fiber-reinforced composite may contain no internal structure. [ABSTRACT FROM AUTHOR]

This article proposes a new constitutive model for the cyclic behavior of rubberized concrete confined with fiber‐reinforced polymer (FRP) sheets. The model is calibrated with experimental results from 18 confined rubberized concrete (CRuC) cylinders tested in cyclic compression. The cylinders had 60% total aggregate volume replacement with recycled tyre rubber. Parameters investigated include the type of confining material (Carbon or Aramid FRP) and number of layers (two, three, or four). The results indicate that using FRP confinement leads to a strong (up to 100 MPa) and highly deformable (axial strains up to 7%) rubberized concrete that can be used in structural applications. The proposed constitutive model predicts accurately the material response under cyclic loading and can thus be used for design/analysis of highly deformable components made of FRP CRuC. This article contributes toward the development of advanced constitutive models for FRP CRuC, thus promoting the wider use of recycled materials in construction industry. [ABSTRACT FROM AUTHOR]

Flax fiber-reinforced plastics have an innate eco-friendly nature due to the fiber reinforcement and reduced energy requirements in fabrication when compared to current fiber reinforced composite materials. They possess a complex time-dependent material behavior, which is investigated in the present paper. A composite material with flax fiber reinforcement on the load direction, embedded in an epoxy resin matrix, was studied. The procedures used were tensile tests, repeated loading-recovery, and creep-recovery tests, which were meant to expose the components of the response with respect to stress level and load duration. The results showed an elastic bi-linear behavior, a yield point at approximately 20% of the ultimate tensile stress, and tensile moduli of 35.9 GPa and 26.3 GPa, before and after yield. This is coupled with significant non-linear viscoelastic and, after yield, viscoplastic components, accounting for up to 14% of the strain response. The behavior is inherited from both the matrix and the fiber reinforcement and is attributed to the amorphous nature of the matrix combined with the microstructural re-organization of the fiber under load, which are partially reversible. [ABSTRACT FROM AUTHOR]

Unreinforced masonry (URM) is one of the most popular construction materials around the world, but vulnerable during earthquakes. Due to its brittle nature, the URM structures may lead to a possible collapse of the wall of a building during earthquake events causing casualties. In the current research, an attempt is made to enhance the seismic capacity of URM structures by proposing a new innovative composite material that can improve the shear strength and deformation capacity of the URM wall systems. The results revealed that the fiber-reinforced plastic having high tensile and shear stiffness can significantly increase in-plane as well as out-of-plane bending strength of the URM wall. It was recorded that the bending moment of the prism increased up to 549.5% by increasing the bending moment from 490 N*mm to 3183 N*mm per mm deflection of prism upon using glass fibers. Moreover, the ductility ratio amplified up to 5.73 times while the stiffness ratio increased up to 4.16 times with the aid of glass fibers. Since the material used in this research work is low cost, easily available, and no need for any skilled labor, which is economically good. Therefore, the URM walls retrofitted with fiber-reinforced plastic is an economical solution. [ABSTRACT FROM AUTHOR]

Natural fiber-reinforced matrix polymer composites have shown great potential for engineering applications including ballistic protection. However, The Amazon region is full of natural fibers that have not yet been the fully studied and that might have important properties making them more attractive than synthetic fibers. This work presents a novel composite material consisting of titica vine fibers (Heteropsis flexuosa) reinforcing epoxy resin, for possible application in ballistic armor. Composite plates with different volumetric fractions of titica vine fibers (TVF) were subjected to a ballistic test, which consisted of firing multiple shots using .22 LR caliber ammunition. Through the results, it was possible to observe, with statistical validation by Weibull and ANOVA analyses, as well as the Tukey test, that a greater absorption of energy occurred for the conditions of 0 to 20 vol%, but with considerable loss of integrity. On the other hand, the 30 and 40 vol% samples have shown better integrity. In addition, the VL calculated for the samples with the highest percentage of fibers was lower than those found for the composites with 10 and 20 vol%. Thus, the higher the volumetric fraction of TVF, the lower the impact energy absorption capacity. This behavior corroborates the analysis by scanning electron microscopy (SEM) of the fracture surfaces of the composites after the ballistic test. For composites with less than 20 vol% TVF, brittle fractures evidences were observed, responsible for absorbing more impact energy. On the other hand, for other compositions, there was a predominance of complex mechanisms characteristic of ductile fracture, responsible for absorbing less energy, but still maintaining the integrity of the protection. [ABSTRACT FROM AUTHOR]

Although bamboo fiber-reinforced polymer has been extensively studied, its utilization has been limited by its unfavorable performance. This study developed a non twisting bamboo textile-reinforced polymer (BTRP) through vacuum resin transfer molding and then used two weaving methods, different layers, different edge treatments, two stacking sequences, and two sizes as factors to investigate the effect of woven structures on the hygroscopic behavior of BTRP, such as water absorption, diffusion, dimensional stability, and moisture transportation. The differences in the results of long-term immersion and the swelling at different locations of BTRP were also examined. The results of this study indicate that the weaving method directly affected the water absorption from the fiber area and that the size of the specimens affected the saturation rate. The swelling behavior differed with the weaving method and number of layers, which indicates that rate of water ingress and transverse fiber swelling were the reasons that cause the different swelling behavior. This study found that moisture may be transferred differently through different parts of BTRP due to variations in fiber saturation. Moreover, the analysis of the center and periphery of BTRP specimens indicated that textile structure significantly affected water uptake and indirectly caused two moisture transport mechanisms. [ABSTRACT FROM AUTHOR]

Fiber-reinforced polymer (FRP) composite materials are very versatile in use because of their high specific stiffness and high specific strength characteristics. The main limitation of this material is its brittle nature (mainly due to the low stiffness and low fracture toughness of resin) that leads to reduced properties that are matrix dominated, including impact strength, compressive strength, in-plane shear, fracture toughness, and interlaminar strength. One method of overcoming these limitations is using nanoparticles as fillers in an FRP composite. Thereby, this present paper is focused on studying the effect of nanofillers added to glass/epoxy composite materials on mechanical behavior. Multiwall carbon nanotubes (MWCNTs), nano-silica (NS), and nano-iron oxide (NFe) are the nanofillers selected, as they can react with the resin system in the present-case epoxy to contribute a significant improvement to the polymer cross-linking web. Glass/epoxy composites are made with four layers of unidirectional E-glass fiber modified by nanoparticles with four different weight percentages (0.1%, 0.2%, 0.5%, and 1.0%). For reference, a sample without nanoparticles was made. The mechanical characterizations of these samples were completed under tensile, compressive, flexural, and impact loading. To understand the failure mechanism, an SEM analysis was also completed on the fractured surface. [ABSTRACT FROM AUTHOR]

Pultruded fiber-reinforced polymer (PFRP) profiles have started to find widespread use in the structure industry. The position of the web openings on these elements, which are especially exposed to axial pressure force, causes a change in the behavior. In this study, a total of 21 pultruded box profiles were tested under vertical loads and some of them were strengthened with carbon-FRP (CFRP) and glass-FRP (GFRP). The location, number and reinforcement type of the web openings on the profiles were taken into account as parameters. As a result of the axial test, it was understood that when a hole with a certain diameter is to be drilled on the profile, its position and number are very important. The height-centered openings in the middle of the web had the least effect on the reduction in the load-carrying capacity and the stability of the profile. In addition, it has been determined that the web openings away from the center and especially the eccentric opening significantly reduces the load carrying capacity. Furthermore, when double holes were drilled close to each other, a significant decrease in the capacity was observed and strengthening had the least effect on these specimens. It was also determined that the specimens reinforced with carbon FRP contribute more to the load-carrying capacity than GFRP. [ABSTRACT FROM AUTHOR]

When an elastoplastic material undergoes large plastic deformations, the elastic law and particularly the stiffness tetrad will evolve. This evolution is strongly dependent on the particular material. In the present paper, we consider a fiber-reinforced composite with fibers in different distinct directions. These directions introduce the anisotropy into the material behavior, particularly into the elastic law. Under plastic deformations, these directions are deformed together with the material (in contrast to crystal plasticity). This effect is called material plasticity and gives the basis for our new method. It consists of superimposing transversely isotropic stiffnesses for each fiber direction at any stage of the deformation process. A comparison for different composites and deformation paths shows the range of applicability of this method. [ABSTRACT FROM AUTHOR]

This document provides a list of upcoming conferences and congresses related to composites and advanced materials. The conferences cover a range of topics including non-destructive testing, computational methods, renewable materials, mechanics of composites, composite materials, materials design and applications, theoretical and applied mechanics, composite structures, thermoplastic composites, mechanics of solids, durability and maintenance of structures, composite testing and model identification, fiber-reinforced polymer composites in civil engineering, vehicle body engineering, and composite materials. The conferences will be held in various locations around the world, including Korea, Portugal, Germany, France, Canada, Bulgaria, Italy, Northern Ireland, Latvia, and the United States. [Extracted from the article]

Ultrafast laser processing has recently emerged as a new tool for processing fiber-reinforced polymer (FRP) composites. In the astronautic industry, the modified epoxy resin (named 4211) and the modified cyanate ester resin (known as BS-4) are two of the most widely used polymers for polymer-based composites. To study the removal mechanism and ablation process of different material components during the ultrafast laser processing of FRPs, we isolated the role of the two important polymers from their composites by studying their femtosecond UV laser (260 fs, 343 nm) ablation characteristics for controllable machining and understanding the related mechanisms. Intrinsic properties for the materials' transmission spectrum, the absorption coefficient and the optical bandgap (Eg), were measured, derived, and compared. Key parameters for controllable laser processing, including the ablation threshold (Fth), energy penetration depth (δeff), and absorbed energy density (Eabs) at the ablation threshold, as well as their respective "incubation" effect under multiple pulse excitations, were deduced analytically. The ablation thresholds for the two resins, derived from both the diameter-regression and depth-regression techniques, were compared between resins and between techniques. An optical bandgap of 3.1 eV and 2.8 eV for the 4211 and BS-4 resins, respectively, were obtained. A detectable but insignificant-to-ablation difference in intrinsic properties and ablation characteristics between the two resins was found. A systematic discrepancy, by a factor of 30~50%, between the two techniques for deriving ablation thresholds was shown and discussed. For the 4211 resin ablated by a single UV laser pulse, a Fth of 0.42 J/cm2, a δeff of 219 nm, and an Eabs of 18.4 kJ/cm3 was suggested, and they are 0.45 J/cm2, 183 nm, and 23.2 kJ/cm3, respectively, for the BS-4 resin. The study may shed light on the materials' UV laser processing, further the theoretical modeling of ultrafast laser ablation, and provide a reference for the femtosecond UV laser processing characteristics of FRPs for the future. [ABSTRACT FROM AUTHOR]

Structural health monitoring systems for composite laminates using guided ultrasonic waves become more versatile with the structural integration of sensors. However, the data generated within these sensors have to be transmitted from the laminate to the outside, where polyimide-based printed circuit boards play a major role. This study investigates, to what extent integrated polyimide inlays with applied sensor bodies influence the guided ultrasonic wave propagation in glass fiber-reinforced polymer specimens. For reasons of resource efficiency, narrow specimens are used. Numerical simulations of a damping-free specimen indicate reflections of the S 0 -mode at the integrated inlay. This is validated experimentally with an air-coupled ultrasonic technique and a 3D laser Doppler vibrometry measurement. The experimental data are evaluated with a method including temporal and spatial continuous wavelet transformations to clearly identify periodically occurring wave packages as edge reflections and distinguish them from possible inlay reflections. However, even when separating in-plane and out-of-plane movements using the 3D measurement, no reflections at the inlays are detected. This leads to the conclusion that polyimide inlays are well suited as substrates for printed circuit boards integrated into fiber-reinforced polymer structures for structural health monitoring, since they do not significantly influence the wave propagation. [ABSTRACT FROM AUTHOR]

E-glass fiber-reinforced polymer (FRP) composite wind turbine blades are nonbiodegradable, and their end-of-life recycling solutions are limited. Research on reusing and repurposing applications, where minimal amounts of refabrication are needed, is being conducted to address this issue. To design new structures from decommissioned blades, their as-received mechanical and physical properties are needed. Even though some long-term property data for FRP composites exist in the literature, very little actual data for the as-received residual properties of decommissioned blades have been reported. The current work is aimed at developing a methodology to obtain as-received material property data for decommissioned wind turbine blades that are being proposed for use as second-life structural components. In this paper, details of the methods used and the test results for the key physical and mechanical properties of glass FRP material specimens extracted from the spar cap of a decommissioned 1.5-MW GE37 wind turbine blade are reported (the blade is from a General Electric 1.5 MW turbine which is known as a GE37 blade), including burnout testing for constituents' weight and volume fractions as well as fiber architecture and tension, compression, and shear testing in the longitudinal and transverse material directions. Comparisons between test results of other investigators and the experimental data obtained show promising strength and stiffness retention levels of the material for different properties. The results show that structural integrity still exists for the tested composite materials and no deterioration, crack propagation, or delamination was observed in the materials due to the cyclic loading levels experienced in their first life. [ABSTRACT FROM AUTHOR]

Web openings often need to be created in structural elements for the passage of utility ducts and/or pipes. Such web openings reduce the cross-sectional area of the structural element in the affected region, leading to a decrease in its load-carrying capacity and stiffness. This paper experimentally studies the effect of web openings on the response of pultruded fiber-reinforced polymer (PFRP) composite profiles under compressive loads. A number of specimens have been processed to examine the behavior of PFRP profiles strengthened with one or more web openings. The effects of the size of the web opening and the FRP-strengthening scheme on the structural performance of PFRP profiles with FRP-strengthened web openings have been thoroughly analyzed and discussed. The decrease in load-carrying capacity of un-strengthened specimens varies between 7.9% and 66.4%, depending on the diameter of the web holes. It is observed that the diameter of the hole and the type of CFRP- or GFRP-strengthening method applied are very important parameters. All CFRP- and GFRP-strengthening alternatives were successful in the PFRP profiles, with diameter-to-width (D/W) ratios between 0.29 and 0.68. In addition, the load-carrying capacity after reinforcements made with CFRP and GFRP increased by 3.1–30.2% and 1.7–19.7%, respectively. Therefore, the pultruded profiles with openings are able to compensate for the reduction in load-carrying capacity due to holes, up to a D/W ratio of 0.32. The capacity significantly drops after a D/W ratio of 0.32. Moreover, the pultruded profile with CFRP wrapping is more likely to improve the load-carrying capacity compared to other wrappings. As a result, CFRP are recommended as preferred composite materials for strengthening alternatives. [ABSTRACT FROM AUTHOR]

Fiber-reinforced thermoplastic polymer composites are widely applied in engineering. The use of continuous fibers in these composites provides superior mechanical properties and material performance compared with those achieved when short fibers are used. In this study, pure poly(ethersulfone) (PES) and its continuous fiber-reinforced composites were manufactured using fused deposition modeling 3D printing technology. PES composite filaments reinforced with continuous basalt fiber (BF) were prepared. The method and temperature for printing the BF-reinforced PES, the strength of the interfacial bonding between the BF and the PES matrix, and the abrasiveness of the composite were all studied in detail. The results revealed that PES printed at 360 °C exhibits the highest tensile strength. Furthermore, the tensile and bending strengths of the PES/BF composite were found to be increased by 217.06 % and 87.96%, respectively, compared with those of pure PES. To improve the interfacial bonding properties between the fiber and resin matrix, the fiber was modified using a silane coupling agent. This decreased the mass wear and the wear scar width by 80% and 45%, respectively, compared with those for pure PES. [ABSTRACT FROM AUTHOR]

A new three-dimensional (3D) boundary element method (BEM) strategy was developed to solve fractional-order thermo-elastoplastic ultrasonic wave propagation problems based on the meshless moving least squares (MLS) method. The temperature problem domain was divided into a number of circular sub-domains. Each node was the center of the circular sub-domain surrounding it. The Laplace transform method was used to solve the temperature problem. A unit test function was used in the local weak-form formulation to generate the local boundary integral equations, and the inverse Laplace transformation method was used to find the transient temperature solutions. Then, the three-dimensional elastoplastic problems could be solved using the boundary element method (BEM). Initial stress and strain formulations are adopted, and their distributions are interpolated using boundary integral equations. The effects of the fractional-order parameter and anisotropy are investigated. The proposed method's validity and performance are demonstrated for a two-dimensional problem with excellent agreement with other experimental and numerical results. [ABSTRACT FROM AUTHOR]

Structural steel and concrete are essential materials for the construction of social infrastructures. However, these materials undergo degradation over time, thereby causing steel corrosion. To address this problem, a fiber-reinforced polymer (FRP) is used for reinforcement. In this study, tensile tests were performed to evaluate the material properties for the application of the FRP to cable bridge structures. These tests aimed to investigate various parameters to improve bond performance. Based on experiments with different parameters, sufficient bond performance could be achieved if the following conditions are met: mortar water ≤16%, regardless of the manufacturer; a depth of splitting and steel pipe length ratio ≥75%; upward/downward directions for the mortar injection; and the use of fiber-sheet reinforcement. In addition, the steel pipe used in the test (length of 410 mm and outer diameter of 42.7 mm) performed the best in terms of workability and cost effectiveness. By conducting more accurate tests to study the basic properties of materials, more accurate conditions to accomplish sufficient bond performance can likely be achieved. This will contribute to improved cost effectiveness and safety in the use of carbon FRP cables in cable bridge constructions. [ABSTRACT FROM AUTHOR]

Epoxy resin used commonly as a matrix for polymer composite materials has good handling properties, but is too brittle. That is why various modifiers are used to increase the flexibility of products based on epoxy resin. This leads to two issues: how to efficiently increase the toughness of the resin without impacting significantly other properties, as well as how to measure the toughness in composite materials. The work aimed to show how the addition of a reactive rubber modifier will affect the fracture toughness of the obtained laminates during the longitudinal shear test (Mode II fracture). In total, three epoxy-glass laminates with different matrices were made and subjected to the End-Notched Flexure test according to ASTM D7905/D7905M standard: (1) the basic matrix of Epidian 6 resin, (2) Epidian 6 modified with the addition of 10% of Albipox 1000 reactive liquid rubber and (3) Epidian 6 modified with the addition of 10% of Hypro 1300X16 ATBN reactive liquid rubber. Based on the obtained results, it can be seen that the modulus of elasticity for the modified laminates was decreased compared to the laminate of pure epoxy resin (by ~ 25%). However, the addition of reactive rubbers increased the fracture toughness of the modified epoxy-glass laminates in the Mode II longitudinal shear test (GIIc) by ~ 40–60%. Thus the benefits of modification outweigh the drawbacks if fracture toughness is an important designing consideration in a given application. The applicability of ENF method is successfully tested, but potential drawbacks are indicated—careful control of specimen thickness is necessary. [ABSTRACT FROM AUTHOR]

Composite materials have been increasingly used to produce hybrid structures together with concrete. This system is commonly applied to bridges and roof structures. The main idea of the current research was to extend this approach by replacing the concrete with a fabric-reinforced cementitious matrix (FRCM) composite, resulting in a combination of composite materials. The main aim was to characterize the structural behavior of fiber-reinforced polymer (FRP) profiles and FRCM hybrid superficial elements. Two different prototypes of the hybrid superficial structural typology were tested to cover bidimensional and three-dimensional application cases of the proposed technology. After mortar cracking, the experimental results revealed a ductile response and a high mechanical capacity. A finite element model was implemented, calibrated, and validated by comparing numerical data with experimental results of the two prototypes. The output was a validated model that correctly captured the characteristic response of the proposed technology, which consisted of changing the structural response from a stiff plate configuration to a membrane type due to cracking of the FRCM composite part of the full solution. The suggested numerical model adequately reflected the experimental response and proved valuable for understanding and explaining the resistive processes established along this complicated FRP-FRCM hybrid structure. [ABSTRACT FROM AUTHOR]

The drilling is a very important machining process to increase the joining efficiency of assembled parts. In this review, the consolidation of various composite materials with different fibers are discussed. Different drill tools, their materials and geometries, and drilling methods, such as conventional, vibration-assisted, and high-speed ones, are considered, and various numerical models for determining the critical thrust force and delamination are analyzed. It is concluded that unconventional geometries and materials give better results in reducing the thrust force and delamination compared than the traditional materials and geometrical shapes of drill tools [ABSTRACT FROM AUTHOR]