Fiber-reinforced Composite Materials Research Articles

Effective Elasticity Tensor of Fiber-Reinforced Orthorhombic Composite Materials with Fiber Distribution Parallel to Plane

An orthogonal composite material Ω with fibers consists of a matrix and orthothombic distribution fibers. In addition to the matrix properties, the fiber properties and the fiber volume fraction, the effective (macroscopic) elastic stress–strain constitutive relation of Ω is related to the fiber direction distribution. Until now, there have been few papers that give an explicit formula of the macroscopic elastic stress–strain constitutive relation of Ω with the effect of the fiber direction distribution. Taking the expanded coefficients of the Fourier series as the fiber direction distribution coefficients, we give a formula of the fiber direction distribution parallel to a plane computed through the fiber directions. By the self-consistent estimates, we derive an explicit formula of the macroscopic elastic stress–strain constitutive relation of Ω with the fiber direction distribution coefficients. Since all tensors are represented in Kelvin notation, the macroscopic elastic stress–strain constitutive relation of Ω can be derived and computed only by matrix manipulations. To check the explicit formula, we use the FEM computation to obtain the macroscopic elastic stress–strain relation of Ω for three examples. The computational results of the explicit formula for the three examples are consistent with those of the FEM simulations.

Effect of Fiber Orientation on the Tribological Performance of Abaca-Reinforced Epoxy Composite under Dry Contact Conditions

This paper presents tribological research of an abaca fiber-reinforced epoxy composite material, analyzing fiber orientation and its effect on the tribological performances of the composite. The extremely low viscosity epoxy resin reinforced with NaOH-treated long abaca fibers is investigated under the different operating conditions. The unidirectional abaca fibers reinforced the epoxy resin and formed composite specimens with fibers in three directions, parallel (P-O), anti-parallel (AP-O) and normal (N-O), while keeping the sliding direction. The specimens were fabricated using fiber volume fractions of 10 vol%, 20 vol% and 30 vol% using the vacuum infusion technique. The block-on-disc (BOD) apparatus has been used to exhibit the tribological tests. Normal loads of 35 N and 45 N have been used for testing purposes. The experimental results indicated that the presence of abaca fiber significantly improved the wear characteristics of the matrix. An increased coefficient of friction was observed in samples with anti-parallel-oriented fibers at an applied load of 35 N. The conducted research shows that the use of abaca fibers as fillers could improve the tribological characteristics of the epoxy resin-based composite material.

Assessment of dynamic mode-I delamination driving force in double cantilever beam tests for fiber-reinforced polymer composite and adhesive materials

The double cantilever beam (DCB) tests are widely used to assess the interfacial delamination properties of laminated composites. For quasi-static loads, the DCB tests are standardized based on the beam mechanics; for dynamic loads, however, such as high-loading-rate impact and cyclic loads, there is no established analytical theory. This presents a significant obstacle preventing the research community from assessing the delamination behavior of composites or adhesives for their application under complex in-service loads. In this paper, the theory of evaluating dynamic mode-I delamination driving force for DCBs under general displacement loads is developed for the first time, accounting for structural vibration effects. The developed theory is demonstrated by two examples: high-loading-rate split Hopkinson bar impact and cyclic fatigue loads. The analytical solutions are validated by published experiment results and in-house tests. This work provides a fundamental analytical tool to study and assess the fracture behavior of fiber reinforced-polymer composite and adhesive materials under various loading conditions.

Research on a Fiber Corner Compensation Algorithm in a 3D Printing Layer of Continuous Fiber-Reinforced Composite Materials

Fused filament fabrication (FFF) 3D printing technology for continuous fiber-reinforced composite (CFRC) printing has become a trend. This article is based on ‘independent extrusion’ FFF CFRC printing. The continuous fiber-reinforced filament (CFRF) printing solution is the contour offset method for obtaining executable g-code. When the CFRCF prints at the corner, it is found that the actual CFRC printing trajectory is inconsistent with the ideal laying trajectory. The causes of the error are analyzed, and an angle optimization algorithm is proposed. The corner optimization algorithm is verified by theoretical analysis and experimental analysis. From the experimental results, the corner optimization algorithm improves the 30° angle fit of CFRF printing by 90% and reliability has also been improved. When the printing length is 127,200 mm, there are 960 printing corners, and the failure rate is 0.

Development of a Tensile Performance Prediction Model based on the Impregnation Rate of Fiber-reinforced Composite Material

Development of a Tensile Performance Prediction Model based on the Impregnation Rate of Fiber-reinforced Composite Material

Influence of Stress Level and Fibre Volume Fraction on Fatigue Performance of Glass Fibre-Reinforced Polyester Composites.

Fibre-reinforced polymeric composite materials are becoming substantial and convenient materials in the repair and replacement of traditional metallic materials due to their high stiffness. The composites undergo different types of fatigue loads during their service life. The drive to enhance the design methodologies and predictive models of fibre-reinforced polymeric composite materials subjected to fatigue stresses is reliant on more precise and reliable techniques for assessing their fatigue life. The influences of fibre volume fraction and stress level on the fatigue performance of glass fibre-reinforced polyester (GFRP) composite materials have been studied in the tension–tension fatigue scenario. The fibre volume fractions for this investigation were set to: 20%, 35%, and 50%. The tensile testing of specimens was performed using a universal testing machine and the Young’s modulus was validated with four different prediction models. In order to identify the modes of failure as well as the fatigue life of composites, polyester-based GFRP specimens were evaluated at five stress levels which were 75%, 65%, 50%, 40%, and 25% of the maximum tensile stress until either a fracture occurred or five million fatigue cycles was reached. The experimental results showed that glass fibre-reinforced polyester samples had a pure tension failure at high applied stress levels, while at low stress levels the failure mode was governed by stress levels. Finally, the experimental results of GFRP composite samples with different volume fractions were utilized for model validation and comparison, which showed that the proposed framework yields acceptable correlations of predicted fatigue lives in tension–tension fatigue regimes with experimental ones.

Design and Analysis of Solid Rocket Composite Motor Case Connector Using Finite Element Method.

The connector is an essential component in the solid rocket motor case (SRMC), and its weight and performance can directly affect the blasting performance of SRMC. Considering the lightweight design of these structures, fiber-reinforced composite materials are used for the major components. In this study, the finite element analysis of the SRMC connector was performed. The lay-up design and structure optimum design of the connector were studied. Furthermore, the strain distribution on the composite body was compared with experimental measurements. The results demonstrate that the calculated value of the final preferred solution was within the allowable range, and at least 31% weight loss was achieved, suggesting that the performance of the optimum design was optimized. The comparison between the finite element calculation and the test results suggests that the design was within the allowable range and reasonable.

Smart Self-Sensing Piezoresistive Composite Materials for Structural Health Monitoring

The use of fiber-reinforced composite materials has widely spread in various sectors, including aerospace, defense, and civil industry. The assessment of these heterogeneous material systems is important for safer and risk-free applications and has contributed to the need for self-sensing composites. This work is focused on the development of piezoresistive composites, the prediction of their performance and structural health monitoring (SHM). Additionally, this work unpacks the complexity of carbon nanotubes (CNTs) micro-fabrication and the development of piezoresistive and electromagnetic (EM) waves detection electrodes. Scanning electron microscopy (SEM) was used to characterize the CNTs structure and morphologies. The manufactured CNTs were incorporated in epoxy systems to fabricate glass fiber reinforced polymer (GFRP)-CNTs smart composites with piezoresistive properties. The detection of micro-damage onset and its progression was carried out in mode I, to evaluate the sensitivity of the smart composites to damage development. The change in electrical conductivity of the nanotubes-reinforced composite systems due to localized mechanical strains enabled crack propagation detection. The relationship between crack propagation, fracture toughness, and electrical resistivity of the smart composite was analyzed.

Recycling technologies for fibre-reinforced plastic composite materials: A bibliometric analysis using a systematic approach

Fibre-reinforced plastic composite materials are increasingly employed in several industries. This extensive use has resulted in a huge increase of generated waste that has to be managed without causing significant environmental issues. Recycling fibre-reinforced plastic composite materials in accordance with circular economy principles might be a way to overcome such problems. Thus, this paper aims to empirically analyse the existing scientific literature regarding recycling technologies for fibre-reinforced plastic composite materials. The main goal is to provide a holistic and comprehensive analysis of the topic, as well as research gaps and future directions following a rigorous and transparent approach. Overall, 201 articles were selected through a systematic approach and then analysed using a bibliometric analysis. Results show that this topic has been increasingly gaining momentum in recent years and that researchers have mostly carried out experimental studies on chemical and thermal recycling technologies for recovering carbon fibres. Lastly, this article provides an in-depth research agenda based on identified research gaps and an enhanced managerial grasp of this field of research.

Self-Sensing Hybrid Fibre-Reinforced Polymer for Structural Health Monitoring (SHM)

Hybrid composite material has been widely used in many engineering applications (e.g., for automobiles)and has several advantages over conventional fibre-reinforced composite materials, such as high strength-to-weight ratio and low cost. However, combining two kinds of reinforcement fibre within a common matrix may lead to different failure modes, such as delamination between the layers and fragmentation when the structure is subjected to high loads. To avoid this problem, real-time damage detection should be integrated into the hybrid composite structures for structural integrity. This paper outlines the working mechanisms and the initial fabrication of an integrated capacitive sensor into the intra-ply hybrid composite. The tensile test was conducted to perform the basic characterization of the proposed sensor and provide self-sensing functionality (smart structure). The results illustrate that damage between layers can be detected by in-situ monitoring. It is shown that the initial damage was detected at the turning point where the relative change in capacitance begins to decrease and when the axial tensile force increases. In addition, the developed smart material has shown a linear sensitivity toward crosshead displacement up to the turning point, and applying the monitoring is useful in self-sensing for hybrid composites.

Selection Methodology of Composite Material for Retractable Main Landing Gear Strut of a Lightweight Aircraft

The design and development of high-strength and low-weight composite landing gear struts is still a challenge in today’s world. In this study, a selection methodology for fiber-reinforced composite material for retractable main landing gear struts for specified lightweight aircraft up to 1600 kg mass is proposed. Four different fiber-reinforced composite materials, two each from the glass-fiber and carbon-fiber families, including E-glass fiber/epoxy, S-glass fiber/epoxy, T300 carbon fiber/epoxy, and AS carbon fiber/epoxy, were considered for analysis. For the design and analysis of a main landing gear strut, maximum landing loads for one point and two point landing conditions were calculated using FAA FAR 23 airworthiness requirements. Materials were categorized based on their strength-to-weight ratio and the Tsai-Wu failure criterion. Landing gear struts meeting the Tsai-Wu failure criterion, and having a maximum strength-to-weight ratio, were then modeled for performance under a collision detection test. This research concludes that T300 carbon fibre/epoxy is a recommended material for the manufacture of landing gear struts for specified lightweight aircraft.

Stress field prediction in fiber-reinforced composite materials using a deep learning approach

Stress analysis is an important step in the design of material systems, and finite element methods (FEM) are a standard approach of performing computational analysis of stresses in complex material systems. The significant cost associated with multi-scale FEM analysis motivates replacement of FEM with a significantly faster data-driven machine learning based approach. In this study, we consider the application of deep learning tools to local stress field prediction in a fiber-reinforced matrix composite material system as an efficient alternative to FEM. The first challenge is to predict stress field maps for composite cross-sections with a fixed number of fibers and varying spatial configurations. Specifically, a mapping between the spatial arrangement of fibers and the corresponding von Mises stress field is achieved by using a convolutional neural network (CNN), specifically a U-Net architecture. The CNN is trained using data with the same number of fibers as the target systems. A robustness analysis uses different initializations of the training samples to find the evolution of the prediction accuracy with increasing number of training samples. Systems with a larger number of fibers typically require a finer finite element mesh discretization, leading to an increase in the computational cost. Thus, the secondary goal here is to predict the stress field for systems with larger number of fibers using CNNs that are pretrained on data from relatively cheaper systems with smaller fiber number.

Analysis of Drilling of Coir Fiber-Reinforced Polyester Composites Using Multifaceted Drill Bit

Composite materials are continuously replacing the conventional materials and alloys owing to their weight reduction. Biodegradable fiber-reinforced composite materials are one of the prime attractions to the researcher due to their easy availability and low cost. During drilling of these Natural Fiber Reinforced Plastic composites (NFRP), delamination and surface roughness are the problems encountered, which are to be minimized to get better output by adopting different cutting conditions and tools. This work aims at the drilling of naturally available coir fiber-reinforced composite materials by using a multifaceted drill bit. Material thickness, spindle speed, feed rate, and multifaceted bit diameter are input against the output delamination. After modeling of the output result, a sensitivity analysis tool is introduced to rate the input factor to minimize delamination. SEM images are used to analyze the fracture morphology.

Editorial: Multi-Scale Investigation on Fiber-Reinforced Composite Materials: From Structural Design, Property Characterization to Engineering Applications

With rapid development of society and economics, frequent population flow and transportation 14 activities have increased the demand for improving load capacity and resilience of building 15 construction and civil infrastructures. Compared with traditional building materials, fiber-reinforced 16 composite (FRC) materials possess outstanding properties including light weight, high stiffness and 17 strength, and excellent fatigue resistance. Consequently, FRC materials, such as fiber-reinforced 18 polymer (FRP) and ultra-high performance concrete (UHPC), have emerged as viable candidates for 19 load-bearing components in new constructions and strengthening components in existing structures (as 20shown in Figure 1).

Coassembly of a New Insect Cuticular Protein and Chitosan via Liquid-Liquid Phase Separation.

Insect cuticle is a fiber-reinforced composite material that consists of polysaccharide chitin fibers and a protein matrix. The molecular interactions between insect cuticle proteins and chitin that govern the assembly and evolution of cuticles are still not well understood. Herein, we report that Ostrinia furnacalis cuticular protein hypothetical-1 (OfCPH-1), a newly discovered and most abundant cuticular protein from Asian corn borer O. furnacalis, can form coacervates in the presence of chitosan. The OfCPH-1-chitosan coacervate microdroplets are initially liquid-like but become gel-like with increasing time or salt concentration. The liquid-to-gel transition is driven by hydrogen-bonding interactions, during which an induced β-sheet structure of OfCPH-1 is observed. Given the abundance of OfCPH-1 in the cuticle of O. furnacalis, this liquid-liquid phase separation process and its aging behavior could play critical roles in the formation of the cuticle.

Experimental investigation of buckling behavior of E-glass/epoxy laminated composite materials with multi-walled carbon nanotube under uniaxial compression load

This study experimentally investigated the effects of nanoparticle reinforcement on the buckling behavior of composite materials. Different sizes of carboxylic acid functionalized multi-walled carbon nanotubes were used as nanoparticles. E-glass fiber-reinforced composite materials with polymer matrix in the [0°/90°/0°/90°]s cross-ply array with and without carbon nanotube reinforcement were produced by hand lay-up and vacuum bagging. Three types of carbon nanotubes in different sizes and proportions of 0.1%, 0.2%, 0.3%, 0.4%, and 0.5% by weight were added to the epoxy resin. For the buckling test, the samples with two clamped and two free sides were attached to the universal testing machine to apply a uniaxial compressive load. As a result of the experiments, it was found that the addition of carbon nanotube in certain proportions increases the critical buckling load of composite materials. The highest increase in the critical buckling load (26.10% increase) was achieved with a carbon nanotube reinforcement of 0.2% by weight, having an outer diameter of 10–20 nm, internal diameter of 5–10 nm, and length of 0.5–2 mm. As the carbon nanotube sizes added to the epoxy resin decreased, the buckling strength increased.

Influence of Woven-Fabric Type on the Efficiency of Fabric-Reinforced Polymer Composites.

The greatest advantage of fiber-reinforced composite materials is the freedom to tailor their strength and stiffness properties, while the most significant disadvantage consists in their high costs. Therefore, the design process and especially the optimization phase becomes an important step. The geometry of the fabric of each lamina as well as their stacking sequence need to be carefully defined, starting from some basic geometric variables. The input parameters are the widths and the heights of the tows, the laminate-stacking sequence and the gaps between two successive tows or the height of the neat matrix. This paper is a follow-up to a previous work on using and improving an in-house software called SOMGA (Satin Optimization with a Modified Genetic Algorithm), aimed to optimize the geometrical parameters of satin-reinforced multi-layer composites. The final goal is to find out the way in which various types of woven fabrics can affect the best possible solution to the problem of designing a composite material, able to withstand a given set of in-plane loads. The efficiency of the composite structure is evaluated by its ultimate strains using a fitness function that analyses and compares the mechanical behavior of different fabric-reinforced composites. Therefore, the ultimate strains corresponding to each configuration are considered intermediate data, being analyzed comparatively until obtaining the optimal values. When the software is running, for each analysis step, a set of intermediate values is provided. However, the users do not have to store these values, because the final result of the optimization directly provides the composite configuration with maximum efficiency, whose structural response meets the initially imposed loading conditions. To illustrate how the SOMGA software works, six different satin-woven-fabric-reinforced composites, starting from plain weave (satin 2/1/1), then satin 3/1/1, satin 4/1/1, satin 5/1/1, satin 5/2/1 and finally satin 5/3/1, were evaluated in the SOMGA interface. The results were rated against each other in terms of the composite efficiency and the case characterized by minimal reinforcement undulation (thinnest laminate) were highlighted.

Influence of Hydrothermal Aging under Two Typical Adhesives on the Failure of BFRP Single Lap Joint

Facing increasingly serious resource crises, energy conservation is becoming the development trend of various delivery vehicles, and lightweight is an important way to achieve energy conservation. In this paper, the basalt fiber-reinforced resin composite material (BFRP) was selected to study the effect of its bonding structure, and it was used to make BFRP-BFRP joints. Two adhesives, Araldite®2012 and Araldite®2015, were used to make single-lap joints and dumbbell-shaped specimens. Aging environments of 80 °C/95% RH and 80 °C/pure water were used for the 0-day (unageing), 10-day, 20-day, and 30-day aging tests, respectively. According to Fick’s second law, the moisture absorption change model of two adhesives was established, and it was found that the water absorption process could be divided into two stages, which explains the precipitation of water molecules and the reaction of water molecules with functional groups. The maximum average failure load and load-displacement curves under different environments and different joints were obtained by using the electronic universal tensile machine, and the exposure time was more important than the effect of humidity. At the same time, the change law of failure strength and ductility were analyzed. The change of Tg (Glass transition temperature) was analyzed by differential scanning calorimetry (DSC) equipment, and the results showed that molecular chain rupture was the reason for the decrease of Tg. It could be seen from the joint failure mode distribution that Araldite®2012 adhesive was easily affected by the environment, and the joint of Araldite®2015 adhesive was affected by the combined effect of the adhesive and BFRP.

A Simplified Modelling Approach for the In-Plane Analysis of Masonry Structures Strengthened by FRCMs

Among the many strengthening techniques introduced for the seismic retrofitting of the masonry structures, FRCM strategies, based on the application of fibre-reinforced composite materials on the masonry surface through inorganic mortar layers, has become object of research due to their good performances in terms of physic and mechanic compatibility with historical substrate, low invasiveness and capacity to improve both the in-plane and the out of plane masonry behaviour increasing the capacity and the ductility of the structure. In this paper, a simplified discrete model is proposed to simulate the in-plane behaviour of masonry panels strengthened by FRCM systems. The proposed modelling approach is based on the DMEM model, whose numerical configuration can adapt to encompass the properties of the externally bonded strengthening system. According to the proposed strategy, the masonry support and the FRCM layers are simulated by an equivalent homogeneous material, discretized by a mesh of shear-deformable articulated quadrilaterals interacting along their edges by means of cohesive-friction links. The model is implemented in OpenSees and validated by simulating experimental shear-diagonal tests, available in literature.

Prediction of the Deterioration of FRP Composite Properties Induced by Marine Environments

In this paper, a model for the prediction of fatigue life degradation of fiber-reinforced (FRP) composite materials exposed for prolonged periods to real marine environments is proposed. The data collected during the previous phases of a more comprehensive research of real marine environment-induced changes of mechanical properties in FRP composites are used to assess the influence of these changes on the durability characteristics of composites. Attention is paid to the classification societies’ design and exploitation rules on this matter. The need for the modification of the process used for obtaining composite material S–N curves, considering the influence of the marine environment, is studied. A regression analysis of the experimental data is conducted, resulting in a mathematical model of strength degradation over time. The regression analysis shows an acceptable correlation value. The S–N curves for E-glass/polyester composites with three different fiber layout configurations are evaluated and modified to encompass the findings of this research.