Unidirectional Fiber Research Articles

Evaluation of mechanical properties for Ricinus communis L plant fiber/epoxy composite

AbstractThis research explores the mechanical properties of castor oil plant (Ricinus communis L) natural fiber‐reinforced epoxy composites, addressing the need for sustainable materials. Cortex and xylem fibers extracted from castor oil plant residue using a standardized method were used to fabricate unidirectional long fiber and short random fiber composites. Various fiber volume fractions (10 %, 20 %, 30 %, 40 %) and fiber lengths (5 mm to 40 mm) of cortex fibers were tested according to ASTM standards and results showed that fibers of diameters 275 μm to 325 μm, have superior tensile strength (290 MPa to 346 MPa) compared to xylem fibers (90 MPa to 140 MPa). Composites of 40 % volume fraction cortex fibers aligned longitudinally exhibited the highest tensile (76.35 MPa), flexural (121.45 MPa), and impact strength (6.99 kJ/m2) significantly improved compared to the epoxy matrix. For short random cortex fiber composites, the optimal mechanical performance was achieved with 20 mm fibers and a 40 % volume fraction, resulting in the highest tensile strength (32.12 MPa), flexural strength (84.31 MPa), and impact energy (40 J/m). These results highlight the potential of castor oil cortex fibers to enhance the mechanical properties of epoxy composites for various engineering applications.

Quasi‐Homogeneous Integrated Strain Vector Sensors for Natural Human–Machine Interaction

AbstractBody motion capture is a vital approach that underpins natural human–machine interaction. Strain sensors that can detect both motion amplitude and direction are the basis for discerning interactive intent. However, most strain sensors with heterogeneous architecture fail to perceive motion direction accurately. Here, quasi‐homogeneous integrated strain vector sensors are constructed by vertically stacking elastomer meshes with different fiber orientations in order. By varying fiber orientation, the proportion of intrinsic elastic and structural deformation in elastomer mesh can be adjusted, achieving effective regulation of its electromechanical properties. A highly anisotropic elastomer mesh with unidirectional fibers is customized, enabling the strain vector sensors to perceive stretch amplitude and direction simultaneously. Notably, the strain vector sensors demonstrate a minimum directional resolution of 2° and a linear working range of up to 100% strain. The tough bonding between quasi‐homogeneous interlayers ensures high robustness even after 10 000 loading cycles. Moreover, a wearable 3D motion capture system is built that can acquire comprehensive data regarding motions, including amplitudes, directions, and modes, and visually synchronize them in virtual reality. Natural human–machine interaction is achieved by intuitively and effortlessly altering motion amplitudes and directions. This work provides an alternative insight for immersive human–machine interaction in the future.

Fiber random contact model for evaluating electrical resistance variation of carbon fiber composites under various damage modes

AbstractThe variations in electrical resistance of carbon fiber composites under different damage modes are critical for the design of electrically conductive components. Here, we developed a fiber random contact model to analyze the changes in electrical resistance of carbon fiber composites subjected to various damage scenarios. An ideal rectangular grid was constructed in matrix form utilizing the nodal voltage and current method. The electrical resistance of each fiber branch was calculated based on the normal distribution of fiber orientation angles. To simulate the random distribution of contact branches among fiber contact points within the resistor network, contact branches were randomly removed from the ideal rectangular grid. The electric conductive properties of carbon fiber tows, unidirectional carbon fiber composites, and 3D woven carbon fiber composites were measured to validate the fiber random contact model. The findings are anticipated to contribute to the optimization of carbon fiber composites for electrical applications.Highlights Fiber random lap model for evaluating electrical behavior was developed. The conductive behaviors of the composites were measured. Electrical resistance variation under various damages was investigated.

Designing Bouligand‐inspired reinforcement for creating wood fiber‐reinforced composites with excellent bending properties

AbstractFiber‐reinforced composites with a bionic Bouligand structure are known for their excellent mechanical properties. Currently, most of the research in this field focuses on man‐made fibers, and research on natural unidirectional fiber materials is still limited. This paper designing Bouligand‐inspired reinforcement for creating wood fiber‐reinforced composites. We investigate the effects of the helix angle on the bending properties, impact resistance and extreme environments of the material through a combination of experimental methods, finite element analysis, and theoretical modeling. Morphological analysis using scanning electron microscopy (SEM) to further explore fracture mechanisms. The findings reveal that the load–displacement curves predicted by the finite element method closely align with the experimental results. The bionic composites demonstrate not only strong bending properties but also significant impact resistance. Notably, the highest bending strength, bending modulus, and impact strength were achieved at a small helix angle of 12.8°, reaching values of 184.66 MPa, 10.21 GPa and 28.03 kJ/m2. The bouligand structure is designed to withstand extreme environments. This research significantly expands the potential applications of the bionic Bouligand structure within the realm of wood fiber‐reinforced composites.Highlights Preparation of Bouloigand‐like composites utilizing wood. Helix stacking angle affects the performance of WFRCs. Finite element analysis was employed to predict the mechanical properties. “Green” composites exhibit exceptional mechanical properties. Expanding the application areas of wood fiber‐reinforced composites.

Effect of Displacement Rate on Delamination Growth Rate in Unidirectional Glass Fiber Composites in Both Bridging and Non-Bridging Scenarios

Effect of Displacement Rate on Delamination Growth Rate in Unidirectional Glass Fiber Composites in Both Bridging and Non-Bridging Scenarios

Drop‐Weight Impact Analysis of Unidirectional Sisal Fiber –Reinforced Epoxy Resin Composite Material for Automotive Application Based on ASTM D‐7136 Standard

The main goal of this study is to investigate the drop‐weight impact analysis of sisal fiber–reinforced epoxy resin composite materials for automotive applications using Abaqus/CAE software based on the ASTM D‐7136 standard. For this simulation, a [0/0]s unidirectional sisal/epoxy composite laminate with an overall thickness of 2.16 mm was used, and 0.5, 1, 2, and 3 kg of a rigid hemispherical impactor mass with 1, 2, and 3 m/s of velocities were used to deal with their effects on the composite laminates. The result revealed that the initial damage mechanism in the impact event is the interplay matrix crack. After that, matrix and fiber debonding, fiber breakage, and penetration occurred depending on the mass and velocity of the impactor. In addition, when the impactor mass and velocity increase, the composite plate’s reaction forces and energy absorption increase up to 1 kg of the impactor at 3 m/s. However, for 2 and 3 kg of the impactor mass, the energy absorption capacity of the material is decreased due to the high damage and perforation of the composite laminate. In general, it is found that the unidirectional sisal fiber–reinforced epoxy resin composite material has a moderate energy absorption capacity in the transverse direction and has the potential to be used for different automotive interior body applications.

Mechanical Properties Evaluation of PMC’s With Hybrid Reinforcement

To enhance the properties of composites composed of steel, ceramic, or polymeric elements, they can be reinforced with fibers, particles, or whiskers that serve the same purpose. Natural reinforcement has been proven to be the most efficient usage of the minimal quantity of effort required in PMC, which is required in lightweight applications. The presence and influence of the unidirectional fiber in the composites manufactured with an epoxy matrix have been the subject of a limited number of research that is being carried out. The purpose of this research is to create, evaluate, and assess a polymer compound composed of both natural and synthetic elements in various proportions by hand layup process. The hand-laying process is used to process the materials and several mechanical parameters are being evaluated to establish the fabric's capacity under various loads and operating situations. A blend of glass fibers, jute, and basalt fibers combination is selected for the polymer preparation.

Study of Adhesive Bonded Joints between Metallic Plates and Composite Laminates

Many researchers studied influences of various parameters on the failure behavior on the composites. One of the challenges in the analysis and design of bonded joints is the valuation of the stress and strain fields at the adhesive layer and adherents. The present investigation deals with the analysis of adhesively bonded dissimilar material single lap joints (SLJ) between mild steel and unidirectional carbon fibres reinforced polymer (CFRP) laminates. The primary objective of this study is to investigate the effects of various parameters, such as bonding strength, overlap length, adherend thickness, and adhesive thickness, on the failure load and failure mode of joints with dissimilar materials. Failure process, mode and strength of unidirectional composite to mild steel single lap adhesive bonded joints were investigated numerically by using finite element methods. Numerical methods based on finite element models can be very useful in describing the stress and strain responses for each load step. The SLJ specimens are done nonlinear analysis and predict the force -displacement and force- strains curves and conclusions regarding joint stiffness and strength are obtained for different cases of SLJ

Relaxation Modeling of Unidirectional Carbon Fiber Reinforced Polymer Composites Before and After UV-C Exposure

Carbon fiber-reinforced polymers (CFRPs) are widely used in aerospace for their lightweight and high-performance characteristics. This study examines the long-term viscoelastic behavior of CFRP after UV-C exposure, simulating low Earth orbit conditions. The viscoelastic properties of the polymer were evaluated using dynamic mechanical analysis and the time-temperature superposition principle on both unexposed and UV-C-exposed samples. After UV-C exposure, the polymer’s instantaneous modulus decreased by about 15%. Over a 32-year period, the modulus of the unexposed resin is expected to degrade to approximately 25% of its initial value, while the exposed resin drops to around 15%. These experimental results were incorporated into finite element method models of a unidirectional CFRP representative volume element. The simulations showed that UV-C exposure caused only a slight reduction in the CFRP’s axial relaxation coefficient along the fiber’s axis, with no significant time-dependent degradation, as the fiber dominates this behavior. In contrast, the axial relaxation coefficient perpendicular to the fiber’s axis, as well as the off-diagonal and shear relaxation coefficients, showed more notable changes, with an approximate 10% reduction in their initial values after UV-C exposure. Over 32 years, degradation became much more severe, with differences between the pre- and post-exposure coefficient values reaching up to nearly 60%.

Dynamic characteristics of laminated composite sandwich plates with graphene-reinforced magnetorheological elastomer

This research examines the dynamic characteristics of laminated composite sandwich plates with magnetorheological elastomer (MRE) and graphene-reinforced MRE (hybrid-MRE) cores. The laminated composite was fabricated with unidirectional glass fiber with [0°/90°]s ply orientation, epoxy resin (LY556), and hardener (HY951) using a vacuum bagging-assisted hand-layup technique. The experiment was performed to determine the natural frequencies of the sandwich plates under clamped-clamped (CC) boundary conditions with various magnetic fields. The laminated composite sandwich plate with MRE and graphene-reinforced MRE was developed by using Abaqus, and the results are validated with experimental results and existing literature. Further, the MRE and graphene-reinforced MRE sandwich plates parametric study evaluates the impact of the applied magnetic field, ply orientation, different boundary conditions, aspect ratio, and core-skin layer thickness ratio. Under clamped-free (CF) boundary conditions, The MRE and hybrid-MRE sandwich plate natural frequencies exhibit an increase of 14.64% and 16.27%, respectively, as the applied magnetic field increased from 0 G to 750 G. The MRE and hybrid-MRE sandwich plates demonstrate their highest natural frequencies under CC conditions and [0°]4 ply orientation, in contrast to other boundary conditions and ply orientations. The sandwich plate’s natural frequencies decrease with an increase in both the core-skin thickness ratio and aspect ratio. This research will guide design engineers in replacing pure MRE with hybrid MRE in certain aerospace applications.

Asymptotic homogenization, domain decomposition and finite elements combined for calculating effective elastic properties of periodic fiber-reinforced composites with imperfect interfaces

A methodology is presented for calculating the effective elastic properties of periodic multi-phase composites made of an anisotropic linear elastic matrix reinforced with a periodical distribution of unidirectional fibers and exhibiting spring-type imperfect contacts at the interfaces. The periodicity cell contains any finite number of parallel fibers and exhibits arbitrary cross-section. Fibers also exhibit arbitrary cross-sections and are made of a different anisotropic linear elastic material each. The methodology uses asymptotic homogenization (AH) to obtain the mathematical expressions of the effective properties and to formulate the so-called local problems on the periodicity cell on whose solutions the effective properties depend on. In order to deal with the discontinuities arising from the spring-type interfaces, the local problems are then restated via domain decomposition (DD) in a way allowing for an iterative resolution scheme in which the solution of the problem to be solve in each iteration is obtained via finite elements (FE). Results in the examples are obtained via a computational implementation of the methodology based on the FreeFEM open-source software, which allows for the variational formulation of the iteration problem to be dealt with directly.

Implications of end cooling rates on the Mechanical, Viscoelastic, and interlaminar fracture properties of the unidirectional glass Fiber/Epoxy composites

This research explores the impact of different end cooling rates on the mechanical, viscoelastic, and fracture properties of Glass Epoxy (GE) composites. Unidirectional (UD) glass fiber and epoxy resin were utilized to prepare composite laminates, subjected to three distinct end cooling conditions (slow cooling, air cooling and fast cooling). The composites were characterized through tensile, flexural, viscoelastic, interlaminar shear strength (ILSS), mode I and II fracture tests. Results revealed a higher degree of cure in slow cooled samples (87.23 %) compared to air cooled (85.11 %) and fast cooled specimens (81.56 %). Results also revealed that cooling rates significantly influenced the mechanical, viscoelastic and fracture properties, with higher cooling rates improving ILSS(38.92 MPa to 46.31 MPa), mode I (256.28 J/m2 to 373.85 J/m2) and mode II (1044.19 J/m2 to1151.85 J/m2) interlaminar fracture toughness (ILFT). Tensile strength, modulus and strain at break was found to decrease with higher cooling rates. End rate of cooling (ROC) had limited effect on the flexural strength and modulus. Varied end cooling rates significantly influence the fracture behavior of glass fiber-reinforced epoxy composites under mode I and mode II loading as evidenced by SEM analysis, with fast-cooled composites exhibiting better fiber–matrix interfacial bonding and higher delamination resistance compared to other composites.

Clinical Survival of Indirect, Posterior Fiber-Reinforced Composite Fixed Dental Prosthesis: Up to 15 Years of Prospective Clinical Follow Up.

This prospective clinical study evaluated the survival of indirect, posterior fiber-reinforced composite fixed dental prosthesis (FRC FDP). Between June-1999 and June- 2000, 58 patients received 65 FCR FDPs made of unidirectional E-glass fibers (Vectris) veneered with resin composite (Signum) that were adhesively cemented (Variolink II). The evaluation protocol involved technical (chipping, debonding or fracture of tooth/restoration) and biological failures (caries, endodontic complications). Altogether, 6 technical failures were observed after a mean observation time of 180 months (survival rate: 89.2%, Kaplan-Meier) in the form of fractures (n=2) and partial debondings (n=4). All defective restorations were repaired or recemented. Secondary caries occurred in one patient after 11 years. The 3-unit posterior FRC FDPs showed good clinical survival rate up to 15 years of clinical function. Limited numbers of experienced failures were due to mainly debonding followed by fracture of the veneering composite.g composite.

Considering the Bottom Edge Cutting Effect of the Carbon Fiber Reinforced Polymer Milling Force Prediction Model and Optimization of Machining Parameters.

The milling force plays a pivotal role in CFRP milling. Modeling of the milling force is helpful to explore the changing law, optimize the processing parameters, and then reduce the appearance of defects. However, most of the existing models ignore the effect of the bottom edge. In this paper, the prediction of milling force in CFRP milling processes is taken as the research object. By analyzing the milling mechanism and considering the end milling cutter's bottom cutting edge, the prediction model of milling force was established. Based on the experimental data and simulation data of milling force, the milling force coefficient was obtained by inverse calculation. Subsequently, the predicted cutting force was compared with the experimental cutting force, showing a maximum error of 14.5%, which is within a reasonable range, and the correctness of the model was verified. Furthermore, combined with the delamination damage and the milling force prediction model, a multi-objective optimization model of milling parameters was established, and the genetic algorithm was used to solve the model. The unidirectional carbon fiber plate with a fiber direction angle of 45° was selected as the optimization example. The minimum delamination damage was obtained under the cutting conditions of a spindle speed of 4903.1569 r/min, feed rate per tooth of 0.01 mm/z, and an axial depth of cut of 0.5 mm, and the experimental verification was carried out. The feasibility of the genetic algorithm in CFRP milling parameter optimization modeling was also verified.

Multi-scale numerical calculations for the interphase mechanical properties of carbon fiber reinforced thermoplastic composites

This study employs a multi-scale numerical calculations method based on molecular dynamics and finite element modeling to investigate the stress transfer mechanisms within the interphase of unidirectional (UD) carbon fiber reinforced thermoplastic polymers (CFRTP) composites, based on which exponential decay model (EDM) was developed to predict the interphase strength and modulus. Revealing that the interphase strength and modulus are approximately 0.5–0.7 times that of the fibre/interphase interface or 1.2 to 1.7 times matrix. The EDM was validated using a coupled experimental-representative volume element modeling method. By calibrating the interphase fracture energy, the mechanical properties predicted by the EDM aligned well with the experimental results of UD CFRTP composites. Finally, the damage evolution and failure modes were analyzed, revealing that the transverse failure of UD CFRTP composites is dominated by the interphase, while longitudinal failure is primarily governed by the fibers, consistent with scanning electron microscope observations. This confirms the accuracy of the EDM, and application this method can be used to quickly and accurately assess the strength and modulus of the interphase in CFRTP composites to significantly reduce the numerical analysis time.

Antiplane effective properties of two‐phase micropolar elastic fiber‐reinforced composites with parallelogram‐like unit cells

AbstractIn this contribution, heterogeneous micropolar elastic fiber‐reinforced composites (FRCs) with a periodic structure are analyzed using the two‐scale asymptotic homogenization method (AHM). We focus on predicting the antiplane effective properties of micropolar two‐phase FRCs with parallelogram‐like unit cells. The periodic structure is defined by unidirectional, infinitely long, and concentric cylindrical fibers embedded in a homogeneous matrix. Constituent materials are assumed centro‐symmetric isotropic materials, and perfect interface conditions are considered. The AHM allows us to address the local problems on the periodic cell and determine the corresponding effective properties. This is achieved by employing two‐scale asymptotic expansions for the displacement and microrotation fields, which depend on both macro‐ and micro‐scales. The complex variable theory, combined with the complex‐potential method and doubly periodic Weierstrass elliptic functions, is applied to determine the solution of the antiplane local problems. Simple closed‐form formulas are provided for the antiplane stiffness and torque effective properties of two‐phase micropolar elastic FRCs, which depend on the physical properties and volume fractions of constituents. Finally, numerical examples are reported and discussed. Comparisons with other theoretical models are also presented, and good agreements are obtained.

Enhancing carbon fiber thermoplastic sandwich structures with springback effect

In this research, a sandwich structure is manufactured using a thermally deformed (springback) core. Non-woven carbon fiber reinforced thermoplastic (NW-CFRTP) was used for the core, and uni-directional carbon fiber reinforced thermoplastics (UD CFRTP) and carbon fiber reinforced thermoplastics sheet molding compound (CFRTP-SMC) were used for the skin. Statistical flexural properties were investigated by conducting three-point bending experiments. Specimens with different springback ratios were assessed, and the critical springback ratios of the individual core and whole sandwich structure indicated the peak points of mechanical properties in the corresponding tests. Diverse results were acquired and a springback ratio of approximately 1.7 was found to give optimal static mechanical properties during various scenarios. Different fracture models that appeared during the research were also studied, and improvements were made based on the findings. To improve the properties along the thickness direction, the molding method and material set were improved, and the enhancement of interlaminar properties also contributed to better mechanical properties. Specifically, the energy absorption capacity of the structure more than doubled. Stable and ductile sandwich structures were achieved with a density lower than water, and the excellent specific mechanical properties could open up new avenues for the application of recycled carbon fibers.

Investigation on mechanical, physico-chemical and thermal properties of recycled polyamide 6 reinforced with continuous glass fibers

The study primarily deals with recycled plastics, mainly polyamide 6 (rPA6), obtained from recycled fishing nets. These plastics are converted into reusable plate-like materials using the compression molding process. Moreover, the material was subjected to compression at different ratios of UD tape (4 wt%, 8 wt% and 12 wt%). In fact, reinforcement was added by incorporating a tape made of PA6 and unidirectional glass fibers, often known as PA6-GF UD tape. This research will investigate the physico-chemical structure, thermal properties, mechanical behavior, and microstructure of recycled Polyamide 6 (rPA6) and its composites, specifically rPA6 reinforced with glass fibers (rPA6GF) at different weight ratios. Besides this research makes a three analytical model (ROM, IROM, Hirsch) to predict the tensile properties of rPA6GF. The study’s findings demonstrate that recycled plastics sourced from fishing nets displayed favorable mechanical characteristics, after the addition of reinforcement materials, such as tensile strength (74.65 MPa), elastic modulus (5.64 GPa), flexural strength (≈155 MPa), impact resistance (143.36 KJ/m2), and hardness (79.5 D). While these improvements have been achieved, the presence of impurities and moisture still pose long-term performance problems that cause the degradation of the material and increased variability associated with it, complicating predictive modeling. Analytical modeling, while useful in explaining fiber reorientation, needs also to include these variabilities in order to improve long-term accuracy and performance prediction. The current study has approved the feasibility of locally reinforced composites with continuous fiber development by thermocompression, hence a promising approach toward the attainment of sustainable and reliable performance for the recycled plastic composites.

Experimental and numerical investigation on the size effect of interlaminar shear strength for thick composites

The study investigates the variation of interlaminar shear properties for unidirectional glass fiber reinforced polymer (GFRP) composites with different thickness using the short-beam shear (SBS) test in conjunction with DIC. To verify the scaling principle and clarify possible mechanisms of the interlaminar shear strength size effect, the quantitative parameters for characterizing randomly distributed irregular voids are proposed. It is seen that the variation of probability for void characteristics with thickness is one of the mechanisms for the interlaminar shear strength size effect. Furthermore, a micromechanical representative volume element (RVE) model with randomly distributed irregular voids is developed for numerical verication. The analysis indicates that the weakest link is related to not only the void size but also the void irregularity and void concentration. The void concentration has a pronounced negative impact on shear strength due to the intersection of the microcracks around the voids.

Cluster analysis of acoustic emission signals for bending damage mechanism of flax fiber reinforced composites under hydrothermal aging

Despite the eco-friendly and lightweight features, natural fiber reinforced composites (NFRCs) are more susceptible under hydrothermal conditions than artificial synthesis fibers reinforced composites. Cluster analysis on damage evolution of hydrothermal aged NFRCs by using acoustic emission techniques and machine learning also remains scare. To figure out these challenges, unidirectional flax fiber reinforced composites (FFRCs) were prepared and submerge into distilled water at three different temperatures to systematically study the influence and damage mechanism under hydrothermal aging by acoustic emission (AE). After hydrothermal aging for 60 days, AE signals revealed that the FFRCs were more likely to cause defects in the early loading stage at the higher temperature. Cluster analysis showed an increase in the proportion of delamination during the process of failure. The proportion of fiber breakage AE signals with higher PF also increased. Microscope view proved the bending damage behavior of FFRCs after hydrothermal aging.