Fiber Pull-out Research Articles

Graphene nanoplatelets inclusion effects on mechanical properties of the hybrid kevlar/basalt fiber reinforced epoxy composites

Abstract This study experimentally examined the effects of hybridizing Basalt and Kevlar fibers on the tensile, and flexural performance of composite materials with the inclusion of Graphene nanoplatelets (GnPs). Various hybrid composites were fabricated, incorporating Basalt and Kevlar fiber composites with 1, 3, and 5 wt% of GnPs as well as without GnPs, as well as hybrid composites featuring different weight content of GnPs reinforcing with with Basalt and Kevlar fibers. The findings of this study indicated that the mechanical properties of epoxy resin were significantly enhanced through the synergistic effects of hybridization with basalt and Kevlar fibers, as well as the incorporation of graphene nanoplatelets (GnPs). The significant increasing in mechanical properties was attributed to the strong interfacial interactions between the epoxy matrix and GnPs nanoparticles, which facilitate improved stress transfer from the fibers and nanoparticles to the matrix. This enhanced stress transfer capability accounts for the superior resistance to fiber pullout observed in composites reinforced with GnPs compared to those without nanoparticles.

The Effect of Differences in Fiber Sizes on the Cutting Force During the Drilling Process of Natural Fiber-Reinforced Polymer Composites

This experiment aimed to analyze the impact of different fiber sizes on cutting forces during the drilling of Natural Fiber-Reinforced Polymer Composites (NFRPC) while also evaluating surface quality attributes, including delamination, fiber pullout, and overhanging fibers, influenced by variations in coconut fiber dimensions within the NFRPC material. The manufacturing process for composite panels utilized various methods, including hand layup for 200 mm long coconut fibers and composite casting for shorter fibers (2, 4, and 6 mm) mixed with polymer-epoxy. The results indicate that panels made from NFRPC with continuous fiber lengths of 200 mm exhibit higher cutting force values (253,650 N) compared to epoxy panels without fibers (235,288 N), suggesting that a significant force is required to sever the continuous fibers within the NFRPC. Conversely, the incorporation of short coconut fibers measuring 2, 4, and 6 mm reduces the cutting forces on the composite panels. However, excessive surface roughness in the final hole quality can be detrimental, primarily due to issues of delamination and fiber pull-out.

Dynamic behaviour and failure mechanism of bamboo scrimber panels under single and repeated impacts: Experimental tests

Bamboo scrimber, as a renewable and sustainable material engineered from bamboo, is inevitably subjected to impact loadings in engineering applications. To study the dynamic behaviour and failure mechanism of bamboo scrimber panels under low-velocity impact, a series of drop hammer impact tests were conducted on 36 panels. The peak force, deformation and energy absorption of bamboo scrimber panels were obtained and analysed. The influence of impact energy, impactor shape and impact angle on the dynamic behaviour of panels was quantitatively characterised. Besides, based on test observations and microscopic views, the failure mechanism of bamboo scrimber panels under different impact types was revealed, including the energy absorption mechanism through fibre fracture, fibre debonding, fibre pull-out and matrix failure. Test results showed that with increasing impact energy, the peak force of panels impacted by the spherical and flat impactors increased, while that of panels impacted by the wedge impactor did not vary significantly. The deformation and energy absorption of panels also increased with increasing impact energy. Notably, the impactor shape obviously influenced the dynamic behaviour of panels, causing a higher peak force of panels impacted by the flat impactor and a larger deformation of panels impacted by the wedge impactor. The failure mechanism of panels depended highly on the impact energy and the impactor shape. Finally, a comparative study of single versus repeated impacts revealed that the deformation of bamboo scrimber panels under repeated impacts was less than that of panels under a single impact when the same amount of energy was imposed to the panel. This study provided a basis for the use of bamboo scrimber to resist impact loadings.

Whole process analysis on splitting tensile behavior and damage mechanism of 3D/4D/5D steel fiber reinforced concrete using DIC and AE techniques

In recent years, the application of a new type of end hook steel fiber (ESF) in concrete has gradually become a hot spot due to its excellent properties. In order to investigate the influences of ESF content, end hook number and aspect ratio on the splitting tensile properties and damage characteristics of end hook steel fiber reinforced concrete (ESFRC), a set of splitting tensile test device was improved in this study to measure the complete splitting tensile load-deformation curves of ESFRC. The influence of 3D/4D/5D steel fiber on the crack development and damage evolution of ESFRC specimens under splitting tensile load was analyzed by digital image correlation (DIC) and acoustic emission (AE) techniques. The results showed that the splitting tensile strength and crack resistance of ESFRC were gradually improved by increasing the content and end hook number of ESF. The splitting tensile load-deformation curves of the specimens with single-ended hook (3D) steel fibers could be divided into five stages, and the curves appeared two or even more fiber strengthening stages with the increase of end hook number, which mainly depends on the end hook form of steel fiber. Concrete cracking, ESF debonding and end hook straightening were the main reasons for the development of AE events and ringing counting. As the ESF content or the number of end hooks increased, the proportion of shear cracks gradually increased from 59.82% to 71.34%, and the AE energy of cracking damage also increased accordingly. The strain band at the failure interface first appeared in the middle of the specimen and gradually extended to the loading end, and the failure mode gradually changed from a single crack to a main crack, accompanied by multiple scattered cracks. Finally, a prediction model for the splitting tensile strength of ESFRC was proposed and verified based on the fiber pull-out bonding theory.

Study on dynamic mechanical properties and damage characteristics of wollastonite fiber reinforced oil well cement paste

In cement engineering, the cement sheath is not only influenced by elevated temperatures, increased pressure, and the static load confining pressure within the formation but also encounters external impact loads. These loads can rupture the cement paste, compromising the cement sheath’s interlayer sealing capability. Consequently, this can give rise to an annular flow of oil, gas, and water. Hence, this study introduces wollastonite fiber (WF) into the cement slurry to modify the cement paste. The investigation explores the mechanical properties, energy evolution, and damage characteristics of the cement paste with WF under dynamic impact loads. This is achieved by simulating the dynamic impact loads experienced downhole using the separated Hopkinson pressure bar (SHPB) technique. A straightforward SHPB model is constructed using ABAQUS finite element simulation software, and its accuracy is confirmed through experimental validation. The impact test outcomes revealed a notable enhancement in the dynamic load peak strength of the cement paste cured for 14 days. Specifically, there was an increase of 136.75%, 202.10%, and 320.55% compared to the control group at impact speeds of 6 m/s, 8 m/s, and 10 m/s, respectively. The absorption energy increased remarkably, showing 356.03%, 388.61%, and 142.14%, respectively. The simulation findings confirm that the devised simple SHPB model effectively replicates electrical signals aligned with the observed experimental results. The dispersed fibers create a three-dimensional network within the cement paste. This network enhances the impact resistance of the cement paste by leveraging the mechanisms of crack deflection, fiber fracture, and energy dissipation through fiber pull-out.

Prediction of bond strength between fibers and the matrix in UHPC utilizing machine learning and experimental data

The bond strength between fibers and the matrix plays a crucial role in the tensile strength and post-cracking performance of ultra-high-performance concrete (UHPC). However, existing studies have not attempted to utilize machine learning models for the prediction of bond strength. In this study, machine learning techniques were employed to predict the bond strength of fibers in UHPC. A dataset comprising 658 experimental records was compiled and advanced unsupervised Isolation Forest techniques were utilized to identify and remove outliers, thereby ensuring the accuracy and reliability of the data. Six machine learning models, including ANN, GBDT and XGBoost are utilized in this study, with a focus on evaluating their performance in predicting the maximum pull-out force of fibers. The results indicate that the XGBoost model exhibits exceptional predictive performance, achieving R² value of 0.98, which demonstrates the model's capability to accurately predict the fiber pull-out process. Furthermore, feature importance analysis, visualized through advanced techniques, reveals the significant influence of fiber tensile strength on the pull-out force. A new equation is proposed to predict the maximum pull-out force of fibers and correction factors for different fiber shapes are introduced, significantly enhancing the precision of the calculations. The newly proposed predictive equation has R² value of 0.72, which increases to 0.74, 0.77, and 0.86 after the introduction of shape correction factors, significantly enhancing the accuracy of the computed results. This study not only provides an efficient and reliable method for predicting fiber bond strength in UHPC but also offers an innovative tool for calculating fiber pull-out force.

Assessment of surface quality and damages induced during dry helical milling of hybrid composite fiber metal laminates

Abstract The present work investigates the effectiveness of helical milling for making holes with excellent surface quality in carbon fiber aluminum laminates (CARALL) under dry-cutting conditions. The impact of cutting speed and axial pitch on hole surface quality was analyzed. The findings show that axial pitch and cutting speed significantly impact surface roughness. Utilization of lower cutting speed (30 m/min) and axial pitch (0.1 mm/rev) results in material adhesion and feed marks, thus lowering the surface roughness. Nevertheless, the surface finish was enhanced by using higher levels of process variables. Surface defects like chip adhesions, deformation marks, and material smearing were observed. The orientation of the cutting edge with the fibers greatly influenced the surface morphology. Exposed fibers with varying lengths were noted when machining fiber layers oriented at 135°, thus creating an irregular surface. Scanning Electron Microscopic observation of the carbon fiber layers displayed a cleanly cut surface without fiber pullout and crack or interlayer burrs. Moreover, the holes in the CARALL were devoid of delamination/debonding for all the combinations of process variables. In general, results demonstrate the suitability of helical milling for processing holes with superior surface quality and satisfying the stringent requirements of the aircraft industries.

An organic-inorganic interface structure for CFRP and the enhancement of mechanical properties at room/high temperature

The performance of carbon fiber reinforced polymers (CFRP) depends on various factors, with particular emphasis on the intricate microscopic interface. Through the combined interface modification by nanomaterials (ZrO2) and polyimide (PI), an organic-inorganic interface enhanced structure of CFRP with phenolic resin (PR) have been successfully devised and fabricated. The analysis encompassed the surface morphology, contact angle and surface energy of carbon fibers (CF), aimed at characterizing the interaction of grafted ZrO2/PI on interfacial properties. Single fiber pull-out testing was employed to ascertain both the failure mode of the interface and the interfacial shear strength (IFSS). The results revealed that the surface modification augmented the IFSS by 70 %. The fortified organic-inorganic interface layer resulted in enhancements of 14 % and 15 % in tensile strength and flexural strength, respectively, in comparison to untreated CFRP. Moreover, even under high-temperature condition (300 °C), the tensile properties of modified CFRP exhibited only 22 %–26 % reduction, which demonstrated the advantages of composites in harsh environments. This can be primarily attributed to the strengthened layers of ZrO2/PI, which securely anchored the matrix and reinforcement, thereby mitigating stress concentration in CFRP under extreme conditions.

Research progress on laser processing of carbon fiber composite materials

AbstractCarbon fiber reinforced polymer (CFRP) is a high‐performance composite material composed of carbon fibers embedded in a polymer matrix. CFRP is extensively used in various sectors such as aerospace, automotive, sports equipment, and construction due to its advantageous properties. Laser processing offers numerous advantages when working with carbon fiber‐reinforced composites, including its non‐contact nature, precision, efficiency, and controllability. However, disparities between carbon fibers and the polymer matrix can lead to challenges during laser processing, such as delamination, heat‐affected zones, and fiber pullout. Consequently, there is a substantial body of literature focusing on improving the quality and efficiency of laser processing for CFRP materials. This paper provides a comprehensive review of various studies investigating the impact of laser parameters (laser mode, pulse frequency, pulse width, and laser wavelength) on carbon fiber‐reinforced plastics. It discusses how different laser parameters affect the processing quality and performance of these materials. Additionally, drawing from recent research findings, the paper explores potential future trends in laser processing for carbon fiber‐reinforced plastics.Highlights The application of laser technology in CFRP, including laser cutting, drilling, welding, and surface treatment, has been extensively researched. A detailed discussion is held regarding the impact of laser mode, wavelength, frequency, and pulse width on the quality of machining. More auxiliary processing has evolved in CFRP manufacturing due to the ongoing advancements in laser technology. The goals of laser processing CFRP technology are increasingly focused on reducing carbon emissions, enhancing energy efficiency, and minimizing waste.

Synergistic effect of alkali treatment and graphene filler on the mechanical characteristics of nettle fiber reinforced polymer composite

This study examines the synergistic effects of alkali treatment and the addition of graphene fillers to nettle fiber-reinforced polymer (NFRP) composites. NFRP composites were fabricated using NaOH-treated nettle fibers at concentrations of 3%, 5%, and 7%. Gr-NFRP composites were produced by varying the graphene content (1wt%, 2wt%, and 3wt%) in the epoxy resin that impregnated 5% NaOH-treated nettle fibers. The composites were prepared using a hand layup combined with a compression molding technique. A comprehensive analysis of the physical, mechanical, and wear properties of the treated NFRP composites was performed. FTIR analysis confirmed the effect of alkali surface treatment on the nettle fibers, whereas SEM was employed to examine the morphology of the fractured specimens. The experimental results revealed that a 5% NaOH solution was the optimal concentration for improving the characteristics of nettle fibers within the polymer composite. Moreover, the inclusion of 2wt% graphene noticeably enhanced the mechanical properties of the NFRP composites, resulting in increases of 21%, 17%, 65%, and 10% in the tensile strength, flexural strength, impact strength, and Shore D hardness, respectively. The wear resistance improved by 38%, and the water absorption decreased by 32%. SEM images revealed that a balanced contribution between fiber breakage and pullout was the primary failure mechanism in the Gr-NFRP composites. The NFRP composite containing 2wt% graphene demonstrated significant improvements in both mechanical and wear properties, along with reduced water absorption, making it a highly promising material for structural applications.

Optimizing superelastic shape-memory alloy fibers for enhancing the pullout performance in engineered cementitious composites

Abstract This study explores the effect of integrated superelastic shape-memory alloy fibers (SMAFs) on the mechanical performance of engineered cementitious composites (ECCs). Various SMAF configurations – linear-shaped SMAFs (LS-SMAFs), hook-shaped SMAFs (HS-SMAFs), and indented-shaped SMAFs (IS-SMAFs) – with diameters of 0.8 and 1.0 mm were incorporated into ECC matrices, and surface texturization was achieved through abrasive paper treatment. Their mechanical properties were assessed through single fiber pullout tests on ECC mixtures containing 1.5 and 2.0% polyvinyl alcohol (PVA), subjected to both monotonic and cyclic loading conditions. Qualitative analysis, employing scanning electron microscopy, demonstrated that the IS-SMAF configuration provided superior mechanical interlocking and fiber–matrix adhesion, with a distinct flag shape observed during tensile testing. Quantitative data indicated that IS-SMAFs significantly improved the tensile strength and pullout resistance, with slip distances of ≥5 mm and average pullout loads ranging from 263 to 403 N. LS-SMAFs demonstrated better performance compared to HS-SMAFs and LS-SMAFs in terms of tensile and pullout characteristics. Additionally, ECCs with increased PVA content exhibited enhanced withdrawal performance. Thermogravimetry analysis and X-ray diffraction provided insights into the high-temperature stability and crystalline structure of the composites. These results underscore the effectiveness of IS-SMAFs in enhancing ECC properties, offering significant implications for the development and optimization of high-performance composite materials in civil engineering applications.

Performance augmentation of fiber reinforced concrete through in situ mineralization of polycrystalline calcium carbonate on fiber surfaces

Enhancing the performance of fiber-reinforced concrete through the meticulous regulation of interfacial microstructure and interaction mode stands as a pivotal area of research. Notably, there are significant differences in the microstructure of several polycrystalline forms of calcium carbonate, which can profoundly influence the interaction behavior between them and the matrix. However, the tailored modulation of calcium carbonate polymorphism for the purpose of fiber surface modification remains unreported. In this paper, polycrystalline mineralization was induced by polydopamine on the surface of polyvinyl alcohol fiber by biomimetic method, and the fiber surface was modified by calcite and aragonite. The cubic calcite and acicular aragonite minerals notably roughened the fiber surface, enhancing interfacial properties between PVA fibers and cement matrix. The damaged form of the interface changed from adhesion failure to cohesive failure. Quantitative assessment of fiber-matrix interfacial interactions via single-fiber pullout tests revealed aragonite's unique morphology and exceptional mechanical attributes yielding higher frictional resistance against pullout loads. The good bonding between calcite and the cement matrix improves the strain-hardening behavior of fiber pullout and significantly enhances energy dissipation. In addition, enhanced interfacial properties bolster composites' mechanical strength. The acicular and cubic mineralized layers increased the flexural strength of the fiber cementitious materials by 35 % and 41 %, respectively. The energy absorbed in resisting the impact of a falling ball increased by 25 % and 36 %, respectively. Analysis reveals calcite promotes hydration more significantly at comparable particle sizes, bolstering interfacial bond strength with cement, and offering superior reinforcement over aragonite for fiber matrix bridging. This research provides a theoretical basis for promoting the application of polycrystalline CaCO3 and the sustainable development of high-performance fiber-reinforced concrete.

Fabrication of dense Cf/SiC ceramic matrix composites using 3D printing and PIP with short carbon fibre as a toughening material

ABSTRACT To achieve weight reduction, toughness enhancement, and the fabrication of complex structures in SiC composites, a combination of SLS and PIP processes was used. Silicon carbide powder served as the matrix material, while short carbon fibres were used for toughening, resulting in dense Cf/SiC ceramic matrix composites. The effects of varying carbon fibre sizes and contents on the microstructure and mechanical properties of Cf/SiC composites were examined. Results indicated that adding 8% carbon fibre increased the fracture toughness of Cf/SiC composites by 33.33%. Further increases in carbon fibre content showed minimal effects on fracture toughness. Based on experimental results and finite element simulations, toughening mechanisms, including fibre pull-out, fibre debonding, and crack deflection, were further elucidated. Consequently, Cf/SiC composites with complex structures, such as turbine specimens and lattice structures, were successfully fabricated.

Comparative Analysis of Mechanical and Morphological Properties of Cordenka and Ramie Fiber-Reinforced Polypropylene Composites.

The depletion of conventional materials and their adverse environmental impacts have prompted a shift toward sustainable alternatives in composite materials engineering. In pursuit of this objective, this study investigated the mechanical properties of polypropylene matrix composites reinforced with Cordenka, an artificial cellulose fiber, and compared them to those reinforced with ramie, a natural cellulose fiber. Continuous strand composites were developed using the Multi-Pin-assisted Resin Infiltration (M-PaRI) process. The strands were subsequently sectioned into 15 mm lengths and injection-molded into dumbbell and strip specimens for mechanical characterization. The results showed that 20 wt% Cordenka/PP composites exhibited a tensile strength of 68.7 MPa, 2.04 times higher than neat PP and 1.66 times greater than the 20 wt% ramie/PP composites. Impact testing further demonstrated that Cordenka/PP composites absorbed 2 to 2.5 times more impact energy than ramie/PP composites, regardless of the presence of notches. Fiber length analysis indicated that Cordenka fibers maintained their length beyond the critical fiber length, allowing for efficient stress transfer and acting as a more effective reinforcement compared to ramie fibers, which were below this threshold. Consequently, the Cordenka/PP composites exhibited significantly enhanced mechanical performance. Scanning electron microscopy (SEM) analysis revealed fewer fiber pullouts in ramie-reinforced composites, suggesting superior interfacial adhesion to the PP matrix, although it did not translate to higher mechanical properties. These findings underscore the potential of Cordenka as a sustainable alternative to synthetic, non-biodegradable fibers in PP composites, providing improved mechanical properties and promising prospects for advanced composite applications.

Nitric acid-modified amorphous alloy fiber and its effects on mechanical properties of ultra-high performance concrete (UHPC)

The traditional steel fiber UHPC has the phenomenon of low strength and poor durability, which can not give full play to the practical value of UHPC. Nevertheless, amorphous alloy fibres possess notable strength, flexibility and corrosion resistance. The incorporation of amorphous alloy fibres into ultra-high performance concrete (UHPC) has been demonstrated to enhance the strength and toughness of UHPC. However, the surface of amorphous alloy fibres is characterised by a smooth and hydrophobic quality, which presents a challenge in terms of the interface bond with the cement matrix. In order to address this issue, three concentrations of nitric acid (HNO3, 2 mol/L, 4 mol/L and 6 mol/L) were employed to modify the surface of amorphous alloy fibres, and then the amorphous alloy fibres were incorporated into the cement matrix for fiber pull-out test, compression, flexural strength and impact testing. The changes in the physical and chemical properties of the amorphous alloy fibres before and after modification were analysed, and the effects on the interface bond strength and dynamic and static mechanical properties of UHPC were studied by means of SEM. The results demonstrate that the adhesion strength of the modified amorphous alloy fibre with 4 mol/L HNO3 is the most robust, with an increase of 18.7 % in compressive strength, 13.8 % in flexural strength, and 5.4 % in impact resistance. The method has been demonstrated to be effective in strengthening and toughening the cement matrix with HNO3-modified amorphous alloy fibres.

Analysis of aging effects on the mechanical and vibration properties of quasi-isotropic basalt fiber-reinforced polymer composites

Eco-friendly natural fiber composites, such as basalt fiber composites, are gaining traction in material science but remain vulnerable to environmental degradation. This study investigates the mechanical and vibrational properties of quasi-isotropic basalt fiber composites subjected to aging in two different environments: ambient (30 ºC) and subzero (-10 ºC), both in distilled water until moisture saturation. Aged specimens absorbed 8.66% and 5.44% moisture in ambient and subzero conditions, respectively. Mechanical testing revealed significant strength reductions in tensile, flexural, impact, and short beam shear tests, with ambient-aged specimens showing the largest decline (up to 31.7% in flexural strength). Vibrational analysis showed reduced natural frequencies, particularly under ambient conditions (27.27%). Sound absorption tests showed that pristine specimens had the highest transmission loss, while moisture-rich ambient-aged specimens had the lowest. SEM analysis confirmed surface degradation, with fiber pull-out and matrix debonding contributing to property loss. This research provides valuable insights into the environmental limitations of basalt fiber composites, emphasizing the need for enhanced durability in eco-friendly materials.

Internal shear damage evolution of CFRP laminates ranging from −100 °C to 100 °C using in-situ X-ray computed tomography

Carbon Fiber Reinforced Polymer (CFRP) composites have been widely used in aerospace due to their high specific stiffness, strength, and fatigue properties. However, the ambient temperature significantly influences CFRP's mechanical properties and damage evolution, deriving from the temperature effect on the microstructural behavior and the mesoscopic damage evolution. In this study, the temperature-dependent in-plane shear failure behavior of CFRP composites was investigated. In-situ X-ray Computed tomography (CT) tensile experiments of laminates ([45°/-45°]2s) at RT, −100 °C, and 100 °C were carried out to study the in-plane shear failure mechanisms. The 3D fracture morphology was extracted with internal damage evolution process estimated and quantified. The in-situ 3D deformation fields of critical regions were acquired using the Digital Volume Correlation (DVC) method. The effect of temperature on strain field and the correlation between the high-strain region and the fracture location were analyzed. The results revealed the temperature correlations and failure mechanisms of CFRP's mechanical characteristics and internal damage evolution process. Compared to room temperature (RT), the delamination damage area of the sample increased by 80 % at 100 °C. Meanwhile, the shear modulus of CFRP decreases by 78.4 % from −100 °C to 100 °C, and the fracture strain increases by 95 % from RT to 100 °C. The DVC results indicated a dispersion of high-strain regions at −100 °C, reflecting the brittle damage characteristics, while an extensive ductile deformation region was captured at 100 °C. Fiber-matrix debonding is the dominant failure mode of composites under shear loading, whereas significant matrix cracking was observed at −100 °C and partial fiber pullout occurred at 100 °C.

Buckling and failure mechanisms of asymmetric composite sandwich panels subjected to shear loadings

Asymmetric sandwich technology serves as an effective option for introducing loads into sandwich structures in lieu of conventional inserts and joints in lightweight design of thin-walled aeronautical applications. In this study, buckling and failure behaviors are investigated on asymmetric sandwich panels with tapered regions subjected to shearing, where the panels are composed of CFRP laminates as skins and PMI foam as the core. Experimental data and observations are analyzed regarding critical loads, strain distributions, macro- and micro-scaled failure mechanisms. Detailed damage evolution is captured with the developed material and structural models. The influence of the core thickness on stability, load-bearing capacity and failure mechanisms is further investigated. Results show that the shear failure is mainly induced by buckling with an extensive matrix splitting fracture along the diagonal direction for sandwich panels with thin cores. Nonlinearity is observed in strain and deflection responses. Fiber pull-out is formed due to losing support of neighboring matrix. The fracture morphology of fiber breakage roughly appears oblique, indicating that the failure is mainly caused by the combination of tension and shearing. For sandwich panels with a thicker core, i.e. 10 mm and 12 mm, the failure mode switches to pure shear failure. Due to the intensification of tapered edges, local bugling occurs simultaneously with ultimate failure. The ultimate load presents a mounting-up and declining trend with the increase of core thickness, other than a monotonic trend. Conclusively, optimal design parameters exist, such as 10 mm core thickness in the studied case, regarding the load-bearing capacity.

Influence of stacking sequence on the mechanical properties of banana-glass fiber hybrid laminates for automotive shells

The development of composite materials using natural fibers has garnered significant global research interest. Banana fibers, due to their abundant availability and rapid growth cycle, present a promising option for composite material development. When combined with synthetic fibers to form hybrid composites, the resulting material may exhibit significantly improved properties, which is desirable for automotive body manufacturing. The hybrid properties of such composites, however, remain largely unexplored and require thorough evaluation. This study investigates the mechanical performance of hybrid laminated composites fabricated from banana and woven glass fibers bonded with epoxy resin. The composites were produced using non-crimp banana (B) fiber and woven glass (WG) fiber fabrics through the hand lay-up process with four distinct stacking sequences: [WG/B-0⁰/B-0⁰/WG], [WG/B-0⁰/B-45⁰/WG], [WG/B-0⁰/B-60⁰/WG], and [WG/B-0⁰/B-90⁰/WG]. Comprehensive mechanical testing, including tensile, flexural, impact, and hardness tests, along with environmental testing (water diffusion) was conducted in accordance with ASTM standards. Results indicated that the [WG/B-0⁰/B-0⁰/WG] configuration exhibited the highest tensile strength, while the [WG/B-0⁰/B-60⁰/WG] configuration achieved superior flexural strength. The [WG/B-0⁰/B-45⁰/WG] configuration demonstrated the highest impact strength and energy absorption. Rockwell hardness testing revealed that the average hardness numbers for all orientations were approximately 79, which is considered moderate for composite materials. Water absorption tests showed maximum water saturation in [WG/B-0⁰/B-90⁰/WG] of ∼5.5 %, where the other laminates had water saturation between 4.5 and 4.9 %. The microscopic analysis of the [WG/B-0⁰/B-45⁰/WG] laminate suggests fiber-matrix debonding and fiber pull-out as the major cause of failure under tensile and flexural loading. These findings suggest that the hybrid laminated composites, particularly the [WG/B-0⁰/B-0⁰/WG] and [WG/B-0⁰/B-45⁰/WG] configurations, exhibit mechanical properties suitable for automotive body applications.

Electro-mechanical-carrier coupling model of single piezoelectric semiconductor fiber pull-out

Recently, piezoelectric semiconductor (PS) fiber composite materials are widely used in flexible and wearable optoelectronics owing to their unique properties of possessing piezoelectricity and semiconduction simultaneously. It is of great importance to investigate the interfacial characteristics of PS fiber composites in case of interfacial damages between PS fiber and elastic matrix. In this paper, a theoretical model of single piezoelectric semiconductor fiber pull-out is established to study the electro-mechanical-carrier coupling characteristics and interfacial behaviors of fiber/matrix system. Based on the shear-lag theory, the stress transfer relationship between PS fiber and elastic matrix is investigated. Closed form solutions of distributions of relevant electromechanical fields and carrier perturbation are obtained as well. The results show that the change of material parameters and structure parameters can effectively tune the mechanical, electrical and interfacial properties of composite system. In addition, the value of initial carrier concentration which reveals the semiconducting property of PS fiber has a significant influence on the distributions of electromechanical fields. The findings are valuable for adjusting the electromechanical coupling behaviors of PS fiber via specific structure design and material combination in practical applications of piezotronics.