Hybrid Fiber Research Articles

3D mesoscale discrete element modeling of hybrid fiber-reinforced concrete

To investigate the relationship of hybrid fiber volume friction on the mechanical properties and failure mechanisms of steel-polypropylene hybrid fiber reinforced concrete (HFRC), the study constructs a three-dimensional, five-phase mesoscale model using the Discrete Element Method (DEM), which consists of mortar, coarse aggregate, polypropylene fibers (PPF), steel fibers (SF), and the interfacial transition zone (ITZ). The axial compression test results of twelve cubic specimens with four different hybrid fiber combinations (0.5 % SF + 0.05 % PPF, 0.5 % SF + 0.1 % PPF, 1.0 % SF + 0.05 % PPF, 1.0 % SF + 0.1 % PPF) were used to validate the model’s accuracy, examining the influence of fiber content on the mechanical performance and cracking features of HFRC. Directed by experimental mix proportions, the model employed cluster particle modules with realistic aggregate geometries and randomly distributed SFs to simulate concrete microstructure. Utilizing the Flat-Joint Model (FJM) in DEM software (PFC3D), two contact models are developed: one FJM with bi-nonlinear softening segments to describe the ITZ between steel fibers and PPF-reinforced mortar (PFRM); another FJM considering the volume fraction effect of SF to describe the ITZ between coarse aggregate and FRM. Both models were experimentally validated, proving their accuracy. The results indicate that the established DEM model can accurately simulate the stress-strain relationship and failure modes of HFRC under compression. The hybrid fibers increased the compressive strength by 2.13–17.33 % and reduced the cracking strain by 5.25–9.33 %. Furthermore, the computational findings reveal that PPF primarily affects the crack initiation phase, while SF plays a significant role in the overall crack propagation stage. This discovery holds significant importance for understanding and optimizing the structural performance of HFRC.

Mechanical properties and damage modeling of hybrid fiber reinforced concrete under freeze-thaw cycles

This study aimed to investigate the mechanical properties of steel-polyacrylonitrile hybrid fiber reinforced concrete and its durability under freeze-thaw damage. Firstly, the mechanical properties of hybrid fiber reinforced concrete were studied by compressive strength and flexural strength tests. Secondly, with the help of rapid freeze-thaw test, the variation rules of mass loss rate and relative dynamic elastic modulus were characterized. Based on the test results and freeze-thaw damage theory, the evolution equation of freeze-thaw damage of hybrid fiber reinforced concrete based on Weibull distribution was established. The results show that the enhancement effect of hybrid fiber on the mechanical strength of concrete is better than that of single mixed fiber, especially in the improvement of flexural strength; Accordingly, compared with the single mixing of steel fibers or single mixing of polyacrylonitrile fibers, hybrid fibers are more effective in improving the durability of concrete against freezing and this improvement effect increases with the increase of steel fiber content; The freeze-thaw damage model of Weibull distribution can better reflect the freeze-thaw damage process of hybrid fiber reinforced concrete .Through the freeze-thaw damage evolution curve, it can be found that after 500 freeze-thaw cycles, the freeze-thaw damage degree of the hybrid fiber reinforced concrete with different steel fiber content has been very close, which means that the influence of steel fiber content on the freeze-resistant performance of hybrid fiber reinforced concrete will be limited. This study provides a theoretical basis and technical basis for the design of concrete structures in alpine regions.

An experimental study on mechanical and fracture characteristics of hybrid fibre reinforced concrete

This research investigates the impact of polypropylene and glass fibres on the mechanical and fracture properties of concrete. Prepared specimens consisted of plain concrete (PC), polypropylene fibre-reinforced concrete (PPFC), glass fibre-reinforced concrete (GFC), and polypropylene-glass hybrid fibre-reinforced concrete (HFC). The specimens were evaluated for their mechanical and fracture properties. PPFC indicated a little drop in compressive strength and GFC demonstrated a moderate gain; HFC, as a result of synergistic effect of polypropylene fibre and glass fibre, demonstrated a marginal increase in compressive strength. The substantial increase in flexural and split tensile strength was observed in all the fibre reinforced concrete specimens, compared to plain concrete. The incorporation of polypropylene fibre yields the greatest improvement in concrete's split tensile strength, whereas the incorporation of glass fibres results in the highest improvement in concrete's flexural strength. The fracture characteristics also showed significant improvement in fibre incorporated concrete. The coaction of polypropylene and glass fibre in HFC resulted in 30.1 % increase in first crack strength and a threefold rise in flexural toughness compared to plain concrete. Compared to plain concrete, the critical crack tip opening displacement of PPFC, GFC, and HFC increased by 43.90 %, 26.25 %, and 39.02 %, while the critical stress intensity factor increased by 15.73 %, 13.10 %, and 14.22 %. Subsequently, it was determined that the fracture energies of PPFC, GFC, and HFC were 3.35, 1.78, and 2.50 times those of PC, respectively. In addition, the synergistic effect of polypropylene and glass fibres in concrete was studied, and it was found that when used together, the fibres have better fracture characteristics than when used alone, without compromising mechanical strength. Subsequently, different bilinear softening curves were used to predict fracture parameters, and it was seen that the computed values agreed with the experimental values.

3D printing hybrid-fiber reinforced engineered cementitious composites (3DP-HECC): Feasibility in long-open-time applications

Hybridization of multi-scale and multi-functional fibers to generate Hybrid-fiber Engineered Cementitious Composites (HECC) offers a promising approach for enhancing ECC in 3D printing (3DP), addressing limitations such as restricted build-up height and operation time. This study strategically combined polyethylene (PE) fiber (1.0 %), steel fiber (0.5 %) and cellulose filaments (CF) at various dosages (0–0.25 %) to investigate the evolution of rheological behavior over different time intervals (0–60 min with 15 min intervals) and optimize the printability of 3DP-HECC with long-open-time. Incorporating of CF or steel fiber enhanced static yield stress, dynamic yield stress and plastic viscosity, particularly benefiting buildability with steel fiber inclusion. Moreover, CF integration effectively moderated the growth rates of static yield stress and dynamic yield stress while maintaining thixotropic index, mitigating extrusion defects and extending operation time to 60 min for structure-level printing. Conversely, steel fiber exhibited contrasting behavior. By integrating the evolution of time-dependent rheological parameters and practical printing observations, an optimum CF dosage of 0.20 % was identified for high-quality 3DP with superior build-up layers. Finally, a fiber hybridization strategy was suggested to optimize the printability of 3DP-HECC, providing theoretical guidance for implementing high-quality applications with extended operation time.

Fatigue performance and damage of partially prestressed concrete beam with fiber reinforcement

Ordinary concrete exhibits low strength and a propensity for cracking. Carbon fibers and aramid fibers, as materials characterized by high strength, high toughness, and excellent fatigue resistance, can effectively limit the propagation of micro-cracks and enhance the strength of concrete. To explore the influence of different fiber types on the fatigue performance of prestressed concrete beams, this study initiates from the perspective of beam components. Employing a combination of experimental research and theoretical analysis, it conducts bending and constant-amplitude fatigue tests on 12 prestressed concrete beams with various fiber types. Based on the stiffness of the beam section and residual strain, the damage evolution patterns of the tested beams were described. The results indicated that the utilization of fiber-reinforced concrete significantly improves the fatigue life and residual bearing capacity of the beam components. Specifically, the residual bearing capacities of beams reinforced with carbon fibers, aramid fibers, and hybrid fibers increased by 58.6 %, 49.5 %, and 64.9 %, respectively. The analysis revealed that residual strain is a suitable indicator for describing fatigue damage in specimens and recommends prioritizing the concrete residual strain index. These findings provided a theoretical basis for the application of fiber-reinforced concrete in practical engineering projects and lifespan assessment.

Fracture properties and self-healing assessment of superabsorbent polymer modified hybrid fibre concrete

The aim of this study is to develop durable concrete with improved crack repair abilities by using a superabsorbent polymer (SAP). The experimental program investigates the effect of four different SAP concentrations, viz., 0.2 %, 0.4 %, 0.6 %, and 0.8 %, by weight of cement, on the properties of hybrid fibre concrete (HFC). The findings reveal that the mechanical properties, namely compressive strength, flexural strength, and tensile strength, are nearly equivalent to HFC up to 0.4 % SAP concentration. Specimens exhibit a decrease of 9.29 % and 17.3 % in compressive strength for SAP concentrations of 0.6 % and 0.8 %, respectively, in comparison to the HFC. Conversely, adding SAP to HFC specimens results in an increase in flexural toughness and fracture energy, with a maximum increase of 56.80 % and 55.13 % at a 0.4 % SAP concentration, respectively. Microstructural study reveals that SAP did not undergo any chemical reactions with the hydration products of concrete. However, because of SAP's internal curing effect, the hydration improved, especially in the vicinity of SAP particles. Thermogravimetric analysis (TGA) demonstrates that SAP concentration increases the degree of hydration proportionately. Crack healing efficiency was evaluated in terms of crack closure ratio and strength recovery ratio. The results indicate that cracks of up to 465 μm were completely sealed for all SAP concentrations studied. Furthermore, a 93 % and 90 % recovery in compressive strength was observed for 0.2 % and 0.4 % SAP-incorporated HFC specimens, respectively, after 28 days of healing. Conclusively, the addition of SAP at lower concentrations, in addition to crack-healing, enhances the fracture characteristics of concrete. It is reckoned that the current investigation will help in developing durable concrete with improved crack repairing abilities.

Identification of Effects of Parylene-C Coating on Electrospun Fibers

As various healthcare technologies such as regenerative medicine, precision medicine, and alternative approaches to animal testing develop, the interest in the use and application of nano- and microfibers is steadily increasing. In this study, the effect of parylene-C coating on electrospun fibers was investigated, and a pattern coating method was developed to expand the potential utilization of parylene-C-coated electrospun fibers. An SEM analysis demonstrated that parylene-C was successfully deposited on the electrospun fibers without any failure such as pinholes or air bubbles. Biocompatibility was investigated through cell tests, which indicated that the coated fibers were non-toxic and supported cell growth well. Tensile tests demonstrated a significant increase in the elastic modulus of the parylene-C-coated fibers, with it nearly quadrupling compared to the original PCL fibers, and the fracture strength almost doubled. At the same time, hydrophobicity was well maintained without any statistically significant changes. In particular, a non-adhesive magnet–metal masking was proposed in order to selectively coat the electrospun fibers with parylene-C with a specific pattern. Furthermore, it was presented that the magnet–metal mask-based coating electrospun nanofibers with parylene-C could be used in the fabrication of hybrid fibers composed of different diameters and materials.

Understanding Toughening Mechanisms and Damage Behavior in Hybrid-Fiber-Modified Mixtures Using Digital Imaging

Pavement cracking is a primary cause of early damage in asphalt pavements, and fiber-reinforcement technology is an effective method for enhancing the anti-cracking performance of pavement mixtures. However, due to the multi-scale dispersed structure of pavement mixtures, it is challenging to address cracking and damage with a single fiber type or fibers of the same scale. To investigate the toughening mechanisms and damage behavior of hybrid-fiber-modified mixtures, we analyzed the fracture process and damage behavior of these mixtures using a combination of basalt fiber and calcium sulfate whisker hybrid fiber modification, along with semicircular bending tests. Additionally, digital imaging was employed to examine the fracture interface characteristics, revealing the toughening mechanisms at play. The results demonstrated that basalt fibers effectively broaden the toughness range of the modified mixture at the same temperature, reduce mixture stiffness, increase residual load at the same displacement, and improve crack resistance in the mixture matrix. While calcium sulfate whiskers enhanced the peak load of the mixture, their high stiffness modulus was found to be detrimental to the mixture’s crack toughness. The fracture interface analysis indicated that the three-dimensionally distributed fibers form a spatial network within the mixture, restricting the relative movement of cement and aggregate, delaying crack propagation, and significantly improving the overall crack resistance of the mixture.

Capacity reinstatement of reinforced concrete one-way ribbed slabs with rib-cutting shear zone openings: Hybrid fiber reinforced polymer/steel technique

This study examined the use of two configurations for capacity restoration of reinforced concrete (RC) one-way ribbed slabs containing openings in shear zones. Four specimens of half-scale comprised three ribs in addition to a top RC slab. The test plan included a control specimen without openings, one with two rib-cutting shear openings, one strengthened using a blend of carbon FRP (CFRP) composites and steel plates, and another retrofitted with a combination of glass FRP (GFRP) composites and steel plates. The two strengthening schemes were found successful at fully restoring the ultimate load of the specimens. The ultimate load of specimen strengthened using the hybrid CFRP/steel system exceeded the control slab without openings by 52%. However, in the other specimen where a mix of steel plates and GFRP sheets was used, the load capacity was only 5% less than the control specimen without openings. While the dissipated energy and stiffness were reinstated and improved for the hybrid CFRP/steel system, they were partially restored for the GFRP/steel system. Additionally, a prediction approach was developed to estimate the maximum load of the slabs. The developed approach considered potential shear and flexural modes of failure, providing close predictions of the ultimate load.

Prediction of the failure behavior of pseudo-ductile composites using a multi-scale finite element model

The hybridization technique has recently been used to produce a new generation of composites called pseudo-ductile composites, which have shown higher failure strain compared to conventional composites, minimizing the risks of the occurrence of a catastrophic failure. The pseudo-ductility behavior in these composites is obtained by hybridization of fibers with high and low failure strains. In this study, a multi-scale finite element (FE) model incorporating micro and macro-scales is proposed to predict the failure behavior of pseudo-ductile composites. A micro-scale representative volume element (RVE), consisting of randomly distributed fibers, was generated using a Python code. Periodic boundary conditions (PBCs) were applied to the RVE generated with a periodic geometry. To account for fiber failure and ply fragmentation, the tensile strength of fibers was distributed based on the Weibull distribution function and a user-defined UMAT subroutine was developed. Tensile loading was then applied to the RVE to simulate the composite’s mechanical behavior. For validation, an RVE was developed based on experimental data from recent research on thinply and conventional thickness composites. Numerical results were compared to experimental data, demonstrating acceptable agreement. In the final step, following a sequential multi-scale modeling approach, a macro-scale model was constructed based on the outputs of the micro-scale model subjected to tensile and shear loads. The results were compared with experimental data, revealing good agreement. The proposed model allows for the optimization of pseudo-ductile composite structures to achieve a desired set of mechanical properties without the need for conducting extensive experimental material tests.

Synthesis and characteristics of natural fiber reinforced nano hybrid composite – an experimental study

Abstract Recently, research on natural hybrid composites has occupied a significant role in the materials science sector. Due to the low density, high specific strength, dimensional stability, and biodegradability, natural fiber composite has become a predominant research area. The present study deals with the fabrication of a jute–banana fiber hybrid composite using the hand layup method with compression molding. A fixed concentration of 5 % carbon nanotubes (CNT) is included over the fiber surfaces as an additional reinforcement material to improve their thermal and electrical conduction properties. The prepared composite material is subjected to different fiber loading (0, 10, 20, and 30 wt.%) with jute and banana weight ratios of 1:1, 1:3, and 3:1. The investigation is conducted for testing the physical, mechanical, and thermal properties of the prepared composites along with morphological studies. Final results revealed a maximum longitudinal tensile strength of 68.8 MPa, 67.0 MPa, and 86.7 MPa and the maximum transverse tensile strength of 41.2 MPa, 40.5 MPa, and 48.0 MPa at 30 wt.% with respective fiber ratio of 1:1, 1:3, and 3:1. The maximum longitudinal flexural strength of this hybrid composite is noticed as 94 MPa, 90 MPa, and 103 MPa for the weight ratio of 1:1, 1:3, and 3:1. Higher impact energy is obtained for the composition ratio of 1:3 (JBC 1:3) which has more banana fiber than the other two. A new attempt at adding carbon nanotubes has improved their thermal conductivity compared to regular composites of jute–banana.

Experimental study on the mechanical properties and impermeability of basalt-PVA hybrid fibre reinforced concrete

Numerous studies have indicated that the incorporation of chopped fibres can significantly improve the mechanical properties and durability of concrete. To further explore the effect of chopped basalt fibres, PVA fibres and their hybrid fibres on the improvement of concrete mechanics and impermeability, mechanical property and impermeability tests of chopped basalt fibres/PVA fibres of different lengths and hybrid ratios mixed with concrete of disparate benchmark strengths were carried out. By comparing the characteristic values of each group and their variation rules, the optimal length and hybrid ratio of the fibres were determined. The results show that the enhancement effect of chopped basalt fibres of different lengths on the mechanical and impermeability properties of concrete is different, showing a trend of first increasing and then decreasing. The enhancement effect of chopped basalt fibres on the mechanical and impermeability performance of concrete with different benchmark strengths is better than that of PVA fibres. Compared with those of the C30 plain concrete, the mechanical and impermeability properties of the chopped basalt-PVA hybrid fibre concrete significantly improve to varying degrees. When the proportion of chopped basalt fibres is greater than or equal to the proportion of PVA fibres, a positive hybrid effect on the mechanical and impermeability performance of concrete with the same benchmark strength occurs. With increasing benchmark strength, the enhancement effect of the two types of fibres on the mechanics and impermeability of the concrete decreases. The attenuation range of PVA fibres is greater than that of chopped basalt fibres, and even a reduction in the mechanical and impermeability properties of concrete occurs. This results in the enhancement effect of chopped basalt-PVA hybrid fibres on concrete mechanics as well as a significant decrease in the impermeability. The improvement rates of the compressive performance and impermeability of concrete by a single or a hybrid of the two fibres are highly similar, and the enhancement effect of the fibre compressive performance is significantly greater than that of the impermeability.

A study on the mechanical performance, shrinkage and morphology of high-performance fiber reinforced concrete with varying SCMs and geometry of steel fibers

This paper investigates the effects of silica fume (SF) and metakaolin (MK) as cement substitutes on the mechanical properties, shrinkage, and toughness performances of steel fiber reinforced concrete (SFRC). Initially, a reference concrete mix with a water-to-binder ratio of 0.4 is blended with different volume fractions of steel fibers with varying geometries (crimped steel and straight steel), both individually and in combination, to examine their mechanical properties. Also, the possible influence of pozzolans on the variation of drying shrinkage and flexural toughness of hybrid steel fiber reinforced concrete (Hy-SFRC) was evaluated. An increase in workability was observed as a result of hybridization of steel fibers. Pozzolanic steel fiber reinforced concrete (SFRC) exhibited a more significant enhancement in compressive strength and flexural strength compared to non-pozzolanic SFRC. The hybrid combination of CS 1.5 % and SS 0.5 % was found to be the best in terms of mechanical properties. The addition of SF and MK reduced the shrinkage strain by up to 50 % compared to the reference mix. The flexural toughness values for both binary and ternary pozzolanic Hy-SFRC were notably higher than those for non-pozzolanic Hy-SFRC, indicating a stronger bond between the fibers and the matrix. Hy-SFRC containing a ternary pozzolanic mix of SF 10 % and MK 10 % gave the best results in flexural toughness. The results were consistent with morphology analysis, which revealed an increase in hydration products at the interface between the aggregate and concrete matrix, as well as between the steel fiber and concrete matrix, due to the ternary blending of SF and MK.

Investigation of Kevlar and Basalt fiber hybridization on vibrational characteristics of composite plates

The study of vibrational characteristics of plates, specifically composite plates, has gained significant importance in contemporary and cutting-edge industries involved in industrial plate manufacturing. This paper investigates the vibrational behavior of composite plates made of Kevlar, basalt, and a hybrid combination of Kevlar and basalt fibers embedded in an epoxy matrix. The investigation was carried out through experimental methods utilizing the D3560 analyzer device. Furthermore, in order to ensure the reliability of the findings, the experimental data were simulated and compared with finite element modeling using the ABAQUS software. The results demonstrate that hybridizing the fibers in the first and second modes leads to an increase in the natural frequency compared to pure Kevlar, while the hybridization effect compared to pure basalt has a negative impact. However, in the third to fifth modes, the layered arrangement shows an increase in the natural frequency compared to pure Kevlar and pure basalt. The experimental results obtained and the simulated ones in the finite element software exhibit a consistent trend.

Enhancement of electrical conductivity and band gap of epoxy/MWCNT/GNP/glass fibers hybrid materials

Polymer composites containing carbon nanoparticles have attracted considerable attention because of their special functional characteristics. Characterization of optical and dielectric characteristics was done. To comprehend the impact of nanofillers, dielectric characteristics, UV–Vis spectroscopy, XRD, and Fourier transform spectroscopy were employed. The role of carbon fillers on metrics, such as band gap energy, absorption coefficient, and dielectric characteristics of nanocomposites was examined to differentiate between the effects of nanofillers. The AC conductivity is explained following the classical percolation theory. The percolation threshold is discovered to be 1 wt.% of a hybrid system of nanofillers consisting of graphene nanoplatelets (GNPs) and multi-walled carbon nanotubes (MWCNTs). The presence of carbon nanofillers significantly enhances the electrical conductivity of the nanocomposites. The optical band gap energy of nanocomposites was obtained from the Tauc method. The study establishes the relationship between band gap energy and AC conductivity using Tauc’s relation and Jonscher’s power law. The results show that the band gap energy of composites decreases with the addition of hybrid nanofillers, with values observed at 2.65 eV and 2.95 eV, while without fillers of 3.1 eV and 3.05 eV attributed to increased localized states within the bandgap. Composites with nanofillers show an AC conductivity of 1.86 S/m at 1 wt% of nanofillers, compared to 1.52 × 10−6 S/m and 1.09 × 10−6 S/m for composites without nanofillers. The UV–Vis spectra reveal a significant blue shift in the absorption peak when the weight percentage of carbon nanoparticles is increased. The findings of this study point toward the possibilities of the development of novel nanocomposites with enhanced performance for electronics and energy storage.

Optimization of Hybrid Fiber-Reinforced Concrete for Controlling Defects in Canal Lining.

Losses in irrigation canals occur during the process of water transportation. In irrigation conveyance water losses, seepage loss is the main contributor to total water loss. The most problematic factors are cracks and settlement of the lined canal in canal lining structures. Water loss occurs in earth channels, mainly due to erosion and the permeability of the material. The concrete, as it does not present cracks, will have a less impermeable layer. Usually, seepage loss comprises 20-30% of the total water loss, and it can be reduced to 15-20% with canal linings. By enhancing the flexure and split tensile strength of concrete, the rate of cracking in the canal lining can be controlled. Concrete's split tensile strength is one of the most important factors in crack control. The behavior (compressive, flexural, and split tensile properties, water absorption, linear shrinkage mass loss, etc.) of hybrid polypropylene and jute fiber-reinforced concrete (HPJF-RC) for the application of canal linings was studied. In this experimental work, a total of nine mixes were made with different lengths and contents of hybrid polypropylene and jute fiber-reinforced concrete (HPJF-RC) and a control mix. The SEM analysis was performed to explore the hybrid fiber cracking mechanism and the bonding of fibers with the concrete. The crack arresting mechanism of the HPJF-RC will help to reduce water losses in concrete canal linings. With this modern material, the water losses in canal linings can be minimized. The results of this experimental work would be helpful as a reference for both industry experts and academic researchers interested in the advancement of HPJF-RC composites.

Hybrid fiber reinforced ultra-high performance coal gangue geopolymer concrete (UHPGC): Mechanical properties, enhancement mechanism, carbon emission and economic analysis

The low carbonization of ultra-high performance concrete (UHPC) has become a hot topic for sustainable development in the construction industry. Calcined coal gangue was used as aggregate and binder to prepare ultra-high performance coal gangue geopolymer concrete (UHPGC) in this paper. The hybrid reinforcement effect of steel fibers, calcium carbonate whiskers (CW), and carbon nanotubes (CNTs) on UHPGC was studied in the experiment. The results indicated that when the mixing ratio of straight steel fibers and hooked-end steel fibers was 2:1, the 28 d-compressive strength of UHPGC reached 145.94 MPa. However, excessive hooked-end steel fibers deteriorated the reinforcement effect of adjacent fibers and reduced the mechanical properties of UHPGC. CW and CNTs had a more significant improvement in the flexural properties of UHPGC. The bridging effect of CNTs and CW dispersed the stress on the matrix and delayed the formation and development of micro-nano cracks. Meanwhile, CNTs and CW improved the fiber bridging energy dissipation, thereby improving the flexural properties of UHPGC. The UHPGC had the highest flexural strength and flexural deflection of 13.59 MPa and 4.12 mm, respectively. The UHPGC prepared in this paper had lower carbon emissions and economic costs compared to traditional UHPC. Overall, this study provided valuable references for the resource utilization of coal gangue and the multi-scale strengthening and toughening of UHPGC.

Hybrid Fibers with Subwavelength-Scale Liquid Core for Highly Sensitive Sensing and Enhanced Nonlinearity.

Interest grows in designing silicon-on-insulator slot waveguides to trap optical fields in subwavelength-scale slots and developing their optofluidic devices. However, it is worth noting that the inherent limitations of the waveguide structures may result in high optical losses and short optical paths, which challenge the device's performance in optofluidics. Incorporating the planar silicon-based slot waveguide concept into a silica-based hollow-core fiber can provide a perfect solution to realize an efficient optofluidic waveguide. Here, we propose a subwavelength-scale liquid-core hybrid fiber (LCHF), where the core is filled with carbon disulfide and surrounded by a silicon ring in a silica background. The waveguide properties and the Stimulated Raman Scattering (SRS) effect in the LCHF are investigated. The fraction of power inside the core of 56.3% allows for improved sensitivity in optical sensing, while the modal Raman gain of 23.60 m-1·W-1 is two times larger than that generated around a nanofiber with the interaction between the evanescent optical field and the surrounding Raman media benzene-methanol, which enables a significant low-threshold SRS effect. Moreover, this in-fiber structure features compactness, robustness, flexibility, ease of implementation in both trace sample consumption and reasonable liquid filling duration, as well as compatibility with optical fiber systems. The detailed analyses of the properties and utilizations of the LCHF suggest a promising in-fiber optofluidic platform, which provides a novel insight into optofluidic devices, optical sensing, nonlinear optics, etc.

Comparison of the dynamic characteristics of GFRP, CFRP, and hybrid composites subjected to repeated low‐velocity impact

AbstractThe current study used the vacuum‐assisted hand lay‐up method (VAHLM) to manufacture glass fiber‐reinforced polymer (GFRP), carbon fiber‐reinforced polymer (CFRP), and glass/carbon fiber‐reinforced hybrid composites to examine the influences of fiber materials and hybridization on the repeated low‐velocity impact (LVI) responses. In this regard, the manufactured composites were exposed to repeated LVI loading at 3 m/s under 25.2 J impact energy, and thus dynamic characteristics such as total impulse, contact/bending stiffness, interaction time, peak force/displacement, and absorbed‐rebounded energies depending on the impact number were acquired. LVI tests were continued until penetration was observed in the composites, at which point the penetration threshold numbers for each composite type were acquired. Furthermore, the macro‐scale damage analyses depending on the impact number were gradually examined, and the impacts of hybridization and fiber material on the damage mechanisms were determined. The study found that GFRP, hybrid and CFRP composites had the highest impact resistance, respectively, and that glass fiber‐reinforcement is well‐suited for applications that require higher impact resistance. When the average penetration threshold numbers for the composites were examined, it was observed that GFRP composites had approximately five times higher penetration threshold numbers than CFRP composites and that hybrid specimens exhibited similar properties to CFRP composites in terms of impact resistance. This scenario was linked to the various deformation capabilities of glass and carbon fibers, and it was concluded that the high‐deformation capability of the fibers improved the penetration threshold numbers.Highlights Effects of hybridization and fiber material on LVI responses were examined. Fiber material has a significant influence on impact resistance. Penetration threshold number can be associated with the fibers' strain capability. The adhesion factor plays an active role in the damage of hybrid specimens.

Viscoelastic Performance of Bagasse/Glass Fiber Hybrid Epoxy Composites: Effects of Fiber Hybridization on Storage Modulus, Loss Modulus, and Damping Behavior

Abstract This study aimed to investigate the viscoelastic properties of bagasse/glass fiber multilayered hybrid reinforced epoxy composites, focusing on how fiber hybridization affects dynamic mechanical performance. Epoxy composites with various layering sequences, including all-glass (AG), all-bagasse (AB), bagasse-glass-bagasse (BGB), and glass-bagasse-glass (GBG), were fabricated and analyzed using dynamic mechanical analysis (DMA) to measure storage modulus (E'), loss modulus (E''), and damping factor (tan δ). The results showed that hybrid composites (GBG and BGB) experienced a decrease in storage modulus by approximately 25% compared to AG, indicating enhanced polymer molecular chain mobility and improved interfacial adhesion between bagasse fibers and the epoxy matrix. The glass transition temperature (Tg) was slightly lower in hybrid composites, with GBG at 61 °C and BGB at 60 °C, compared to 62 °C for AG. In terms of energy dissipation, AG exhibited the highest loss modulus peak at 62 °C, while AB showed the lowest with a Tg at 53 °C. The damping factor analysis revealed that AB had the highest damping peak (tan δ = 0.9) at 61 °C, although this occurred at a lower temperature than the AG composite (tan δ = 0.7 at 76 °C). These findings suggest that bagasse and glass fiber hybrid composites offer tailored viscoelastic properties, making them suitable for applications in automotive components, aerospace structures, and sports equipment.