Tensile Modulus Research Articles

Enhancing Building Energy Efficiency: Leaf Transpiration Inspired Construction of Lignin-Based Wood Plastic Composites for Building Energy Conservation

Incorporating phase change materials (PCMs) into buildings represents a strategic method for reducing reliance on air conditioning systems and decreasing energy usage consequently. Inspired by leaf veins providing channels for transpiration, lignin porous carbon (LPC) was synthesized by chemical activation, showing a vein pore structure. The capillary network system of the LPC provided more channel to adsorb PCM through surface tension and capillary force, achieving an impressive loading capacity of LPC for polyethylene glycol (PEG) (75%), which demonstrated exceptional heat storage capability (133.21 J/g). The lignin-derived wood-plastic composite (L-WPC) was further prepared. With the gradual increase of LPC/PEG, the latent heat of L-WPC increased gradually. The ΔHm, ΔHc and energy storage efficiency of L-WPC-50 (incorporated 50 wt% LPC/PEG-75) reached 39.99 J/g, 42.65 J/g and 90.26%, respectively. The vein pore structure of LPC also provided a thermal conductivity link for L-WPC. L-WPC-50 demonstrated an increased thermal conductivity (0.66 W/(m·K)) and a reduced thermal diffusion coefficient (0.24 mm2/s), optimizing the effectiveness of the phase transition. Additionally, L-WPC-50 displayed satisfactory mechanical properties and dimensional stability, with tensile strength, bending modulus and water absorption thickness swelling rate measuring 14.40 MPa, 1043.72 MPa, and 1.61% respectively. It introduced a feasible approach for utilizing biomass in enhancing building energy efficiency, marking a significant stride towards reducing building energy consumption and advocating sustainable energy practices.

On the essential work of fracture of polylactic acid/thermoplastic polyurethane/halloysite

The goal of this work is to investigate the mechanical and fracture characteristics of polylactic acid (PLA)/thermoplastic polyurethane (TPU)/halloysite (HNT). HNT with three levels (0, 3, and 6 wt.%) and TPU with three levels (10, 20, and 30 wt.%) were used as variables. The investigation of tensile properties revealed contrasting effects of TPU and HNT levels. Increasing TPU content to 30 wt.% led to a decrease in strength and modulus by 36% and 42% in turn, however resulted in a remarkable 338% improvement in elongation at break. Conversely, the addition of 3 wt.% HNT enhanced both tensile strength and modulus, although it caused a reduction in elongation at break. The results concerning fracture properties showed by incorporating TPU up to 30 wt.% EWF ( w e) and non-EWF ( βw p) rose by 459% and 178%, respectively. Additionally, the inclusion of 3 wt.% HNT further elevated the EWF compared to the compound containing 10 wt.% TPU without HNT. Through optimization, the compound with 10 wt.% TPU and 3 wt.% HNT was shown to have the optimum strength, stiffness, and toughness balance.

Valorisation of Agricultural Residue Bio-Mass Date Palm Fibre in Dry-Blended Polycaprolactone (PCL) Bio-Composites for Sustainable Packaging Applications

Abstract Purpose This study experimentally developed and characterised dry-blended Polycaprolactone (PCL)/date palm fibre biodegradable composites for sustainable packaging applications. Date palm fibres are collected from date palm trees as by-products or waste materials. They will be valorised in bio-composite application to promote fibre-based sustainable packaging items over their non-biodegradable synthetic polymer based conventional packaging products. In the dry-blending process, fibre and polymer are mixed with a shear mixer, while, in a melt-blending process, an extruder is used to extrude fibre/polymer blends after applying heating and high shear pressure to melt and mix polymer with fibres. Dry-blending process offers many comparative advantages, such as less equipment, steps, cost, process degradation, energy consumption and hence, lower harmful environmental emissions; while, a proper fibre/polymer mixing is a challenge and it needs to be achieved properly in this process. Therefore, it is important to understand the effects of dry-blending process on manufacturing of PCL/date palm fibre bio-composites for packaging applications, before promoting the dry-blending as a suitable alternative to the melt-blending process. Methods Short chopped fibres were grinded as powders and dry-blended at a ratio of (0 − 10%) (w/w) with PCL polymer using hand and a shear mixer for 30 min, following a compression moulding process to produce bio-composite samples. Tensile, water contact angle, SEM, TGA, DSC and DMA tests and analysis were conducted. The dry-blended PCL/date palm fibre composites’ properties were compared with reported melt-blended samples’ results found in literature. Results Dry-blended samples showed an increase in tensile modulus values (up-to 20%) with fibre inclusion and these values were found close to the melt-blended samples in the literature. Tensile strength and strain values were reduced which could be related to the poor fibre/polymer interface. Fibre addition affected the thermal, thermo-mechanical and crystallisation processes in PCL polymer matrix. Conclusion Dry-blending is capable of producing bio-composites with a very comparable properties to melt-blended counterparts, although a more details study is needed to conduct in future. The results of this study, could be used carefully to design dry-blended PCL/date palm fibre bio-composites for possible packaging applications. The irregular fibre distribution in dry-blended samples could be improved in different ways which should be investigated in future. Graphical Abstract

Analyzing Sustainable 3D Printing Processes: Mechanical, Thermal, and Crystallographic Insights

In this study, the objective was to optimize energy consumption in the fused deposition modeling (FDM) 3D printing process via a detailed analysis of printing parameters. By utilizing thermal analysis techniques, this research aimed to identify lower printing temperatures that could lead to reduced energy usage. Experimental analysis was conducted using a three-level L9 Taguchi orthogonal array, which involved a systematic combination of different extruder temperatures and cooling fan capacities. Furthermore, the research incorporated differential scanning calorimetry (DSC) and X-ray diffraction (XRD) methods to analyze the thermal properties and crystallinity of the 3D-printed specimens. The results indicated that temperature was a key factor affecting crystallinity, with samples printed at 190 °C and 60% fan capacity showing the highest mean values. By conducting a multi-objective desirability analysis, the optimal conditions for maximizing ultimate tensile strength (UTS), tensile modulus, and elongation at break while minimizing energy consumption for PLA 3D-printed samples were determined to be a temperature of 180 °C and a fan speed of 80%.

Ti3C2Tx MXene‐Reinforced Natural Rubber Nanocomposites with Tailored Mechanical and Antiaging Properties

Recently, MXene has been identified as a novel reinforcing material for elastomers. Also, the free‐radical scavenging ability of MXene can be used to improve the antiaging properties of unsaturated elastomers, such as natural rubber (NR). Herein, Ti3C2Tx MXene is incorporated into NR at 0–0.8 wt% to investigate the mechanical and antiaging properties of NR/MXene nanocomposites (NRMX). The resultant nanocomposites with increasing MXene content show improved tensile properties and storage modulus due to the homogeneous distribution of MXene in the nanocomposite, interfacial interaction between MXene and NR molecules, and immobilization of NR polymer chains by MXene. Also, the reduced permanent deformation and hysteresis indicate a lowered heat build‐up with increasing MXene concentration. Finally, the improved mechanical properties retention, increased glass transition temperature, reduced free radical, and –OH and CO formation upon accelerated aging confirm the enhancement of the antiaging properties of NRMX nanocomposites.

Properties of road subbase materials manufactured with geopolymer solidified waste drilling mud

In this study, geopolymer was adopted as an eco-friendly binding material to solidify waste drilling mud to fabricate geopolymer solidified waste drilling mud (GSWDM) as a pavement material in the subbase. Using precursor dosage, Na2SiO3 solution dosage, and slag powder (SP) dosage as parameters of mix proportion, the optimal mix proportions of GSWDM were determined through compressive strength tests. Based on a series of tests of unconfined compressive strength, splitting tensile strength, elastic modulus, and compressive resilient modulus, the effects of the SP percentage in the precursor and curing age on the mechanical properties of GSWDM were analyzed. The results indicated that all the mechanical properties of GSWDM were improved with the increasing SP percentage in the precursor. The 28-day unconfined compressive strength, splitting tensile strength, elastic modulus, and compressive resilient modulus of GSWDM were improved by 80.8%, 56.3%, 65.3%, and 76.72%, respectively, when the SP percentage in the precursor increased from 60% to 100%. A nonlinear increase in the mechanical properties of GSWDM was observed as the curing age increased, with a significant increase in the curing age from 7 days to 14 days and a slight increase in the curing age from 14 days to 28 days. Moreover, the microstructure of GSWDM was denser as the curing age and the SP percentage in the precursor grew. The results of this study verified that GSWDM can be used as construction material for road subbase.

DESIGN AND OPTIMIZATION OF ESCITALOPRAM OXALATE ORAL DISSOLVING FILMS BY RESPONSE SURFACE METHODOLOGY

Objective: To develop and optimise the oral dissolving films of escitalopram oxalate by response surface methodology. Methods: Oral dissolving film compositions were optimized by central composite design. The films are prepared by solvent casting method. Initially, different polymers were screened and based on the results polyvinyl alcohol was selected as polymer, propylene glycol was selected as plasticizer. Concentration of polymer and concentration of plasticizer were fixed as independent variables; tensile strength, percent elongation, elastic modulus and amount dissolved up to 5 min (%D5 min) were taken as responses. Results: The prepared films exhibited good surface characteristics. The thickness, uniformity of weight, surface pH and drug content are within acceptable range. The mechanical properties like tensile strength, folding endurance, percent elongation and elastic modulus were determined. The statistical analysis showed that polymer concentration has a positive effect on disintegration time and the plasticizer concentration has a significant effect on folding endurance. The prepared film relesases nearly 95% at the end of 5 min. The design space was used to optimize the quantities of polymer and plasticizer. The comparison of checkpoint experiment batch responses are corelating with the predicted responses. Conclusion: Escitalopram oxalate oral dissolving films was successfully designed and optimized by response surface method. It was concluded that the prepared films exhibit good mechanical properties and maximum release within 10 min.

Sonochemical synthesis of bioinspired graphene oxide–zinc oxide hydrogel for antibacterial painting on biodegradable polylactide film

Graphene oxide nanosheet (GO) is a multifunctional platform for binding with nanoparticles and stacking with two dimensional substrates. In this study, GO nanosheets were sonochemically decorated with zinc oxide nanoparticles (ZnO) and self-assembled into a hydrogel of GO–ZnO nanocomposite. The GO–ZnO hydrogel structure is a bioinspired approach for preserving graphene-based nanosheets from van der Waals stacking. X-ray diffraction analysis (XRD) showed that the sonochemical synthesis led to the formation of ZnO crystals on GO platforms. High water content (97.2%) of GO–ZnO hydrogel provided good property of ultrasonic dispersibility in water. Ultraviolet-visible spectroscopic analysis (UV–vis) revealed that optical band gap energy of ZnO nanoparticles (∼3.2 eV) GO–ZnO nanosheets (∼2.83 eV). Agar well diffusion tests presented effective antibacterial activities of GO–ZnO hydrogel against gram-negative bacteria (E. coli) and gram-positive bacteria (S. aureus). Especially, GO–ZnO hydrogel was directly used for brush painting on biodegradable polylactide (PLA) thin films. Graphene-based nanosheets with large surface area are key to van der Waals stacking and adhesion of GO–ZnO coating to the PLA substrate. The GO–ZnO/PLA films were characterized using photography, light transmittance spectroscopy, coating stability, scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopic mapping (EDS), antibacterial test and mechanical tensile measurement. Specifically, GO–ZnO coating on PLA substrate exhibited stability in aqueous food simulants for packaging application. GO–ZnO coating inhibited the infectious growth of E. coli biofilm. GO–ZnO/PLA films had strong tensile strength and elastic modulus. As a result, the investigation of antibacterial GO–ZnO hydrogel and GO–ZnO coating on PLA film is fundamental for sustainable development of packaging and biomedical applications.

Influence of intermetallic phase (TiFe) on the microstructural evolution and mechanical properties of as-cast and quenched Ti–Mo–Fe alloys

This study presents the phase analysis, microstructural characteristics, and mechanical property evaluation of the as-cast and quenched Ti–15Mo–xFe alloys with high iron content ranging from 4 to 12 weight percent. All the four alloys were produced in a vacuum-arc melting furnace. Heat treatment in the form of solution treatment was performed in a muffle furnace at a temperature of 1100 °C, with 1-h holding time and the samples were rapidly quenched in ice-brine. X-ray diffractometer (XRD) was used to analyses the phases present in each alloy whereas the optical microscope (OM) was employed to track the microstructural evolution and percentage porosity. The mechanical properties of the alloys were evaluated using a tensile test and compression test method while the micro-Vickers hardness measurements were conducted to evaluate hardness of the alloys. The XRD patterns of as-cast showed peaks belonging to the β and α″ phases and intermetallic B2 TiFe phases. The as quenched XRD peaks illustrated β phase only and Fe·Ti·O2 phases. The as-cast OM micrographs revealed equiaxed β grains, substructures, dendritic structure, and pores forming around the grain boundaries. The quenched OM showed only β equiaxed grains with pores throughout the grain boundaries. The tensile properties such as ultimate tensile strength (UTS) and elastic modulus (E) of as-cast TMF0 were 264 MPa and 79 GPa respectively and these properties changed upon quenching to 411 MPa and 66 GPa respectively. The elastic modulus of TMF1 in as-cast condition was 74 GPa. The UTS and E of TMF1, TMF2, and TMF3 in as-cast and quenched conditions were not recorded due to the fragility of the samples that failed prior to yielding any useful data. The compressive strength in as-cast and in quenched condition decreased with an increase in Fe content. The micro-Vickers hardness in as-cast and quenched conditions showed a similar trend with hardness increasing slightly upon quenching for TMF0, TMF1, and TMF3 alloys but slightly decreased in the case of TMF2. The fracture surfaces of all the as-cast and quenched alloys were comprised of ductile and brittle fracture.

Oxygenated moiety enhanced thermal stabilization, mechanical, and thermomechanical performance of polyacrylonitrile/single wall carbon nanotubes films

AbstractThermo‐oxidative stabilization of polyacrylonitrile (PAN)‐copolymer and PAN/single‐walled carbon nanotube (SWCNT) composite films were studied in the presence of oxygenated entities which may act as an internal oxygen supplier. The oxygenated moiety exhibited dual behavior, enhancing the stabilization efficiency of PAN while also improving the dispersion of SWCNT. The addition of oxygenated moiety treated SWCNT to PAN resulted in a significant reduction in activation energy from 118 kJ/mol to 99 kJ/mol, owing to a more stable oxidation reaction. Thermogravimetric analysis showed weight loss due to stabilization, and polymer chain degradation was lower in treated SWCNT composite films, resulting in an approximate 6% increase in residual weight. Mechanical testing showed a significant increase in tensile strength to 54.15 MPa and tensile modulus to 2.53 GPa with elongation at break of 13.2%, which is attributed to the enhanced interfacial shear strength resulting from the improved dispersion of oxygenated moiety‐treated nanotubes. Furthermore, thermomechanical analysis studies showed improvement in dimension stability with oxygenated moiety treated SWCNT composite films, attributed to better dispersion and increased interfacial strength between the polymer and filler.Highlights Oxygenated entities stabilize PAN and improve SWCNT dispersion. Activation energy was reduced from 118 to 99 kJ/mol with Tween‐80. Residual weight increased by 6% with treated SWCNT in TGA. Improved tensile strength (54.14 MPa), modulus (2.53 GPa) with modified SWCNT. Dimension stability is enhanced by interfacial strength with modified SWCNT.

Study of Mechanical and Surface Properties of Multi-Walled Carbon Nanotube Grafted Flax Fiber and Its Composites

ABSTRACT The modification method of grafting multi-walled carbon nanotubes (MWCNT, abbreviated as CNT in this paper) on the surface of flax fibers was investigated, i.e. CNT were grafted onto the surface of flax fibers by silane coupling agent under the action of ultrasonic waves to form covalent bonding. The tensile strength of CNT grafted flax fiber is 22% higher than that of untreated flax fiber monofilament. The tensile strength of FFRP composites after CNT grafting treatment increased by 14.2%; however, the tensile modulus of single fiber and composites did not show a significant increase, the interfacial shear strength of the fiber-resin is 38.3% higher than that of untreated filament. The improvement of the contact angle after grafting was investigated by observing the surface morphology, and the surface of flax filament was characterized by scanning electron microscopy and atomic force microscopy. Also the elemental changes of the flax single fiber surface before and after the treatment were analyzed using X-ray photoelectron spectroscopy. The results showed that the tensile strength of flax single fibers, its composites, and interfacial shear strength of fiber-matrix was improved after CNT grafting treatment but the increase of modulus was not obvious.

Sweet or bitter? Preliminary data on the biomechanics, physiology, and possible nutritional quality of Cretaceous gymnosperms leaves (Patagonia, Argentina)

This study provides the first data on the relationship between chemical composition and biomechanical/physiological characteristics of foliar gymnosperm compressions from the Lower Cretaceous of Santa Cruz, Argentina. Studied taxa include: Squamastrobus tigrensis, Pseudoctenis ornata, Ginkgoites tigrensis, Ruflorinia orlandoi, and Ptilophyllum micropapillosum. The properties determined include: density, tensile strength (resistance to fracture), tensile modulus of elasticity (stiffness), and leaf mass per area (metabolic cost of tissue construction). They are calculated using a 3D-multivariate model based on data obtained by Fourier transform infrared (FTIR) spectroscopy and trait relationships linking density and the properties mentioned above. Samples have a predominantly aromatic chemical composition with variable carbonyl contents. The chemical groups detected are associated with diagenetically-resistant molecules, possibly including lignins, phenylpropanoids, tannins, and resin-like compounds. The results indicate that these plant taxa may have allocated variable amounts of resources (metabolic costs) for the development of aromatic, biomechanically resistant, and relatively long-lived foliar tissues. The determined chemical, biomechanical, and physiological properties of these leaves suggest their potential as a food source for herbivores. Thus, S. tigrensis leaves might have been unpleasantly astringent, difficult to eat and digest due to their hard tissues, and possibly even hazardous. Conversely, the leaves of G. tigrensis, P. ornata, R. orlandoi, and P. micropapillosum may have been easy to eat due to their softer tissues, offering food of intermediate-high nutritional value. The use of FTIR spectroscopy proves useful to perform detailed and realistic studies on the biomechanics, physiology, and autecology of extinct plants.

Hybridization of woven kenaf and unidirectional glass fibre roving for unsaturated polyester composite

Hybridization of woven kenaf and unidirectional glass fibre roving for unsaturated polyester composite

Investigating of epoxy nanocomposites structure and properties that contain both pristine and aminosilane-treated silicon carbide (SiC) particles

This article presents a methodology for functionalization of silicon carbide (SiC) through chemical modification using γ-aminopropyltriethoxysilane (APTES) and its subsequent dispersion in an epoxy composition. The research revealed that functionalizing SiC particles with γ-aminopropyltriethoxysilane (SiC(APTES)) enhanced their chemical compatibility with the epoxy composition, facilitating the dispersion of SiC particles. Furthermore, it was observed that the functionalization of the filler had a profound impact on the structure, curing kinetics, and physical and mechanical properties of epoxy nanocomposites. The addition of SiC(APTES) into the epoxy composition resulted in a significant reinforcement of the material. Specifically, the flexural stress and flexural modulus of elasticity increased by 179% and 74%, respectively, while the impact strength experienced a remarkable improvement of 462%. Additionally, the tensile strength and tensile modulus of elasticity increased by 83% and 70%, respectively, compared to the epoxy composite without SiC. The application of SiC(APTES) also played a crucial role in initiating the polymerization process through the involvement of reactive amino groups, leading to a reduction in the initial curing temperature and an amplification of the thermal effects of the polymerization reaction. Moreover, the presence of functionalized SiC significantly influenced the structure of the epoxy composite, thereby contributing to its enhanced strength. In summary, the inclusion of SiC in the epoxy composition not only bolstered the material but also improved its thermal stability.

Bioceramic Filled PLA Based Nanocomposites for Biomedical Application: An Experimental Investigation

Orthopaedic implants require innovative biodegradable materials to eliminate the need for a second surgery post-healing and to counteract the stress shielding issues associated with conventional metallic implants. Polylactic acid (PLA) was chosen for its biocompatibility and biodegradability within the human body. Hydroxyapatite (HAP) and eggshell nanoparticles (ESNPs) were selected as bioceramics due to their similarity to the major constituents of human bone. In the present study, ESNPs were prepared through a ball mill. HAP and Mg particles coated with TiO2 (TiO2@Mg) were synthesized through chemical precipitation and the sol-gel technique, respectively. Subsequently, four samples were prepared: PLA/ESNP/Mg (PEM), PLA/HAP/Mg (PHM), PLA/ESNP/TiO2@Mg (PEMT), and PLA/HAP/TiO2@Mg (PHMT) using the solvent casting process. The addition of Mg demonstrated an enhancement of degradation rates, and TiO2@Mg served to eliminate hydrogen release from Mg. The confirmation of synthesized NPs and PLA nanocomposites was validated through Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), and Field-Emission Scanning Electron Microscopy (FE-SEM) analysis. The prepared PEMT and PHMT showed tensile strength (42.70±7.55 MPa and 31.57±3.84 MPa), tensile modulus (1624.49±155.05 MPa and 1674.25±87.04 MPa), and shore D hardness (79.41±2.40 SHN and 77.81±3.18 SHN), respectively. The findings showed that PEMT and PHMT composites exhibited enhanced surface roughness, hydrophilicity, degradation rate, and swelling behavior compared to PEM and PHM samples. Moreover, the viability of MG63 cells cultured in different diluted extracts of both samples reached approximately 80%, indicating no observable cytotoxicity and a hemolysis rate of less than 1.4%, indicating the potential for use in maxillofacial region implants.

Non-destructive strategy to extract sustainable helix and high-strength Musa core fibers for rapid water conduction and evaporation

The reuse and development of natural waste resources is a hotspots and challenges in the research of new fiber materials and the resolution of environmental concern globally. Herein, this study aimed to develop a simple and direct manual extraction process to extract Musa core fibers (MCFs) for rapid water conduction and evaporation. Through simple processes such as ring cutting and stretching, this green and non-destructive inside-out extraction strategy enabled Musa fibers to be naturally and harmlessly degummed from natural Musa stems, with good maintenance of the fiber structure and highly helical morphology. The extracted fibers are composed of regularly and closely arranged cellulose nanofibrils in the shape of ribbon spirally arranged multi-filaments, and the single filament is about 2.65 μm. The high-purity fibers exhibit ultra-high tensile strength under a non-destructive extraction process, and the ultimate tensile strength in dry state is as high as 742.95 MPa. The tensile strength is affected by the number of fiber bundles, which shows that tensile strength and tensile modulus is higher than those of vascular bundle fibers in dry or wet condition. In addition, the MCFs membrane indicates good water conductivity, with a water absorption height of 50 mm for the sample in only 60 s. Moreover, the water evaporation rate of MCFs reaches 1.37 kg m−2 h−1 in 30 min, which shows that MCFs have excellent water conductivity and evaporation rate compared with ordinary cotton fibers. These results indicate that MCFs have great potential in replacing the use of chemical methods to extract fibers from vascular bundles, providing an effective way to achieve sustainability in quick-drying applications, as well as in the sustainable development of natural waste resources.

The moisture absorption of 3D printed short carbon fibre reinforced polyamide

Polymer composites are commonly exposed to humid conditions and undergo reductions in mechanical properties. It is challenging to describe the moisture absorption dynamics of 3D printed parts due to manufacture-induced microstructures. This work investigates the moisture absorption of 3D printed short carbon fibre reinforced polyamide with varied microstructures and resulting influence on mechanical properties. The printed composites have inferior microstructures compared to the polyamide and diffusivity increases with the number of interlayer interfaces by up to 119 % (three times that of compression moulded composite). The microstructure is permanently aggravated by moisture resulting in more significant and irreversible reductions in yield stress (39 to 59 %) and tensile modulus (65 to 79 %) compared to injection moulded samples. Additionally, the shear modulus of printed polyamide and composites decrease by up to 63 % and 74 %, respectively. The results are helpful for prediction, evaluation, and maintenance of 3D printed applications subject to moisture environment.

The fabrication of organic-inorganic hybrid structure towards high mechanical property and improved flame retardancy

In order to design UPR composites with high mechanical property and improved flame retardancy, an organic-inorganic hybrid flame retardant (DA-Si-HNT) was fabricated by grafting silane coupling agent (KH560) and the phosphorus-nitrogen containing structure (DOPA-A, the production of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and adenine) on the surface of halloysite nanotube (HNTs). The UPR/DA-Si-HNT15 composites exhibited significant improvements in tensile strength, tensile modulus, and flexural strength, with respective increases of 65.6%, 140.6%, and 80.2% compared to neat UPR. These enhancements can be attributed to the enhanced compatibility and interfacial force between the flame retardants and the polymer matrix. Meanwhile, it passed the UL-94 V-0 rating at a limiting oxygen index (LOI) value of 34.5%. The peak of heat release rate (PHRR) and total heat release (THR) decreased by 49.5% and 43.5% comparing to that of UPR, indicating a sharp decline in the heat hazard. Moreover, an obvious catalytic carbonization effect in the condensed phase accompanied with moderate gas-phase effect jointly improved flame retardancy of the UPR/DA-Si-HNT15 composites.

Impact of ply stacking sequence on the mechanical response of hybrid Jute-Banana fiber phenoplast composites

Natural fiber composites are increasingly gaining popularity as a cost-effective and environmentally friendly alternative to synthetic fibers. Incorporating a variety of fibers enhances mechanical properties. The arrangement of fibers plays a crucial role in determining the mechanical characteristics of laminate composites. Therefore, the primary objective of this study is to investigate how the stacking order of jute (J) and banana (B) fibers affects the mechanical behaviour of composites made from phenolic resins. Four different fiber mat stacking sequences (J/B/B/J, B/J/J/B, J/B/J/B, and J/J/B/B) were used for developing the eco-fiber composites using the heat-press technique. Several mechanical parameters were assessed, including tensile strength, flexural strength, impact strength, and inter-laminar shear strength (ILSS). The experimental results indicated that the JBBJ composite exhibits superior tensile strength (46.65 MPa) and modulus (993 MPa) compared to the other composites due to the presence of high-strength jute fibers on the surface. Additionally, the flexural strength of the JBBJ composite (87.24 MPa) was found to be noteworthy. It was observed that the impact strength of jute fibers surpasses that of banana fibers. Consequently, the JBBJ composite demonstrates higher values for energy absorption (0.482 J) and impact strength (120 J m−1) compared to the other composites tested. Moreover, the JBBJ composite displays higher inter-laminar shear strength and hardness values compared to BJJB, JBJB, and JJBB by 30%, 35%, and 43%, respectively. Scanning electron microscope microphotographs reveal strong correlational fracture failure mechanisms, indicative of improved mechanical properties in the JBBJ composite. Based on the experimental results, it is evident that the JBBJ composite can be utilized in lightweight applications.

Durability of concrete-encapsulated GFRP bars subjected to seawater immersion

Glass fiber reinforce polymer (GFRP) bars have better durability than traditional steel bars, but there are few studies on their long-term performance in actual service environments especially the marine environment. To investigate the durability of GFRP bars used in cross-sea bridges, this research delves into the performance of 200 such bars, spanning diameters of 10, 12, 16, and 25mm, in an environment that closely mimics real-world conditions. The GFRP bars, encapsulated in concrete, were submerged in seawater solutions, maintained at either room temperature or 60°C, for periods spanning from 0 to 183 days. Then the tensile strength and elastic modulus degradation of GFRP bars were investigated by tensile tests. Scanning electron microscope (SEM) was also used to analyze the micro-degradation mechanism of GFRP bars. In addition, this paper compares the four existing models for predicting long-term mechanical properties of GFRP bars with the experimental data, so as to determine the formulas and methods to be used in the design. The result shows that the elastic modulus of GFRP bars after 183 days of immersion in concrete pore solution was almost unchanged while the tensile strength decreased significantly. Among them, the elastic modulus and tensile strength of 10mm diameter GFRP bars decreased by 5% and 35%, respectively, after 183 days of immersion at high temperatures (60°C). The SEM method revealed that the main cause of such phenomena was the weakening of the bond between the fibers and the matrix, which led to a decrease in the interface properties. Finally, by fitting and comparing the relationship between the test data and the existing prediction models for the long-term mechanical properties of GFRP bars, the residual tensile strength of GFRP bars used in the actual project of Yanzhou Bridge for 100 years was predicted according to the optimal prediction model, i.e. the Bank model, and the results showed that the residual strength of GFRP bars is able to meet the current standard requirements.