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This study looks at how incorporating nanofiller into sisal/flax-fibre-reinforced epoxy-based hybrid composites affects their mechanical and water absorption properties. The green Al₂O₃ NPs are generated from neem leaves in a proportion of leaf extract to an acceptable aluminium nitrate combination. Both natural fibres were treated with different proportions of NaOH to eliminate moisture absorption. The following parameters were chosen as essential to achieving the objectives mentioned above: (i) 0, 5, 10, and 15% natural fibre concentrations; (ii) 0, 2, 4, and 6% aluminium powder concentrations; and (iii) 0, 1, 3, and 5% NaOH concentrations. Compression moulding was used to create the hybrid nanocomposites and ASTM standards were used for mechanical testing such as tension, bending, and impact. The findings reveal that combining sisal/flax fibre composites with nanofiller improved the mechanical features of the nanocomposite. The sisal and flax fibre hybridised successfully, with 10% fibres and 4% aluminium filler. The water absorption of the hybrids rose as the fibre weight % increased, and during the next 60 h, all of the specimens achieved equilibrium. The failed samples were examined using scanning electron Microscopic (SEM) images better to understand the composite’s failure in the mechanical experimentations. Al₂O₃ NPs were confirmed through XRD, UV spectroscope and HPLC analysis. According to the HPLC results, the leaf’s overall concentrations of flavonoids (gallocatechin, carnosic acid, and camellia) are determined to be 0.250 mg/g, 0.264 mg/g, and 0.552 mg/g, respectively. The catechin concentration is higher than the phenolic and caffeic acid levels, which could have resulted in a faster rate of reduction among many of the varying configurations, 4 wt.% nano Al₂O₃ particle, 10 wt.% flax and sisal fibres, as well as 4 h of NaOH with a 5 wt.% concentration, producing the maximum mechanical properties (59.94 MPa tension, 149.52 Mpa bending, and 37.9 KJ/m² impact resistance). According to the results, it can be concluded that botanical nutrients may be used effectively in the manufacturing of nanomaterials, which might be used in various therapeutic and nanoscale applications. Full article

The focus of our study is to identify physical properties of different impact-resistant/toughened structural adhesives and identify/develop an elastic-viscoelastic-plastic model as a function of loading rate by using Ludwik-type equations to be able to predict adhesive behavior at higher loading rates and to make cars more crashworthy. For this purpose, we first characterized eight different commercial toughened epoxy structural adhesives to provide detailed information about their constituents using X-ray diffraction (XRD), differential thermal analysis (DTA), thermogravimetric analysis (TGA), scanning electron microscope (SEM) and energy dispersive x-ray spectrometer (EDS). Most (but not all) of the model adhesives contained organic tougheners in the form of carboxyl terminated butadiene acrylonitrile (CTBN) copolymer, as well as polyurethane adducts. The main crystalline inorganic phases were found as calcite (CaCO₃), wollastonite (CaSiO₃) or calcium silicate (CaSiO₃), talc (Mg₃Si₄O₁₀ (OH)₂), zeolite which is an alumina silicate based mineral and has many different elements in its composition (M₂/nO·Al₂O₃·xSiO₂·yH₂O, M can be Mg, Na, Ca, K, Li). The total amount of inorganic fillers was found to be different in each adhesive. Material behavior of the model adhesives were determined via tensile tests and Single Lap Joint (SLJ) tests in shear. Split Hopkinson pressure bar (SHPB) was also used to measure the strain and stress values at higher strain rates in the order of 10² s⁻¹, which is generally encountered in impact related loading situations. Toughness values in the range ~0.5 to ~1.35 MJ/m³ were observed with the model adhesives tested in tensile mode within the ~3 × 10⁻³ to 0.18 m/m/s strain rate range. The softening behavior of the elastic moduli at higher strain rates observed during tensile testing was also observed with SHPB testing. It is remarkable that, overall, the modulus magnitudes seem to be similar between the tensile test and SHPB specimens within this softening range of the initial bilinear elastic behavior observed. When the results from bulk (tensile) and bonded (shear) specimens were compared, it was clearly seen that the toughness responses of the adhesives to (tensile/shear) strain rates in the bulk and bonded forms, respectively, were different, with the bonded shear toughness values in the ~25 to ~120 MJ/m³ range within ~1.25 to ~25 mm/mm/s shear strain range. The model adhesive which included just inorganic fillers had the lowest tensile toughness at the lowest tensile strain rate, but the highest slope in its tensile toughness regression line, exhibited the second highest bonded shear toughness. When tested at the extension rates of 25 mm/min and 100 mm/min in bonded lap shear, the same adhesive exhibited limited interfacial failure areas, however the dominant failure mode was cohesive failure. When the extension rate increased further, transition to interfacial (adhesive) failure was observed revealing that interfacial failures do not necessarily diminish adhesive bond toughness. Our observations point to the fact that cohesive deformation/failure processes indicating interfacial separations, inter-particle interactions as well as polymer matrix deformation in high deformation loading scenario as in bonded shear loadings may provide the highest toughness. Apparently, a large inorganic filler weight fraction is not necessary to obtain high shear toughness in bonded form since the highest bonded shear toughness was obtained with the adhesive which had the least amount of inorganic fillers among the model adhesives with 14.72 wt %. Full article