Epoxy based sandwich composite using three-dimensional integrally woven fabric as core strengthened with additional carbon face-sheets.

Sandwich composites are three-dimensional (3D) composite structures that offer higher stiffness with overall low density. However, they suffer from low strength; thus, not suited for load bearing applications. In this work, an attempt is made to develop a high strength lightweight sandwich composite suited for load-bearing applications. A sandwich composite based on 3D integrally woven fabric with thickness 3 mm as the core and strengthened with additional 2x2 twill woven carbon fabric face-sheets is reported. The samples were manufactured by wet hand lay co-lamination process using Araldite® LY 1564 epoxy as the matrix polymer and with fiber fraction of 50% by weight. The number of additional carbon face-sheets over the core was varied from two to eight in steps of two. The composite samples were experimented under three-point bending and edgewise compression tests to determine the flexural and compressive strengths in both warp and weft directions. The weft direction samples yielded higher flexural and compressive strengths due to the continuous arrangement of the core pile yarn. The samples with six carbon face-sheets tested along the weft direction offered the highest specific strengths of ~409 kN m/kg and 259 kN m/kg in bending and compression tests. Similarly, the flexural strength was ~340 MPa, and compressive strength was ~217 MPa. A detailed fractography study revealed no core crushing or compression failure of the core during bending tests.

Green synthesis of chitosan-cinnamaldehyde cross-linked nanoparticles: Characterization and antibacterial activity.

Traditional method of chitosan (naturally available abundant biopolymer) nanoparticles synthesis is the ionic cross-linking between chitosan and say, sodium tri-polyphosphate (TPP). These nanoparticles are structurally less stable and are basically obtained viaconversion of chitosan, a pure bio-based material, into a hybrid structure of biopolymer and a synthetic chemical. The present work reports a novel attempt to synthesize antimicrobial chitosan nanoparticles by chemical cross-linking with cinnamaldehyde, another eco-friendly bactericidal agent. The synthesized nanoparticles (size range, 80-150 nm) were analysed for their surface morphology. X-ray diffraction pattern denoted the amorphous characteristics of the formed nanoparticles. The FTIR analysis revealed formulation of chitosan nanoparticles to be based on Schiff reaction between amino group of chitosan and aldehyde group of cinnamaldehyde. NMR analysis also confirmed the formulation of cinnamaldehyde cross-linked chitosan nanoparticles. TGA and DSC were performed to analyse thermal characteristics and stability of prepared nanoparticles. Subsequently, the study successfully indicated that the synthesized nanoparticles exhibit synergistic antibacterial activity (98%) against Staphylococcus aureus (Gram-positive) and (96%) Escherichia coli (Gram-negative) bacteria. The MIC and MBC values were found to be 5 mg/mL and 10 mg/mL, respectively, for both types of bacteria.

Single-walled carbon nanotube incorporated novel three phase carbon/epoxy composite with enhanced properties.

In the present work, single-walled carbon nanotubes were dispersed within the matrix of carbon fabric reinforced epoxy composites in order to develop novel three phase carbon/epoxy/single-walled carbon nanotube composites. A combination of ultrasonication and high speed mechanical stirring at 2000 rpm was used to uniformly disperse carbon nanotubes in the epoxy resin. The state of carbon nanotube dispersion in the epoxy resin and within the nanocomposites was characterized with the help of optical microscopy and atomic force microscopy. Pure carbon/epoxy and three phase composites were characterized for mechanical properties (tensile and compressive) as well as for thermal and electrical conductivity. Fracture surfaces of composites after tensile test were also studied in order to investigate the effect of dispersed carbon nanotubes on the failure behavior of composites. Dispersion of only 0.1 wt% nanotubes in the matrix led to improvements of 95% in Young's modulus, 31% in tensile strength, 76% in compressive modulus and 41% in compressive strength of carbon/epoxy composites. In addition to that, electrical and thermal conductivity also improved significantly with addition of carbon nanotubes.