This work investigated the influence of carbon nanofibers (CNFs) and aggregate of CNFs with micro‐sized short carbon fibers (SCFs) on the mechanical, thermal, and fracture properties of epoxy (80%) ‐ Polylactic acid (PLA) (20%) composite. Epoxy‐PLA composite loaded with CNFs (0.2, 0.3, and 0.4 wt.%) and a combination of CNFs and SCFs (0.2 and 0.4 wt.% with equal content of each filler) were manufactured by sonication and manual casting. The synergistic effects of CNFs and SCFs in the epoxy matrix were investigated through mechanical and fracture characterization of nanocomposites. In comparison to CNF‐reinforced nanocomposites, the composites reinforced with integrated multiscale fillers have higher tensile, flexural, impact strength, and fracture toughness. Tensile, flexural and impact strength increased by 17.18–25.72%, 39.24–44.07%, and 39.87–97.05% respectively with the incorporation of both CNFs and SCFs into epoxy‐PLA matrices. An improvement in fracture toughness in the range of 37.93–38.77% was observed in hybrid nanocomposites in comparison to pristine epoxy‐PLA composite. The synergetic mechanism of nano and micro fillers was studied by using the fracture surfaces from tensile tests using scanning electron microscopy. The numerical analysis was also carried out to simulate the effects of filler concentration on the tensile and bending strength of nanocomposites through representative volume element using an ANSYS workbench.

The built-in heterogeneity of the composite laminates has been exploited to tailor the stiffness and strength requirements of modern structures to meet the specific functional demands. However, the non-homogeneity in these composites is the root cause for most of their failures. One of the undesirable consequences of the inherited heterogeneity is the development of cure-induced stresses during composite manufacturing. This work aims to investigate the influence of process-induced stresses on interlaminar radial strength in curved composite laminates. Glass-Epoxy (GE) laminates of two different thicknesses were prepared by hand lamination technique using V-shaped tooling and cured under room temperature. The state of residual stresses in GE laminates is varied by post-curing these laminates at different temperatures. Curved bending strength (CBS) and corresponding interlaminar radial stress for delamination of L-bend laminates were evaluated experimentally using four points bending test. The residual stress profile in each GE laminate is experimentally characterized by employing the Slitting method. The results indicate that the residual stresses have a negligible effect on the critical stress for initial delamination in GE laminates. But, the critical stress for delamination was found to be independent of the laminate thickness and increased with higher curing temperatures. The delaminated surfaces of L-bend laminates were studied using a scanning electronic microscope (SEM). The enhancement in the critical stress due to post-curing can be attributed to the improved fiber-matrix interfacial bonding with higher curing temperature.

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The work presented is an effort to realize the changes occurring for convective coefficients of heat transfer in STHX fitted with inclined baffles. Effort has been undertaken using Fluent, a commercially available CFD code ona CAD model of small STHX with inclined baffles with cold liquid flowing into the tubes and hot liquid flowing in the shell. Four sets of CFD analysis have been carried out. The hot liquid flow rate through shell compartments varied from 0.2 kg/sec to 0.8 kg/sec in steps of 0.2 kg/sec, while keeping the cold liquid flow condition in tube at 0.4 kg/sec constant. Heat transfer rates, compartment temperatures, and overall heat transfer coefficients, for cold liquid and hot liquid, were studied. The results given by the software using CFD approach were appreciable and comparatively in agreement with the results available by the experimental work, which was undertaken for the same set of inlet pressure conditions, liquid flow rates, and inlet temperatures of liquid for both hot and cold liquids. The experimental output results were also used to validate the results given by the CFD software. The results from the CFD analysis were further used to conclude the effect of baffle inclination on heat duty. The process thus followed also helped realize the effects of baffle inclination on convective heat transfer coefficient of the liquid flow through the shell in an inclined baffle shell and tube heat exchanger. The temperature plots for both cold and hot liquid were also generated for understanding the compartmental temperature distributions inclusive of the inlet and outlet compartments. The heat duty for a heat exchanger has been found to increase with the increase in baffle inclinations from zero degree to 20 degrees. Likewise, the convective heat transfer coefficients have also been found to increase with the increase in baffle inclinations.