Short Fibre-Reinforced Flowable Composites for Dental Restorations: Computational and Experimental Study

As the demand for dental composite restorations has grown over the past decade, extensive research has taken place to find materials that match the properties of natural teeth. Though resin-based dental composites have proven to bond strongly to the enamel with minimal work, they lack the mechanical properties of conventional restorative materials. To address this, studies on dental restorations using low aspect ratio fibre-reinforced composites (FRC) are performed which require extensive material characterisations. Therefore, this thesis primarily aims to develop novel flowable dental composites by incorporating short S-2 Glass fibres through a comprehensive examination of how material properties affect dental restoration behaviour in oral environment. The research focuses on developing a dental composite with increased longevity and physico-mechanical performance. Initial parametric computational investigations analysed the dynamic response of dental composites' mechanical and thermal properties in an oral environment. Subsequently, the study extended to examine the effect of polymerisation shrinkage (PS%) and elastic modulus (E) on a restored molar tooth with a pre-existing crack. The principal stress values and their locations at the restoration-enamel junction (REJ) and restoration are identified during analysis. The optimum values for E, coefficient of thermal expansion (CTE) and PS% are established for improved stress-dissipating characteristics. Contact angle experimental tests using the Washburn method were conducted in the next phase of the study to optimise silane coupling agent (SCA) with varying concentrations on S-2 Glass fibres to improve interfacial mechanical properties (flexural strength and fracture toughness) and physical properties (hydrolytic degradation). Based on the optimised SCA and weight percentages (wt.%) concentration, the study further explores the effect of S-2 Glass fibres with a combination of fibre lengths and wt.% on dental composites' mechanical and physical properties. The increase in fibre wt.% generally enhances load-bearing capacity; however, this study reveals a negative impact on FRCs' physico-mechanical behaviour due to the reduction in the degree of conversion. The hybridisation of fibre lengths displays a delicate balance, as reduced load transfer may compromise the physico-mechanical properties of FRCs. The computational optimisation findings from this study enable dental clinicians to select the most appropriate composite restoration to repair large cavities. The experimental optimisation study also highlights the adverse effects of increased SCA functionalisation on S-2 Glass fibres and increased wt.% concentration of S-2 Glass fibre in FRCs. In conclusion, through established computational and experimental methods, a novel dental composite with improved mechanical and physical properties is developed, which significantly reduces catastrophic failures and extends the restoration lifespan

DESIGN AND FABRICATION OF LOW COST OPEN CIRCUIT SUBSONIC WIND TUNNEL

A subsonic wind tunnel is a device used to create a fast stream of air through a test area in which an object is kept. This paper will focus primarily on the fabrication process of small scale subsonic wind tunnel, flow visualization analysis on an object and calculation of lift and drag coefficient of an object through experiment. In the present world of obtaining excellence with the most extreme cost sparing and almost all the aircrafts are composed utilizing CAD programming. These plans however should be checked and tried continuously which gives imperatives results in the full scale. The momentum research not just incorporates confirmation of withdrawal cone outline by looking at the speed of air at various segments got amid CFD investigation with the trial values at comparing forces. This design explains the whole method to plan an open circuit subsonic wind tunnel which will be utilized to concentrate on the wind impact on the diverse models of basic components. The plans were made and broke down, bringing about different examinations of various geometries, and giving the required information of course from the outlines. The profile includes a contraction cone area of side 750mm, square test area of side 500 mm, to suit the model and required instrumentation in it, for power and weight estimation. The test section has a dimension of 340mm x 360mm x 500mm which is companionable to the outlet and inlet of the nozzle and diffuser respectively with the mean velocity of 15 m/s. A straight portion before the test chamber is given to allow the yield of withdrawal zone to offset before it accomplishes the test section