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Cementitious Porous Material Applied to Precision Aerostatics Bearings
Leandro Jos da Silva,Tulio Hallak Panzera,Luciano Machado Gomes Viera,Christopher Rhys Bowen,Jaime Gilberto Duduch,Juan Carlos Campos Rubio 한국정밀공학회 2018 International Journal of Precision Engineering and Vol.19 No.2
The use of porous materials as restrictor in aerostatic bearings provides many advantages over conventional restrictors, such as small variation of temperature, high damping, high operational speeds, limited wear and capacity to support radial, axial, and combined loads, being considered important features for precision machines and instruments. This work evaluates the load carrying capacity for different air gaps and pressures of thrust porous bearing made with cementitious composites. The cementitious composites consisted of Portland cement and monomodal silica particles (44 μm) were fabricated via uniaxial cold-pressing (10 MPa). The load capacity was determined for different air pressures, such as 3, 4, 5 and 6 bar. The air gap was measured using pneumatic transducers. A pneumatic instability was observed when the air pressure level increased from 3 to 6 bar. A similar loading capacity, for bearing gaps between 7 and 30 μm, was achieved in comparison to hot-pressed porous alumina found in the literature. In addition, the cementitious porous bearing provided a superior loading capacity for gaps higher than 10 μm when compared to graphite porous bearing found in the literature. The results revealed the cementitious composites are promising materials for porous restrictor in aerostatic thrust bearings.
Eco-friendly Sandwich Panel Based on Recycled Bottle Caps Core and Natural Fibre Composite Facings
Pablo Resende Oliveira,Julio Cesar dos Santos,Sergio Luiz Moni Ribeiro Filho,Bruna Torres Ferreira,Tulio Hallak Panzera,Fabrizio Scarpa 한국섬유공학회 2020 Fibers and polymers Vol.21 No.8
This is the first attempt to combine disposed bottle caps and natural fibres into sandwich panels. A full factorialdesign is performed to identify the effects of the skin type (aluminium or coir fibre reinforced laminates) and bottle cap corepacking (cubic and orthotropic) on the mechanical properties of the proposed panels. The coir fibre composite skin providesmaximum core shear strength, 29 % higher than the aluminium-based panels, in cubic packing, while the flexural modulus isreduced by 45 %. An interlocking effect between the skin and the core is evidenced when coir fibre composites are used. Inaddition, the cubic cell packing increases the specific mechanical properties, even though with a higher density. The resultshighlight a promising association of green components and plastic bottle caps for secondary structural applications.