Browsing by Author "Sales, Flaminio C.P."
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- Low-cost multifunctional vacuum chamber for manufacturing PDMS based compositesPublication . Ariati, Ronaldo; Sales, Flaminio C.P.; Noronha, Verônica Teixeira; Lima, Rui A.; Ribeiro, J.E.Polydimethylsiloxane (PDMS) is one of the best known elastomers and has been used in several areas of activity, due to its excellent characteristics and properties, such as biocompatibility, flexibility, optical transparency and chemical stability. Furthermore, PDMS modified with other materials promotes the desired changes to broaden its range of applications in various fields of science. However, the heating, mixing and degassing steps of the manufacturing process have not received much attention in recent years when it comes to blending with solid materials. For instance, PDMS has been extensively studied in combination with waxes, which are frequently in a solid state at room temperature and as a result the interaction and manufacturing process are extremely complex and can compromise the desired material. Thus, in this work it is proposed a multifunctional vacuum chamber (MVC) with the aim to improve and accelerate the manufacturing process of PDMS composites combined with additives, blends and different kinds of solid materials. The MVC developed in this work allows to control the mixing speed parameters, temperature control and internal pressure. In addition, it is a low cost equipment and can be used for other possible modifications with different materials and processes with the ability to control those parameters. As a result, samples fabricated by using the MVC can achieve a time improvement over 133% at the heating and mixing step and approximately 200% at the last degassing step. Regarding the complete manufacturing process, it is possible to achieve an improvement over 150%, when compared with the conventional manufacturing process. When compared to maximum tensile strength, specimens manufactured using the MVC have shown a 39% and 65% improvement in maximum strain. The samples have also shown a 9% improvement in transparency at room temperature and 12% at a temperature of about 75 C. It should be noted that the proposed MVC can be used for other blends and manufacturing processes where it is desirable to control the temperature, agitation speed and pressure.
- Manufacture of bone fracture plates based on glass fiber reinforced polyurethane composite: a gravity casting adapted processPublication . Sales, Flaminio C.P.; Moura, P. Ana de; Costa, Romeu R.C. da; Ribeiro, J.E.The development of materials and devices to replace or restore damaged tissue functions has a prominent position in the scientific community, promoting the interest for metal-free alternatives, like composites. These proved to be a promising option as, besides new matrix and reinforcement combinations, new manufacturing methods tend to fulfil tailored requirements of the medical field. In this sense, we manufactured glass fiber/polyurethane composite plates for Osteosynthesis. Models based on commercial LCP implants were 3D printed and used to generated molds through a new adapted resin casting process. Additional mechanical tests showed that reinforcement additions between 10 wt% and 25 wt% caused an increase in the bending structural stiffness by 126%-165% when compared to pure polymer implants. In addition, if the number of holes is increased, from 4 to 6, the maximum stress reduces by 40%. The manufacturing process was an effective alternative as it presented low cost, high customization and allowed the development of complex geometries, resin injection and degassing.
- Mechanical characterization of PDMS with different mixing ratiosPublication . Sales, Flaminio C.P.; Ariati, Ronaldo; Noronha, Verônica Teixeira; Ribeiro, J.E.Polydimethylsiloxane (PDMS) is a transparent, biocompatible, flexible, simple processing, chemically and thermally stable polymer that has been attracting attention due to its wide range of applications in mechanical, civil and electronic engineering and biomedical field. In order to improve PDMS’ properties, many studies have been investigating the effect of the mixing ratios of its components (base polymer and curing agent) on the mechanical properties, once they affect the number of interactions between the polymer chains of the material. With the aim to make a comparison of the mechanical response of pure PDMS (SYLGARD 184) with different ratios of the base elastomer and the curing agent, tensile and hardness tests were performed. The tested mixing ratios were 10:1, 10:2 and 10:3 (base: curing agent). Tensile tests were executed in a universal tester machine, set up with a velocity of 500 mm/min and pre-load of 1 N. An analogical portable durometer type Shore A was used to carry out the hardness test, according to ASTM D2240. The results for the tensile test showed that an increase in the amount of cure agent reduced the tensile strength. The hardness values obtained were 41.7±0.95, 43.2±1.03 and 37.2±1.14 Shore A for pure PDMS with ratios equal to 10:1, 10:2 and 10:3, respectively.
- PU tensile tests: conventional and digital image correlation analysisPublication . Sales, Flaminio C.P.; Ariati, Ronaldo; Noronha, Verônica Teixeira; Costa, Romeu R.C. da; Ribeiro, J.E.Polyurethane (PU) is a polymer, used as coating, paint, foam, adhesive, and even in biomedical devices. To furthermore expand its applications, it can be combined with additives such as Calcium Carbonate (CaCO3), an inexpensive material, widely available in nature, or with fibers, such as glass fibers explored in several sectors, likewise the aerospace and automobile industries. To determine the mechanical properties of these materials, the tensile test is the most used due to its great ease of application and flexibility. However, conventional processes, such as the use of strain gauges or crosshead displacement data, may not provide detailed information about the strain field, or cannot be able to evaluate the Poisson's ratio and the true stresses for the entire stressstrain curve. Thus, digital image correlation (DIC) methods are a promising alternative, consisting of strain field measurement without contact with the surface of the structure. In this context, this study carried out the tensile characterization of two main polyurethane samples: one petrochemical, distributed by Sika (R), reinforced with type E glass fiber: and the other, natural, manufactured by Kehl (R) from castor oils, and combined with CaCO3 particles. During the tests, DIC was applied to evaluate the Poisson's ratio and, subsequently, Scanning Electron Microscopy (SEM) analyses were performed, revealing a higher number of bubbles on Sika's polymer, which contributes to the reduction of the maximum supported stresses, since these pores, with dimensions of up to 25 hm, were regions where the cracks started and headed the breakage. Poisson's ratios were all around 0.4 and the highest tensile strength values were obtained from E-glass reinforced samples (TS015), around 117.24 +/- 13.20MPa. CaCO3 particles also acted as reinforced, increasing maximum stress reached from 20MPa to values between 29 and 37MPa.