Fabricação de corpos de prova de tração em compósitos com matriz biopolimérica

Abstract

The crescent interest in validating new materials, for using within the universe of engineering in the technical aspects and economic issues and the growing environmental concernment have motivated this research. The increasing range of applicability of the composite materials within structural, automotive, aeronautical and mainly medical applications drives to a large necessity of ensuring the reliability of these elements. Thus, in order to avouch that a material is reliable some tests are necessary. In most cases, these tests are destructive. On this research, the group has chosen a composite material, compound of a polymeric matrix obtained from the castor oil (polyurethane) as a stress conveyor element and fiberglass as the reinforcing agent. Polymeric matrixes present several advantages comparing to those derived from petroleum, such as: they do not contaminate the environment where people in general deposit them and the natural decomposition time is shorter. Recognizing the mechanical properties of this material requires the fabrication of normalized test bodies in order to create the adequate atmosphere for the traction test, which can display reliable results of the polyurethane mechanical behavior. Therefore, two manufacturing processes are necessary to build the bodies according to the ASTM D3039: the Hand Lay-UP and the Spray-UP Modified. They consist of an interleaving of reinforcing boards with polymeric matrix, following by the cure process under pressure. The most significant difference between them is the way to insert the polymeric matrix. Hand Lay-UP add the polyurethane through the hands of the operator, directly on the reinforcing board. In the other hand, the process of Spray-UP Modified pulverizes the polymer along with compressed air. All of the boards obtained passed by an analyze that verified the quality of the homogeneity and the dimensional precision. Only after the analysis, the test bodies are valid to the traction test. Finally, the wreckage from the bodies were brought to the induction furnace in order to eliminate the polymeric matrix from the material. So that the material proprieties of the bodies could be obtained, proprieties such as mass and volumetric fraction. This knowledge is very important in validating the fabrication process. With this information, the comparison between the final and initial fractions obtained in the beginning of the mixture process is possible. Moreover, the results found for the Young Modulus (modulus of elasticity), presented values of standard deviation less than one per cent in comparison to the theoretical ones, ensuring the efficiency of Hand Lay-UP and Spray-UP as a manufacturing process to composite materials.