Mechanical characterization of fireproof composite materials for aerospace application

The present work has been carried out in collaboration with B.M.C. Air Filters, and it is mainly focused on the mechanical characterization of fireproof composite materials, which are designed to be implemented in an engine covering for an aerospace application. The covering needs to ensure sufficient mechanical strength in combination with low weight in order to be in compliance with loading and producibility requirements. Three different types of pre-preg composite materials have been previously identified by the company: a woven fabric carbon fiber, a fiberglass fabric and an unidirectional carbon fiber. The purpose of the work concerns the study of aerospace regulations in order to identify the guidelines for the implementation of the mechanical tests, which are: tension, compression, in-plane shear and interlaminar shear. The test speciments are made by hand lay-up process, which is followed by autoclaving. The tests are conducted through an Instron 68TM-50 at room temperature and then at 120°C. At ambient temperature, the carbon fabric and fiberglass show excellent mechanical strength in accordance with the values provided by the datasheets. Unidirectional carbon, on the other hand, shows lower values than expected. However, this behavior finds an explanation in the variability of the production process. In fact, in hand-lay up lamination, the quality of the product is highly influenced by the worker's ability to handle the material. Subsequently, the tests are repeated using a thermal chamber in order to understand the influence of temperature on the mechanical behavior of the materials, to which they might be subjected during use. As expected, the temperature used, close to the glass transition temperature of the resin, causes a significant decrease in the mechanical properties of the material. However, the breaking points still remain good confirming the high mechanical performance that composite materials can provide.