Abstract

Abstract

Abstract

Abstract

Abstract

The aeronautical industry tries continuously to find different strategies to optimize structural components with the aim of reducing their weight and hence achieving a more sustainable transport. The new developments that will come in the following years, will probably use incorporate open rotor engines since they have lower consume. These engines have a series of counter-rotating blades made of composite materials, which could impact the aircraft fuselage in case of failure. Impacts on aeronautic structures can be caused by rigid (metallic fragments), or by highly deformable bodies (hail, bird). Apart from these, which have already been studied, there are other types of impacts, practically unexplored, which are the fragments of carbon/epoxy laminates. In this work, high speed impact tests of carbon/epoxy fragments have been carried out in a wide range of impact velocities, from 80 to 190 m/s. These tests have been monitored using high-speed cameras which, using a specific tracking software, could calculate their acceleration and therefore the force exerted. The erosion suffered during impact has also been quantified. In order to study the failure process, a simple analytical model has been proposed to evaluate the influence of the different mechanisms of energy absorption during the impact and hence predict the erosion of the fragment during the impact.

Abstract

The manufacture by means of a pultrusion process allows to obtain structural profiles of composite materials, avoiding discontinuous processes that need the use of an autoclave to cure the material. This process usually uses fiberglass as reinforcement, not reaching the necessary qualities in structural aeronautical applications. The present work develops a numerical simulation of the pultrusion with composite materials reinforced with carbon fiber for aeronautical structural applications. In order to obtain high quality materials, a product development is required where the process parameters are studied. In this sense, a complete study of the pultrusion process has been carried out through the development of numerical simulations using the software ABAQUS and NASTRAN / PATRAN from the point of view of the material manufactured and the pultrusion mold used.

These two approaches have been developed by generating finite element models. In the first place, models that simulate and predict the physical-chemical properties of the material, such as the glass transition temperature and the degree of final curing of the material before processes with different temperature settings, draft speeds and geometries. Second, the pultrusion mold was simulated to obtain the expansions and loads applied to the fabricated profile to evaluate the influence of this on the pultrusion process and the quality of the obtained profile.

The results obtained have been correlated by mechanical and physical-chemical tests as well as manufacturing tests that obtained the simulated profiles in order to introduce the technology and the parts manufactured in future aeronautical structures.

Abstract

The behaviour of composite materials under dynamic loading conditions has been a subject of research for the last two decades. When subjected to dynamic conditions, composite materials show a significant sensitivity to strain rate. This is critical for a correct simulation of the behaviour of composite structures under impact. Currently, a few studies have been carried out on the analysis of strain rate sensitivity of the fracture toughness. These studies have reported different conclusions for the same material (IM7/8552), indicating that the optimal technique for characterising this property under high strain rate loading remains unresolved. In this work, it has been carried out dynamic characterization test on the fracture toughness using the Split Hopkinson Pressure Bar. It has been developed a new methodology for obtaining an accurate synchronization between Hopkinson bar data and high speed camera. Using the proposed methodology a good repeatability has been obtained for dynamic tests.

Abstract