THE STRUCTURAL BEHAVIOUR OF COMPOSITE LAMINATES MANUFACTURED USING RESIN INFUSION UNDER FLEXIBLE TOOLING

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

200511

RESUMO

This thesis presents a detailed investigation on the structural behaviour of hybrid plain weave composite laminates manufactured using Resin Infusion under Flexible Tooling (RIFT) process under static and dynamic impact loading conditions. Composite laminates were manufactured using a newly developed RIFT manufacturing facility marking the beginning of a new composite research field in the Department of Aeronautics at the Imperial College London. Optimum manufacturing parameters associated with the proposed RIFT setup were experimentally derived and good quality laminates with relatively low void content could be manufactured using the proposed setup. A testing programme was carried out to characterise the mechanical and physical behaviour of the RIFTed laminates in which properties commonly used for design purposes were experimentally obtained. The mechanical tests included uniaxial tension/compression in the warp and fill directions, in-plane shear tests and interlaminar fracture toughness in mode I, mode II and mixed mode I/II loading while the measured physical properties were density, fibre volume fraction and void content. Additionally, the damage resistance and damage tolerance performance of the laminates were evaluated under low velocity impact loading. After gaining some understanding on the structural mechanical behaviour a semi-analytical 3D micro mechanical model was developed to predict the macro mechanical elastic behaviour of the RIFTed laminates. In order to predict the gradual material degradation during the impact event, a damage mechanics based failure model was then developed and implemented into LS-DYNA3D explicit finite element code. The proposed damage model is based on the Continuum Damage Mechanics (CDM) approach and enables the control of the energy dissipation associated with each failure mode regardless of mesh refinement, element topology and fracture direction by using an advanced mesh insensitivity algorithm. Internal thermodynamically irreversible damage variables were defined in order to quantify damage concentration associated with each possible failure mode and predict the gradual stiffness reduction during the impact event. The fracture energies required by the model were obtained by measuring the mode-I intralaminar fracture toughness using four different pre-cracked geometries namely, Overhead Compact Tension (OCT), Overhead Compact Compression (OCC), Double Edge Notch (DEN) and Four Point Bending (FPB) specimens. A methodology to derive the stress intensity factor for anisotropic materials is also presented and discussed. The proposed model was validated by a series of static and dynamic impact testing under different energy levels.

ASSUNTO(S)

elementos finitos resin infusion under flexible tooling - rift impacto materiais compostos fabricação de compósitos mecânica do dano estruturas aeroespaciais composite laminates

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