Banca de QUALIFICAÇÃO: ANA PAULA PEREIRA FULCO

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
DISCENTE : ANA PAULA PEREIRA FULCO
DATA : 10/11/2017
HORA: 14:00
LOCAL: Sala de reuniões do DEMat
TÍTULO:

Fatigue Damage Mechanisms of Carbon/Epoxy Laminates Under Aging Induced Degradation

PALAVRAS-CHAVES:

Composites, carbon/epoxy, accelerated aging, mechanical properties, fatigue test.

PÁGINAS: 120
GRANDE ÁREA: Engenharias
ÁREA: Engenharia de Materiais e Metalúrgica
RESUMO:

Composite materials are widely used in aerospace industry due to combination of properties such as low specific weight and mechanical resistance. However, these materials are subject to inclement weather by temperature and humidity action and cyclic loading conditions by dynamic fatigue during their lifetime, which can cause degradation and decrease in structural integrity during their use. Therefore, the objective of this work is to study the effects of aging under high temperatures and humidity in the mechanisms of damages in polymer matrix composites reinforced with carbon fibers and products subjected to cyclic loading. Initially, an accelerated aging study was performed on carbon fiber reinforced epoxy matrix composites after exposure to ultraviolet radiation, temperature and humidity.  Changes in the material were evaluated by Fourier Transform Infrared Spectroscopy (FTIR), Dynamic Mechanical Analysis (DMA), Interlaminar Shear Strength (ILSS), compressive strength, Electrical Scanning Spectroscopy (SEM), and weight variation. Although no significant changes in the composite material regarding mechanical properties were observed, the accelerated aging effects were evidenced by mass loss, fiber exposure, chemical changes, increased in crack density, and fiber twisting in fractured samples after compression test.  Based on this preliminary work, an accelerated aging study of the composite carbon/epoxy and epoxy 8552 was also performed. Samples were exposed to alternate temperature loads (160 °C and 70 °C with humidy). Composites were characterized by the following techniques: FTIR, DMA, SEM and weight variation, before and after hygrothermal exposure. Samples of pure Epoxy 8552 were characterized by FTIR, Optical Microscopy (OM) and weight variation. Mechanical properties of the composites samples were evaluated by fatigue tests under traction with controlled load (stress ratio R = 0.1 and frequency of 5 Hz), before and after aging. Based on the obtained fatigue diagrams, a shift function (shift) was proposed for the prediction of number of cycles to failure of aged composites based on data from test defaults on non-aged composites. Mechanical fatigue results also showed that rupture failure my not be the best parameter to evaluate the effect of hygrothermal aging on fatigue life of carbon fiber reinforced polymer composites. Other parameters such as delamination failure and crack saturation are also essential to assess durability of composite materials.

MEMBROS DA BANCA:
Presidente - 1202134 - JOSE DANIEL DINIZ MELO
Interno - 2042234 - ANA PAULA CYSNE BARBOSA
Externo ao Programa - 1338331 - RAIMUNDO CARLOS SILVERIO FREIRE JUNIOR