Banca de DEFESA: ANA PAULA PEREIRA FULCO

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE : ANA PAULA PEREIRA FULCO
DATA : 30/11/2017
HORA: 14:00
LOCAL: Sala S22B11 (Sala de aulas do PPGCEM)
TÍTULO:

DAMAGE MECHANISMS OF CARBON/EPOXY LAMINATES UNDER FATIGUE LOADING AND HIGROTHERMAL AGING

PALAVRAS-CHAVES:

Composite materials, carbon/epoxy, aging, mechanical properties, fatigue.

PÁGINAS: 142
GRANDE ÁREA: Engenharias
ÁREA: Engenharia Aeroespacial
SUBÁREA: Materiais e Processos para Engenharia Aeronáutica e Aeroespacial
RESUMO:

Carbon fiber reinforced polymer (CFRP) composites used in aeronautic and aerospace structures are often exposed to cyclic loading and environmental effects such as temperature and humidity, which can lead to degradation and failure of the component. The objective of this work was to study the effects of aging under exposure to high temperature and humidity on the damage mechanisms of carbon/epoxy composites subjected to cyclic loading. Initially, a preliminary accelerated aging study was conducted with unidirectional AS4/8552 samples using an exposure cycle of 8 h of UVA-340 at 80 °C followed by 4 h of condensation at 80 °C, for a total exposure period of 2,160 h.  The effects of aging were evidenced by weight loss, fiber exposure, chemical changes, increased crack density in interlaminar shear strength tests, and fiber buckling in fractured samples after compression tests, even though no significant changes mechanical properties were observed. Based on this preliminary work, a study was conducted on [0₂/90₂]_s laminates of the same material, using an exposure cycle of 8 h at 160 °C followed by 4 h of 80% relative humidity at 70 °C, for a total exposure period of 2,880 h. Afterwards, stress-controlled tension-tension fatigue tests were conducted using a stress ratio R = 0.1 and frequency of 5 Hz. Composites were characterized using Fourier transform infrared spectroscopy (FTIR), Dynamic Mechanical Analysis (DMA), Scanning Electron Microscopy (SEM) and weight change, before and after hygrothermal exposure. Samples of plain epoxy 8552 were also exposed to the same aging conditions and characterized by optical microscopy (OM), FTIR spectroscopy and weight change. Based on the fatigue life diagrams, a shift function was proposed for the prediction of number of cycles to failure of aged composites based on data from unaged specimens. The study also showed that failure by fracture may 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 and crack saturation are also essential to assess durability of these composites.

MEMBROS DA BANCA:
Presidente - 1202134 - JOSE DANIEL DINIZ MELO
Interno - 2042234 - ANA PAULA CYSNE BARBOSA
Externo ao Programa - 1338331 - RAIMUNDO CARLOS SILVERIO FREIRE JUNIOR
Externo à Instituição - CARLOS ALBERTO CIMINI JUNIOR - UFMG
Externo à Instituição - FLAMINIO LEVY NETO - UnB