Investigation of corrosion fatigue behavior of carbon nanotube, nanofiber and e-glass reinforced epoxy nanocomposites

In this thesis, the corrosion fatigue behavior of the [0/90] E-Glass/epoxy composite laminate was investigated. In the laminate production, the interface of the fiber-matrix was functionalized with γ-glycidoxypropyltrimethoxysilane. The sulfuric acid/nitric acid solution in the ratio of 1: 1 was used for purification of multi-walled carbon nanotubes and hexamethylene diamine for functionalization with the amine. Cetylpyridinium chloride was used as a cationic surfactant to distribute carbon nanotubes homogeneously. In the symmetry layer of produced laminate, there was a nanofiber mat manufactured from polyacrylonitrile by the electro-spinning method. The semi-finished samples were also produced separately to examine the effects of nanofibre, silane application, and carbon nanotube functionalization on fracture strength and toughness. Tensile, three-point bending, and inter-laminar fracture tests were carried out to measure Mode- I fracture strength and the toughness of the samples. The produced samples were kept in a 10% concentration of sodium hydroxide (NaOH) for four weeks and the effect of the medium was compared with the samples that were not left in the corrosive environment. It was determined that the absorption amount decreased from 4.7% to 0.7% concerning the native specimen. It was found that the fracture strength and toughness values of the samples left in the corrosive environment showed a dramatic decrease of 54% in the first two weeks, but the loss of mechanical properties remained stable from the second week. In the fatigue tests at a frequency of 3 Hz and R = 0.1, it was found that the samples exposed to corrosion had less slope (76.7%) in the applied maximum stress versus the number of cycles to failure (S-N) plots due to the loss of tensile strength. The highest mechanical properties were achieved for samples containing carbon nanotubes treated with silane and homogeneous distribution with a cationic surfactant. It has been determined that the combination of acid purification and amine functionalization does not give positive results in terms of fracture toughness.