Although epoxy resins are used in a broad variety of applications due to their good mechanical an... more Although epoxy resins are used in a broad variety of applications due to their good mechanical and thermal properties, their low fracture toughness is a limitation, exhibiting brittle behavior. This study explored the potential use of imidazolium ionic liquids (IL) as toughening agents for epoxy resin based on diglycidyl ether of bisphenol A (DGEBA) with triethylenetetramine (TETA) as curing agent. Fracture toughness was evaluated for DGEBA-TETA epoxy resins with eleven imidazolium IL and the best results were found for the IL with the chloride anion and the shortest N-alkyl side chain, C4MImCl. The use of 1.0 phr of C4MImCl lead to the reduction of the crosslink density of the post-cured resin, resulting in the increase of 25.5% in stress intensity factor and 8.2% in tensile strength with no significant loss in other mechanical properties.
Journal of the Brazilian. Society of Mechanical Science & Engineering, 2011
This work presents a study about the correlations between the characteristics of the acoustic wav... more This work presents a study about the correlations between the characteristics of the acoustic waves and the mechanical properties of low carbon hot rolled steel bars, through the comparison between the wave velocity or attenuation and the tensile strength, yield point or elongation of the material. The aim is the possibility of using this technique to predict the production quality of ASTM A36 steels. Acoustic velocity and attenuation measurements by gain acquisition were carried out with the use of longitudinal waves and transducers of 5 and 15 MHz. Samples of hot rolled reinforcement steel bars with one inch diameter were used. A metallographic study of grain size and inclusion content was made along with chemical composition to verify the influence of these factors to the acoustic measurements. Results indicated that it is possible to use the presented methodology to estimate the mechanical properties, in especial, the tensile strength in steel rebars.
Although epoxy resins are used in a broad variety of applications due to their good mechanical an... more Although epoxy resins are used in a broad variety of applications due to their good mechanical and thermal properties, their low fracture toughness is a limitation, exhibiting brittle behavior. This study explored the potential use of imidazolium ionic liquids (IL) as toughening agents for epoxy resin based on diglycidyl ether of bisphenol A (DGEBA) with triethylenetetramine (TETA) as curing agent. Fracture toughness was evaluated for DGEBA-TETA epoxy resins with eleven imidazolium IL and the best results were found for the IL with the chloride anion and the shortest N-alkyl side chain, C4MImCl. The use of 1.0 phr of C4MImCl lead to the reduction of the crosslink density of the post-cured resin, resulting in the increase of 25.5% in stress intensity factor and 8.2% in tensile strength with no significant loss in other mechanical properties.
Journal of the Brazilian. Society of Mechanical Science & Engineering, 2011
This work presents a study about the correlations between the characteristics of the acoustic wav... more This work presents a study about the correlations between the characteristics of the acoustic waves and the mechanical properties of low carbon hot rolled steel bars, through the comparison between the wave velocity or attenuation and the tensile strength, yield point or elongation of the material. The aim is the possibility of using this technique to predict the production quality of ASTM A36 steels. Acoustic velocity and attenuation measurements by gain acquisition were carried out with the use of longitudinal waves and transducers of 5 and 15 MHz. Samples of hot rolled reinforcement steel bars with one inch diameter were used. A metallographic study of grain size and inclusion content was made along with chemical composition to verify the influence of these factors to the acoustic measurements. Results indicated that it is possible to use the presented methodology to estimate the mechanical properties, in especial, the tensile strength in steel rebars.
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