Epocast 50-A1/946 epoxy was primarily developed for joining and repairing of composite aircraft structural components. The objective of the present work is to modify the Epocast epoxy resin by different nanofillers in...Epocast 50-A1/946 epoxy was primarily developed for joining and repairing of composite aircraft structural components. The objective of the present work is to modify the Epocast epoxy resin by different nanofillers infusion. The used nanofillers include multi-walled carbon nanotubes（MWCNTs）, SiC and Al2O3 nanoparticles. The nanofillers with different weight percentages are ultrasonically dispersed in the epoxy resin. The sonication time and amplitude for MWCNTs are reduced compared to Al2O3 and SiC nanoparticles to avoid the damage of MWCNTs during sonication processes. The fabricated neat epoxy and twelve nanocomposite panels were characterized via standard tension and in-plane shear tests. The experimental results show that the nanocomposites materials with 0.5wt% MWCNTs, 1.5wt% SiC and 1.5wt% Al2O3 nanoparticles have the highest improvement in the tensile properties compared to the other nanofiller loading percentages.The improvements in the shear properties of these nanocomposite materials were respectively equal to 5.5%, 4.9%, and 6.3% for shear strengths, and 10.3%, 16.0%, and 8.1% for shear moduli. The optimum nanofiller loading percentages will be used in the following papers concerning their effect on the bonded joints/repairs of carbon fiber reinforced composites.展开更多
Dynamic tension tests were employed to investigate the effect of strain rate on mechanical behaviors of Ti10V2Fe3Al and 30CrMnSiNi2A. The strain rate ranges from 10 -4 to 10 3 s -1 . Experimental results showed that t...Dynamic tension tests were employed to investigate the effect of strain rate on mechanical behaviors of Ti10V2Fe3Al and 30CrMnSiNi2A. The strain rate ranges from 10 -4 to 10 3 s -1 . Experimental results showed that the yield strength ( σ s), ultimate strength( σ u) and elongation( δ 5) increase, but strain hardening exponent( n ) decreases with the rise of strain rate( ) by refractive lines. The reasons that σ s and σ u increase with increasing are concerned with thermal activation. The high strain rate induced increasing plasticity is associated with adiabatic heating of specimen, impact twinning and suppression of strain induced phase transformation. Strain hardening exponent n can be considered a constant under quasi static loading, but decreases rapidly till an ideal plastic state( n =0) after strain rate surpassing a critical value(10 2 s -1 ). The mechanism of n decreasing with the increase of is related to the increase of σ s and suppression of strain induced phase transformation.展开更多
Tensile stiffness of ocean dynamic power umbilical is an important design parameter for functional implementation and structural safety. A column with radial stiffness which is wound by helical steel wires is construc...Tensile stiffness of ocean dynamic power umbilical is an important design parameter for functional implementation and structural safety. A column with radial stiffness which is wound by helical steel wires is constructed to predict the tensile stiffness value of umbilicals in the paper. The relationship between the tension and axial deformation is expressed analytically so the radial contraction of the column is achieved in the relationship by use of a simple finite element method. With an agreement between the theoretical prediction and the tension test results, the method is proved to be simple and efficient for the estimation of tensile stiffness of the ocean dynamic power umbilical.展开更多
基金funded by King Abdulaziz City for Science and Technology (KACST), Riyadh, Saudi Arabia under Grant DRP-5-3financial support of KACST
文摘Epocast 50-A1/946 epoxy was primarily developed for joining and repairing of composite aircraft structural components. The objective of the present work is to modify the Epocast epoxy resin by different nanofillers infusion. The used nanofillers include multi-walled carbon nanotubes（MWCNTs）, SiC and Al2O3 nanoparticles. The nanofillers with different weight percentages are ultrasonically dispersed in the epoxy resin. The sonication time and amplitude for MWCNTs are reduced compared to Al2O3 and SiC nanoparticles to avoid the damage of MWCNTs during sonication processes. The fabricated neat epoxy and twelve nanocomposite panels were characterized via standard tension and in-plane shear tests. The experimental results show that the nanocomposites materials with 0.5wt% MWCNTs, 1.5wt% SiC and 1.5wt% Al2O3 nanoparticles have the highest improvement in the tensile properties compared to the other nanofiller loading percentages.The improvements in the shear properties of these nanocomposite materials were respectively equal to 5.5%, 4.9%, and 6.3% for shear strengths, and 10.3%, 16.0%, and 8.1% for shear moduli. The optimum nanofiller loading percentages will be used in the following papers concerning their effect on the bonded joints/repairs of carbon fiber reinforced composites.
文摘Dynamic tension tests were employed to investigate the effect of strain rate on mechanical behaviors of Ti10V2Fe3Al and 30CrMnSiNi2A. The strain rate ranges from 10 -4 to 10 3 s -1 . Experimental results showed that the yield strength ( σ s), ultimate strength( σ u) and elongation( δ 5) increase, but strain hardening exponent( n ) decreases with the rise of strain rate( ) by refractive lines. The reasons that σ s and σ u increase with increasing are concerned with thermal activation. The high strain rate induced increasing plasticity is associated with adiabatic heating of specimen, impact twinning and suppression of strain induced phase transformation. Strain hardening exponent n can be considered a constant under quasi static loading, but decreases rapidly till an ideal plastic state( n =0) after strain rate surpassing a critical value(10 2 s -1 ). The mechanism of n decreasing with the increase of is related to the increase of σ s and suppression of strain induced phase transformation.
基金financially supported by the National High Technology Research and Development Program of China(863 ProgramGrant No.2012AA09A212)+1 种基金the National Natural Science Foundation of China(Grant No.11372060)the China Postdoctoral Science Foundation(Grant No.20110491521)
文摘Tensile stiffness of ocean dynamic power umbilical is an important design parameter for functional implementation and structural safety. A column with radial stiffness which is wound by helical steel wires is constructed to predict the tensile stiffness value of umbilicals in the paper. The relationship between the tension and axial deformation is expressed analytically so the radial contraction of the column is achieved in the relationship by use of a simple finite element method. With an agreement between the theoretical prediction and the tension test results, the method is proved to be simple and efficient for the estimation of tensile stiffness of the ocean dynamic power umbilical.
