The feasibility of longer spans relies on the successful implementation of new high-strength light weight materials such as carbon fiber reinforced polymer(CFRP). First, a dimensionless equilibrium equation and the co...The feasibility of longer spans relies on the successful implementation of new high-strength light weight materials such as carbon fiber reinforced polymer(CFRP). First, a dimensionless equilibrium equation and the corresponding compatibility equation are established to develop the cable force equation and cable displacement governing equation for suspension cables, respectively. Subsequently, the inextensible cable case is introduced. The formula of the Irvine parameter is considered and its physical interpretation as well as its relationship with the chord gravity stiffness is presented. The influences on the increment of cable force and displacement by λ2 and load ratio p′ are analyzed, respectively. Based on these assumptions and the analytical formulations, a 2000 m span suspension cable is utilized as an example to verify the proposed formulation and the responses of the relative increment of cable force and cable displacement under symmetrical and asymmetrical loads are studied and presented. In each case, the deflections resulting from elastic elongation or solely due to geometrical displacement are analyzed for the lower elastic modulus CFRP. Finally, in comparison with steel cables, the influences on the cable force equation and the governing displacement equation by span and rise span ratio are analyzed. Moreover, the influences on the static performance of suspension bridge by span and sag ratios are also analyzed. The substantive characteristics of the static performance of super span CFRP suspension bridges are clarified and the superiority and the characteristics of CFRP cable structure are demonstrated analytically.展开更多
To study the response characteristics of the carbon fiber fabric reinforced composites under impact loading, one dimensional strain impact test, multi gauge technique and Lagrange analysis method are used. The decay...To study the response characteristics of the carbon fiber fabric reinforced composites under impact loading, one dimensional strain impact test, multi gauge technique and Lagrange analysis method are used. The decaying rule of the stress σ , strain ε , strain rate ε · and density ρ with time and space is obtained. By the theory of dynamics, the impact response characteristics of the material is analyzed and discussed.展开更多
Formation of entrance and exit defects in coarse pitch orbital drilling(CPOD)of carbon fiber reinforced plastic(CFRP)plates was investigated.Deep observation on entrance and exit morphology shows tear and burr are typ...Formation of entrance and exit defects in coarse pitch orbital drilling(CPOD)of carbon fiber reinforced plastic(CFRP)plates was investigated.Deep observation on entrance and exit morphology shows tear and burr are typical defects.Meanwhile,tear is more obvious than burr,and more entrance tears emerge than exit tears.As one of the major causes of entrance and exit defects in CPOD,cutting forces were substaintially studied by contrast experiments.Then,the effect of cutting parameters on entrance and exit tear was qualitatively analyzed through a single factor test.Experiment results indicate that the variation of rotation speed has little influence on entrance and exit tear.Increasing tangential feed per tooth can enlarge entrance tear,but bring little effect on exit tear.By increasing axial feed pitch,the hole entrance and exit show severe tear.When revolution radius grows bigger and bigger,entrance and exit tear firstly decreases,and then increases.Finally,the models of tear and delamination during CPOD of CFRP were established,the formation mechanisms of entrance and exit defects were revealed,and the control strategies were accordingly put forward.展开更多
Twenty-one square concrete columns were constructed and tested. The testing results indicate that bonded carbon fiber reinforced plastics(CFRP) sheets can be used to increase the strength and improve the serviceabilit...Twenty-one square concrete columns were constructed and tested. The testing results indicate that bonded carbon fiber reinforced plastics(CFRP) sheets can be used to increase the strength and improve the serviceability of damaged concrete columns at low temperatures. The failure of the specimens,in most cases,takes place within the middle half of the columns. And the failure of strengthened columns is sudden and explosive. The CFRP sheets increase both the axial load capacity and the ultimate concrete compressive strain of the columns. The ultimate loads of strengthened columns at-10,0 and 10 ℃ increase averagely by 9.09%,6.63% and 17.83%,respectively,as compared with those of the control specimens. The axial compressive strength of strengthened columns is related to the curing temperatures. The improvement of axial compressive strength decreases with reducing temperature,and when the temperature drops to a certain value,the improvement increases with falling temperature.展开更多
The fracture toughness of carbon fiber reinforced epoxy composite(CFRP)was investigated through mode I and mode II shaped fracture system in this paper.A novel polyimide with trifluoromethyl groups and grafted nanosil...The fracture toughness of carbon fiber reinforced epoxy composite(CFRP)was investigated through mode I and mode II shaped fracture system in this paper.A novel polyimide with trifluoromethyl groups and grafted nanosilica were used to modify epoxy resin.Effect of modified resin and unmodified resin on fracture toughness of CFRP was compared and discussed.Lay-up angles and thicknesses effects on fracture toughness of composites were also investigated.The fracture toughness of CFRP was obtained through double cantilever beam(DCB)and end notched flexure(ENF)tests.The results showed that the composites prepared by modified resin exhibited high fracture toughness compared with unmodified composites.The fracture toughness value of mode I increased from 1.83 kJ/m2 to 4.55 kJ/m2.The fracture toughness value of mode II increased from 2.30 kJ/m2 to 6.47 kJ/m2.展开更多
Damage caused due to low-velocity impacts in composites leads to substantial deterioration in their residual strength and eventually provokes structural failure.This work presents an experimental investigation on the ...Damage caused due to low-velocity impacts in composites leads to substantial deterioration in their residual strength and eventually provokes structural failure.This work presents an experimental investigation on the effects of different patch and parent laminate stacking sequences on the enhancement of impact strength of Carbon Fiber Reinforced Polymers(CFRP)composites by utilising the adhesively bonded external patch repair technique.Damage evolution study is also performed with the aid of Acoustic Emission(AE).Two different quasi-isotropic configurations were selected for the parent laminate,viz.,[45°/45°/0°/0°]s and[45°/0°/45°/0°]s.Quasi Static Indentation(QSI)test was performed on both the pristine laminates,and damage areas were detected by using the C-scan inspection technique.Damaged laminates were repaired by using a single-sided patch of two different configurations,viz.,[45°/45°/45°/45°]and[45°/0°/0°/45°],and employing a circular plug to fill the damaged hole.Four different combinations of repaired laminates with two configurations of each parent and patch laminate were produced,which were further subjected to the QSI test.The results reveal the effectiveness of the repair method,as all the repaired laminates show higher impact resistance compared to the respective pristine laminates.Patches of[45°/0°/0°/45°]configuration when repaired by taking[45°/45°/0°/0°]s and[45°/0°/45°/0°]s as parents exhibited 68%and 73%higher peak loads,respectively,than the respective pristine laminates.Furthermore,parent and patch of configuration[45°/0°/45°/0°]s and[45°/0°/0°/45°],respectively,attain the highest peak load,whereas[45°/45°/0°/0°]s and[45°/45°/45°/45°]combinations possess the most gradual decrease in the load.展开更多
The earthquake resistant property of reinforced concrete members depends on the interaction between reinforcing bars and surrounding concrete through bond to a large degree. In this paper a general system aimed at dea...The earthquake resistant property of reinforced concrete members depends on the interaction between reinforcing bars and surrounding concrete through bond to a large degree. In this paper a general system aimed at dealing with the failure analysis of reinforced concrete columns strengthened with carbon fiber reinforced plastic (CFRP) sheets including bond slip of the anchored reinforcing bars at the foot of the columns is presented. It is based on the yield design theory with a mixed modeling of the structure, according to which the concrete material is treated as a classical two dimensional continuum, whereas the longitudinal reinforcing bars are regarded as one dimensional rods including bond slip at the foot of the columns. In shear reinforced zones both the shear CFRP sheets and transverse reinforcing bars are incorporated in the analysis through a homogenization procedure and they are only in tension. The approach is then implemented numerically by means of the finite element formulation. The numerical procedure produces accurate estimates for the loading carrying capacity of the shear members taken as an illustrative application by correlation with the experimental results, so the proposed approach is valid.展开更多
This paper discusses the results of tests on the shear capacity of reinforced concrete columns strengthened with carbon fiber reinforced plastic (CFRP) sheet. The shear transfer mechanism of the specimens reinforced w...This paper discusses the results of tests on the shear capacity of reinforced concrete columns strengthened with carbon fiber reinforced plastic (CFRP) sheet. The shear transfer mechanism of the specimens reinforced with CFRP sheet was studied. The factors affecting the shear capacity of reinforced concrete columns strengthened with CFRP sheet were analyzed. Several sug-gestions such as the number of layers, width and tensile strength of the CFRP sheet are proposed for this new strengthening technique. Finally, a simple and practical design method is presented in the paper. The calculated results of the suggested method are shown to be in good agreement with the test results. The suggested design method can be used in evaluating the shear capacity of reinforced concrete columns strengthened with CFRP sheet.展开更多
基金Project(2010-K2-8)supported by Science and Technology Program of the Ministry of Housing and Urban Rural Development,ChinaProject supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions,China
文摘The feasibility of longer spans relies on the successful implementation of new high-strength light weight materials such as carbon fiber reinforced polymer(CFRP). First, a dimensionless equilibrium equation and the corresponding compatibility equation are established to develop the cable force equation and cable displacement governing equation for suspension cables, respectively. Subsequently, the inextensible cable case is introduced. The formula of the Irvine parameter is considered and its physical interpretation as well as its relationship with the chord gravity stiffness is presented. The influences on the increment of cable force and displacement by λ2 and load ratio p′ are analyzed, respectively. Based on these assumptions and the analytical formulations, a 2000 m span suspension cable is utilized as an example to verify the proposed formulation and the responses of the relative increment of cable force and cable displacement under symmetrical and asymmetrical loads are studied and presented. In each case, the deflections resulting from elastic elongation or solely due to geometrical displacement are analyzed for the lower elastic modulus CFRP. Finally, in comparison with steel cables, the influences on the cable force equation and the governing displacement equation by span and rise span ratio are analyzed. Moreover, the influences on the static performance of suspension bridge by span and sag ratios are also analyzed. The substantive characteristics of the static performance of super span CFRP suspension bridges are clarified and the superiority and the characteristics of CFRP cable structure are demonstrated analytically.
文摘To study the response characteristics of the carbon fiber fabric reinforced composites under impact loading, one dimensional strain impact test, multi gauge technique and Lagrange analysis method are used. The decaying rule of the stress σ , strain ε , strain rate ε · and density ρ with time and space is obtained. By the theory of dynamics, the impact response characteristics of the material is analyzed and discussed.
基金supported in part by the Major Project of the Ministry of Science and Technology of China(No.2012ZX04003-031)the Innovation Project of Jiangsu Province(No.2016-05)
文摘Formation of entrance and exit defects in coarse pitch orbital drilling(CPOD)of carbon fiber reinforced plastic(CFRP)plates was investigated.Deep observation on entrance and exit morphology shows tear and burr are typical defects.Meanwhile,tear is more obvious than burr,and more entrance tears emerge than exit tears.As one of the major causes of entrance and exit defects in CPOD,cutting forces were substaintially studied by contrast experiments.Then,the effect of cutting parameters on entrance and exit tear was qualitatively analyzed through a single factor test.Experiment results indicate that the variation of rotation speed has little influence on entrance and exit tear.Increasing tangential feed per tooth can enlarge entrance tear,but bring little effect on exit tear.By increasing axial feed pitch,the hole entrance and exit show severe tear.When revolution radius grows bigger and bigger,entrance and exit tear firstly decreases,and then increases.Finally,the models of tear and delamination during CPOD of CFRP were established,the formation mechanisms of entrance and exit defects were revealed,and the control strategies were accordingly put forward.
基金Project(04043076) supported by the Outstanding Youth Foundation for Scientific and Technological Research of Anhui Province, ChinaProject(2007jq1035) supported by the Scientific Research Projects for Young College Teachers of Anhui Province, China
文摘Twenty-one square concrete columns were constructed and tested. The testing results indicate that bonded carbon fiber reinforced plastics(CFRP) sheets can be used to increase the strength and improve the serviceability of damaged concrete columns at low temperatures. The failure of the specimens,in most cases,takes place within the middle half of the columns. And the failure of strengthened columns is sudden and explosive. The CFRP sheets increase both the axial load capacity and the ultimate concrete compressive strain of the columns. The ultimate loads of strengthened columns at-10,0 and 10 ℃ increase averagely by 9.09%,6.63% and 17.83%,respectively,as compared with those of the control specimens. The axial compressive strength of strengthened columns is related to the curing temperatures. The improvement of axial compressive strength decreases with reducing temperature,and when the temperature drops to a certain value,the improvement increases with falling temperature.
基金National Natural Science Foundation of China(No.11802192)Natural Science Foundation of Jiangsu Province,China(No.BK20180244)Nantong Science and Technology Project,China(No.JC2019012)。
文摘The fracture toughness of carbon fiber reinforced epoxy composite(CFRP)was investigated through mode I and mode II shaped fracture system in this paper.A novel polyimide with trifluoromethyl groups and grafted nanosilica were used to modify epoxy resin.Effect of modified resin and unmodified resin on fracture toughness of CFRP was compared and discussed.Lay-up angles and thicknesses effects on fracture toughness of composites were also investigated.The fracture toughness of CFRP was obtained through double cantilever beam(DCB)and end notched flexure(ENF)tests.The results showed that the composites prepared by modified resin exhibited high fracture toughness compared with unmodified composites.The fracture toughness value of mode I increased from 1.83 kJ/m2 to 4.55 kJ/m2.The fracture toughness value of mode II increased from 2.30 kJ/m2 to 6.47 kJ/m2.
基金the financial support by the Council of Scientific&Industrial Research(CSIR)-Research Scheme,India(22/0809/2019-EMR-II)。
文摘Damage caused due to low-velocity impacts in composites leads to substantial deterioration in their residual strength and eventually provokes structural failure.This work presents an experimental investigation on the effects of different patch and parent laminate stacking sequences on the enhancement of impact strength of Carbon Fiber Reinforced Polymers(CFRP)composites by utilising the adhesively bonded external patch repair technique.Damage evolution study is also performed with the aid of Acoustic Emission(AE).Two different quasi-isotropic configurations were selected for the parent laminate,viz.,[45°/45°/0°/0°]s and[45°/0°/45°/0°]s.Quasi Static Indentation(QSI)test was performed on both the pristine laminates,and damage areas were detected by using the C-scan inspection technique.Damaged laminates were repaired by using a single-sided patch of two different configurations,viz.,[45°/45°/45°/45°]and[45°/0°/0°/45°],and employing a circular plug to fill the damaged hole.Four different combinations of repaired laminates with two configurations of each parent and patch laminate were produced,which were further subjected to the QSI test.The results reveal the effectiveness of the repair method,as all the repaired laminates show higher impact resistance compared to the respective pristine laminates.Patches of[45°/0°/0°/45°]configuration when repaired by taking[45°/45°/0°/0°]s and[45°/0°/45°/0°]s as parents exhibited 68%and 73%higher peak loads,respectively,than the respective pristine laminates.Furthermore,parent and patch of configuration[45°/0°/45°/0°]s and[45°/0°/0°/45°],respectively,attain the highest peak load,whereas[45°/45°/0°/0°]s and[45°/45°/45°/45°]combinations possess the most gradual decrease in the load.
文摘The earthquake resistant property of reinforced concrete members depends on the interaction between reinforcing bars and surrounding concrete through bond to a large degree. In this paper a general system aimed at dealing with the failure analysis of reinforced concrete columns strengthened with carbon fiber reinforced plastic (CFRP) sheets including bond slip of the anchored reinforcing bars at the foot of the columns is presented. It is based on the yield design theory with a mixed modeling of the structure, according to which the concrete material is treated as a classical two dimensional continuum, whereas the longitudinal reinforcing bars are regarded as one dimensional rods including bond slip at the foot of the columns. In shear reinforced zones both the shear CFRP sheets and transverse reinforcing bars are incorporated in the analysis through a homogenization procedure and they are only in tension. The approach is then implemented numerically by means of the finite element formulation. The numerical procedure produces accurate estimates for the loading carrying capacity of the shear members taken as an illustrative application by correlation with the experimental results, so the proposed approach is valid.
文摘This paper discusses the results of tests on the shear capacity of reinforced concrete columns strengthened with carbon fiber reinforced plastic (CFRP) sheet. The shear transfer mechanism of the specimens reinforced with CFRP sheet was studied. The factors affecting the shear capacity of reinforced concrete columns strengthened with CFRP sheet were analyzed. Several sug-gestions such as the number of layers, width and tensile strength of the CFRP sheet are proposed for this new strengthening technique. Finally, a simple and practical design method is presented in the paper. The calculated results of the suggested method are shown to be in good agreement with the test results. The suggested design method can be used in evaluating the shear capacity of reinforced concrete columns strengthened with CFRP sheet.
