To study the bridging effect of partly-cured Z-pin,Z-pins with different curing degrees are manufactured by controlling pultrusion parameters.A unit cell is selected to analyze the stress of Z-pinned laminates and the...To study the bridging effect of partly-cured Z-pin,Z-pins with different curing degrees are manufactured by controlling pultrusion parameters.A unit cell is selected to analyze the stress of Z-pinned laminates and the quantitative relationship between the maximum bridging force and Z-pin diameter,embedded length,interfacial shear strength and tensile strength is acquired.The Z-pin″bridging law″test and Z-pin tensile test are carried out to study the effect of Z-pin′s curing degree on bridging effect,and the bridging efficiency is defined to evaluate the reinforcement effect of Z-pin.The modeⅠinterlaminar fracture toughness(G_(ⅠC))is measured by the double cantilever beam test.The experimental results show that Z-pin′s co-curing with laminate matrix can improve the bridging force significantly and the fitting results show a linear relationship between Z-pin curing degree and interfacial shear strength.The three-dimensional images of the surface of pullout Z-pins indicate that the failure mode changed from totally interfacial debonding to a mixed mode.Finally,the reinforcement by partly-cured Z-pin can be used to further enhance the interlaminar toughness.Compared with completely-cured Z-pin,G_(ⅠC) of Z-pin with 67.6% curing degree increases by 47.0%.展开更多
The Huanghe River(Yellow River)Delta has a wide distribution of fine-grained soils.Fluvial alluviation,erosion,and wave loads affect the shoal area,resulting complex physical and mechanical properties to sensitive fin...The Huanghe River(Yellow River)Delta has a wide distribution of fine-grained soils.Fluvial alluviation,erosion,and wave loads affect the shoal area,resulting complex physical and mechanical properties to sensitive finegrained soil located at the river-sea boundary.The cone penetration test(CPT)is a convenient and effective in situ testing method which can accurately identify various soil parameters.Studies on undrained shear strength only roughly determine the fine content(FC)without making the FC effect clear.We studied four stations formed in different the Huanghe River Delta periods.We conducted in situ CPT and corresponding laboratory tests,examined the fine content influence on undrained shear strength(S_(u)),and determined the cone coefficient(N_(k)).The conclusions are as follows.(1)The fine content in the area exceeded 90%,and the silt content was high,accounting for more than 70%of all fine particle compositions.(2)The undrained shear strength gradually increased with depth with a maximum of approximately 250 kPa.When the silt content was lower than 60%–70%,the undrained shear strength decreased.(3)The silt and clay content influenced undrained shear strength,and the fitted f_(s)h/q_(t) function model was established,which could be applied to strata with a high fine content.The cone coefficients were between 20 and 25,and the overconsolidated soil layer had a greater cone coefficient.展开更多
A newly developed hybrid pin (HP), composed of a compressed wooden dowel inserted into a stainless steel pipe is suggested in this research. This configuration is expected to grant high stiffness by bending performanc...A newly developed hybrid pin (HP), composed of a compressed wooden dowel inserted into a stainless steel pipe is suggested in this research. This configuration is expected to grant high stiffness by bending performance of the metal pipe and rich ductility through shear deformation of compressed wooden dowel without brittle split of the joint member. Experimental tests were performed in order to verify your assumptions and pursue an optimum design. Double shear test perpendicular to the grain of HP was conducted with parameter of thickness and loading direction for base member for pin’s diameter. Rotational test for mortise and tenon joint inserted with HP was performed in order to evaluate the moment resisting performance. Consequently, the hybrid pin showed satisfactory performance as shear type fastener by virtues of not only relatively high stiffness but also rich ductility originated from the properties of each component, stain less steel pipe and compressed wood.展开更多
基金financially supported by the Aeronautical Science Fund(No.2015ZE52049)the Priority Academic Program Development of Jiangsu Higher Education Institutionsthe Fundamental Research Funds for the Central Universities(No.3082615NS2015056)
文摘To study the bridging effect of partly-cured Z-pin,Z-pins with different curing degrees are manufactured by controlling pultrusion parameters.A unit cell is selected to analyze the stress of Z-pinned laminates and the quantitative relationship between the maximum bridging force and Z-pin diameter,embedded length,interfacial shear strength and tensile strength is acquired.The Z-pin″bridging law″test and Z-pin tensile test are carried out to study the effect of Z-pin′s curing degree on bridging effect,and the bridging efficiency is defined to evaluate the reinforcement effect of Z-pin.The modeⅠinterlaminar fracture toughness(G_(ⅠC))is measured by the double cantilever beam test.The experimental results show that Z-pin′s co-curing with laminate matrix can improve the bridging force significantly and the fitting results show a linear relationship between Z-pin curing degree and interfacial shear strength.The three-dimensional images of the surface of pullout Z-pins indicate that the failure mode changed from totally interfacial debonding to a mixed mode.Finally,the reinforcement by partly-cured Z-pin can be used to further enhance the interlaminar toughness.Compared with completely-cured Z-pin,G_(ⅠC) of Z-pin with 67.6% curing degree increases by 47.0%.
基金The National Natural Science Foundation of China under contract Nos S42177153,U2006213 and 41806075the Shandong Province Focused Research and Development Program under contract No.2019GHY112075the National Major Scientific Research Instrument Development Project under contract No.41627801.
文摘The Huanghe River(Yellow River)Delta has a wide distribution of fine-grained soils.Fluvial alluviation,erosion,and wave loads affect the shoal area,resulting complex physical and mechanical properties to sensitive finegrained soil located at the river-sea boundary.The cone penetration test(CPT)is a convenient and effective in situ testing method which can accurately identify various soil parameters.Studies on undrained shear strength only roughly determine the fine content(FC)without making the FC effect clear.We studied four stations formed in different the Huanghe River Delta periods.We conducted in situ CPT and corresponding laboratory tests,examined the fine content influence on undrained shear strength(S_(u)),and determined the cone coefficient(N_(k)).The conclusions are as follows.(1)The fine content in the area exceeded 90%,and the silt content was high,accounting for more than 70%of all fine particle compositions.(2)The undrained shear strength gradually increased with depth with a maximum of approximately 250 kPa.When the silt content was lower than 60%–70%,the undrained shear strength decreased.(3)The silt and clay content influenced undrained shear strength,and the fitted f_(s)h/q_(t) function model was established,which could be applied to strata with a high fine content.The cone coefficients were between 20 and 25,and the overconsolidated soil layer had a greater cone coefficient.
文摘A newly developed hybrid pin (HP), composed of a compressed wooden dowel inserted into a stainless steel pipe is suggested in this research. This configuration is expected to grant high stiffness by bending performance of the metal pipe and rich ductility through shear deformation of compressed wooden dowel without brittle split of the joint member. Experimental tests were performed in order to verify your assumptions and pursue an optimum design. Double shear test perpendicular to the grain of HP was conducted with parameter of thickness and loading direction for base member for pin’s diameter. Rotational test for mortise and tenon joint inserted with HP was performed in order to evaluate the moment resisting performance. Consequently, the hybrid pin showed satisfactory performance as shear type fastener by virtues of not only relatively high stiffness but also rich ductility originated from the properties of each component, stain less steel pipe and compressed wood.
