Many works have been made for predicting the failure of composite joints.However,there is still lack of method for multi-bolted composite joints subjected to the hygrothermal environment.In this work,a characteristic ...Many works have been made for predicting the failure of composite joints.However,there is still lack of method for multi-bolted composite joints subjected to the hygrothermal environment.In this work,a characteristic curve-based numerical framework is proposed,which includes two main steps and shows low computational cost.Firstly,a 3D finite element model considering hygrothermal effects is established to analyze the bolt-load distribution of multi-bolted joints.Secondly,a new characteristic curve considering the hygrothermal influence is used to obtain the failure pattern and strength of composite joints.The two-,three-and four-bolted composite joints with-55℃/dry(CTD),23℃/dry(RTD)and 70℃/wet(ETW)conditions are investigated.The test outcomes present good agreement with predicted results,which illustrates the effectiveness and applicability of the proposed method.Meanwhile,it is shown that the environmental condition affects the bolt-load ratio slightly,but does not change the location of the key loaded hole.Furthermore,deviations of the strengths in CTD and ETW conditions are about 5%and-16%from that in the RTD condition,respectively.The environmental condition does not affect the failure modes of two-and three-bolted joints,whereas changes the failure mode of the four-bolted joint.The proposed method is efficient,reliable and needs only linear elastic FE analysis,making it applicable for engineering practice.展开更多
Hybrid joints have better tensile properties than pure bonded and bolted bolts,and are increasingly used in the aerospace field.Tensile tests are carried out for the Hybrid Bonded/Bolted(HBB)joints of Carbon Fiber Rei...Hybrid joints have better tensile properties than pure bonded and bolted bolts,and are increasingly used in the aerospace field.Tensile tests are carried out for the Hybrid Bonded/Bolted(HBB)joints of Carbon Fiber Reinforced Polymer(CFRP)laminate and titanium alloy plate under different bolt numbers,and the corresponding load–displacement curves are obtained.At the same time,based on Continuum Damage Mechanics(CDM)theory,which is derived from 3D Hashin failure criteria,and a Cohesive Zone Model(CZM),the tensile strength prediction model of the composite laminate-titanium alloy plate multi-bolted HBB joint was established,and the numerical simulation results were in good agreement with the experimental height,which validate the feasibility of the model.The difference in the bearing capacity of HBB joints under different numbers of bolts is compared and analyzed.On this basis,the influence of inter-bolt distance on the tensile properties of the HBB joints is explored.The results show that the double-nail HBB joints can effectively improve the end warpage and low bearing capacity of the single-nail HBB joints.The tensile failure load of the double-nail HBB joints under the standard lap width(30 mm)is 82.6%higher than that of the single nail,the tensile failure load of the three-bolt HBB joints is 34.1%higher than that of the double nail.For the three-bolt HBB joint,the joint strength is controlled by the adhesive and the external bolt,while the internal bolt is redundant,the hybrid joint can be simplified by reducing the middle bolt.The inter-bolt distance has a great influence on the failure load of the hybrid joint.Increasing the inter-bolt distance can effectively improve the bearing capacity of the structure.展开更多
The stress distribution surrounding the fastener hole in thick laminate mechanical joints is complex. It is time-consuming to analyze the distribution using finite element method. To accurately and efficiently obtain ...The stress distribution surrounding the fastener hole in thick laminate mechanical joints is complex. It is time-consuming to analyze the distribution using finite element method. To accurately and efficiently obtain the stress state around the fastener hole in multi-bolt thick laminate joints, a global-local approach is introduced. In the method, the most seriously damaged zone is 3D modeled by taking the displacement field got from the 2D global model as boundary conditions. Through comparison and analysis there are the following findings: the global-local finite element method is a reliable and efficient way to solve the stress distribution problem; the stress distribution around the fastener hole is quite uneven in through-the-thickness direction, and the stresses of the elements close to the shearing plane are much higher than the stresses of the elements far away from the shearing plane; the out-of-plane stresses introduced by the single-lap joint cannot be ignored due to the delamination failure; the stress state is a useful criterion for further more complex studies involving failure analysis.展开更多
基金supported by the China Postdoctoral Science Foundation(No.2020M680325)the Chinese National Natural Science Fund(Nos.12172067 and 12072005)+4 种基金the Fundamental Research Funds for the Central Universities,China(No.2023CDJXY-007)the Aeronautical Science Foun-dation of China(No.2022Z0570Q9002)the Young Elite Sci-entists Sponsorship Program by CAST,China(No.2020QNRC001)the Chongqing Talent Plan,China(No.cstc2022ycjh-bgzxm0144)the Project of High-Level Talents Introduction of Hebei Province,China(No.2021HBQZYCSB009)。
文摘Many works have been made for predicting the failure of composite joints.However,there is still lack of method for multi-bolted composite joints subjected to the hygrothermal environment.In this work,a characteristic curve-based numerical framework is proposed,which includes two main steps and shows low computational cost.Firstly,a 3D finite element model considering hygrothermal effects is established to analyze the bolt-load distribution of multi-bolted joints.Secondly,a new characteristic curve considering the hygrothermal influence is used to obtain the failure pattern and strength of composite joints.The two-,three-and four-bolted composite joints with-55℃/dry(CTD),23℃/dry(RTD)and 70℃/wet(ETW)conditions are investigated.The test outcomes present good agreement with predicted results,which illustrates the effectiveness and applicability of the proposed method.Meanwhile,it is shown that the environmental condition affects the bolt-load ratio slightly,but does not change the location of the key loaded hole.Furthermore,deviations of the strengths in CTD and ETW conditions are about 5%and-16%from that in the RTD condition,respectively.The environmental condition does not affect the failure modes of two-and three-bolted joints,whereas changes the failure mode of the four-bolted joint.The proposed method is efficient,reliable and needs only linear elastic FE analysis,making it applicable for engineering practice.
基金co-supported by the National Natural Science Foundation of China(No.U1833116)Key Scientific Research Project of Colleges and Universities in Henan Province,China(No.20A460023)。
文摘Hybrid joints have better tensile properties than pure bonded and bolted bolts,and are increasingly used in the aerospace field.Tensile tests are carried out for the Hybrid Bonded/Bolted(HBB)joints of Carbon Fiber Reinforced Polymer(CFRP)laminate and titanium alloy plate under different bolt numbers,and the corresponding load–displacement curves are obtained.At the same time,based on Continuum Damage Mechanics(CDM)theory,which is derived from 3D Hashin failure criteria,and a Cohesive Zone Model(CZM),the tensile strength prediction model of the composite laminate-titanium alloy plate multi-bolted HBB joint was established,and the numerical simulation results were in good agreement with the experimental height,which validate the feasibility of the model.The difference in the bearing capacity of HBB joints under different numbers of bolts is compared and analyzed.On this basis,the influence of inter-bolt distance on the tensile properties of the HBB joints is explored.The results show that the double-nail HBB joints can effectively improve the end warpage and low bearing capacity of the single-nail HBB joints.The tensile failure load of the double-nail HBB joints under the standard lap width(30 mm)is 82.6%higher than that of the single nail,the tensile failure load of the three-bolt HBB joints is 34.1%higher than that of the double nail.For the three-bolt HBB joint,the joint strength is controlled by the adhesive and the external bolt,while the internal bolt is redundant,the hybrid joint can be simplified by reducing the middle bolt.The inter-bolt distance has a great influence on the failure load of the hybrid joint.Increasing the inter-bolt distance can effectively improve the bearing capacity of the structure.
文摘The stress distribution surrounding the fastener hole in thick laminate mechanical joints is complex. It is time-consuming to analyze the distribution using finite element method. To accurately and efficiently obtain the stress state around the fastener hole in multi-bolt thick laminate joints, a global-local approach is introduced. In the method, the most seriously damaged zone is 3D modeled by taking the displacement field got from the 2D global model as boundary conditions. Through comparison and analysis there are the following findings: the global-local finite element method is a reliable and efficient way to solve the stress distribution problem; the stress distribution around the fastener hole is quite uneven in through-the-thickness direction, and the stresses of the elements close to the shearing plane are much higher than the stresses of the elements far away from the shearing plane; the out-of-plane stresses introduced by the single-lap joint cannot be ignored due to the delamination failure; the stress state is a useful criterion for further more complex studies involving failure analysis.
