Thermal Effect Analysis Of Composite Laminates And Metal Connections For Aircraft

In aircraft structures,with the extensive use of composite structures,there are many joint regions between composite materials and metals.Because of the significant difference in thermal expansion characteristics between composites and metals,there is a significant temperature stress in the composite-metal hybrid structure,which makes the static strength design change from mechanical design to thermal-mechanical design.Firstly,the tension test of composite-aluminum alloy single-row three-screw connection structure was carried out,and the bolt load distribution ratio of the test piece was obtained.A three-dimensional solid model is established by using ABAQUS general finite element software.Through numerical simulation analysis,the bearing load of bolts is obtained,and compared with the test results,a more accurate simulation model is obtained.Then,on the basis of the above-mentioned finite element model,the thermal-mechanical coupling analysis of the model is carried out by adding temperature variation conditions.The effects of cryogenic temperature(CT)and elevated temperature(ET)environments on stress distribution and bolt loads of composite-metal hybrid joints are studied for eight groups of models respectively.By means of thermo-mechanical coupling analysis,the variation of bolt load distribution in lap plates with different layers and metal materials at cryogenic,room and elevated temperatures was studied.The ideal bolted connection structure will deform due to the different thermal expansion coefficients of the components when the temperature changes,thus producing temperature stress.In order to coordinate the deformation of the two plates at the bolt joint,the load will be generated.When the ambient temperature is-75?,the metal plate shrinks and produces a force pointing to the middle of the two external bolts.W hen the ambient temperature is 100?,the metal plate expands and produces a force pointing to both sides of the two external bolts,and produces corresponding stress and strain in the structure.Through thermo-mechanical coupling analysis,the variation law of bolt load distribution under the influence of temperature change for different connection forms,different metal lap plate materials and two typical composite lamination sequence composite bolt connection structures is studied.The change of temperature will lead to the uneven distribution of bolt load.The load will be concentrated to a bolt on the outside.The most serious bolt load-bearing ratio is more than 55%.The influence of temperature variation on the connection structure obtained in this paper has certain reference value in aircraft design.