The Effect Of Temperature On The Torsional Strength Of CFRP Automobile Drive Shaft

Compared with traditional metal materials,Carbon Fiber Reinforced Plastic(CFRP)features excellent mechanical properties,such as high specific strength,high specific modulus,high specific stiffness,fatigue resistance,and flexibility in design.Generally,automobile drive shaft made of CFRP shaft tube and metallic by bonding technique can not only minimize the weight of automobile drive shaft,but also further decrease the noise,improve the natural vibration frequency and critical speed,and greatly reduce the power consumption of drive shaft.However,as automobiles are used in relatively complex environment,the CFRP automobile drive shaft is inevitably affected by the external ambient temperature,which has exerted a certain impact on its mechanical performance.Therefore,it is of great significance to study the variation law of torsional strength of CFRP automobile drive shafts under the influence of high and low ambient temperatures.In this dissertation,the CFRP automobile drive shaft subjected to torsion load was taken as the research object,it puts forward “the effect of temperature on the torsional strength of CFRP automobile drive shaft”,and carries out an in-depth study on the failure torque changes of CFRP automobile drive shaft at three different temperatures(i.e.high,low and room temperatures),with the purpose of obtaining the effect law of high and low temperatures on the torsional strength of CFRP automobile drive shaft and providing the basis for the design of CFRP automobile drive shaft based on high and low temperatures.The main research contents of this dissertation are as follows:Firstly,the causes of effect of temperature on the performance of adhesive layer and tube of CFRP automobile drive shaft was analyzed,and the thermal stress of CFRP automobile drive shaft under the effect conditions of temperature was also analyzed based on the theory of mechanics of composite materials.The structural parameters of CFRP automobile drive shaft test specimens based on the failure of adhesive layer and shaft tube were designed,and the corresponding test specimens were prepared respectively.In addition,a testing program was designed,and the high and low temperatures were chosen respectively as the temperature environments that can affect the torsional strength of CFRP automobile drive shafts.A series of related experimental researches were conducted,including high temperature and low temperature tests,as well as the torsional strength test of specimens.Secondly,for the CFRP automobile drive shaft test specimen based on the failure of adhesive layer,the torsion tests of test specimens were carried out after 336 hours under the controlled environments of high temperature(70?),low temperature(-25?)and room temperature,so as to study the evolution law of failure torque of adhesive layer.The experimental results showed that the failure torque of adhesive layer decreased in varying degrees after exposure to high and low temperature environments for 336 hours,while the decline of torsional strength of adhesive layer was more obvious under low temperature environment,of which the failure torque dropped by 4.58% at 70?,and 6.41% at-25?.Furthermore,a simulation analysis in the failure propagation process of adhesive layer under torsional loading was performed on the basis of cohesive zone model(CZM);the temperature degradation parameter was introduced and applied to the CZM of adhesive layer,so that the simulation analysis of the failure of adhesive layers under high and low temperatures can be achieved.The results of experiment and simulation tests were basically consistent,verifying that it was a rational choice to introduce temperature degradation parameter for the analysis of the properties of adhesive layers under different temperatures.Through the output of internal stresses of adhesive layers at different temperatures,the variation of internal stresses of adhesive layers under high and low temperatures was further studied.It was shown that the internal stress values of adhesive layers under high and low temperatures were higher than those at room temperature.Thirdly,for the CFRP automobile drive shaft test specimen based on the failure of shaft tube,the torsion tests of test specimens were also carried out after 336 hours under the environments of high temperature(70?),low temperature(-25?)and room temperature,so as to study the evolution law of failure torque of shaft tube.The experimental results showed that there were different changing tendency in the failure torque of the specimen shaft tube after exposure to the environments of 70? and-25? for 336 hours.The failure torque of specimen basically had no change at the experimental temperature of 70?,while it was down by 8.51% at-25?.