Analysis And Experimental Study On The Strength Of CFRP Impeller Connection Structure

Non-destructive suction excavator can effectively avoid the destruction of underground interlaced cables and pipelines in urban construction by using the vacuum excavation technology.Among them,the centrifugal impeller is one of the key components of the onboard suction system.The traditional metal impeller brings a series of problems,such as large starting torque,high power consumption and serious equipment wear.Carbon fiber reinforced plastic?CFRP?has the advantages of light weight,high strength,fatigue resistance,etc.The lightweight impeller made of CFRP can effectively reduce equipment load and improve the efficiency of suction system.The connection area between the CFRP impeller and the metal hub is the weak link of the centrifugal fan.Its reliability is the premise of normal operation of centrifugal fan,and it is also the key problem that must be solved when CFRP is used as primary structure.In this paper,the key factors that affect the connection strength of CFRP impeller have been studied by means of numerical simulations and experiments,thus providing the theoretical basis for the design of CFRP impeller connection structure.The research contents in this paper are as follows:The progressive failure analysis process of CFRP impeller connection structure under torsional load has been established in this paper by combining the three-dimensional stress-strain relationship of composite materials,the three-dimensional failure criteria based on strain,the material performance degradation model based on fracture toughness and the ultimate failure evaluation method of CFRP impeller connection structure.Based on the progressive failure analysis process of the CFRP impeller connection structure,a user-defined subroutine VUMAT has been written.At the same time,the finite element model of the CFRP impeller connection structure has been established in ABAQUS.The failure mode of the connection structure under torsional load and its evolution process have been analyzed.The results show that both of the five failure modes start from one end of the CFRP connector,then expand along the thickness direction,and finally expand to the entire plate.Among them,the matrix tensile failure first appears,fiber compression failure occurs in the end.The effects of the stacking parameters and geometric parameters on the connection strength of the CFRP impeller have been studied by numerical simulations.The results show that proper bolt pretightening can improve the bearing capacity of the CFRP impeller connection structure.The increase of the ratio between margin and aperture can only increase the ultimate failure load in a small range,and the ultimate failure load will no longer increase when the the ratio reaches 2.5.Increasing the proportion of±45oand 0ocan improve the bearing capacity of the CFRP impeller connection structure,and the stacking scheme of the highest bearing capacity is[0/?±45?₃/0].The failure load is not proportional to the laminate thickness,and the increasing trend of the ultimate load will slow down when the thickness reaches a certain value.Meanwhile,the excessive size will also lead to the decrease of the connection efficiency.CFRP specimens which differ in stacking parameters and geometry parameters have been made,and the torsion test and the ultrasonic C-scan test have been carried out respectively.The results show that the experimental results are in good agreement with the simulation results,which prove that the effects of stacking parameters and geometric parameters on the strength of the connection structure obtained in simulations are reliable.