Effects Of Hole-Perpendicularity Error On The Mechanical Behavior Of Composite Single-lap Double-bolt Joints

Carbon fiber reinforced epoxy composites material has the advantages of high strength and specific modulus,excellent fatigue durability,satisfactory vibration damping performance,significant erosion resistance,reliable damage tolerance,making it out-standing in the lightweight design.With the decline in its manufacturing costs,more and more composite parts widely used in bearing components of automotive.Mechanical connection is the most common method in composite parts assembling.However,the drilling process of composite parts destroys the continuity of the fibers and makes the connection the most fragile part of the structure.It is necessary to carry out detailed research and analysis on the mechanical connection of the composite materials,which provides theoretical basis for the structural design.However,there is no corresponding study of connection hole perpendicularity error in the previous study.Therefore,the effects of hole perpendicularity error on the mechanical behavior of composite single-lap double-bolt joints is analyzed in this paper:(1)First,a progressive damage model based on Chang-lessard damage criterion was established.The model considers the nonlinear shear stress-strain relationship and combines the stiffness reduction scheme for sudden drop degradation of material properties.The criterion was implemented in ABAQUS/Standard using a UMAT subroutine.Good agreement was found when comparing numerical simulation results with experimental outcomes of open-hole tensile test,which verifies the correctness of the progressive damage model.(2)By designing and carrying out tensile test for single-lap double-bolt joints of composite material,the bearing capacity and failure mode of the joints were obtained and the influence of hole-perpendicularity error on the connection performance was investigated.Moreover,the damage mechanism of carbon fiber composite was studied via evaluating the damage observed by optical microscope.The validity of the simulation analysis was demonstrated through the comparison of numerical results and the experimental outcome.In addition,the relevant parameters were analyzed by finite element software.(3)The three-dimensional finite element model of composite double-bolt single-lap joint was established,and the influence of the damage of composite material on the distribution of bolt load was considered.According to the results,the influence of hole-perpendicularity error tilt patterns and tilt angle on the load distribution of bolts was analyzed.