Effects of Bolt-Hole Clearance on Static Tensile Failure of Composite Bolted Joints Under Hygrothermal Environment
The hygrothermal environment has a significant impact on the mechanical properties of composite bolted joints.In this paper,static tensile tests were carried out under two environmental conditions:room temperature and dry(RTD)and 70 ℃ equilibrium moisture absorption(ETW),to analyze the static strength variation laws of composite bolted joints with three different pin-hole clearances of 0 mm,0.2 mm,and 0.4 mm.Combined with scanning electron microscopy(SEM)test,the microscopic failure mechanism of the joints was revealed,and a finite element model was established to analyze the stress state around the holes of specimens with different pin hole clearances.The results show that both pin-hole clearance and hygrothermal environment have significant effects on structural strength.Compared with the specimens with a 0 mm clearance,the ultimate failure loads of the specimens with 0.2 mm and 0.4 mm clearances are decreased by 2.78％and 3.45％,respectively,under the RTD condition,and by 4.64％and 5.01％,respectively,under the ETW condition.By comparing the specimens with 0 mm,0.2 mm,and 0.4 mm clearances,the ultimate loads under the ETW condition are decreased by 9.34％,11.07％,and 10.81％,respectively,compared with those under the RTD condition.The damage around the holes in ETW environment is more severe,while the fracture surface of the substrate is relatively rough,the cracks are more obvious.And it could also find some fiber bundle pulling and fiber fragmentations.In the thickness direction of the laminated board,it could be noticed that there is less adhesive resin,and the fiber distribution morphology is relatively flat.
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