Study On Shearing Mechanical Properties Of Plain Woven Composite Laminates After Bonding Repair

The glass fiber plain weave laminate has high specific strength,high specific rigidity and good electromagnetic wave transmission performance,and is widely used in aircraft radome and fairing structures.However,the aircraft often encounters bird strikes,strong air currents,and sand and gravel impacts during flight,causing damage to the composite structure of the aircraft.Therefore,the damage d area needs to be replaced or repaired.As a typical repair method of aerospace composite material structure,adhesive repair can effectively restore the safety and functionality of structural parts.Therefore,it is particularly necessary to study the shear mechanical properties of plain weave laminates after adhesive repair.Firstly,The VUMAT subroutine was written referring to the two-dimensional Hashin failure criterion,and the failure criterion and stiffness degradation model of plain woven composite laminates were set.Then,the adhesive layer was simulated by the cohesive force model of ABAQUS,and the progressive damage analysis of plain woven composite laminates under in-plane shear and interlaminar shear was carried out.Secondly,According to ASTM D5379/D3846-08,the in-plane shear and interlaminar shear performance test of plain weave laminates were carried out,and the non-damage test piece and the control group of the adhesive repair test piece were set respectively.Focus on the analysis of test strength,strength recovery rate,stiffness,and failure mode.The results show that the in-plane shear strength recovery rate of the test piece after the bonding repair is greater than the interlaminar shear strength recovery rate.The final failure modes of the in-plane shear non-damage test piece and the glued joint repair test piece all present a mixed failure mode of vertical fracture and transverse crack along the V-notch.The failure mode of the glued repair test piece also includes the debonding of the patch,which is consistent with The failure mode specified by the ASTM standard.The appearance of the fracture of the bonding repair test piece was observed with a SEM electron microscope,and it was found that the fracture of the 0°radial direction fiber bundle was relatively neat,part of the fiber bundle was pulled out,and the90° weft direction fiber bundle was basically intact.The failure mode of the interlayer shearing non-damage test piece is the failure of the adhesive layer,and there is no damage to the adhered surface.The failure mode of the adhesive repair test piece is the fiber damage of the repair layer and the debonding of the adhesive layer.Finally,The ABAQUS software was used to establish a 1:1 finite element analysis model,and the simulation analysis was carried out on the shear strength,stress concentration area and damage propagation.The results show that the predicted strength of the in-plane shear nondamage test piece and the bonded repair test piece is within a reasonable range.The initial inplane shear damage of the in-plane shear non-damage test piece and the bonded repair test piece occurs in the vertical plane of the V port,and gradually expands to both sides along the vertical line of the V port,until the failure of the entire V-port plane is complete.The stress concentration area of the non-damaged test piece expands along the top of slot V to the surface of slot V.The trend of stress concentration phenomenon of the bonded repair test piece is consistent with that of the non-damaged test piece.However,in the process of stress concentration change,the patch takes the lead in ending the stress concentration phenomenon,which proves that the patch loses its bearing capacity first.The simulation results show that the predicted strength is also within a reasonable range,which proves the validity of the prediction.By observing the failure mode of the adhesive layer of the non-damaged test piece,it is found that the damage extends inward from both ends,and the stress at the position of the double cut is more concentrated.The damage of the adhesive layer extends from one end of the adhesive layer to the other end of the adhesive layer,and the stress concentration phenomenon is observed,and the stress concentration phenomenon of the unilateral incision is more serious.