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Research On Residual Stress Of Cfrpwing Tanks Corner Based On FBG Sensors

Posted on:2015-12-20Degree:MasterType:Thesis
Country:ChinaCandidate:L WeiFull Text:PDF
GTID:2298330452950425Subject:Composite materials science
Abstract/Summary:PDF Full Text Request
Residual stress of wing tanks corner affects wing safety. Residual stress testingof composite structures has been an industrial problem. In this paper, the residualstress during the curing process of CFRP corner structures is monitored FBG sensorsto monitor. Based on the principle of reducing the residual stress, the structure of thecorner molding process is optimized.Firstly, carbon fiber prepreg’s flexural propertie and its resin content are detected.Then the stress sensitive coefficient, the temperature sensitive coefficient and thethermal stability performance are determined. The results reveal that both the axialstress and the temperature show linear relation with the central wavelength of thesame batch sensors. The axial stress and the coefficient of temperature sensitivitycoefficient are1.383×10-5pm/Pa and10.173pm/℃. Temperature stability of FBGsensors in high temperature is worse than them in low temperature.Secondly, there are six aspects (locations, ply angle, ply thickness, number oflayers, spread inside and outside corners, different molds) which studied the residualstress of CFRP wing corner. The curing process of the stress and temperature aremonitored, the residual stress in the inner plate laminated is detected after24hours.Then refresher tests of the laminate which made of invar mold are conducted to studythe effects of residual stress.It can be concluded:①Residual stress the corner in the same layer of plywood is littler than the plate2.1MPa.②The thicker laminate, corner residual stress tends to tensile stress, the greaterthe shrinkage stress at the plate.③The bigger ply angle, the greater the residual stress around the corner.④The laminate is thicker, shrinkage stress of the bottom which is constrainedby the mold is larger than the surface, the difference is40.89MPa.⑤When the laminates are made by using the inside corner and the outsidecorner of mold, the smaller the radius then the smaller curvature, the greaterthe shrinkage stress at the corner.⑥The more difference of thermal expansion coefficient between mold and laminate, the greater the compressive stress, the residual stress is mainlycompressive stress, the minimum value is-1.92MPa.⑦Refresher tests are in favor of the release of residual stress and the value is1.16MPa.Finally, ANSYS is used to simulate the residual stress of flat and corner. Theresults show that the maximum deviation between simulated value and experimentalvalues is1.15MPa, and the ratio is6.01%. The data are within the acceptable range,and the use of FBG sensors is thus reliable to detect residual stress.
Keywords/Search Tags:FBG sensor, Residual stress, Corner, Ply, Autoclave curing process
PDF Full Text Request
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