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Mode ? Interlaminar Fracture Toughness Of GLARE By Double And Single Cantilever Beam

Posted on:2020-12-28Degree:MasterType:Thesis
Country:ChinaCandidate:X G HuaFull Text:PDF
GTID:2381330590472475Subject:Materials Processing Engineering
Abstract/Summary:PDF Full Text Request
GLARE(Glass Fiber Reinforced Aluminium Laminates)has been developed as the crucial materials for fuselage and wing skin owing to the excellent fatigue,good damage tolerance.As the main failure mode of GLARE,interfacial delamination is the major factor determining the comprehensive performance.However,GLARE suffers complicated failure mechanism and has a complex multi-interface system.Obviously,characterizing the Mode I interlaminar fracture toughness of GLARE with the reliable method is essential.In our work,Mode I interlaminar fracture toughness was investigated with Double Cantilever Beam(DCB)method and Single Cantilever Beam(SCB)method based on the in-depth study of GLARE interfacial fracture properties.Meanwhile,the insufficiency of DCB and the applicability of SCB were also explored for GLARE.Firstly,the interlaminar fracture toughness of GLARE was studied by DCB method.The theoretical calculation,finite element simulation as well as DCB test were investigated to reveal the interfacial fracture behavior of GLARE with different layers under different loading rates(1mm/min,5mm/min and 10mm/min).The DCB tests indicated that the absence of mode mixity and the measured interlaminar fracture toughness value was larger than the true value.When the loading rate was 1-5mm/min,the interfacial fracture toughness was obtained efficiently.Furthermore,the finite element simulation results demonstrated that in-plane shear failure existed in the fibre layer,leading to the Mode II fracture.The theoretical calculation results were basically consistent with DCB results at the initial stage of crack propagation.Moreover,the deviation between theoretical calculations and experimental results gradually increased with the crack propagation and they were conformed to the linear function.Secondly,the feasibility and accuracy of SCB method for GLARE were explored by combining finite element simulation with experiments.Meanwhile,the effect of fiber laying and loading rate on the Mode I interlaminar fracture properties of GLARE was studied in detail.The results indicated that pure Mode I interlaminar fracture failure was produced in SCB tests.Then,the specimen exhibited mixed failure modes of interfacial fracture and cohesive fracture.Moreover,reasonable and effective Mode I interlaminar fracture toughness could be obtained at loading rate of 1 mm/min-5 mm/min.In addition,finite element simulation results showed that there was no in-plane shear failure in the fiber layer,which produced pure Mode I interlaminar fracture.Finally,the rationality and validity of SCB method were focused on in this study frommechanical principle and failure form through investigating the interlaminar fracture toughness of Al/Epoxy/Al laminated materials and GLARE respectively by DCB and SCB.The results indicated that the load and displacement were conformed to the linear relationship in the initial stage of loading.Then,the load of DCB decreased rapidly.On the contrary,cracks propagated slowly in SCB with obvious loads and displacements.Besides,both DCB and SCB tests could produce pure Mode I interlaminar fracture in Al/Epoxy/Al laminated materials.However,SCB method presented obviously stable crack propagation and single interface failure mode for evaluating the interlaminar fracture toughness of GLARE,when compared with DCB tests.Therefore,the Mode I interlaminar fracture toughness of GLARE can be accurately evaluated by means of SCB method.
Keywords/Search Tags:GLARE, Mode ? interlaminar fracture toughness, Double cantilever beam method, Single cantilever beam method, Interfacial properties
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