Influence of transverse cracks on the onset of delamination: application to L-angle specimens. F. Laurin*, A. Mavel, P. Nuñez, E.

Transcription

1 Influene of transverse raks on the onset of delamination: appliation to L-angle speimens F. Laurin*, A. Mavel, P. Nuñez, E. Auguste

2 Composite strutures subjeted to 3D loading Wings Strutures under 3D loadings 53% omposite materials L-angle speimens loated in the different parts of an airraft Different thiknesses, different lay-ups 3D omplex loadings In-plane membrane loading ombined with unfolding loading VTP HTP Multiaxial omplex 3D loading 0 Thin speimens disoriented laminates (-4 plies) Centre wing box Thik speimens oriented laminates (up to 00 plies)

3 Failure mehanisms in L-angle speimens Delamination in L-angle speimens Failure is due to delamination in the radius Most loaded interfae y x Delamination starts at the most loaded interfae The propagation of delamination is instantaneous and indues failure of L-angle speimens Strength predition an be performed using a 3D failure riterion e yy Strain field measured with Digital Image Correlation Delamination Coupling between transverse raks and delamination Transverse raks an be observed in the radius prior the final failure due to delamination Transverse raks indue loal delamination at the tips of the raks Premature delamination in the radius Transverse rak Loal delamination Coupling between transverse rak and delamination must be added to obtain onservative preditions 3 [Huhette 05], [Lubineau 09], [Charrier 3], [Laurin 3]

4 Failure mehanisms in L-angle speimens Delamination in L-angle speimens Failure is due to delamination in the radius Most loaded interfae y x Delamination starts at the most loaded interfae The propagation of delamination is instantaneous and indues failure of L-angle speimens Strength predition an be performed using a 3D failure riterion e yy Strain field measured with Digital Image Correlation Delamination Coupling between transverse raks and delamination Transverse raks an be observed in the radius prior the final failure due to delamination Transverse raks indue loal delamination at the tips of the raks Premature delamination in the radius Failure pattern Transverse rak Loal delamination Coupling between transverse rak and delamination must be added to obtain onservative preditions 4 [Huhette 05], [Lubineau 09], [Charrier 3], [Laurin 3]

5 Contents of the presentation Objetive Proposition of a 3D failure approah and the assoiated proedure of identifiation whih should be used in design offie Presentation of the 3D failure approah Presentation of the 3D failure progressive failure riterion Introdution of the oupling between TTS strength and damage Presentation of the tests Design of four-point bending tests on L-angle speimens Determination of the onset of delamination Determination of oupling between the inter/intra damages Comparisons between model and test results Predition of the interfibre damage in L-angle speimens Predition of the final failure of L-angle speimens 5

6 Priniple of the 3D Onera progressive failure approah Idea UD ply onsidered as elementary entity of modelling Preditive approah for different staking sequenes Unidiretional ply Struture Applied loading to the struture Determination of stress / strain in eah ply Mesosopi Material Behaviour Methods of hange of sale Ply failure in laminate Mesosopi Failure Criterion Definition of Final failure Final failure of laminate Degradation of failed ply Degradation of Mehanial Properties 6 [Laurin 05], [Charrier ], [Charrier 3]

7 Priniple of the 3D Onera progressive failure approah Idea UD ply onsidered as elementary entity of modelling Preditive approah for different staking sequenes Unidiretional ply Struture Applied loading to the struture Methods of hange of sale Finite element Methods of of simulations hange of of sale sale 3D analytial methods Determination of stress / strain in eah ply Mesosopi Material Behaviour s 33 Ply failure in laminate Mesosopi Failure Criterion Definition of Final failure Final failure of laminate Degradation of failed ply Degradation of Mehanial Properties 7 [Laurin 05], [Charrier ], [Charrier 3]

8 Unidiretional Unidiretional ply ply Struture Non linear behaviour of the unidiretional ply Idea UD ply onsidered as elementary entity of modelling Preditive approah for different staking sequenes Applied loading to the struture Final failure of laminate Methods of hange of sale Definition of Final failure Mesosopi behaviour 3D non linear behaviour Determination of stress Thermal residual / strain stresses in eah ply Visosity of the matrix Mesosopi Material Non linear elastiity Behaviour in the fibre diretion Ply failure in laminate Mesosopi Carbon/Epoxy Failure [±45 ] Criterion s laminate Degradation of failed ply Degradation of Mehanial Properties 8 [Shieffer 03], [Laurin 05]

9 9 Mesosopi 3D failure riterion UD ply onsidered as elementary entity of modelling Preditive approah for different staking sequenes Idea 3D mesosopi failure riterion In-plane interfibre failure s s s p S p S Y f t s s s p S p S Y f s s s p S p S X f f f, 3 d d X f t s Fibre failure Out-of-plane interfibre failure s s s p S p S Z f t s s s p S p S Z f Physial meaning of oeffiients Coupling trans. / shear loading Coupling longi. / shear loading Coupling between the 3 failure modes [Laurin 05], [Charrier 3], [Laurin 3] [Hashin 80]

10 Mesosopi 3D failure riterion Idea UD ply onsidered as elementary entity of modelling Preditive approah for different staking sequenes 3D mesosopi failure riterion Fibre failure f f 3 f f X S p s S3 p3s 33 In-plane interfibre failure f f s X t d, d3 s Yt S 3 s s p s S p s 3 3 Y S ps S3 p3s [Hashin 80] 3 Out-of-plane interfibre failure f f s Zt S s Z S 3 p s S p s p s S p s Physial meaning of oeffiients Coupling trans. / shear loading Coupling longi. / shear loading Coupling between the 3 failure modes 0 [Laurin 05], [Charrier 3], [Laurin 3]

11 Progressive degradation modelling Idea UD ply onsidered as elementary entity of modelling Preditive approah for different staking sequenes Degradation of the elasti properties Degradation of the out-of-plane strengths Degradation of the 3D elasti stiffness S S 0 d Unilateral aspet of damage H if s 0 0 instead with H d f H ( ) H opened rak d d losed rak Coupling between in-plane damage d and the out-of-plane strengths with Zt Zt h d Z 3t Z h t 3 d and S S 3 3 S h 3 3 S h 3 3 d d Thermodynamially onsistent d 0 Strengths depend on the ply thikness [Parvizi 78], [Camanho 06], [Martin 0], [Charrier 3], [Laurin 3]

12 Definition of the final rupture of the struture Idea UD ply onsidered as elementary entity of modelling Preditive approah for different staking sequenes Unidiretional ply Struture Applied loading to the struture Determination of stress / strain in eah ply Mesosopi Material Behaviour Definition of final failure Not restrited to fibre failure Ply failure in fibre mode Failure in transverse ompression Out-of-plane failure (delamination) Loss of marosopi rigidity Ply failure in laminate Mesosopi Failure Criterion Definition of Final failure Instantaneous propagation Final failure of laminate Degradation of failed ply Degradation of Mehanial Properties

13 Definition of the final rupture of the struture Idea UD ply onsidered as elementary entity of modelling Preditive approah for different staking sequenes Unidiretional ply Struture Applied loading to the struture Determination of stress / strain in eah ply Mesosopi Material Behaviour The 3D Onera progressive failure is atually evaluated in Airbus on different test ases Ply failure in laminate Mesosopi Failure Criterion Final failure of laminate Degradation of failed ply Degradation of Mehanial Properties 3

14 Contents of the presentation Objetive Proposition of a 3D failure approah and the assoiated proedure of identifiation whih should be to be used in design offie Presentation of the 3D failure approah Presentation of the 3D failure progressive failure riterion Introdution of the oupling between TTS strength and damage Presentation of the tests Design of four-point bending tests on L-angle speimens Determination of the onset of delamination Determination of oupling between the inter/intra damages Comparisons between model and test results Predition of the interfibre damage in L-angle speimens Predition of the final failure of L-angle speimens 4

15 Tests performed on laminated L-angle speimens Four point bending tests Speifi unfolding tests Unfolding tests Carbon/Epoxy manufatured by CRITT Carbon Epoxy manufatured by CRITT Carbon/Epoxy manufatured by CRITT Determination of the intrinsi out-of-plane tensile strength Z t Determination of the out-ofplane shear strength S 3 R Validation of the proposed 3D failure riterion f 3 Determination of the oupling between damage and strength Determination of the out-ofplane shear strength S 3 R Validation of the oupling between damage and strengths Different lay-ups and thiknesses 00/0/0 determination Z t 50/40/0 determination Z t 5/50/5 determination Z t 0/60/0 oupling d / Z t 0/40/50 oupling d / Z t Different lay-ups and thiknesses 00/0/0 determination S 3 R 50/40/0 determination S 3 R Different lay-ups and thiknesses 00/0/0 failure s 33 / 3 50/40/0 failure s 33 / 3 0/60/0 failure s 33 / 3 0/40/50 oupling d / Z t >70 speimens >0 speimens >75 speimens 5 Tests ampaign performed in STAF and STRENGTH projets piloted by Airbus and finaned by DGAC

16 Design of FPB test on L-angle speimens Norm ASTM D645/D645M [ASTM 06] Design proposed by the norm ASTM available only for one thikness onstituted with only 0 plies FE simulations are neessary to design the FPB experimental devie Presentation of the FE simulations U y imposed Impliit odes: ZeBuLoN Abaqus U x =0 (rigid body) U y imposed Hypothesis of FE simulations One element per ply (3d8 element) Contat without frition Noses in steel (linear elasti) Speimens simulated with OPFM Design of the speimens U y =0 z y x U z =0 (rigid body) U y =0 Maximize the out-of-plane normal stress in the orner of the speimen Minimize the out-of-plane shear stress in the radius and in the legs Avoid (or reate) trans. rak prior failure 6

17 Design of FPB test on L-angle speimens Norm ASTM D645/D645M [ASTM 06] Design proposed by the norm ASTM available only for one thikness onstituted with only 0 plies FE simulations are neessary to design the FPB experimental devie Presentation of the FE simulations Shear stress Distanes between the noses determined with FE simulations Shear stress Hypothesis of FE simulations One element per ply (3d8 element) Contat without frition Noses in steel (linear elasti) Speimens simulated with OPFM Design of the speimens Maximize the out-of-plane normal stress in the orner of the speimen Minimize the out-of-plane shear stress in the radius and in the legs Avoid (or reate) trans. rak prior failure 7

18 Presentation of FPB experimental devie FPB experimental devie Optimisation of distane between the loading and support noses: Obtain (or avoid) transverse raks prior delamination Minimize the out-of-plane shear stresses in radius X Y Fixed Y Fixed Y Y X R r The noses an rotate due to ball bearing Minimize frition between noses and tested speimen The measurement tehniques LVDT sensor strain gauge (upper fae) Aousti emission Stereo - Digital image orrelation (DIC) Image analysis during loading Eletro-mehanial Shenk mahine apaity5t 8

19 Identifiation of the out-of-plane strength Z t Determination of the onset of delamination Load 7N FPB tests indue quasi-pure out-of-plane normal stress in the radius Test performed on 0/50/5 laminates No transverse raks prior delamination No signifiant aousti events prior delamination Validation of FE simulation through omparisons with test results Comparison with strain gauge or strain field measured with DIC Identifiation of out-of-plane tensile strength Z t =5MPa Predition of loalisation of delamination aurate Predited failure pattern Observed failure pattern 9

20 Detetion of intra-ply damage with aousti emission Final failure Final failure FPB-DIS90-00 speimen Measurement tehniques LVDT sensor Strain gauge (upper fae) Aousti emission Detetion of damage prior delamination To pilot other measurement tehniques Mirographs during loading Aousti sensor Determination of rak density Comparison with aousti emission Disontinuous evolution of the umulated energy Digital image orrelation Control displaement measurement Control strain measurement Crak density estimation Aousti emission performed with MISTRAS, Euro Physial Aoustis FPB-DIS90-00 speimen 0/40/50 laminates 0 [Barré 99], [Godin 05], [Gutkin ]

21 Detetion of intra-ply damage with image analysis 0/40/50 laminates Measurement tehniques Objetives of Mirosope LVDT sensor Strain gauge (upper fae) Aousti emission Detetion of damage prior delamination To pilot other measurement tehniques Mirographs during loading Determination of rak density Comparison with aousti emission Crak density in plies FPB-DIS Digital image orrelation Control displaement measurement Control strain measurement Crak density estimation Camera CCD bits assoiated with mirosope (x,5 or x5) fixed on a mirometer table with 3 axes [Huhette 05], [Revest ]

22 Detetion of intra-ply damage with image analysis 0/40/50 laminates Measurement tehniques Objetives of Mirosope LVDT sensor Strain gauge (upper fae) Aousti emission Detetion of damage prior delamination To pilot other measurement tehniques Mirographs during loading Determination of rak density Comparison with aousti emission Crak density in plies FPB-DIS Digital image orrelation Control displaement measurement Control strain measurement Crak density estimation Damaged area Camera CCD bits assoiated with mirosope (x,5 or x5) fixed on a mirometer table with 3 axes [Huhette 05], [Revest ]

23 Detetion of intra-ply damage with image analysis 0/40/50 laminates Measurement tehniques Objetives of Mirosope LVDT sensor Strain gauge (upper fae) Aousti emission Detetion of damage prior delamination To pilot other measurement tehniques Mirographs during loading Determination of rak density Comparison with aousti emission Crak density in plies FPB-DIS Digital image orrelation Control displaement measurement Control strain measurement Crak density estimation Damaged area Camera CCD bits assoiated with mirosope (x,5 or x5) fixed on a mirometer table with 3 axes 3 [Huhette 05], [Revest ]

24 Detetion of intra-ply damage with image analysis 0/40/50 laminates Measurement tehniques Objetives of Mirosope LVDT sensor Strain gauge (upper fae) Aousti emission Detetion of damage prior delamination To pilot other measurement tehniques Mirographs during loading Determination of rak density Comparison with aousti emission Digital image orrelation Transverse raks Crak density in plies FPB-DIS Control displaement measurement Control strain measurement Crak density estimation Camera CCD bits assoiated with mirosope (x,5 or x5) fixed on a mirometer table with 3 axes 4 [Huhette 05], [Revest ]

25 Detetion of intra-ply damage with image analysis 0/40/50 laminates Measurement tehniques Objetives of Mirosope LVDT sensor Strain gauge (upper fae) Crak density in plies Aousti emission Detetion of damage prior delamination To pilot other measurement tehniques Mirographs during loading Determination of rak density Comparison with aousti emission Digital image orrelation Control displaement measurement Control strain measurement Crak density estimation Camera CCD bits assoiated with mirosope (x,5 or x5) fixed on a mirometer table with 3 axes 5 [Huhette 05], [Revest ]

26 Detetion of intra-ply damage with digital image orrelation Measurement tehniques e xx y x LVDT sensor Strain gauge (upper fae) Aousti emission Detetion of damage prior delamination To pilot other measurement tehniques Mirographs during loading Cameras CCD Determination of rak density e yy Comparison with aousti emission Digital image orrelation Control displaement measurement DIC y x Control strain measurement Crak density estimation Digital image orrelation performed with Commerial ode Vi3D Crak detetion 6 [Hild 06], [Avril0], [Roux ] Cross-hek validation for rak density measurement 0/40/50 laminates

27 Detetion of intra-ply damage with digital image orrelation Measurement tehniques e xx y x LVDT sensor Strain gauge (upper fae) Aousti emission Detetion of damage prior delamination To pilot other measurement tehniques Mirographs during loading Determination of rak density Comparison with aousti emission Digital image orrelation Control displaement measurement Control strain measurement Crak density estimation Cameras CCD Digital image orrelation performed with Commerial ode Vi3D 7 [Hild 06], [Avril0], [Roux ] Cross-hek validation for rak density measurement 0/40/50 laminates

28 Detetion of intra-ply damage with digital image orrelation Measurement tehniques e xx y x LVDT sensor Strain gauge (upper fae) Aousti emission Detetion of damage prior delamination To pilot other measurement tehniques Mirographs during loading Determination of rak density Comparison with aousti emission Digital image orrelation Control displaement measurement Control strain measurement Crak density estimation Cameras CCD Digital image orrelation performed with Commerial ode Vi3D 8 [Hild 06], [Avril0], [Roux ] Cross-hek validation for rak density measurement 0/40/50 laminates

29 Contents of the presentation Objetive Proposition of a 3D failure approah and the assoiated proedure of identifiation whih should be to be used in design offie Presentation of the 3D failure approah Presentation of the 3D failure progressive failure riterion Introdution of the oupling between TTS strength and damage Presentation of the tests Design of four-point bending tests on L-angle speimens Determination of the onset of delamination Determination of oupling between the inter/intra damages Comparisons between model and test results Predition of the interfibre damage in L-angle speimens Predition of the final failure of L-angle speimens 9 Remark: All omputations are performed with average rigidity and strength to analyse the preditive apabilities of the proposed approahes

30 Load at first trans. Crak (N) Predition of in-plane damage within the strutures Conlusions Aurate preditions of loalisation of damage within the struture Damage only in the lower plies, in the radius and in front of the loading noses. Aurate preditions of the onset of in-plane damage within the struture Due to the introdution of the influene of ply thikness on the strength and TRS. Good estimation of the effet of damage on the loal or global response Comparisons with strain gauge or load/displaement urves. d Transverse raks 0/40/50 laminates 0/40/50 laminates 30

31 Load at first trans. Crak (N) Predition of in-plane damage within the strutures Conlusions Aurate preditions of loalisation of damage within the struture Damage only in the lower plies, in the radius and in front of the loading noses. Aurate preditions of the onset of in-plane damage within the struture Due to the introdution of the influene of ply thikness on the strength and TRS. Good estimation of the effet of damage on the loal or global response Comparisons with strain gauge or load/displaement urves. d 0/60/0 laminates 0/40/50 laminates Transverse raks 0/40/50 laminates 3

32 Identifiation of the oupling between inter / intra damages Conlusions Identifiation of the oupling term h 3t on the FPB-DIS-45 speimen The oeffiient is determined at h 3t =.6 MPa - with Z t =5MPa The oupling d / Z t permits to predit the observed failure pattern for all the speimens Delamination at the interfae between the damage ply The inter/intra oupling permits to predit aurately the failure load Zt Zt h Neessary to obtain onservative preditions for speimens with important in-plane damage 3t d 3

33 Identifiation of the oupling between inter / intra damages Conlusions Identifiation of the oupling term h 3t on the FPB-DIS-45 speimen The oeffiient is determined at h 3t =.6 MPa - with Z t =5MPa The oupling d / Z t permits to predit the observed failure pattern for all the speimens Delamination at the interfae between the damage ply The inter/intra oupling permits to predit aurately the failure load Zt Zt h Neessary to obtain onservative preditions for speimens with important in-plane damage 3t d Predition with oupling Aurate failure pattern Predition without oupling Erroneous failure pattern 33

34 Identifiation of the oupling between inter / intra damages Conlusions Identifiation of the oupling term h 3t on the FPB-DIS-45 speimen The oeffiient is determined at h 3t =.6 MPa - with Z t =5MPa The oupling d / Z t permits to predit the observed failure pattern for all the speimens Delamination at the interfae between the damage ply The inter/intra oupling permits to predit aurately the failure load Zt Zt h Neessary to obtain onservative preditions for speimens with important in-plane damage 3t d 34

35 Conlusions / Perspetives Proposition of 3D progressive failure approah Proposition of 3D failure multi-riterion taken into aount ouplings between the different rupture mehanisms Coupling between transverse raks and delamination is also addressed in this progressive failure approah Improve design of tests to identify TTS failure mehanisms Design of tests through FE simulations to highlight some TTS physial phenomena Use of different measurement tehniques (EA, IA, DIC ) to improve the omprehension of the rupture mehanisms Perspetives Validation of the 3D failure approah through omparisons with unfolding tests Performed simulations using more advaned damage and failure approah able to predit rak density and loal delamination rate [Laurin 3] 35

36 Conlusions / Perspetives Proposition of 3D progressive failure approah Proposition of 3D failure multi-riterion taken into aount ouplings between the different rupture mehanisms Coupling between transverse raks and delamination is also addressed in this progressive failure approah Improve design of tests to identify TTS failure mehanisms Design of tests through FE simulations to highlight some TTS physial phenomena Use of different measurement tehniques (EA, IA, DIC ) to improve the omprehension of the rupture mehanisms Perspetives Validation of the 3D failure approah through omparisons with unfolding tests Performed simulations using more advaned damage and failure approah able to predit rak density and loal delamination rate [Laurin 3] 36

37 37 Aknowledgements This work was arried out under the STRENGTH projet direted by AIRBUS and funded by the DGAC whih is gratefully aknowledged