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Thin ply technology advantages

Thin ply technology advantages. In partnership with North-TPT, FHNW, RUAG Technology, RUAG space, and Connova. An overview of the TPT-TECA project Joel Cugnoni , Robin Amacher , John Botsis Laboratory of applied mechanics and reliability (LMAF)

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Thin ply technology advantages

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  1. Thin ply technology advantages In partnership with North-TPT, FHNW, RUAG Technology, RUAG space, and Connova An overview of the TPT-TECA project Joel Cugnoni , Robin Amacher, John Botsis Laboratory of applied mechanics and reliability (LMAF) Ecolepolytechniquefédérale de Lausanne (EPFL) , Switzerland

  2. Introduction to Project TPT-TECA Goal: Characterize, optimize and demonstrate the technical and economical advantages of the Thin-ply technology developed by North TPT Intro Industrial / academic collaboration project Lamina level Laminatelevel Bearing strength Satellite panel demonstrator part Mechanical performance Prediction models Optimal design of benchmark parts Elementlevel Checklist Material development Production technology & implementation Simulation Design Helicopter structural part demonstrator Evaluation of production time and cost savings Rheo-kinetics testing and modeling Process cycle optimisation TPT-TECA CTI project

  3. Introduction to Project TPT-TECA start March 1st 2012 Intro Lamina level Laminatelevel Project timeline 24 months WP6: vaccuum bag process optimization Elementlevel Checklist Today Simulation Design End: march 2014 TPT-TECA CTI project

  4. Study of ply size effects Intro Method: • Comprehensivestudy of composite properties and ‘thinply’ effects • Propertiesat Lamina/Laminate/Elementlevels (same as Mil Hdbk 17) • Resin and fibre fixed (same batch) : UD prepreg TP80ep toughenedepoxy / 55%vol M40JB, autoclave production • Tests perfomedatthreeplythicknesses: 30g/m2, 100g/m2, 300g/m2 • Constant laminatethickness and specimen dimension, only change plythickness • Scaling: Ply or sub-laminaterepetition(+ half-angle / optimizedlaminates) Questions to beaddressed: • Will thin plies makemy part stronger – qualitatively? • How to simulate / predictply size effects? • Design methodstowards part levelmodeling and design? Lamina level Laminatelevel Elementlevel Checklist Simulation Design

  5. ThinPly composites: design performance advantages Click one of the icons below to learn more about Thin Ply composites performance in a specific area ? Part Design & Analysis Lamina & Laminate Impact Damage Resistance Open Hole & Fatigue Bolted joint & Ageing … or just continue reading normally to have a full overview

  6. Measurements: Strain gages Acoustic emission Digital image correlation C-Scan Intro Lamina level Ply size effect Laminatelevel (*) Elementlevel Checklist Simulation Ply and interface failure Design

  7. Lamina properties TP80ep/M40JB 55%vol Intro • Overall no change in intrinsic lamina properties except compression Lamina level Laminatelevel Elementlevel Checklist Simulation Design ThinPregTM80EP 55%vol M40JB

  8. Lamina level ‘thin ply’ effects Compressive strength UD 0° (ASTM D5467*) Thick 300 g/m2 Intro • Thin Ply leads to a more uniform microstructure and improved 0° compressive strength +20% Lamina level Laminatelevel Intermediate 100g/m2 Elementlevel Checklist Simulation Thin 30g/m2 Design

  9. Laminate properties Quasi isotropic laminate tensile test (ASTM D3039) [45°/90°/-45°/0°]ns • Failure mode transition from progressive transverse cracking & delamination to quasi brittle failure • For thick ply (n=1), onset of damage at ~50% of ult. strength • Nearly no damage in thin ply before failure Intro Lamina level Laminatelevel Elementlevel Acoustic emission damage monitoring +42% n=10 Checklist n=3 n=1 Thin 30g/m2 & Interm. 100g/m2 Thick 300g/m2 Simulation +227% Design

  10. Laminate properties Quasi isotropic laminate tensile test (ASTM D3039) [45°/90°/-45°/0°]ns Intro Lamina level Laminatelevel • Thin Ply “ply-level” scaling not better than Thick => Thin ply effect is not an intrinsic ply property. • Strong effect of number of ply thickness is related to the number of sub-laminate repetition: • Thick, n=1 : progressive damage, low onset of damage • Intermediate, n=3 : mixed failure (delamination and macro “through” crack), improvement in strength and damage onset • Thin, n=10: brittle failure with one macro “through” crack, best strength and damage onset, behaves like an homogeneous brittle solid • Half angle laminate slightly weaker than standard QISO Elementlevel Checklist Simulation Design

  11. Open Hole Tensile fatigue Open Hole Tensile: static and fatigue [45°/90°/-45°/0°]ns(ASTM D5766 & D7615, R=0.1) Intro Fatigue criterion = -10% stiffness • Strong improvement in fatigue life @316MPa (10k vs 1M cycles) • Lower ultimate strength. No damage around hole means no stress concentration relief but better predictability (Wisnom & al , Mollenhauer ) Thick, n=1 Thin, n=10 Lamina level -34% Laminatelevel +31% Elementlevel Thick plies 300g/m2 @10k cycles, 316MPa Thin plies 30g/m2 @1M, 316MPa Checklist Simulation Design

  12. Open Hole Compression Open Hole Compression [+45°/90°/-45°/0°]ns (ISO 14126 / ASTM D6484) Intro Lamina level +18% Laminatelevel OHC Strength [Mpa] Elementlevel Checklist Simulation Design

  13. Bolted joint bearing strength Single lap bearing test*, Hot Wet condition (ASTM 5961), fastener type EN-6115 ThinPregTM80EP 55%vol M40JB as produced @20°C and Hot Wet cond. 95%RH/70°C, test 90°C Intro n=5 n=18 n=2 • Strength improvement for as produced @ 20°C  +18% • Strength improvement for Hot Wet @ 90°C  +58% Lamina level Intermediate 100g/m2 Thin Ply 30g/m2 Thick Ply 300g/m2 sbr_ult = 584 MPa sbr_ult = 573 MPa sbr_ult = 476 MPa Laminatelevel As Produced, 20°C Elementlevel Hot Wet 90°C sbr_ult = 372 MPa sbr_ult = 294 MPa sbr_ult = 156 MPa Checklist As produced, 20°C Simulation Design Hot Wet 90°C *[+45°/90°/-45°/0°]ns

  14. Structural element properties Intro • OHT: lower ult. strength but higher onset of damage, more brittle • Strong improvement of most properties, delamination and damage in off axis plies are nearly suppressed • Much improved hot wet properties as weakening of the matrix is less critical in thin plies (still no delamination) • No damage means a better predictability and durability. Lamina level Laminatelevel Elementlevel Checklist Simulation Design

  15. Low energy impact • Rectangular specimen clamped on the short sides; bending is dominant • QI [0°/+45°/90°/-45°]ns, 300 x 140 x 2.4 mm • Thick (300 g/m2) n=1, Intermediate (100g/m2) n=3, Thin (30g/m2) n=10 • Energy: 11.5 J & 18J THICK INTERMEDIATE THIN Intro • Transition of failure mode from delamination to fiber failure • An optimal ply thickness can be found to achieve the smallest damage area • Thin-Ply technology allows tailoring the material properties wrt impact induced damage INTERMEDIATE THICK THIN Lamina level Backside Laminatelevel Elementlevel n=3 n=10 n=1 Checklist Simulation Design mostly fiber failure delamination & fiber failure delamination

  16. ‘Thin ply’ effects at different scales Microstructure Intro At the lamina level • More uniform microstructure, lower local variation of fiber Vf and finervoids • Improved longitudinal compressive strength At the laminatelevel • Delay or suppression of delamination as damage / failuremechanism • Delayed transverse cracking => apparent increase of transverse tensilestrength • Increased QI laminateonset of damage and ultimatestrength • Increasedlaminate fatigue strength At the structural component level • Notched tests: improvedonset of damage and fatigue life increase; more brittleresponse but betterpredictability • Bolted joint strength: strongstrengthimprovement in hot-wet conditions • Impact effects: fromdelamination to fiberfailure, optimal plythicknessis « intermediate ». Lamina level Laminatelevel Elementlevel But more brittle, sensitive to stress concentrators ! Checklist Change of failure mode (delayed delamination) Simulation Design

  17. Will thin plies make my part stronger ? Intro If it has one or more of the followingfeatures : • Compressive strengthcritical • Free edges • Open holes (damage onset) • Fastener connections • Fatigue and impact loading • Delamination cracks are the main concern • Optimizationislimited by plythickness … the answerisprobablyyes ! But how to quantify the benefits in a predictablemanner? Need new analysismodels and better design & optimizationmethods to deal withpotentially more design degrees of freedom .. but as the failure modes are simpler, predictabilityshouldbeeasier to reachtoo! Read further for on goingdevelopmentstowardsthat goal… Lamina level Laminatelevel Elementlevel Checklist Simulation Design

  18. Simulation of ‘thin ply’ effects Intro • Goal: capture the transition in dominant failure mode in order to understand and predict ply size effects • Hypotheses: no change in lamina and interface properties 2ndply: -45° 3rd ply: 90° 4th ply: +45° First ply: 0° (symetry) Lamina level Cohesiveelements > lateral cracking User materialwith fiberfailure (subroutine) Laminatelevel All data =from testing ! Elementlevel Checklist Between the layers: cohesive surfaces > delamination UD mx. withoutfiberfailure Simulation: force controlled (sigmoidramp, quasi-static) Simulation Work in progress • 3D modeling of quasi isotropicunnotchedtensile test in Abaqus Explicit • Damage models: cohesive interfaces between plies, cohesiveelements for transverse cracking, continuum damage model for fiberfailure Design

  19. Simulation of ‘thin ply’ effects Work in progress • Results: THICK Intro • First results on thick ply QISO unnotched tension Lamina level Laminatelevel Cohesive elements = transverse cracking (all layers) 0° -45° 90° +45° Force – dsp. Interface 0° / -45° Interface -45° / 90° Interface90° / 45° Elementlevel Blue dots = fibre failure Checklist Blue = undamaged >>>Red = delamination Clic to play video Simulation • Damage sequence: • cracking of 90° & 45° plies, delamination 90° / -45° plies from free edges • shearfailure of 45° plies, delamination 0° / -45° from free edges • fiberfailure in 0° plies Design

  20. Simulation of ‘thin ply’ effects Work in progress Intermediate, n=3 – NUMERIC (CSDMG) Thick, n=1 – EXPERIMENTAL (c-scan) Thick , n=1 – NUMERIC (CSDMG) Intro 250 MPa 300 MPa Lamina level 350 MPa Laminatelevel 400 MPa Elementlevel 450 MPa Simulation 500 MPa 550 MPa Design 600 MPa Conclusion 650 MPa 700 MPa

  21. Simulation of ‘thin ply’ effects Work in progress Numerical modeling Intro • Damage energy, QISO unnotched tension Ult. str. THICK = 685 MPa Failureat a « boundary » condition  to beimproved Lamina level Laminatelevel OnsetTHICK = 253 MPa Elementlevel Ult. str. THICK = 595 MPa [mJ] Simulation [+45°/90°/-45°/0°]ns OnsetTHICK = 248 MPa Design Experimental results (normalized for vf 55%) Conclusion • Good predictions for thick ply composites (300g/m2) for both onset of damage and ultimate strength. • Future: parametric study, extension to open hole and other cases

  22. Towards part level modeling and design Intro • Even though ply size effects might be captured by detailed 3D FE modeling, computation cost makes it unsuitable for part level analysis; we need a way to up-scale the analysis (i.e shell models) ! • Homogenization and parametric meso-scale analysis could provide laminate level failure envelopes for shell models. Specific strategy needs to be developed of free-edge crack stability analysis though. • As delamination and transverse cracking are less an issue, standard shell models and laminate theory might be closer to the reality of Thin Ply composites than standard composites! Open questions: • Ply size effects in standard impact tests and compression after impact? • Transverse crack propagation in laminates? Next steps: • Optimization of scarf joints, ply size effects without free edges (tubes) • Design optimization of two demonstrator parts; project continuation? Lamina level Laminatelevel Elementlevel Checklist Example: QISO unnotched tensile test, Classical laminate theory analysis Simulation Design

  23. Next steps within TECA project Scarf joint optimization Parametric FE Experiment Thin ply effects without free edges Test and FE on tubular specimens Intro Lamina level Thin ply Design Guidelines Simple design rules Where to use thin ply? Failure envelopes (limit cases) Laminatelevel Elementlevel Demonstrator Design & Opt Performance & production time / cost optimization to benefit from thin-ply effects and complex building block production approach Checklist • Demonstrator Production & testing • Satellite sandwich panel CE/M55 • Helicopter part (gear box support structure) Simulation Design

  24. Perspectives (new project?) Intro Detailed « plylevel » 3D FE modeling • Moving further towards Part level performance prediction & design criteria Ply size effectwith/without free edges Lamina level Computation time Parametricmeso-scalestudy Laminatelevel Free edge crack stabilityanalysis In-situ strength Failure criteria Homogenization for large n Elementlevel This may look complex, but Thin ply composites behaviour is simpler (less damage mechanisms) than traditional composites. Current designs methods do not consider much damage but 1st ply failure Checklist Shell models Simulation • Combined experimental / modeling work based on realistic demonstrator parts is required. Performance vs cost vs complexity (=1/quality) optimum need to be identified for representative cases • Open for collaboration for a continuation project Design

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