OPTIMAT BLADES Workshop OPTIMAT BLADES: RESULTS AND PERSPECTIVES OPTIMAT BLADES: RESULTS AND PERSPECTIVES Arno van Wingerde

OPTIMAT BLADES State of the Art Available results of research programmes and knowledge: Uni-axial stress state (no complex stress state) Mainly constant amplitude Variable amplitude prediction appears to be not accurate Thin coupons (no thick laminates) Limited data on effect of external conditions Different research programmes used different material and specimens Results of research programmes not consistent No recommendations on repair Limited data on condition assessment, residual strength Current design recommendations have inherent limitations

OPTIMAT BLADES Objectives & Numbers 52 months until ’05 Total budget: 4.4 M€ Partners R&D institutes: 10 Industries: 5 Certification bodies: Person months 3000 Specimens tested > Fatigue cycles > Machine hours 150 Reports 25 Publications OPTIMAT BLADES - numbers Based on consistent material data including: Var. amplitude loading Complex stress states Residual stresses/life Extreme conditions Thick laminates Repair techniques Accurate design recommendations for optimised use of materials for rotor blades with an improved reliability OPTIMAT BLADES

Partners 10 R&D institutes 5 Industries 2 Certification Bodies

OPTIMAT BLADES Project Structure Adm./ Financial Coordinator Tech./ Scientific Coordinator Steering Committee Manufacturers Certification Bodies Technical Committee Task Group leaders & coordination Project Coordination Committee All project partners Task Group 1 Variable Amplitude loading Complex Stress State Extreme Conditions Thick Laminates & Repair Residual Strength & Cond. Ass. Task Group 6 Design recommendations Task Group 2 Task Group 3 Task Group 4 Task Group 5

OPTIMAT BLADES TG1: Variable Amplitude Loading CLD of the material Test frequencies CA/VA/Block tests Update to the Wisper spectrum, used for material tests to modern Wind turbines New Wisper Cycle Level Wisper New Wisper WisperX

OPTIMAT BLADES TG2: Complex Stress State Blades typically not uniaxial stress state Materials sensitive to forces perpendicular to fibre Influence upon strength unknown Tests on tubes (tension-torsion) Tests on Cruciforms

OPTIMAT BLADES TG3: Extreme Conditions At – 40°C: same or improved material results At + 60°C: degraded material results 100% RH: degraded 6/12 submersed Interlaminar strength 0% 50% 100% 150% 200% Temperature [°C] Strength, relative to RT [%] -40°C +20°C +60°C

OPTIMAT BLADES TG4: Thick laminates & Repairs Thick laminate: same fatigue performance Static performance seemed lower Clamping of specimen Repair: 1:50 scarf, about 70% static strength 1:40 much lower More variation per batch 2 m long

OPTIMAT BLADES TG5: Residual Strength Tested to fraction of N f 20 % 50 % 80% Then static tensile/ compressive test

OPTIMAT BLADES CLD diagrams – Linear Goodman

OPTIMAT BLADES CLD diagrams – Shifted Goodman

OPTIMAT BLADES CLD diagrams – Multiple R values

OPTIMAT BLADES CLD diagrams – R = 0.1

OPTIMAT BLADES ….. And their consequences Sequences to failure S max WISPER data Multiple R-ratio (6 R-ratios) Single R; R=0.1 Linear Goodman Shifted Goodman 30% 2000%

OPTIMAT BLADES Residual strength models Relate static strength and fatigue behaviour Strength reduced per cycle, until load exceeds strength Results not significantly better than Miner and more complex models required

OPTIMAT BLADES Test methodology New “universal” test geometry Static tension Compression About 20% lower than ideal value Fatigue (all R values) Standard geometries Better for comparison with earlier tests Often no background provided Rules hard to understand No universal geometry Difficult for combined tests ISO compression OPTIMAT Dogbone OPTIMAT Geometry UD/MD ISO tension

OPTIMAT BLADES Lessons learnt Plate-to-plate and lab-to-lab variations are important in a project of this size More realistic assessment of scatter Preferably: production of all specimens first, then mix and send out Not possible in practice Establishing an alternative test geometry is difficult People perceive standards automatically as “better” even when no background info is provided Material variations sometimes larger than investigated influences Do not show up in lab analysis, such as T g and v f Some plates worse in static strength, better in fatigue

OPTIMAT BLADES OPTIDAT Available (for a small fee) :

OPTIMAT BLADES Agenda for the Workshop (1) Introduction to Optimat Blades Recommendations of material tests Determination of S-N lines Fatigue life prediction Biaxial stress state in blades Biaxial Tests Extreme conditions Break

OPTIMAT BLADES Agenda for the Workshop (2) Repair techniques & thick laminates Residual strength models OPTIDAT, the database of OPTIMAT Implementation of Technical Standards Panel discussion & input from industry A new implementation of CLD Finish: Workshop Presentation of UPWIND ( 6th framework Wind Project)