Caroline McHale PDST Caroline McHale PDST Multiple Intelligences.
Caroline Jones CompTest 2003 January 2003
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Transcript of Caroline Jones CompTest 2003 January 2003
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The application of biaxial cruciform testing to understanding the performance of composite structuresCaroline JonesCompTest 2003January 2003
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Summary
This presentation highlights recent developments in the field of biaxial cruciform testing and discusses how the benefits from these experimental programmes are being used to optimise composite structures and reduce the duration of the certification process.
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Contents
1 Development of the biaxial cruciform test
2 The biaxial test
– Experimental arrangement
3 Using biaxial cruciform test data
– Failure criteria development
– Numerical modelling tools
4 Conclusions
5 Any Questions?
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Development of the biaxial cruciform test
Section 1
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Specimen Design
Cruciform specimen designGRP claddingAluminium end tabs
adhesive with low residual stress post-cure
Test area 90mm-120mmHoneycomb, sandwich panels, structures, through thickness reinforcement
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The biaxial test machine
•Four primary actuators
-500kN/1500kN loads
•Two secondary actuators
-bolt hole loading•Grip system•Safety
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The biaxial test
Section 2
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Experimental Arrangement
•orientation•loading ratios/testing ratios•calibration•performance envelope•failure strength•use of anti-buckle guide•hot/wet testing
X, 0°
Y, 90°
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Use of the bolt hole loading rig
X, 0°, Fx=+1.0
Y, 90°, Fy=-0.7
N.B. Load on bolt is 12kN
•Open hole•Filled hole•Loaded hole
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Using biaxial cruciform data
Section 3
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Uniaxial or biaxial?
•Uniaxial -less expensive per test-high experimental scatter-one result per test-large test programme-time consuming-boundary conditions
unrepresentative
•Biaxial-more expensive per test-minimal experimental
scatter-several results per test-smaller test programme-less time consuming-boundary conditions
representative
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How is the data being used?
Development of failure criteria
Development of structural concepts
More realistic representation of a structure
in service – leading to more efficient designs
Development of novel materials
Development of modelling tools
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13Development of performance and failure criteria
Use failure strength to test and develop biaxial failure
criteria
Use performance envelope to confirm predictions
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14Development of Numerical Modelling tools
Bolted joint structures
Coupled global-local modeling toolsOpen holes
Loaded fasteners
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Global-local analysis (1)
1. Create global model (ABAQUS)(arbitrary curvature and mesh)2. Run Q_global_bolt to add bolts &foundations
3. Run updated global model (ABAQUS)
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Global-local analysis (2)
4. Use Q_global_local to create local models
5. Run local models
6. Run Q_predict for multi-axial strength prediction with bolt load
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ConclusionsSection 4
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Conclusions
• Boundary conditions representative of those found in structures make the data obtained from biaxial cruciform tests extremely valuable.
• Direct benefits being derived from biaxial cruciform test work include the development of performance and failure criteria and numerical modeling tools used to analyse complex composite bolted structures.
• Recent developments made in biaxial cruciform testing represent major steps in understanding materials and their use in structural design
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Any Questions?Section 5
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Appendix
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Instrumentation
• Shadow moiré
• Photoelasticity
• Thermoelasticity
• NDE (ANDSCAN)
• Video strain mapping
• Combined thermo/photoelasticity
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Sensitivity to delamination growth
Photoelastic coatings are used to obtain both the optical and thermal data
High operational strains require multiple coatings to monitor both global and local delamination fronts
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23Thermal monitoring of loading sequence
Deltatherm image (200 f/sec) of specimen surface loaded to
6000-3000