a novel full-scale validation of thermal degradation of polymer foam cored sandwich structures r.k....
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A Novel Full-scale Validation ofThermal Degradation of Polymer
Foam Cored Sandwich Structures
R.K. Fruehmann, J.M. Dulieu-Barton, O.T. Thomsen15.02. 2011
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Outline• Background
• Review of design brief
• Design for mechanical boundary conditions
• Thermal gradient measurement
• Validation tests
• Conclusions
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Background
EC1
EC2
EC1 < EC2PVC foam core
Metal or composite face sheet
Tout
Tin
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Background
Thermal degradation of PVC foam stiffness
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Background
Face sheet displacement at different loads Force / mid-span displacement results from3 different models
(Frostig et al. 2004)
• High-order sandwich panel theory (HSAPT) predicts strongly non-linear interactions between mechanical and thermal loads.
• Strongly non-linear and unstable load response and limit point behaviour in some cases.• Load response strongly sensitive to boundary conditions.• Experimental validation is required.
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Design Brief• Mechanical
1. Simply supported
2. Lower corner fixed – free to rotate
3. Fully clamped
• Thermal
1. Uniform across width
2. Linear through thickness
• Measurement
1. Non-contact (DIC & IR)
Condition 1
Condition 2
Condition 3
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Design space
Loading frame
Actuator
3 point bend rig
Load cell
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Design – End constraint fixture
Platform
Fork
Specimen clamp
Axis CG
Counter balance
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Face sheet thickness
Design – End constraint fixture
Axis
Height adjustment
Platform height
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Design – Boundary condition 3
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Design – Boundary condition 3
Main platformshaft
Platform
Axis
Fixation bolt
Vertical supports
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Design – General arrangement
Radiator
Insulation
Mirror to monitor topface sheet
Mirror to monitor bottomface sheet
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Thermal gradient
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Thermal gradient
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Thermal gradient
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Thermal gradient
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Thermal gradient
Thermal degradation of PVC foam stiffness
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Thermal gradient
Thermal degradation of PVC foam stiffness
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Thermal gradient
Thermal degradation of PVC foam stiffness
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Validation tests• Specimen dimensions:
– 450 x 50 x 27 mm
– 1 mm thick aluminium face sheets
– 25 mm thick H100 PVC foam
• Temperature profile across the width and through the thickness
• Recorded the deformations at the mid-span using DIC
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Thermal gradient
1 second 5 seconds
10 seconds 15 seconds
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Thermal gradient
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Mid-span deformation
1
2
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Mid-span deformation
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Mid-span deformation
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Mid-span deformation
• Careful consideration of face sheet failure loads to avoid indentation failure preceding geometric non-linearity.
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Conclusions
• Thermal and mechanical boundary conditions have been achieved.
• Mid-span deflections correspond qualitatively with model predictions for the simply supported case.
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Future challenges• Optimise specimen configuration (material and
geometry) to remain in the elastic region.
• Obtain DIC data from the thin face sheets.
• Obtain DIC data below the roller during indentation.
Thank you