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www.bris.ac.uk/composites
Michael Elkington
Supervisors: C Ward, K Potter.
University of Bristol
Understanding the Lamination Process
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Understanding the lamination process
Hand layup of prepreg
• Complex parts
• Short lead times
• Low setup costs
• High labour costs
• Low production rates
• Variability
• Potential shortage of laminators
The process has changed little in decades:
Scope for optimisation.
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Understanding the lamination process
• Flat sheet + Double Curved mould = In-plane shear deformation
• VFP (Virtual fabric placement) provides deformation predictions
The knowledge gap:
“How is the deformation achieved…?”
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Understanding the lamination process
Analysis Methodology
1. Record operators at work
Areas
2. Watch the footage
3. Record the frequency and location of specific techniques
6 laminators 19 layup trials 3 Repeats each
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Understanding the lamination process
7 key Techniques
Guiding with two hands (G2H)
One handed Guiding (1HG)
Manually Folding material (MF)
Tension Secured shearing (TSS)
Smoothing with tension (S&T)
Tool interaction shear forming (TIS)
Tension-Tension Shear forming (TTS).
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Understanding the lamination process
Results: Common techniques
Certain techniques saw use across all tasks.
Example: One handed Guiding, (1HG): Used almost exclusively to align edge of plies.
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Understanding the lamination process
Two sample results
A - Starting at the front B - Starting at the back
20˚ shear
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Understanding the lamination process
Common techniques in task A
1. Regular Prepreg
2. Technique applied
3. Prepreg shears
“Tension secured shearing”: Used exclusively 4+ per ply.
4. Prepreg shape formed.
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Understanding the lamination process
Common techniques in task B
1. Regular Prepreg
2. TIS being applied.
3. Prepreg shears
3. Prepreg shape formed.
“Tool interaction shearing” : Used exclusively 12+ times per ply
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Understanding the lamination process
Discovering techniques
Apply tension directly to ply edge.
e.g. Fibres pivot towards the free edge.
1 Layup models: Predict shear deformation.
3 Discover the technique: The techniques most commonly used to shear the material can be predicted
2 Feature analysis:
• Shear deformation angle,
• Direction,
• Location and local topology,
• Overall Drape direction.
Starting point, Undeformed cloth, Sheared Cloth,
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Understanding the lamination process
Conclusions
1. Identified 7 techniques for lamination
2. Links between areas and techniques
3. The shear angle is not the only variable to consider.
Training
Automation
Evolution of the process
What the techniques are and where to use them
What techniques an automated solution might have to replicate
Multiple options to evolve the process
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Understanding the lamination process
Further work: Evolution of the process
Current projects at Bristol:
1. Improved layup tools.
2. Providing detailed layup instructions
3. Utilising VFP to aid layup projection systems.
4. ‘Preshearing’ of the plies.
Starting point
Sheared areas
Grasping sign
Securing sign ?
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Understanding the lamination process
Further work: Pre-shearing
Starting with a kinematic model
Apply shear prior to tool contact.
Ply already fits into tool and deforms easily
Reduced Layup time and effort
Large number of applications = Complex and time consuming Solution: Shearing the plies prior to layup: ‘Preshearing’
Reduction in on tool and overall layup time Less defects
Lamination became ‘easy’
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Understanding the lamination process
Thank you for listening.
Questions and ideas welcome:
Doctoral Training Centre (DTC)
