understanding the lamination process

www.bris.ac.uk/composites

Michael Elkington

Supervisors: C Ward, K Potter.

University of Bristol

michael.elkington@bristol.ac.uk

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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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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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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Two sample results

A - Starting at the front B - Starting at the back

20˚ shear

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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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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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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:

michael.elkington@bristol.ac.uk

Doctoral Training Centre (DTC)