ATOA Scientific Technologies Engineering Simulation For Innovation

Multiscale Damage Detection in Conductive Composites

Raj C Thiagarajan, PhD

ATOA Scientific Technologies Pvt Ltd

ATOA Scientific Technologies Pvt Ltd | www.atoastech.com | COMSOL Conference 2011 | SM Composites

ATOAST

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• We Provide Multiphysics Engineering Design Solutions

• Driven by Material Unity Vision

• We are the first COMSOL Certified Consultant from India

• ATOAST JOTHI foundation

• www.atoastech.com

ATOA Scientific Technologies Pvt Ltd | www.atoastech.com | COMSOL Conference 2011 | SM Composites

Multiscale Damage Detection in Conductive Composites

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• Multiscale nature of damage

• Damage Modes in composites

• Damage detection techniques

• Self sensing Carbon fiber Composites

• Numerical model

– Implementation

– Results and discussion

ATOA Scientific Technologies Pvt Ltd | www.atoastech.com | COMSOL Conference 2011 | SM Composites

Multiscale damage mechanism

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Structure

Part

Laminate

Fiber

Matrix

Molecular

ATOMIC bond breakage

0.3345 nm

0.142 nm

0.669 nm

c

ba

ATOA Scientific Technologies Pvt Ltd | www.atoastech.com | COMSOL Conference 2011 | SM Composites

Why

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• Increase use of composites in safety critical application.

• Increase reliability and safety levels

• Reduce cost and cycle time

• Focus on carbon fiber composites

Time in Operation

Design life

Service

Limit Mild

usage

Designed

usage

Severe

usage

Potential Safety Risk

without diagnostics

(SAFETY)

Additional use may be

gained through

diagnostics

(COST)

ATOA Scientific Technologies Pvt Ltd | www.atoastech.com | COMSOL Conference 2011 | SM Composites

Damage Mechanisms

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• Fiber

– Fiber breaks

• Matrix

– Matrix crack

• Interface

– Delamination

– Longitudinal cracks

(d)

(a)

(b)

(c)

ATOA Scientific Technologies Pvt Ltd | www.atoastech.com | COMSOL Conference 2011 | SM Composites

Structural Health monitoring

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Existing Techniques

• ultrasonic, acoustic emission, X-ray and eddy current Piezo sensors with ultrasonic tomography, Embedded Optical fibers (FBGs)

Limitations

• Based on external or embedded sensors.

• Embedded sensors/electrodes/FBGs lead to initiation of damage in composites.

Self sensing of Carbon fiber composites

ATOA Scientific Technologies Pvt Ltd | www.atoastech.com | COMSOL Conference 2011 | SM Composites

Numerical investigation

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• The electrical conduction mechanism and the effect of damage in CFRP composites were simulated in COMSOL using AC/DC Electric Currents Interface.

• Homogeneous composite model with effective properties

• Micromechanical model with constituent properties

ATOA Scientific Technologies Pvt Ltd | www.atoastech.com | COMSOL Conference 2011 | SM Composites

Results : Fiber breaks

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• UD composites

• Electrode on edge

• Resistance change vs fiber breaks

• Parallel resistance model behavior

• Very sensitive to fiber breaks.

ATOA Scientific Technologies Pvt Ltd | www.atoastech.com | COMSOL Conference 2011 | SM Composites

Results: Matrix Cracks

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• Matrix crack density vs change in resistance

• Can detect matrix cracks also

ATOA Scientific Technologies Pvt Ltd | www.atoastech.com | COMSOL Conference 2011 | SM Composites

Results : Delamination

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• Delamination length vs resistance change.

• Delamination growth between fibres

ATOA Scientific Technologies Pvt Ltd | www.atoastech.com | COMSOL Conference 2011 | SM Composites

Conclusions

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• The COMSOL model results show that the electrical resistance change is sensitive to fiber breaks and delamination.

• The homogenized and micromechanical model demonstrated the changes in resistance as function of damage.

• The methodology developed can be used to improve the damage detection capability and reliability of composite structures by Virtual optimisation.