Janice Dulieu-Barton Professor of Experimental Mechanics - - PowerPoint PPT Presentation

Janice Dulieu-Barton

Professor of Experimental Mechanics

janice.barton@bristol.ac.uk

Developments in Imaging Approaches for Composite Structures

What is experimental mechanics?

• Investigation by experimental means
• f the mechanical behaviour of

engineering systems subjected to load

• System can be a structure, a

material, soft matter such as human tissue, a fluid-structure coupling…..

• Measurement system (image based)

is used to capture a quantity that describes the system’s behaviour

• Seek information on deformation and

the mechanical strain

• Full-field experimental data required

to validate/verify numerical models

• Derivation of failure parameters and

material constitutive relationships

Thermoelastic stress analysis (TSA)

Research Interests

• Imaging for data-rich materials

characterisations and assessments of structural performance.

• Lightweight structural design

particularly composite structures.

• Special focus on the

development of infra-red imaging – thermoelastic stress analysis.

• Integrating imaging and

modelling.

• Non destructive evaluation and

structural health monitoring.

• Structural scale testing

4 Load frames:

• Multi axial loading
• Flexible set up
• Large structures
• Modular design

Actuators:

• Large load range
• Synchronous control
• Flexibility

Imaging Systems

• Full-field data
• DIC
• TSA
• High spatial resolution
• High temporal resolution

Strong floor

• 1m thick reinforced

concrete

• 30 x 15 m
• 1m spaced strong points
• 500 kN vertical 25o kN

Hydraulics

• 1000 l/min ring main
• Large deflections
• High loads
• ‘Plug and play’
• Complex loading

Structures 2025

Structures 2025

• A single integrated system
• Unique internationally
• Assessment of interactions between

material failure mechanisms/modes and structural stiffness/strength driven failure modes

• High level of physical realism and fidelity

3D Wind turbine blade substructure

Global load cases Tip end Root end

Global blade model

x z y N

Isolated substructure

M N M N M N Actual surface Imaged field Imaging device Geometric mapping

3D Wind turbine blade substructure –loading concept

x z y N

Isolated substructure

M N M N M N

Preliminary work – T-joint

Integrating data

FEA TSA DIC All datasets

# Data points DIC – 9 TSA – 25 FEA – 30

Data point window Datum origin

Data point values DIC – subset average TSA – pixel average FEA – nodal value

Fused data – tension loading

Fibre alignment Material property difference Poor surface preparation Misaligned datasets due to motion

Point-wise metric Residual: 𝑔

− 𝑔

• Line comparison

Normalisation point

𝑔

= 𝜏 + 𝜏 ∗

• 𝑔

= Δ𝑈∗

Future challenges

• Accounting for curvature - combining incorporates

two camera infra-red imaging as well as stereo DIC

• Low cost infra-red cameras are essential
• Multiple camera systems
• Devising an imaging approach that work can

address multiple scales

• Development and validation of ‘hybrid testing’ to

enable the physical boundary and load conditions experienced in-service to be replicated and provide a realistic test environment

• Quantify the impact on performance of meso/micro

features and defects – in situ internal defect stress mapping using thermography