F full field measurement methods

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Full Field Mapping of Foam Deformation Pattern at Microscales
F-P Chiang (Stony Brook Univ)
The super-resolution digital speckle photography technique is described in detail. Applications of this technique to foam composites at micro scales are presented showing unusual deformation patterns under various loading conditions. (F14:1)

Digital Image Correlation Failure Analysis of Glass Fibre Composite Sandwich Material
JP Dear, A Puri, P Hooper, H Arora (Imperial College London)
Experiments have been performed on glass fibre foam sandwich specimens manufactured via RIFT, using a variety of different skin orientations and materials. Experiments have been performed in quasi-static indentation, as well as high speed impact, using digital image correlation (DIC) to identify failure mode development. The impact/blast resistance of these materials is of interest for marine and other structures. (F14:2)

Local Strain Concentrations in a Reinforced Microvascular Network
N Sottos, A Hamilton, S Olugebefola, S White (Univ of Illinois)_
Strain concentrations associated with the presence of a microvascular network in a polymer matrix are measured using fluorescent digital image correlation (FDIC). Measurements on fully three-dimensional networks reveal the influence of channel spacing on the mechanical behavior. The influence of localized micro and nanoparticle reinforcement around the channels are examined around a single channel. (F14:3)

Fe-DIC for Identification Purposes
H Leclerc, F Hild, S Roux (LMT-Cachan) J-N Périé (INSA)
An Integrated Digital Image Correlation (I-DIC) scheme is proposed to identify mechanical properties of composites materials. It is based on a new implementation of the Finite Element-DIC method and the use of a modified finite element updating technique. Biaxial tests performed on planar cruciform specimens are used to show the interest and the applicability of the proposed method. (F14:4)

Reducing Damage near Circular Holes in Composite Laminates
L Smith (Washington State Univ)

The following considers the sensitivity of open-hole tension coupons to laminate fibre orientation. The effects are described numerically and experimentally using finite element analysis and Digital Image Correlation, respectively. Improvements in strength exceeding 10% suggest that tailoring fibre orientations may have potential to minimize the effect of strain concentrations. (F14:5)


Finite Elements Model Updating for the Detection of Local Variations in Mechanical Properties
J Molimard, G Silva, R Le Riche, A Vautrin (LTDS - UMR 5513 & SMS)
Composite materials can exhibit local stiffness variations. Non destructive tests lead to the identification of weaker areas; this paper aims to add the quantification of the stiffness loss using optical full field technique coupled with material properties identification using finite element method updating. (F14:6)

Wounded Pattern Effects on the Local Behaviour of Filament Winding Pipes Using Optical Measurements
L Crouzeix, J-N Périé, F Collombet, B Douchin (LGMT) M Torres, H Hernandez (Instituto Politécnico Nacional)
A filament-winding pipe is fabricated and tested to study the mechanical behaviour of this structure, using CCD cameras. An orthotropic variant of the Equilibrium Gap Method is proposed to obtain mechanical properties maps of the pipe to get a relation between mechanical properties and the winding pattern. (F14:7)

Full-Field Strain Measurements at High Rate on Notched Composites
R Moulart, F Pierron (LMPF-ENSAM) S Hallett, MR Wisnom (Univ of Bristol)
Some preliminary results on the use of an ultra high speed (UHS) camera to perform full-field deformation measurements on open hole composite coupons tested in a tensile Hopkinson bar are introduced here. A performance analysis has been undertaken to evaluate the resolution and meaningful strain maps before the initial surface cracks were derived. (F14:8)

Estimation of the Strain Field from Full-Field Displacement Noisy Data : Filtering Through Diffuse Approximation and Application to Interlock Graphite/Epoxy Composite
P Feissel, J Schneider, Z Aboura (Univ de Technologie de Compiègne)
The problem of the reconstruction of the strain from full-field displacement is adressed using the diffuse approximation approach and applied to interlock composites. The aim is to estimate the reconstruction error and to validate the approach on real test data. (F14:9)

Measurement Layer Thickness Effects in Moiré Interferometry and other Full-Field Experimental Techniques
D Mollenhauer (US Air Force RL)
In previous research efforts on scarf-repaired composite panels, it was observed that the grating thickness had an amplification effect on interlaminar strains measured using moiré interferometry. This effect is investigated more thoroughly in this research report in the context of the broad scope of full-field experimental techniques. (F14:10)

Sensitivity Analysis of the Mesh-Free Random Grid Method for Measuring Deformation Fields on Composites
A Iliopoulos*, J Michopoulos (US Naval RL) (*also SAIC)
We are presenting a sensitivity analysis to assess the performance of the mesh free random grid method for the non-contact measurement of displacement and strain fields associated with the deformation of composite materials. This is motivated by the need to establish a design specification for its application on material characterization. (F14:11)


Sub-Surface Damage Location and Identification Using Infra-Red Techniques
P Cunningham (Loughborough Univ), T Emery, J Barton (Univ of Southampton)
The paper presents a new methodology for identifying sub-surface damage in composite components using a combination of Pulse Phase Thermography (PPT) and Thermoelastic Stress Analysis (TSA). (F14:12)
Identification of the Source of the Thermoelastic Response from Orthotropic Laminated Composites
S Sambasivam, S Quinn, J Dulieu-Barton (Univ of Southampton)
In previous work, a series of theoretical considerations have been made aimed at identifying the source and assessing prominent factors influencing the thermoelastic response from laminated composites. In this paper four different methods of interpreting the data are investigated and the theoretical thermoelastic response is compared to experimental data to identify the source of the thermoelastic response. (F14:13)

A Quantitative Investigation on the Thermoelastic Effect of CFRP Laminates
G Pitarresi (Univ of Palermo) U Galietti (Politecnico di Bari)
The strain field induced thermoelastic effect is investigated on CFRP laminates built from low-crimp unidirectional fabrics. The measured thermoelastic signal is compared with predictions from two analytical models based on the strain witness behaviour of a surface resin rich layer and on mesomechanical bulk properties of the lamina. (F14:14)

Material Heterogeneity or Stress Concentration: The Thermoelastic Response from Woven Composite Materials Subjected to Cyclic Fatigue
R Fruehmann, J Dulieu-Barton, S Quinn (Univ of Southampton)
The paper aims to understand and validate the thermoelastic response from a woven composite material and to observe how exposure to cyclic fatigue affects the response. The heterogeneous nature of the material is considered in studying the stress concentrations that occur as a result of the fibre crimp. (F14:15)

Dimensionality Reduction of Full Fields by the Principal Components Analysis
C Gogu, R Le Riche, J Molimard, A Vautrin (Ecole des Mines de Saint Etienne) Raphael Haftka (Univ of Florida)
The Bayesian approach to identification has the advantage of handling different sources of uncertainty and providing an estimate of the uncertainty in the identified parameters. We address here one of the challenges of applying this method to elastic constants identification from full field displacements: reducing the dimensionality of the field. (F14:16)
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