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Published Papers

Flaw and damage assessment in torsionally loaded CFRP cylinders using experimental and numerical methods

Erwin Hack, Richard K Fruehmann, Rene Roos, Mara Feligiotti, Philipp Schuetz, J P Tyler
Composite Structures 11/2015; 132. DOI: 10.1016/j.compstruct.2015.05.025

ABSTRACT CFRP structural elements are prone to failure initiated by defects. While defects are expected after damage has occurred, flaws and voids can already be present after manufacturing. To study the criticality of such defects, CFRP cylinders have been manufactured from a lay-up that was designed to predict damage mode and to allow for controlled damage growth under torsional load. FEA simulations of defect-free and flawed cylinder models were performed to first ply/interface failure. X-ray computed tomography revealed that cylinders manufactured with different finishing had a completely different void content and distribution. Simulations of failure, using finite element models, for the two classes of void distribution are corroborated by experimental results for the ultimate load, and damage initiation from manufacturing flaws is confirmed. Digital speckle pattern interferometry was used to identify flaws using thermal and mechanical loading, while infrared thermography and thermoelastic stress analysis were used to identify possible failure initiation sites and monitor the failure process and damage growth, whilst the specimen was loaded in torsion.

The use of a lock-in amplifier to apply digital image correlation to cyclically loaded components
R. K. Fruehmann, Janice Dulieu-Barton, S. Quinn, J. P . Tyler

Optics and Lasers in Engineering 05/2015; 68. DOI: 10.1016/j.optlaseng.2014.12.021

ABSTRACT – An approach for processing strain data obtained from Digital Image Correlation (DIC) that can be used directly on components subject to cyclic loading, such as in fatigue testing, is described.

A key challenge addressed herein is obtaining an accurate and precise surface strain map without recourse to expensive high speed cameras to capture data to map the load cycle.

The basis of the approach is the application of a lock-in amplifier to the strain data obtained from images taken from low-cost low-frame rate cameras.

The technique enables images to be captured throughout a fatigue test and hence evaluate the effect of any damage on the strain field, without interrupting the test.

The methodology is assessed using an aluminium disc in diametric compression. It is demonstrated that the approach enables accurate strain maps to be obtained using a range of loading frequencies that are greater than the camera frame rate.

A realistic example application of the technique on a fatigue test with an evolving crack in a T-shaped specimen is presented.

Multidisciplinary engineering – an integrated solution

C. Bancroft, R. J. Greene, J. P. Tyler

Int. J. Microstructure and Materials Properties, Vol. 5, Nos. 4/5, 2010

ABSTRACT: Knowledge-enabled process engineering (KEPE) is introduced in the context of its current and potential use for dynamically managing large and complex problem domains.

A brief description of the capability both developed and adopted to support the deployment of KEPE is introduced.

The document then focuses on the knowledge integration activities that enable
multidisciplinary engineering. This includes the integration and combination of these activities and the emerging deliverables derived from this approach that provide an integrated solution for the management of manufacturing-induced part distortion in large aerospace components.

Finite element modelling in a multidisciplinary environment is presented as an example of an integrated solution.

In essence, this creates an ability to integrate FEMS and data models to promote, manage and achieve cross-functional simulation.

Papers Published From Collaborative Research Projects:


Numerical modelling of shot peening process and corresponding products: Residual stress, surface roughness and cold work prediction

G.I. Mylonas, G. Labeas

Surface and Coatings Technology, Volume 205, Issue 19, 25 June 2011, Pages 4480-4494

ABSTRACT: An investigation of the effects of controlled shot peening (CSP) process parameters on the treated material is presented.

For this purpose, a three-dimensional numerical model is developed, comprising the target plate and a number of shot impacts; their number is defined as the minimum required for a realistic simulation and minimum computational cost.

The numerical model is verified by comparing the predicted residual stress (RS) fields to experimental ones.

A parametric study of the shot velocity and impinging angle on the CSP products is performed for 4 shot types, i.e. S110, S230, S330 and S550.

The main advantages of the present numerical model are:

a) the relatively high number of shots introduced in the simulation compared to other publications that use only one shot.

b) the number of shots dependency on the desired coverage

c) the thorough selection of numerical parameters.

d) the high-strain rate material behaviour used for the target plate.

e) the capability to calculate CSP effects on the target plate as a function of coverage.

f) the computed data which include RS field, surface roughness, cold work and geometrical stress concentration factor (Kt).

g) the computed results which are validated by experimental measurements.


Natural vibration loading for damage assessment using thermoelastic stress analysis

Fruehmann, R.K.,  Dulieu-Barton, J.M., Peton-Walter, J. and Benaben, L.

15th International Conference on Experimental Mechanics, 2012, Porto, Portugal, 2 pages on CD.

The application of thermoelastic stress analysis to full-scale aerospace structures.

Fruehmann, R.K.,  Dulieu-Barton, J.M., Quinn, S., Peton-Walter, J. and Mousty, P.A.N.

8th International Conference on Modern Practice in Stress and Vibration Analysis, 2012, Glasgow,.

J. Phys.: Conf. Ser. 382 012058 doi:10.1088/1742-6596/382/1/012058.

Damage assessment in composite materials for remnant life prediction

Fruehmann, R.K. and  Dulieu-Barton, J.M.

SEM Spring Conference on Experimental Mechanics, 2012, Costa Mesa, USA, 2 pages.

Low-cost digital image correlation (DIC) for monitoring components undergoing fatigue loading.

Fruehmann, R.K. and  Dulieu-Barton, J.M.

SEM Spring Conference on Experimental Mechanics, 2014, Greenville, USA, 4 pages.

Resonant loading of aircraft secondary structure plates for use with thermoelastic stress analysis and digital image correlation.

Waugh R.C., Dulieu-Barton, J.M. and Quinn, S.

13th Asian Conference on Experimental Mechanics, 2014, Singapore, SPIE 9302, 9 pages.

A full field stress-based damage assessment approach for in-situ inspection of composite structures.

Dulieu-Barton, J.M., Fruehmann, R.K. and Quinn, S.

Key Engineering Materials, 569-570, 2013, 3-10.

The use of a lock-in amplifier to apply digital image correlation to cyclically loaded components.

Fruehmann, R.K., Dulieu-Barton, J.M. Quinn S. and Tyler, J.P.

Optics and Lasers in Engineering, 68, 2015, Pages 149-159.

Flaw and damage assessment in torsionally loaded CFRP cylinders using experimental and numerical methods.

E. Hack, R. K. Fruehmann, R. Roos, M. Feligiotti, P. Schuetz, J. P. Tyler and J. M. Dulieu-Barton


A fresh look at assessing structural performance using imaging techniques

Fruehmann, R.K., Waugh, R.C. and Dulieu-Barton, J.M.

SPIE Newsroom accepted for publication.

Failure and damage in CFRP torsion tubes
E. Hack, M. Feligiotti, R.K. Fruehmann, and J.M. Dulieu-Barton

Photomechanics, Montpellier, 27-29 May 2013