EXPERIMENTAL DETERMINATION OF KEY PARAMETERS FOR MODELLING THE TENSILE AND COMPRESSIVE FATIGUE BEHAVIOUR OF NOTCHED GRP LAMINATES Bill Broughton , Mike Gower, Maria Lodeiro, Gordon Pilkington and Richard M. Shaw 5th International Conference on Composites Testing and Model Simulation, EPFL, Lausanne, 2011
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EXPERIMENTAL DETERMINATION OF KEY PARAMETERS FOR MODELLING THE TENSILE AND COMPRESSIVE FATIGUE BEHAVIOUR OF NOTCHED GRP LAMINATES Bill Broughton, Mike.
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EXPERIMENTAL DETERMINATION OF KEY PARAMETERS FOR MODELLING THE TENSILE AND COMPRESSIVE
FATIGUE BEHAVIOUR OF NOTCHED GRP LAMINATES
Bill Broughton, Mike Gower, Maria Lodeiro,
Gordon Pilkington and Richard M. Shaw
5th International Conference on Composites Testing and Model Simulation, EPFL, Lausanne, 2011
ContentContent
Introduction
Test Programme
Constant Amplitude Cyclic Fatigue
Tension-Tension
Compression-Compression
Tension-Compression
Multiple Step T-T Block Loading
Concluding Remarks
IntroductionIntroduction
Aims and Rationale: Ensuring the long-term structural integrity and safety of composite structures throughout in-service lifetime
Develop and validate fatigue test methods for composites
Identify and evaluate key parameters for modelling tensile and compressive fatigue behaviour of FRPs
215 mm buffer free region centred on middle grating
12 mm grating length 38 mm end-to-end spacing
50 mm centre-to-centre spacing
3 gratings at different centre wavelengths ~1540, 1550 and 1560nm
Length – 660 mm
Core – glass, 9 m diameter
Coating - 125 m diameter (acrylate re-coated)
Cladding – glass, 125 m diameter
This work is part of a small task in a project we are doing, the aim being to monitor strain during fatigue of an open hole tension (OHT) sample made from a QI 913 glass epoxy composite. Comparisons to be made between extensometers, strain gauges & embedded FBGs at 3 strain levels. Due to the non-uniform strain distribution we ideally want to look at the strain at 3 different points on the sample.
We would need a total of 6 fibres. Depending on the success of the FBG work, the outcome of the project will be written up as either an NPL measurement note or as a section of a larger report detailing all the outcomes of the project tasks plus a possible journal/conference paper. Although you are not permitted to sell the fibres, any work published would acknowledge City University’s help with the provision of the fibres.
Concluding RemarksConcluding RemarksAlignment and rigidity of loading chain is critical for compression-compression and tension-
compression tests
DIC suitable for monitoring local and global strains
Providing critical information on changes in strain distribution around the hole of notched
laminates due to damage formation/growth incurred through either increasing load or number
of loading cycles
Optical fibres (FBGs) suitable for monitoring fatigue performance – superior fatigue performance
compared with strain gauges
Longitudinal strain and stiffness along with surface temperature – indication of level of remnant
life of notched components
Possible to estimate fatigue life for fully reversible and block loading conditions from T-T and C-C
cyclic data
AcknowledgementsAcknowledgements
The work was supported by United Kingdom Department for Business, Innovation and Skills (National Measurement Office), as part of the Materials 2007 Programme.
The authors would also like to thank:
Hexcel Composites Limited
Dr F Surre and Dr T Venugopalan - City University London