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8/3/2019 Efek Ketaksempurnaan Geometrik Pada Renspon Kompresif Dari Panel Komposit_Transportasi Maritim_de_Verdiere_
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Failure criteria such as Tsai-Hill and Tsai-Wu can be applied in Fortran
user subroutine Usermatps.F and compiled in Ansys. Such failure
criteria could not reproduce material non linearties and failure load
predictions well.
An existing damage model in an explicit code was preferred for enhanced load
buckling and damage predictions and ran in PAM-CRASH.
A small amount of defect depth (0.7mm) reduces considerably strength and
stiffness on unidirectional or [0/90] lay ups (more than 20%), but has little
influence on bias direction lay up (less than 8%).
The defect influence is greater on stiff and brittle composites (carbon)
than on more compliant ones (glass).
Results are sensible to the compressive stiffness, strain and strength used which
are difficult to acquire experimentally in the axial direction in the first instance.
An Ansys input file was generated that created various numerical plates withdefects rapidly.
To predict better the compressive response and the defect influence; a damagemodel was used on CFRP and GFRP with the PAM-CRASH code. Implementingsuchmodel in Ansys was rather problematical and was avoided.
Defect influence was considerable on [0/90] lay up and small on [+-45] lay up. It
was also stronger on carbon than glass lay-up.
Small mould defect could reduce strength by 10 to 25% on axial lay up and deeperone up to 40% . It is an issueon long structure subjected to buckling such hasboatmast, wind turbine blades or glider wings. Significant safety factor should be used.
Panels made via resin infusion.
Panel testing:
o The apparatus should allow for regular enlightenment of the panel to permit DIC
algorithm to perform.
o The apparatus should allow for compressive loading of the panel and be
representative of the in service loading as such as the one of the blade spar and skin.
o The panels are compressed by an Instron test machine.
o The apparatus uses anti buckling guides on its side and full clamping at its bottom.
o Defects: bumps in the form of a sinus wave are used (Figure 4).
Monitoring of imperfections
o DIC allows for the capture of the defect changes in 3D through out loading.
Ultimate objective: to asses the effect of
geometrical imperfections on the compressive
strength of carbon and glass composite panels
(CFRP and GFRP).
Currently compressed structures such as wind
turbine blades are produced by resin infusion. As
the blade have important aspect ratio the moulds
can be rather long (Figure 3) and the blade can
then be sensit ive to buckling as compressive
properties of composites are known to be
significantly lower than in tension (15 to 40 %). To
make it worse it is possible to get some bashes on
the mould surface after the production of several
blades due to human error (a tool falling on the
mould surface) or the mould deformation under
heat for example. Such defects on the mould will
be transferred to the blade geometry that would
lead to the reduction of the buckling resistance of
the structure.
This research considers the simulation of
composite panels (GFRP and CRFP) with various
lay-up and geometrical imperfections (size and
depth) to simulate and investigate the reduction in
buckling load and ultimate compressive strength.
Secondly a novel compressive apparatus is being
manufactured to allow for the buckl ing of the
panels and the 3 D monitoring of the deformation
via digital image correlation (DIC).
Effect of geometric imperfections on the compressiveresponse of composite panels
Mathieu Colin de Verdiere [email protected] - School of Engineering SciencesCEC Marstruct funding
Supervisors
Dr Steve Boyd and Professor Ajit Shenoi
FSI Away Day 2010
Fluid Structure Interactions
Research Group
Motivation & Aim
Figure 1: Bending of the windturbine blade Source [1]
Generic Panels
Research has designed generic panels to be representative of wind turbine blade.
[0-90] lay-up 210 x 210 mm, 4 mm thick.
Bump depth vary from 0 mm to 10 mm.
Bump diameter vary from 50 to 100mm.
Parametric simulations are ran under Ansys with basic failure criteria andbuckling analysis on glass and carbon fibres.
A few simulations are run under PAM-CRASH with a damage models. The modelis calibrated in thefirst instance and then ran on panels with and without defects.
References:
[1] : Full scale testing of wind turbine blade to failure - flapwise loadingErik R. Jrgensen, Kaj. K. Borum, Malcolm McGugan, Christian L. Thomsen, FindM. Jensen, Christian P. Debel og Bent F. SrensenRis National Laboratory, Roskilde
June 2004[2]: http://www.bayviewedisonindustries.com
Testing
Results
Concept
Figure 2: typical wind turbinecross section [1]
Figure 3: 60 foot wind turbinemould [2]
Simulations
a) b)
c)
Figure 4: geometrical defect
Future work:
Simulation with various thicknesses
Strain field monitoring
Comparison of damage for different defects
Comparison of numerical and experimental results
Conclusion
Figure 5: Tensile, compressive and shear specimens
Figure 6: axial stresses prior to buckling on small tolarge defects (left to right)
Figure 6: a) complete apparatus, b) GFRP specimen, c) GFRP panel infused
Specimens testing
Compressive apparatus
Figure 7: Ansys input model