JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 29

with defects and, thus, the estimation
of the influence of initial waviness was
determined accurately for four-point
bending loadings.

Fig. 5: Initial defects in 20/60/20 laminated L-angles

the finite element simulations. The idea
consists in generating a virtual twin of
the real structure.
Initial ply waviness was analysed by
optical analysis (micrographs) performed on one of the two polished free
edges of the sample. For the considered
L-angles, with a moderate width, the
initial defects can be reasonably assumed
to be constant through the width. After
performing a morphological analysis of
the different available waviness defects,
it was demonstrated that the initial waviness can be described correctly by a sine
function. It can be noted that it is also
possible to represent more geometrically
complex initial defects through a combination of different sine functions.

Comparison with
available test results
Each non-conformal 20/60/20 L-angle,
containing really observed initial ply
waviness (different for each specimen),
was generated numerically. Four-point
bending simulations, on pristine and
non-conformal L-angles, were performed
for the two test configurations. The
comparisons between the measured and
predicted failure loads are reported in
figure 6. The predicted failure loads were
in good agreement with all the experimental results, especially for L-angles

The non-conformal 20/60/20 and
10/40/50 L-angles were generated
numerically. It can be noted that the
waviness for the 10/40/50 L-angles was
moderate as compared to the 20/60/20
laminates. Unfolding simulations, on
pristine and non-conformal L-angles,
were performed. The comparisons
between the measured and predicted
failure loads are reported in figure 7.
The predicted failure loads were in good
agreement with all the experimental
results, even for L-angles with defects.

Fig. 6: Effects of defects in 20/60/20 L-angles subjected to four-point bending: experimental vs. numerical
results

No106 July 2016 / jec

Feature Aeronautics

Therefore, waviness can be described
through only three main parameters,
namely the angle of the central position
of the waviness in the L-angle, the angular width of the wave and its height at the
different interfaces between the plies. As
illustrated in figure 5, the image analysis
of a free edge of a 20/60/20 L-angle
made it possible to describe initial
waviness accurately with a sine function.
The real geometry of the specimen being
determined, the next step consisted in
meshing the non-conformal radius and
managing the local orientation of the
plies, which is non-trivial for such a complex geometry. Finally, the conformal
radius, used in the whole finite element

model for four-point bending or unfolding already validated for pristine L-angles, was substituted by the non-conformal radius containing defects. The whole
procedure for explicitly introducing real
defects into finite element simulations
was automatized and was applied to each
non-conformal L-angle.

The comparisons between the observed
and predicted failure patterns (delamination cracks) were also reported for the
pristine L-angles and those with defects.
The present approach makes it possible
to describe the failure patterns accurately, even for L-angles with defects, and
to explain the decrease in the failure
load. Indeed, for pristine specimens, the
delamination was mainly due to the outof-plane tensile stress, the out-of-plane
shear stresses being negligible in the
radius. For non-conformal specimens,
additional out-of-plane shear stresses
were generated in the radius because of
the initial waviness. Using a 3D failure
criterion, which takes into account the
interaction between out-of-plane tensile
and shear stresses, the decrease in the
apparent failure load can be naturally
predicted.

composites magazine 29



Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #106 - July 2016

Cover
Edito
Point of view: Europe
Contents
COMPANY & BUSINESS
Development
Agenda of Events
APPLICATIONS
Thermoplastics
Automotive
MARKET
Aircraft engine
FEATURE AERONAUTICS
Aerostructures
Characterisation
Thermoplastics
Aero-engines
Process
CFRP
Semi-product
RESEARCH & DEVELOPMENT
Review
Core material
TECHNOLOGY & INNOVATIONS
NDT
Marine
Index
In the world
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Ad1
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Cover
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 2
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Edito
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Point of view: Europe
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 5
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Contents
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 7
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - COMPANY & BUSINESS
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 9
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Development
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 11
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Agenda of Events
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 13
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - AdHEC
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - AdCro
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Thermoplastics
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 15
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 16
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Automotive
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Aircraft engine
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 19
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 20
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 21
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 22
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Aerostructures
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 24
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 25
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Characterisation
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 27
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 28
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 29
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 30
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Thermoplastics
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 32
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Aero-engines
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 34
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 35
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 36
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Process
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 38
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 39
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - CFRP
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 41
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 42
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Semi-product
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 44
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 45
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Review
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 47
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 48
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 49
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Core material
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 51
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 52
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - NDT
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 54
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Marine
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 56
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Index
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - In the world
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 59
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