JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 62

TECHNOLOGY NDT
lates around 0 m/s. A negative FSV might be induced by two-dimensional effects. The corresponding period for this type of event is about
3 μs, which is coherent with the longitudinal shock velocity of the constitutive materials. Conversely, disbonding implies the creation of a free
surface at the TA6V/epoxy interface, meaning this layer is not unloaded by release waves like the rest of the sample and, therefore, its FSV
profile exhibits a quasi-constant velocity just after the main peak. Back
and forth travels of the shock waves in the TA6V layer will generate
FSV oscillations after disbonding (Figure 5 (a)). However, the temporal resolution of the PDV analysis used here (50 ns) will prevent these
oscillations from being detected. It also seems that FSV curves might
be impacted by two-dimensional effects as negative values are visible
in some cases. These edge effects are hardly understandable without an
appropriate simulation.
Non-destructive testing
Finally, post-shock micrographs of the samples subjected to the highest
intensities did not reveal any failure in the composite or the TA6V layer.
A separate characterization of the TA6V and the 3D composite layer
under laser shock in the same conditions (thickness and laser intensity)
had already resulted in the same observation.
These observations show that in this case, laser-induced shocks do not
seem to have affected the material. The LASAT configuration used
here does not seem to induce damage in the substrates. Regarding the
nature of the substrates and the respective thickness of the materials, it
seems that the LASAT configurations used in this study are non-destructive.
Deeper investigations are required to assess LASAT as a non-destructive method. Mechanical testing after laser shocks is planned to confirm that the substrates and the joint are not degraded below their respective damaging threshold.

Conclusion
The LASAT configuration used can discriminate a weak bond from a
healthy one with the help of disbonding diagnostics. In addition, the
healthy bond's disbonding threshold was clearly identified. This means
that a weak bond just beyond the tolerance (+/- 20% of the healthy
strength) should also be discriminated using the same configuration.
Some further experiments should be conducted with such a bond
quality.
In-situ free surface velocimetry provided encouraging results for detecting disbonding in a given configuration. Deeper investigations are
necessary to confirm this technique's potential to detect disbonding
coupled with laser-induced shock waves.
Post-shock diagnostics confirmed the potential of LASAT as a non-destructive method. However, some modifications of the material due to
the shock might be non-detectable, even with micrographs. Mechanical
testing of samples subjected to laser shocks is necessary to demonstrate
the non-destructive nature of such a technology.
1D simulation was used to build the time-position diagrams required
to understand the shock wave propagation patterns involved. Based on

62

jec composites magazine / N°116 October 2017

Fig. 7: Evolution of the free surface velocity with time for composite illumination
shots on a weak bond - Temporal resolution = 50 ns - Signals in dotted lines
correspond to identified disbonding configurations

these tools, an interpretation of the disbonding threshold dependence
on the illumination side was proposed.
2D or 3D simulations are needed to simulate attenuation phenomena and edge effects more precisely. A quantitative simulation could
provide more information on the evolution of stresses within the substrates and, if needed, help to define a more optimized configuration
to lower stresses in the substrates, while still covering weak bond detection. In addition, the mechanical resistance of bonds under shock
loading could be determined using such a simulation.
More information:
Ducousso Mathieu (Safran), mathieu.ducousso@safrangroup.com
Bergara Tomas (Rescoll), tomas.bergara@rescoll.fr
Laurent Berthe (PIMM laboratory), laurent.berthe@ensam.eu
Acknowledgement
The authors would like to acknowledge the consortium of the Compochoc project composed by the following companies: Alphanove, Airbus, CEA, Cilas, Idil,
Kuka Aerospace,Laser Metrologie, PIMM, PSA Peugeot Citroen, Rescoll, Safran,
Simchoc. This project received funding from the FUI french program and
Nouvelle-Aquitaine and Ile de France regions with the support of Aerospace
Valley, Astech and Route des Lasers.

References
[1] . L. Berthe et al., "State-of-the-art laser adhesion test (LASAT),"
Nondestructive Testing and Evaluation, 26 (3-4), 303-317 (2011)
[2]. R. Ecault et al., "Development of a laser shock wave adhesion
test for the detection of weak composite bonds," 5th International
Symposium on NDT in Aerospace, Singapore (2013)
[3]. P. Mora, "Theoretical model of absorption of laser light by a plasma,"
Phys. Fluids 25, 1051 (1982)
[4]. N. C. Anderholm, "Laser-generated stress waves," Appl. Phys. Lett.
16, 113 (1970)
[5]. A. Sollier et al., "Numerical modeling of the transmission of
breakdown plasma generated in water during laser shock processing,"
The Eur. Phys. J. AP 16, 131-139 (2001)
[6]. R. Fabbro, "Physical study of laser-produced plasma in confined
geometry", Journal of Applied Physics 68, 775 (1990)
[7]. S. Bardy et al., "Numerical study of laser ablation on aluminum
for shock-wave applications: development of a suitable model by
comparison with recent experiments", Opt. Eng. 56, 011014 (2016)
[8]. O. T. Strand et al., "Compact system for high-speed velocimetry using
heterodyne techniques" , Review of Scientific Instruments 77, 083108
(2006)
[9]. L. Tollier et al., "Study of the laser-driven spallation process by
the velocity interferometer system for any reflector interferometry
technique. I. Laser-shock characterization.", Journal of Applied Physics
83, 1224 (1998)
[10]. L. Tollier et al., "Study of the laser-driven spallation process by the
VISAR interferometry technique. II. Experiment and simulation of the
spallation process.", Journal of Applied Physics 83, 1224 (1998)



Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #116 - October 2017

Cover
Edito
Opinion: Renewable energy
Contents
NEWS
In brief
JEC Asia
Agenda
BUSINESS
Strategy - Airbus strengthens its position in China
Database - The new technical database for composites
MANUFACTURING
NDT - New flexibility in 3D digitalisation and defect detection for batch composite production
Thermoplastics - Development of a carbonthermoplastic hub for the H160 helicopter
Feature Wind energy - An increasingly efficient sector
Market news - TPI Composites agreements with Gamesa and Vestas Wind Systems
Overview - Double digit growth again for the wind energy
Focus - lnside lndia’s wind turbine industry
Testimony - Strong growth in wind energy worldwide
Process - Perfect composite parts, thanks to the «direct infusion» process and resin conditioning
Technologies - Evolution of technologies and materials used in wind turbine blade manufacturing
Resin - New products for longer blades help to cut cost
SOLUTIONS
Aeronautics - lnnovative thermoplastic composite wing rib
Bike - Taking the lead with composites
Motorbike - lnnovative SLS front air inlet made with high-performance materials
Solar energy - Ultra-light photovoltaic panel based on polyamide honeycomb technology
TECHNOLOGY
NDT - Non-destructive evaluation of the mechanical strength of a TA6V4/composite bond using LASAT
Efficiency - Cost-efficient preforming using tailored textiles
Index
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JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 68
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - Cover
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 2
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - Edito
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - Opinion: Renewable energy
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 5
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - Contents
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 7
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - In brief
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 9
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - JEC Asia
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 11
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 12
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 13
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 14
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 15
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - Agenda
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 17
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 18
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - Ad1
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - Ad2
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - Strategy - Airbus strengthens its position in China
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 20
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 21
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - Database - The new technical database for composites
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 23
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 24
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - NDT - New flexibility in 3D digitalisation and defect detection for batch composite production
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 26
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 27
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - Thermoplastics - Development of a carbonthermoplastic hub for the H160 helicopter
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 29
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 30
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 31
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 32
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 33
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 34
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - Market news - TPI Composites agreements with Gamesa and Vestas Wind Systems
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 36
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 37
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - Overview - Double digit growth again for the wind energy
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 39
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - Focus - lnside lndia’s wind turbine industry
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 41
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - Testimony - Strong growth in wind energy worldwide
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 43
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - Process - Perfect composite parts, thanks to the «direct infusion» process and resin conditioning
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - Technologies - Evolution of technologies and materials used in wind turbine blade manufacturing
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 46
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 47
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - Resin - New products for longer blades help to cut cost
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 49
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 50
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - Aeronautics - lnnovative thermoplastic composite wing rib
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - Bike - Taking the lead with composites
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 53
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - Motorbike - lnnovative SLS front air inlet made with high-performance materials
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 55
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 56
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - Solar energy - Ultra-light photovoltaic panel based on polyamide honeycomb technology
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - NDT - Non-destructive evaluation of the mechanical strength of a TA6V4/composite bond using LASAT
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 59
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 60
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 61
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 62
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - Efficiency - Cost-efficient preforming using tailored textiles
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 64
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 65
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - Advertisers
JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 67
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