JEC COMPOSITES MAGAZINE - Issue #116 - October 2017 - 61

Non-destructive evaluation of the mechanical strength of a TA6V4/composite bond using LASAT

mismatch between the TA6V and the epoxy.
This propagation pattern generates successive release waves in the
epoxy layer between 1100 and 2000 nanoseconds, progressively inducing tensile stresses in the bond by recombination with the incident
release waves. If the initial loading (laser ablation pressure) is sufficiently high, the resulting tensile stresses can exceed the mechanical
strength of the bond and/or the composite/epoxy interface and hence
generate a disbonding. The maximum tensile stresses in the bond are
reached following shock waves through the thickness of the sample
(t=1500ns).

maximum tensile stresses exceed the mechanical strength of the bond
and/or the composite/epoxy interface.
However, in this case, the shock waves propagate twice through the
composite before generating maximum tensile stresses at the interface
(t=2500 ns).
The shock wave propagation patterns shown here suggest that the
composite illumination side is an optimum configuration for LASAT.
Shock waves propagate on a shorter acoustic path in that configuration
and, hence, are less subjected to attenuation through the composite.
This is believed to account for the dependence of disbonding thresholds on the illumination side. However, 2D or 3D simulations with a
developed composite model, taking anisotropy into account, are required. This should enable a quantitative simulation of shockwave attenuation and thus provide a more precise stress evaluation within the
stacking. A quantitative evaluation of the bond mechanical strength
would be possible with the set of experimental data exposed here.

In the case of TA6V irradiation (Figure 6), the incident shock wave is
generated in the TA6V layer and then partially transmitted as a shock
wave at the TA6V/epoxy interface (X=-0.4mm). The wave reflected at
this interface is a release wave (ZTA6V > ZEpoxy) that goes back to the
front face and reflects again as a shock wave in the TA6V layer. The shock
wave pattern in the TA6V layer is very comparable to the one exposed
in the composite illumination configuration, except that it generates
successive shock waves in the rest of the sample. These shock waves travel
in the epoxy layer and are transmitted in the composite as a shock wave.
The reflection of these shock waves at the epoxy/composite interface
(X=-0.55mm) is neglected here due to their low
amplitude. The first incident shock wave in the composite
reaches the composite free surface of the sample
(X=-4.35mm - t=1100ns), where it is fully reflected as a release wave.
The recombination of this reflected release wave with incident ones
creates a tensile stress zone. This tensile zone then goes backward and
reaches the epoxy layer. As described before, disbonding occurs if the

In fact, the FSVs recorded during the experiments leading to bond failure exhibit a spallation- type curve [9] [10] . In Figure 7, for example,
the laser shot achieved at 0.97GW/cm² (black curve) shows a clear
back and forth travel of shock waves in the whole stacking. FSV oscil-

Fig. 5: (a) Time-position (X-t) stress diagram; and (b)
stress evolution at the epoxy/composite interface in the
composite illumination case

Fig. 6: (a) Time-position (X-t) stress diagram; and (b)
stress evolution at the epoxy/composite interface in the
TA6V illumination case

Free surface velocity measurement
Free surface velocities (FSV) on the back face of the sample also
showed some interesting results. In the configurations with laser illumination on the composite side, a strong correlation between FSVs
and ultrasonic diagnostics can be identified.

N°116 October 2017

/ jec composites magazine

61



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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