JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 53

NDT

Fast and reliable non-destructive
inspection of composites

By

X-ray phase contrast imaging (XPCI) allows for fast and reliable
non-destructive inspection of a broad range of flaws in thick
monolithic components or complex composite structures. Initially developed for aeronautics, XPCI also finds applications in the
automotive, space, medical technology and oil & gas industries.

VINCENT REVOL,
PROJECT MANAGER, CSEM SA, ALPNACH
ANA MARIA MADRIGAL,
HEAD OF AERONAUTICS PROGRAM, CSEM SA
ON BEHALF OF THE EVITA CONSORTIUM

T

he use of composite components is
progressing in new applications and
markets thanks to their high strengthto-weight ratio, high corrosion resistance
and durability, among others. New manufacturing processes make it possible to accelerate production, lower costs and create more
complex shapes and material combinations.

Non-destructive inspection
As composite materials evolve, non-destructive inspection (NDI) with conventional
techniques is becoming more and more
challenging due to the variety of defects, material combinations and complex geometries
(Frost & Sullivan 2013). While standards
and norms exist for metallic parts, there is
a need to develop new NDI techniques for
composites to keep pace with the needs of
end-users, in particular for safety-critical
components. But beyond simply ensuring
safety and reliability, the benefits of NDI
also include shorter development and validation cycles, improved production yields,
reduced waste, lower part weight and an
improved understanding of failure modes.
Within the European project EVITA, a new
NDI technology called grating-based X-ray
phase contrast imaging (XPCI) was devel-

oped for the non-destructive evaluation and
inspection of primary aeronautical composite structures (CSEM 2015). The technique
is now finding widespread applications in
the automotive, space, medical technology
and oil & gas industries.
Compared to other NDI methods, XPCI
provides a unique solution for the fast and
reliable inspection in large composite components (meter-size) of structural defects
such as porosity, cracks, fibre misalignment,
missing foam in sandwiches, or resin rich/
poor areas. An example of impact damage
detection on a carbon fibre-reinforced
polymer (CFRP) panel is shown in Figure
1. The microscopic cracks caused by the
impact can be well detected in the scattering
image (right) while they stay invisible in the
conventional X-ray image (left)

X-ray phase contrast imaging
Compared to conventional X-ray systems,
XPCI measures tiny changes in the phase
front of the X-ray beam propagating through
the sample. This new contrast mechanism
is based on the use of a grating interferometer (Pfeiffer et al. 2006; Revol et al. 2010),
which combines a conventional X-ray source
and detector with transmission gratings.
As shown in Figure 2, the first grating (G1)
creates an interference pattern that can be

Fig. 1: X-ray phase contrast radiography images
of a 5J impact damage on a 3mm-thick CFPR
laminate.

Main features
- Contact-free transmission NDI technique
without coupling agent
- Able to inspect thick composite
components (wall thickness >30mm)
- Able to inspect complex shapes
- High contrast for lightweight materials
- Sensitive to micro- and macrostructural
features such porosity, cracks, foams or
fibre misalignment
- Inspection speed up to 5m2/hr with
further speed improvements planned in
future system generations

No106 July 2016 / jec

composites magazine 53
Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #106 - July 2016
