150-nm in-situ synchrotron tomography of unidirectional cross-ply laminates loaded in tension
Topic(s) : Special Sessions
Co-authors :
Yentl SWOLFS (BELGIUM), Thanasis CHATZIATHANASIOU (BELGIUM), Martin DIEHL (BELGIUM), Mahoor MEHDIKHANI (BELGIUM), Christian BREITE (BELGIUM)Abstract :
Computed tomography is a powerful technique to monitor damage development within a material in 3D. It has been frequently applied to fibre-reinforced composites to monitor fibre break development in 0° plies loaded in the fibre direction [1]. Such studies provide crucial validation data for advanced micromechanical models and are typically performed at synchrotron sources at voxel sizes of 0.65-2 µm. Synchrotron computed tomography has the potential to provide radically new insights, such as the observation that most fibre break clusters tend to be co-planar [2]. Pushing the spatiotemporal resolution limits and the contrast of the technique is, hence, essential to develop further insights.
Here, we report the first use of in-situ holotomography for studying the damage development in fibre-reinforced composites. Holotomography is a technique that takes multiple tomograms at different propagation distances. Thanks to the combination of phase shifts at different distances, this enables holotomography to reconstruct the phase information in the X-rays fully. The high contrast achieved makes holotomography particularly good at capturing mode II cracks, usually invisible in regular tomograms.
We prepared glass fibre-reinforced epoxy composites in a cross-ply configuration and water jet cut them to a typical double-notch configuration [1,2]. These specimens were mounted in an in-house developed manual loading rig with a 1 kN load cell, placed in the path of the synchrotron beam for in-situ scanning. During each scan, the specimen was held at constant displacement. The experiments were performed at the ID16B beamline of the European Synchrotron Radiation Facility (ESRF). Scans were acquired at a voxel size of 150 nm.
The images reveal several noteworthy features. First, they provide 3D images of fibre breaks at unparalleled resolutions (see Figure 1a), making the conversion into a finite element meshes significantly easier than with conventional tomography images. The complex break in Figure 1b is actually typical for glass fibres, which tend to fracture in a few small fragments. Second, we did not observe any fibre-matrix debonding near the fibre break, even though debonding was observed with the same technique in single-fibre composites (not shown here). This observation reveals that debonding is much less common or likely in regular composites than in single-fibre composites and may indicate that single-fibre composites are intrinsically unrepresentative of real composite behaviour. We are convinced that this new technique opens exciting new possibilities to study composite behaviour at unprecedented levels of detail.
Here, we report the first use of in-situ holotomography for studying the damage development in fibre-reinforced composites. Holotomography is a technique that takes multiple tomograms at different propagation distances. Thanks to the combination of phase shifts at different distances, this enables holotomography to reconstruct the phase information in the X-rays fully. The high contrast achieved makes holotomography particularly good at capturing mode II cracks, usually invisible in regular tomograms.
We prepared glass fibre-reinforced epoxy composites in a cross-ply configuration and water jet cut them to a typical double-notch configuration [1,2]. These specimens were mounted in an in-house developed manual loading rig with a 1 kN load cell, placed in the path of the synchrotron beam for in-situ scanning. During each scan, the specimen was held at constant displacement. The experiments were performed at the ID16B beamline of the European Synchrotron Radiation Facility (ESRF). Scans were acquired at a voxel size of 150 nm.
The images reveal several noteworthy features. First, they provide 3D images of fibre breaks at unparalleled resolutions (see Figure 1a), making the conversion into a finite element meshes significantly easier than with conventional tomography images. The complex break in Figure 1b is actually typical for glass fibres, which tend to fracture in a few small fragments. Second, we did not observe any fibre-matrix debonding near the fibre break, even though debonding was observed with the same technique in single-fibre composites (not shown here). This observation reveals that debonding is much less common or likely in regular composites than in single-fibre composites and may indicate that single-fibre composites are intrinsically unrepresentative of real composite behaviour. We are convinced that this new technique opens exciting new possibilities to study composite behaviour at unprecedented levels of detail.