Development of a 25kN In Situ Load Stage Combining X-Ray Computed Tomography and Acoustic Emission Measurement

Abstract

Combination of material testing methods such as X-ray computed tomography with in-situ load stages allows for detailed analysis of damage formation and progression in fibre-reinforced composites. X-ray computed tomography is highly suited to volumetrically analyse the damage evolution induced by the load stage for tensile testing after subsequent load increments. Simultaneous acoustic emission monitoring allows identifying the occurrence of particular failure mechanisms and allows stopping the loading procedure for volumetric scanning. However, typical commercial designs focus on a broad range of materials and are not necessarily optimized for high load capacity at high voxel resolution or the possibility to attach acoustic emission sensors to the test sample. Accordingly, we designed a new load stage to fit larger samples up to 180 mm in length and 18 mm in width, which also allows two piezoelectric acoustic emission sensors to be directly applied on the sample. In order to test fibre reinforced laminate samples with a relevant cross-section, the support structure of the load stage is made of a carbon fibre reinforced polymer tube, which withstands a maximum load of 25 kN and still stays reasonably X-ray transparent. With an outer diameter of 27 mm, a computed tomography scan with a resolution down to 2.6 μm is still possible for these laminate cross-sections. This allows to study in detail how matrix and fibres behave under loads in laminates, which are comparable to specimen sizes by typical test standards. As example, we present results from glass fibre-reinforced epoxy samples with a [±45°]5 layup and carbon fibre-reinforced epoxy samples with a [0,90,90,0] layup.