X-ray microtomography analysis of the damage micromechanisms in 3D woven composites under low-velocity impact

Abstract

ABSTRACT3D woven composites reinforced with either S2 glass, carbon or a hybrid combination of both and containing either polyethylene or carbon z-yarns were tested under low-velocity impact. Different impact energies (in the range of 21-316 J) were used and the mechanical response (in terms of the impact strength and energy dissipated) was compared with that measured in high-performance, albeit standard, 2D laminates. It was found that the impact strength in both 2D and 3D materials was mainly dependent on the in-plane fiber fracture. Conversely, the energy absorption capability was primarily influenced by the presence of z-yarns, having the 3D composites dissipated over twice the energy than the 2D laminates, irrespective of their individual characteristics (fiber type, compaction degree, porosity, etc.). X-ray microtomography revealed that this improvement was due to the z-yarns, which delayed delamination and maintained the structural integrity of the laminate, promoting energy dissipation by tow splitting, intensive fiber breakage under the tup and formation of a plug by out-of-plane shear.

Inclusion of a thermoplastic phase to improve impact and post-impact performances of carbon fibre reinforced thermosetting composites — A review

“…However, this is outside the scope of this review, which is concerned solely with the improvement in damage resistance and tolerance due to the thermoplastic toughening phase. Information on the use of these types of fabrics, and their effect on impact tolerance can be found in references [22][23][24][25][26][27][28][29][30][31][32][33][34][35].…”

Recent advancements in mechanical characterisation of 3D woven composites

“…In contrast to the response of the laminated composites, the effect of the through-thickness binder was significant as it supressed the delamination. An interesting study by Seltzer et al (Seltzer et al 2013) revealed the damage mechanisms of 3D S2-glass, carbon and hybrid woven composites by X-ray Computed Tomography (CT) due to low-velocity impact. In addition, they compared the energy absorption of the 3D woven composites with that of 2D laminated counterparts.…”

“…As the main advantage of 3D woven composites is clearly their out-of-plane enhanced properties, many researchers for example (Ji et al 2007;Luo et al 2007;Hao et al 2008;Walter et al 2009;Gerlach et al 2012;Seltzer et al 2013;Umer et al 2016) studied the effect of the z-binding yarns on the impact damage behaviour and the energy absorption of those material systems. Impact testing in literature was classified based on the impact velocity to low (< 10 m/s) as reported in (Umer et al 2016), high (~20 to 50 m/s) as in (Ji et al 2007;Hao et al 2008) and ballistic (~900 m/s) as discussed in (Walter et al 2009).…”

Optimization of curing cycle in carbon fiber-reinforced laminates: Void distribution and mechanical properties

“…The size of the representative volume for tomography was chosen as a compromise among several factors: the resolution (the smaller the sample the higher the achievable resolution) for the detection of the smallest pores, the detection of a sufficiently large number of pores for statistical relevance and a sufficiently large specimen volume to contain the largest pores in the samples. In addition, the damage introduced by low-velocity impact in the laminates was studied by means of XCT, as in previous studies [14,15].…”