Although 3D woven composites have exceptional out-of-plane properties, there is a lack of understanding for these materials in crash application in automotive and aerospace industries. To encourage the use of 3D wovens in crashworthy automotive structures, knowledge must be gained so that designers can adjust the highly flexible weave parameters to create tailor-made performance materials. Here we show that fabric pick density causes large changes in progressive failure modes and associated energy absorption, particularly in the dynamic regime, where the quasi-static to dynamic energy absorption loss typical of composites is completely removed. Compression and flexure properties, which are known to be linked to crash performance in composites, are also investigated for these 3D woven layer-to-layer interlock carbonepoxy composite structures. 3D fabric preforms are manufactured in three different pick densities: 4, 10 & 16 wefts/cm. with a constant warp density of 12 warps/cm from carbon fibres. Increasing the pick density improved specific energy absorption (SEA) even in relatively inefficient progressive failure modes like folding, which has not previously observed in composite materials. SEA values up to 104 J/g (quasi-static) and 93J/g (dynamic) are recorded. This work shows that minor weft direction (transverse) weave changes can lead to sizeable improvements in warp direction (axial) energy absorption without fundamentally redesigning the weave architecture.
Yarn diameters ranging from 160µm to 720µm of unfilled PPSU and PPSU nanocomposites with 1 wt.% of either carbon nanotubes (CNT) or carbon nanofibers (CNF) were prepared using a twin screw compounder. The tensile properties of these yarns generally improve with the addition of CNT or CNF at higher values of screw speed-to-haul off ratio. This effect is correlated with the yarn draw down ratio and attributed to nanofiller orientation and crystallinity induced in thermoplastic matrix. The fibres have as much as a 23% increase in Ultimate Tensile Strength (UTS) for the same parameter set when loaded with CNT, while the greatest increase observed for larger particle size fillers CNF is just 3.77%. Depending on filler and processing parameters set, yarns varied in UTS from 24.84MPa to 206.23MPa for unfilled PPSU and PPSU-CNT, respectively.
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