Fuzzy overbraids for improved structural performance
Topic(s) : Special Sessions
Co-authors :
Laura Rhian PICKARD (UNITED KINGDOM), Haoxuan LU (UNITED KINGDOM), Charlie SHARP (UNITED KINGDOM), Curtis WONG (UNITED KINGDOM), Iheoma C. NWUZOR (UNITED KINGDOM), Matheo DIAS , François BOYER , Diego ALVAREZ FEITO (SWITZERLAND), Philippe OLIVIER (FRANCE), Giuliano ALLEGRI , Michael R. WISNOM (FRANCE)Abstract :
A hierarchical approach to composites is considered a promising avenue for improving performance under compression [1]. Natural composites which perform well under compression have hierarchical structures, such as cortical bone [2]. To implement this approach in advanced composites, pultruded rods are used as components in larger composite structures (Figure 1).
Natural composites contain features at various length scales which control their behaviour under compression. In the pultruded rod approach, we implement this by micro-overbraiding (Figure 2). The braiding is carried out using a Herzog 1/16/80 circular maypole microbraider with 8 tows (half capacity) in a diamond interlace pattern.
Micro-overbraiding has been shown to improve the compressive performance of pultruded rod based composites, with dry aramid and Zylon™ overbraids of a single pultruded rod delivering 65% and 70% improvement in load at failure respectively [4], in trials carried out using a ‘cradle’ 4 point bend test [5]. Further trials have been carried out with the overbraid infused with an epoxy resin and cured.
A more brittle material than aramid, such as carbon or basalt, undergoes partial breakage when braided at shorter lay lengths. This results in a ‘fuzzy’ braid with the discontinuous fibres extending further into the surrounding matrix. This increases the size of the region with braid-matrix contact, providing extra support.
Such fuzzy overbraids have been used to reinforce both pultruded rod based hierarchical composites, and composite panels containing embedded microvascular channels. A treated PLA cylinder is overbraided before being incorporated into a composite panel, after which the PLA is vaporised leaving a channel behind. Significant improvement in performance has been demonstrated compared to the unreinforced case. Non-fuzzy overbraids, both of carbon at longer lay length and aramid at short lay length delivered notably less improvement than the fuzzy carbon overbraid, demonstrating the validity of this approach.
For the hierarchical composite system, overbraided pultruded rods may be integrated into larger composite parts, such as cylindrical structural members [3].
Funding was provided by UK Engineering and Physical Sciences Research Council (EPSRC) programme Grant EP/T011653/1, Next Generation Fibre-Reinforced Composites: a Full Scale Redesign for Compression in collaboration with Imperial College London.
This research work has been supported financially by the CERN Strategic Programme on Technologies for Future Experiments (WP4 - Mechanics).
Natural composites contain features at various length scales which control their behaviour under compression. In the pultruded rod approach, we implement this by micro-overbraiding (Figure 2). The braiding is carried out using a Herzog 1/16/80 circular maypole microbraider with 8 tows (half capacity) in a diamond interlace pattern.
Micro-overbraiding has been shown to improve the compressive performance of pultruded rod based composites, with dry aramid and Zylon™ overbraids of a single pultruded rod delivering 65% and 70% improvement in load at failure respectively [4], in trials carried out using a ‘cradle’ 4 point bend test [5]. Further trials have been carried out with the overbraid infused with an epoxy resin and cured.
A more brittle material than aramid, such as carbon or basalt, undergoes partial breakage when braided at shorter lay lengths. This results in a ‘fuzzy’ braid with the discontinuous fibres extending further into the surrounding matrix. This increases the size of the region with braid-matrix contact, providing extra support.
Such fuzzy overbraids have been used to reinforce both pultruded rod based hierarchical composites, and composite panels containing embedded microvascular channels. A treated PLA cylinder is overbraided before being incorporated into a composite panel, after which the PLA is vaporised leaving a channel behind. Significant improvement in performance has been demonstrated compared to the unreinforced case. Non-fuzzy overbraids, both of carbon at longer lay length and aramid at short lay length delivered notably less improvement than the fuzzy carbon overbraid, demonstrating the validity of this approach.
For the hierarchical composite system, overbraided pultruded rods may be integrated into larger composite parts, such as cylindrical structural members [3].
Funding was provided by UK Engineering and Physical Sciences Research Council (EPSRC) programme Grant EP/T011653/1, Next Generation Fibre-Reinforced Composites: a Full Scale Redesign for Compression in collaboration with Imperial College London.
This research work has been supported financially by the CERN Strategic Programme on Technologies for Future Experiments (WP4 - Mechanics).