The paper presents the first complete set of test results obtained from quasi-static measurements of the out-of-plane tension, shear and compression properties of novel X-Cor™ and K-Cor™ flat sandwich panels. The cured panels were composed of 0.75mm thick quasi-isotropic IM7/8552 skins, separated by 12.7 mm thick Rohacell ® foam core containing 0.51 mm diameter carbon fibre pins (Z-Fiber ® ), arranged in a truss pattern at pin angle of either 22° or 30° to the vertical. To obtain a suitable baseline comparison, the equivalent set of properties was measured for Nomex honeycomb core panels sandwiched by the same composite skins. The novel Z-pinned cores are found to exhibit higher specific stiffness than conventional sandwich cores, but lower strength.2 inserted at a specific angle to form a truss. The version of Z-Fiber ® used here is a cured pultruded carbon fibre/bismaleimide rod. Initially the pins inserted in the foam extend beyond each surface of the foam, for a so called "reveal length". The core at this stage is called a X-Cor TM preform (see Fig.1a). For the X-Cor TM sandwich construction this preform is then pressed between two uncured composite skins, the pins enter into the surfacing prepreg plies and create a mechanical fastening between the core and the skin, without the need for any adhesive (see Fig.1b).In the case of the K-Cor™ preforms, the Z-pins which extend beyond the foam surface are only partially cured. They can therefore be folded back under the action of moderate heat and pressure, flush with the foam surface (see Fig.2). The required sandwich panel skins, which can be pre-cured composite or metallic plates, are then usually adhesively bonded onto the core. The additional heat supplied in the bonding process serves to complete the cure of the Z-pins. Further detail of the manufacturing processes involved in the production of the preforms can be found in a recent review [1]. The possibility of producing these preforms to net shapes and required pinning densities is attractive where complex sandwich construction is required [2]. The Rohacell ® foam is a 'closed cell' type and is highly resistant to ingress by water. This confers a clear advantage to these sandwich panels in situations where water absorption and freeze-thaw cycles may otherwise present a problem.
Out-of-plane properties of sandwich panelsRelatively little experimental work has been carried out so far on the above described novel sandwich materials. The earliest published work by Vaidya and colleagues was prompted by considerations of whether these new materials could completely replace traditional honeycomb sandwich materials in aerospace applications and consequently it
This investigation focuses on nanoparticle filtration in the processing of multiscale carbon and glass fibre composites via resin transfer moulding. Surface modified and unmodified carbon nanotubes (CNTs) were incorporated into a commercial epoxy resin. The dispersion quality was evaluated using electrical measurements of the liquid suspensions. The manufacturing process was adapted to the challenges posed by the modified rheological behaviour of the CNT loaded resin. Nanoparticle filtration was observed; with some of the unmodified systems following so called 'cake filtration' behaviour. This resulted in non linear flow behaviour that deviated from the ideal response observed in RTM filling in conventional composites. The electrical conductivity of relatively high fibre volume fraction multiscale carbon and glass laminates increased by less than an order of magnitude with the addition of the nanotubes.
The paper details the manufacturing processes involved in the preparation of through-the-thickness reinforced composites via the 'dry preform -tufting -liquid resin injection' route. Samples for mechanical testing were prepared by tufting a 5 harness satin weave carbon fabric in a 3mmx3mm square pitch configuration with a commercial glass or carbon tufting thread, infusing the reinforced preforms with liquid epoxy resin and curing them under moderate pressure. The glass thread reinforcement increases the compression-after-impact strength of a 3.3mm thick carbon fabric laminate by 25%.The accompanying drop-downs in static tensile modulus and strength of the same tufted laminate are below 10%. The presence of tufts is also shown to result in a significant increase in the delamination crack growth resistance of tufted double-cantilever beam specimens and has been quantified for the case of a 6mm thick tufted carbon non-crimped fabric (NCF)/epoxy composite. Keywords (A) 3-dimensional reinforcement, (A) polymer matrix composites (PMCs), (E) preform, tufting.
Since the discovery of graphene, various industries such as aerospace and automotive are trying to utilize this fascinating nanofiller to enhance components' performance. An important issue in the processing of nanoengineered composites is the interaction and potential filtration of nanofillers by the porous microfibre preform during liquid moulding processing. Here we demonstrate the filtration effect of graphene nanoplatelets (GNPs) during resin infusion of nanoengineered hierarchical composites, and for the first time we have successfully quantified this filtration effect by both electrical and optical methods. In addition, an alternative spraying method to deliver GNPs into composite laminates was also evaluated.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.