Dry Fibre Placement: The Influence of Process Parameters on Mechanical Laminate Properties and Infusion Behaviour

Within the dry fibre placement (DFP) process, spread and pre-bindered carbon fibre rovings are automatically processed into dry textile preforms using 2-D and 3-D laying systems. The aim was to automate existing hand lay-up processes, reducing the complexity, increasing robustness, and facilitating the handling of the DFP technology. Process reliability, low waste rates, and flexible production are demonstrated. In this publication, the influences of the process parameters, 2 mm wide gaps and the percentage of 90° plies in the laminate, are investigated with regard to the mechanical properties, the permeability, and the infusion times in the preform z-direction (thickness). The effects on stiffness and strength are compared for several use cases. An approach to determine the infusion times as a function of the laminate thickness, the ply structure, and 2 mm wide gaps is demonstrated and analysed using vacuum-assisted process (VAP) infusion tests. The investigations are performed with carbon fibre tows (24 k), a reactive epoxy-based binder system, and a thermoset infusion resin system.

The Influence of Acid Hardener on the Strength and Hot-Distortion Properties of No-Bake Sand Cores

In this research work, the effects of different amounts of acid hardener (30%, 40%, 60%, 80% weighted to the resin) on the hardening characteristics and hot-distortion properties of no-bake furan and no-bake phenolic bonded sand cores were studied. Bending tests were conducted on test bars with storage times of 1, 2, 3, 5, 7, 24h. Hot-distortion tests were carried out on specimens with storage times of 4h and 24h. The bending tests revealed that in the case of the furan binder system, the acid hardener is best utilized in terms of higher bending strength, in an amount of 40–60%, while in the case of the phenolic binder system, the amount of 60–80% acid hardener resulted in higher bending strength of the sand specimens. Too low (30%) acid hardener (catalyst) level produced low bending strength. Too high (80%) amount of acid hardener decreased the strength of the no-bake furan sand samples, and as can be seen from the SEM analysis, it damaged the binder bridges between the sand grains. The hot-distortion tests showed that there is a correlation between the catalyst content and the max. Deformation of the samples both in the furan and in the phenolic no-bake sand cores, which can be described with a maximum curve. Increasing the acid hardener changes the thermoplastic behavior of the phenolic resin, thus the binder bridges become more rigid and brittle. The acid hardener above 40% decreased the thermal stability of the furan and phenolic bonded test pieces. The research work also revealed significant differences between the specimens made with furan and phenolic binder and the effect of the storage time in terms of the bending strength and hot-distortion properties.

A saccharide-based binder for efficient polysulfide regulations in Li-S batteries

The viability of lithium-sulfur batteries as an energy storage technology depends on unlocking long-term cycle stability. Most instability stems from the release and transport of polysulfides from the cathode, which causes mossy growth on the lithium anode, leading to continuous consumption of electrolyte. Therefore, development of a durable cathode with minimal polysulfide escape is critical. Here, we present a saccharide-based binder system that has a capacity for the regulation of polysulfides due to its reducing properties. Furthermore, the binder promotes the formation of viscoelastic filaments during casting which endows the sulfur cathode with a desirable web-like microstructure. Taken together this leads to 97% sulfur utilisation with a cycle life of 1000 cycles (9 months) and capacity retention (around 700 mAh g−1 after 1000 cycles). A pouch cell prototype with a specific energy of up to 206 Wh kg−1 is produced, demonstrating the promising potential for practical applications.

Bending Properties of Lightweight Copper Specimens with Different Infill Patterns Produced by Material Extrusion Additive Manufacturing, Solvent Debinding and Sintering

Material extrusion additive manufacturing (MEX) is a versatile technology for producing complex specimens of polymers, ceramics and metals. Highly-filled filaments composed of a binder system and a high-volume content of sinterable powders are needed to produce ceramic or metal parts. After shaping the parts via MEX, the binder is removed and the specimens are sintered to obtain a dense part of the sintered filler particles. In this article, the applicability of this additive manufacturing process to produce copper specimens is demonstrated. The particular emphasis is on investigating the production of lightweight specimens that retain mechanical properties without increasing their weight. The effect of infill grades and the cover presence on the debinding process and the flexural properties of the sintered parts was studied. It was observed that covers could provide the same flexural strength with a maximum weight reduction of approximately 23%. However, a cover on specimens with less than 100% infill significantly slows down the debinding process. The results demonstrate the applicability of MEX to produce lightweight copper specimens.