Influence of CaO Content on the Fly Ash–Lime System Hydrothermal Synthesis Reaction Under Autoclave Curing

As a substitute for traditional Portland cement, the development and research of “low-temperature-synthesized fly ash cement” has been receiving extensive attention. This study explores the effects of calcium oxide content on the fly ash–lime system hydrothermal synthesis reaction under autoclave curing, focusing on the effects of CaO content on the strength of the cement paste. The changes in phase composition, microstructure, and morphology were characterized using X-ray diffraction and scanning electron microscopy (SEM) analysis. The results show that with an increase in the CaO content, the amounts of β-C2S and C12A7 in the gelling material also increase. However, when the CaO content is very high, the amounts of β-C2S and C12A7 in the gelling material no longer increase, and the strength is lost.

Assessment of a Computationally Efficient Method for Industrial Simulations of Transient Heat Transfer During Autoclave Curing

A numerical approach for transient CFD analyses of autoclave curing process is presented, aimed at finding a trade-off between accuracy and computational cost that can make it industry-affordable. A steady-state, conjugated heat transfer (CHT) analysis is carried out for the simultaneous simulation of solid and fluid regions to obtain a spatial distribution of the heat-transfer coefficient (HTC). This distribution and the curing temperature diagram are then used as boundary conditions for a transient heat-transfer simulation of the solid parts only. Results are compared to both experiments and coupled fluid-solid steady-state CHT simulations, proving that the proposed methodology is accurate and less computationally expensive than a fully-coupled, fluid-solid simulation.

Comparative life cycle assessment of carbon fiber reinforced compositecomponents for automotive industry

Advanced materials, especially carbon fiber reinforced composites (CFRP), have gained the attention of different industries whichproduce lightweight and high-performance components. The most used manufacturing processes to realize these kinds of products are Resin Transfer Molding (RTM) and vacuum bag molding with autoclave curing. RTM is based on dry fiber technology and it appears the most promising manufacturing process to realized high-quality carbon fiber parts reducing cost and manufacturing time, especially if high pressure variants are employed. On the other hand, vacuum bag molding with autoclave curing is a very consolidated process which is, however, associated with long manufacturing time and costs as well as to low repeatability of the process due to the high labor input. Out-of-autoclave methods, such as pressure bag molding (PBM) have been developed to overcome the issues of vacuum bag molding process. From the environmental point of view, the manufacturing of CFRP components is associated with high environmental loads due to the impacts related to both raw materials and manufacturing processes. For this reason, reducing the energy consumption of production phases can lead to the development of greener CFRP products. In this context, the main scope of the present research is to evaluate and compare the environmental loads of a component for the automotive industry realized exploiting the RTM, the PBM and the bag molding processes to determine which one is eco-friendlier. This analysis has been conducted following the standard Life Cycle Assessment methodology based on a “cradle to gate” approach. In this way, the use phase and the disposal of the CFRP component have not been included in the analysis. Results have been evaluated by comparing the equivalent CO2 related to each manufacturing process.