The influence of microstructure on mechanical properties of 3D printable geopolymer composites

Abstract

The additive manufacturing technologies are fast-developing industrial sector and, potentially, a ground-breaking technology. They have many advantages such as the saving of resources and energy efficiency. However, the full exploitation of 3D printing technology for ceramic materials is currently limited; a lot of research is being conducted in this area. A promising solution seems to be geopolymers, but its application requires a better understanding of the behaviour this group of materials. This article analyses the influence of microstructure on mechanical properties whilst taking the production method into consideration. The paper is based on comparative analysis – the investigation is focused on the influence of material structure on the mechanical properties and fracture mechanism of these kinds of composites, including those reinforced with different kind of fibres. As a raw material for the matrix, fly ash from the Skawina coal power plant (located in: Skawina, Lesser Poland, Poland) was used. The investigation was made by SEM analysis. The results show that the microstructural analysis did not sufficiently explain the underlying reasons for the observed differences in the mechanical properties of the composites.

The Influence of the Material Structure on the Mechanical Properties of Geopolymer Composites Reinforced with Short Fibers Obtained with Additive Technologies

“…The results for the samples reinforced by carbon fibers were 8.3 MPa for the casted sample and 8.1 MPa for the sample made by simulating the 3D printing process, respectively (Figure 1). The unexpected finding in this research was the very high values of compressive and flexural strength of the composite with flax fibers in comparison to the composite with carbon fibers [16,44]. Taking into consideration this fiber's properties, the results should be different, because the carbon fibers have better mechanical properties than flax fibers.…”

“…Figure 10 shows the microstructure where the agglomeration of the carbon fibers is presented. The agglomeration of carbon fibers were previously reported in the literature [44]. It is a consequence of the form of the fibers that are delivered in the form of "small flakes" that are an agglomeration of single fibers.…”

“…The samples were investigated with regard to their mechanical properties after 28 days [16,44]. A summary of these results is presented in Figure 1 [44].…”

“…The samples were investigated with regard to their mechanical properties after 28 days [16,44]. A summary of these results is presented in Figure 1 [44]. The best value of the compressive strength was reached for the sample made by simulating a 3D printing process for the composite reinforced by flax fibers.…”

“…Despite the fact that the flakes are evenly distributed in the volume of the material, there are agglomerations of single fibers in it. This could have a negative influence on the mechanical properties [44,68,69].…”