Abstract
Mullite reticulated porous ceramics (RPC) are one of the key components for porous media burner, the mechanical properties of mullite RPC decided the service life of the burner. However, the irregularities of cellular structure made it difficult to reveal the fracture behavior of mullite RPCs. In this study, the three-dimensional (3-D) structures of mullite RPCs were analyzed by X-ray computed tomography. The strength and damage behavior of mullite RPCs were respectively investigated via the compression tests and finite element modeling based on the actual 3-D model, also the corresponding strengthening mechanism was proposed. The results indicated that the reconstructed 3-D model exhibited the real microstructure of mullite RPCs, containing the hollow struts and strut defects. The Young's modulus calculated from actual 3-D structures was lower than that from Gibson-Ashby theory. In addition, the surface defects preceded triangular tips to generate the area of stress concentration, leading to the fracture behavior first occurred at the strut defects. With the formation of dense strut in mullite RPCs, the stress uniformly distributed in the whole solid skeleton, thus significantly improving the damage resistance of mullite RPCs.
Highlights
With the increasing of the energy crisis and consciousness of environmental issue, porous media combustion has attracted people’s attention due to its low pollutant emission, high powder density and combustion efficiency (Trimis and Durst, 1996; Wood and Harris, 2008; Yu et al, 2013)
X-ray computed tomography (CT) is usually used to in-situ observe the microstructure inside the materials, which is an effective technique to reconstruct the complicated morphology of porous ceramics (Fischer et al, 2009; Ortona et al, 2010; Chen et al, 2017)
The coated polyurethane sponges were dried at room temperature for 24 h, subsequently treated at 1,500◦C for 3 h to prepare mullite reticulated porous ceramics (RPC) with hollow struts, which named as sample MH
Summary
With the increasing of the energy crisis and consciousness of environmental issue, porous media combustion has attracted people’s attention due to its low pollutant emission, high powder density and combustion efficiency (Trimis and Durst, 1996; Wood and Harris, 2008; Yu et al, 2013). Plenty of simulation approaches are performed to reveal the elastic properties of RPCs. In general, the spacefilling polyhedron models including cubic model, Kelvin model and Weaire-Phelan model are widely used for the simulation of porous foams (Gibson and Ashby, 1997; Zhu et al, 1997; Buffel et al, 2014). The model construction based on the real ceramic struts is the critical to obtain the elastic properties of RPCs. X-ray computed tomography (CT) is usually used to in-situ observe the microstructure inside the materials, which is an effective technique to reconstruct the complicated morphology of porous ceramics (Fischer et al, 2009; Ortona et al, 2010; Chen et al, 2017). The effects of strut structures and morphological features on the mechanical properties and fracture behavior of mullite RPCs were investigated based on the compression tests and finite element method. The strengthening mechanism for mullite RPCs are revealed, the corresponding approaches are proposed
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