Identification of microstructural anisotropy of cellulose cement boards by means of nanoindentation

Abstract

The main goal of the paper was to identify mechanical anisotropy of cellulose cement boards at micro scale in order to evaluate the direct cause of the mechanical behavior of boards in the scale of engineering applications (macro scale). Moreover, microstructural anisotropy of thermally treated boards (exposed to a temperature of 230 °C for 3 h) was also investigated. Four specimens were fabricated by applying the Hatschek forming method and examined by the means of nanoindentation. These were labeled A_x1, A_x3 (air-dry reference specimen), B_x1 and B_x3 (heated in electric oven). The “x1” or “x3” symbol denotes direction of nanoindentation tests – parallel or perpendicular to fibres’ spatial orientation, respectively. Obtained results, in the statistical sense, revealed the existence of evident microstructural anisotropy with respect to indentation modulus and hardness. This means that the production process of cellulose fibre cement boards causes the existence of intrinsic microstructural anisotropy which is a direct cause of macroscale mechanical behavior of this material. In the case of thermally treated specimens the microstructural anisotropy with respect to mechanical parameters is even more evident compared to the reference samples.