3Dプリントした積層体の力学特性および耐久性評価
著者らは，材料押出式3Dプリンティング技術の開発と実用化を進めている。材料押出式3Dプリンターで造形物を積層製作する際には，層間や列間に積層境が生じる。積層する方向に由来し方向によって材料特性が異なる性質を異方性というが，異方性は力学特性や耐久性に影響することが知られており，実用化に向けてその性質を適切に把握する必要がある。本報では，突固め作製した均一な供試体と比較しながら，積層体の異方性に関する諸特性を評価した。その結果，力学特性については，割裂引張強度と曲げ強度において積層体で顕著な異方性が見られた。一方，積層体の収縮抵抗性，中性化抵抗性，塩分浸透抵抗性は突固め供試体と同等以上であり，いずれも積層方向に由来する異方性は見られなかった。また，屋外暴露条件下での表層透気性と細孔径分布の変化を測定した結果，暴露1年後には透気係数は低下し，細孔構造が緻密化する傾向が見られた。
キーワード：3Dプリンティング，異方性，強度特性，促進中性化，塩分浸透，表層透気性
＊１ 技術センター 社会基盤技術研究部 材工研究室
＊２ 技術センター 社会基盤技術研究部 先端構造研究室
Study on the Mechanical Properties and Durability of 3D Printed Laminated Structures
The authors have been advancing the development and practical implementation of 3D printing technology. For material extrusion 3D printing, the formation of layer or column boundaries is unavoidable. The term "anisotropy" refers to the property whereby material characteristics differ depending on the direction of layering. Anisotropy is known to affect mechanical properties and durability, and it is necessary to appropriately understand these properties for practical application. In this report, various properties concerning the anisotropy of laminated structures were evaluated in comparison with uniform (isotropic) specimens produced by compaction. As a result, significant anisotropy in mechanical properties was observed in the laminated structures, particularly in terms of splitting tensile strength and flexural strength. On the other hand, the shrinkage resistance, carbonation resistance, and chloride penetration resistance of the laminated structures were equivalent to or higher than those of the compacted specimens, and no anisotropy due to the layering direction was observed in these aspects. Additionally, measurements of changes in surface air permeability and pore size distribution under outdoor exposure conditions indicated a decrease in air permeability coefficient and a tendency for densification of the pore structure after one year of exposure.
Keywords: 3D printing, anisotropy, strength properties, accelerated carbonation, chloride penetration, air permeability
*1 Structure and Material Research Section, Infrastructure Technology Research Department, Taisei Advanced Center of Technology
*2 Advanced Structure Technology Research Section, Infrastructure Technology Research Department, Taisei Advanced Center of Technology