Selection of functional materials for surface-coating of structural synthetic fibres and development of a 3D-printing system for their manufacture

• Published in: Composite structures 2020-10, Vol.249, p.112567, Article 112567
• Main Authors: Eom, Ah-Hyeon, Won, Jong-Pil
• Format: Article
• Language: English
• Subjects: 3D printer; Bond; Crack control; Self-healing; Synthetic fiber
• ISSN: 0263-8223; 1879-1085
• DOI: 10.1016/j.compstruct.2020.112567

This study examined methods to mitigate crack development in cementitious composites caused by insufficient bond strength between the matrix and hydrophobic structural synthetic fibres used for reinforcement. Materials that could improve the surface performance of structural synthetic fibres were identified, and a 3D-printer was used to apply the materials to the fibre surface. Polyurethane resin and urea–formaldehyde resin were evaluated as materials to improve the hydrophobicity of the synthetic fibre surface; calcium nitrate, sodium silicate, and epoxy resin were evaluated for crack control. Self-healing of cracks occurring in the cementitious composite was evaluated by compressive strength, flexural strength, and flexural strength recovery testing. Additionally, fibre pull-out testing was used to assess improvement in bonding between the fibres and cement matrix. Sodium silicate (5 wt%) provided 126% strength recovery and was thus suitable as a crack-control material. The bond strength of composite containing synthetic fibre printed with urea–formaldehyde resin was 34% higher than the strength for plain synthetic fibre, which rendered it suitable as a hydrophobic surface improvement material. A 3D-printing system was developed to apply these materials to the structural synthetic fibre surface.