Automatic strengthening in thickness direction using lap joint of carbon fiber for fused filament fabrication 3D printing

The tensile strength in the thickness direction was lower than that in the horizontal direction when using fused filament fabrication three-dimensional (3D) printers. This study proposes an embedding method using lap joints to automatically embed and strengthen carbon fiber-reinforced plastics (CFRP) in the thickness direction. The proposed method can be applied to continuous carbon fiber 3D printers and 3D printers for construction purposes. Therefore, CFRP-reinforced specimens with lap joints were fabricated, and tensile tests were conducted. The results show that strength loss can be suppressed by sufficiently increasing the length of the lap joint and embedding a subsequent layer before curing the epoxy resin. The relationship between the lap joint length and modeling height was formulated based on the geometric conditions of embedding with lap joints. It was discovered that at least two different lengths of CFRP are necessary irrespective of the modeling height.