Enhanced static and fatigue performance of FDM 3D-printed polycarbonate adhesive joints using bio-inspired surface textures

• FDM technology is a good alternative for manufacturing parts with bio-surfaces. • Bio-inspired textures improve static tensile strength of PC-PC adhesive joints . • Bio-surfaces enhance both tensile and shear fatigue life of PC-PC adhesive joints. • Mechanical interlocking and extension of the effective area are the key parameters. • Cyclic loading increases adherends sensitivity to FDM-induced defects. The bonding potential of additively manufactured polycarbonate (PC) material is still a relatively unexplored area, and the addition of bio-inspired surface texture to enhance adhesion, particularly concerning fatigue performance, has not yet been investigated. This study examines the effects of bio-surface texture on the static and fatigue strength of 3D-printed PC adhesive joints. The methodology involved firstly designing and 3D-printing substrates with as-printed and textured surfaces, inspired by the Tree Frog toe pads (TF) and Fish Scales (FS) surfaces. Subsequently, static and fatigue tensile tests were performed using Arcan joints, while the block shear method was adopted for the fatigue shear tests. The findings indicated that TF and FS textures significantly enhanced static tensile strength and extended both tensile and shear fatigue life by promoting mechanical interlocking and increasing the effective contact area, compared to the as-printed texture. Specifically, the TF and FS textures increased the static tensile strength by 51% and 31%, respectively. Under constant maximum fatigue loading conditions, TF and FS textures extended tensile fatigue life by 266 and 173 times, and shear fatigue life by 134 and 65 times. Moreover, adhesive joints with bio-inspired surfaces exhibit greater resistance than bulk adherends due to the increased sensitivity of 3D-printed adherends to defects, particularly voids, under cyclic loading. Therefore, to improve the static and fatigue resistance of 3D-printed PC adhesive joints, it is advisable to apply the load perpendicularly to the parts’ build orientation, design joints to withstand shear loads and include TF bio-texture on adherend surfaces.