The effects of material type and temperature factors on the adhesive bonding strength of 3D printed multi-material plastic structures

In this study, various test samples were produced using PLA based two filament materials with different fillers (2% calcium carbonate containing polylactic acid / PLA Plus and 15% carbon fiber-reinforced polylactic acid / PLA CF) and two different infill ratios (50% and 100%), in both single-material and multi-material forms. Adhesive joints of single-material and multi-material samples were formed under two different environmental conditions (room temperature and −25°C). The effects of temperature changes on the adhesive bonding strength were investigated. For this purpose, mechanical tests were conducted on single lap joints conditioned at room temperature (unconditioned) and at −25°C for 5 days (exposed at −25°C for 120 h). The reaction of the strength values of single-material parts to temperature varies depending on the material type and infill ratio. On the other hand, for multi-materials, regardless of the infill ratio, the strength values obtained at room temperature are 11%-36% higher than those of specimens conditioned at cold temperatures. In both infill ratios and temperature conditions, it was observed that creating adhesive joints from CF-CF surfaces of multi-materials provided the highest strength. This study examines the mechanical properties (tensile strength and hardness) of multi-materials, the adhesive bonding of multi materials, and the performance of these joints. The highest bonding strength of 4.14 MPa was found in CF-CF with 100% infill ratio at room temperature and the lowest bonding strength of 2.05 MPa was found in PP-PP with 50% infill ratio at −25°C.