Challenges for Thermoplastic-Automated Fiber Placement (TP-AFP) with in situ consolidation on 3D parts

Laser assisted Thermoplastic-Automated Fiber Placement (TP-AFP) is of big interest due to its possibility of the laminate's in situ consolidation during lay-up. On simple geometries like flat plates or cylindrical tubes, the process can be regarded as a steady-state process, as the thermal boundary conditions don't change during placement. Based on an optimized 2D steady-state process this paper focuses on describing the differences for 3D lay-up on v-shaped tools with a rounded corner. Due to the geometry, the heating behavior changes, which leads to local overheating of the material within the laser spot. Overheating occurs especially on the substrate laminate. Test specimens with different leg angles are manufactured and the heating behavior is logged and described. During placement the corner section gets overheated, while the closed loop control of the machine induces too low temperatures behind the corner. The specimens are mechanically tested for their radial out-of-plane tensile strength in the curved segment based on ASTM 6415. A decreasing failure strength was measured for specimens with sharper leg angles.