Automated Fiber Placement (AFP) is a fully-automated manufacturing process for composite parts. A robot guided placement head lays up tows of CFRP material onto a three-dimensional tool surface applying heat and pressure (Figure 1). We investigate the interaction of all process parameters and compare the results with simulation. The aim is the optimization of the process for a pre-defined part quality.
The principal parameters which influence the AFP process are consolidation force, lay-up velocity and temperature. The interactions between these parameters, the material (thermoset, thermoplastic or dry) and the part geometry are investigated. A sophisticated process-optimization is of particular importance for the thermoplastic “in-situ” AFP as the composite is built up and consolidated in one step. Thus defects such as porosity cannot be removed in an additional autoclave or press cycle.
For automated fiber placement the “tack” of the CFRP tows is one of the most important material properties. Using a special test bench we investigate the influences of the process parameters, tool material and surface on the tack. The prediction of lay-up effects and simulation of the AFP process require the characterization of the used CFRP-material.
Typical lay-up effects during automated fiber placement are gaps/overlaps, bridging, in-plane fiber waviness and out-of-plane fiber wrinkling in steered tows. As well as evaluating the influence of these effects on mechanical properties, prediction based on material properties and process parameters is studied.
The AFP-process is also used for part manufacturing within several research projects. Knowledge that is gained by investigating processes and materials is directly applied to real parts. One example is the in-situ joining of preformed fiber-reinforced thermoplastic profiles with fiber placed skins for manufacturing a helicopter door.