Quantification of tape deconsolidation during laser assisted fiber placement

Laser Assisted Fiber Placement (LAFP) is an additive manufacturing technique for thermoplastic composites, with the potential for in-situ consolidation. The achieved consolidation quality, however, is lower than obtained with conventional thermoplastic production techniques. One of the problems is the high interlaminar void content. Formation of interlaminar voids is related to intimate contact development, which is facilitated by a smooth tape surface. However, earlier experiments have shown that the tape might deconsolidate during the heating phase prior to the nip-point. As a result the roughness of the, initially smooth tape, might increase. Proper process modeling is only possible if this deconsolidation is taken into account. An elaborate investigation of the deconsolidation behavior is required. For this purpose an automated image analysis method was developed to characterize consolidation state of pre-preg tapes in terms of fiber, matrix and void distributions and surface roughness. This method enables statistical data collection, by automated analysis of a high number of microscopy images. Tapes were placed with reduced pressure, to capture the state of the tape before entering the nip-point. The consolidation state of the tape after the heating phase is characterized by an increased void content and, more im- portantly, an rough outer surface. The thickness of the rough outer layer of the tape increases with reducing consolidation quality. This quantitative characterization of the surface can be used in more accurate intimate contact development modeling.