Laps and gaps in thermoplastic composites processing

During tape lay-up, laps and gaps result from machine and human inaccuracies, as well as the inability of the tape to conform to complex geometries. This paper examines whether these flaws can be removed through processing by transverse flow during consolidation. Treating unidirectional thermoplastic composites as macroscopically homogeneous materials, it is demonstrated that transverse flow can be described by the equations governing the flow of a power law fluid. This theory is then applied to gaps (with good agreement), and laps (with poor agreement). The differences between theory and experiments are explained, and it is shown that under correct conditions, laps and gaps, an order of magnitude larger than what is currently accepted, can be removed through processing.