Experimental investigation of in situ consolidation of thermoplastic matrix composites

This paper describes an experimental investigation of tape laying. The focus of this investigation is to characterize the tape laying process for closed loop control. Processing parameters for manufacturing composite laminates, via tape laying, were investigated to determine which factors have the greatest effect on the degree of bonding between successive composite layers. The experiments were conducted following statistical experiment design techniques. Two groups of experiments were conducted: control factor experiments and noise factor experiments. In the control factor experiments, a 2⁴ factorial design was utilized to study the process variables: speed (contact time), pressure, nip temperature, and foot temperature. The noise factors considered were variations in material lots, preheat gas contaminants, and variation in layup surface thermal characteristics. It was found that in the control factor experiments temperature and head speed were significant, however there were no statistically significant interactions among the factors. The noise factor study indicated that a method for sensing the "insulative" quality of the substrate is critical to ensuring appropriate speed and temperature settings. A thermal sensor which serves this function is described.