Development of an Ultrasonic Debulking Technique for Composite Laminates Introduction

Manufacturing of thermoset composite materials involves a layup process of material layers or plies, which can trap air between the layers, and cause marcels and voids in rotorcraft composite parts. To curb these anomalies, multiple bulk compactions, or "debulking," with vacuum and heat is usually performed, thereby increasing total cycle time and cost of the part. Ultrasonic debulking offers a low-cost alternative using an ultrasonic head that follows the tape layup head. Laminated composite samples of E773/S2 were treated with ultrasonic energy at various scan speeds, amplitudes, force levels, horn angles, and ply intervals. Ultrasonic consolidation of these samples has successfully decreased the bulk before cure to roughly 4%. While the ultrasonic treatment resulted in significant viscous heating, it did not adversely affect on laminate mechanical properties. The experimental data further suggested that viscoelastic heating is a viable process response that can be measured in real time and correlated with bulk removal efficiency. Therefore, the development of an automated closed-loop ultrasonic debulking system where material temperature is controlled by varying the amplitude of the vibration and scan speed to achieve a target bulk of 3% is presented.