Development of compaction rollers for improved pressure uniformity and reduced overlap-induced defects in automated fiber placement

Automated Fiber Placement (AFP) offers precise and flexible composite manufacturing but is prone to defects, with overlaps being among the most common. Once formed, overlaps disrupt compaction pressure, an important process parameter, leading to poor bonding between adjacent prepreg tows and initiating defects such as wrinkling and bridging. In this study, alternative polyurethane compaction rollers with varying shaft diameters (candidate rollers) were manufactured and compared with series of polyurethane and rigid rollers (reference rollers) to reduce pressure inconsistency while maintaining adequate compaction pressure during AFP of thermoset prepreg tape. Experimental tests, microscopic imaging, and finite element method (FEM) analysis were used to evaluate how each roller localized pressure non-uniformity that occurs adjacent to an overlap. Reference rollers produced non-uniform bonding thickness across the tape width once an overlap was present on the adjacent tow, whereas candidate rollers (with shaft diameters increased from 25 mm to 28 mm, 32 mm, and 35 mm combined with softer polyurethane) maintained more uniform bonding. Single-lap joint tests and FEM simulations confirmed that candidate rollers effectively minimized pressure inconsistency. Overall, results show that managing overlaps while sustaining high compaction pressure is best achieved by increasing shaft diameter and using a soft polyurethane layer rather than relying on higher-stiffness polyurethane.