Effect of AFP induced triangular gaps on manufacturing quality and stress distribution of composite panels

Automated fiber placement technology still faces some significant challenges in fiber path planning for composite laminates with unconventional geometries. Laying triangular gaps can inevitably result in material geometric discontinuities due to geometric constraints such as turning radius, tow angle deviation, and compaction requirements. How to effectively design the distribution of triangular gaps in the thickness direction to reduce the impact on composite parts has become a key issue. This study focuses on the through-thickness staggered distribution of triangular gaps during the path planning process for composite web panels of I-shaped spars. Through ultrasonic scanning analysis and microscopic observation of cross-sections, the effects of differently distributed triangular gaps on the thickness variation, defect distribution, and local waviness of web panels were thoroughly investigated. Afterwards, a finite element model containing gap defects was established to evaluate the effect of different staggered planning schemes of triangular gaps on the stress concentration of web panels by stress concentration factors. Results show that the trajectory planning scheme of layer-by-layer staggering distribution of triangular gaps has obvious advantages compared with the staggered approach with a specific number of layer intervals in terms of forming quality and stress concentration of composite panels.