The effect of tow gaps on compression after impact strength of robotically laminated structures

When (robotic) Automated Fibre Placement (AFP) is used to manufacture aerospace components with complex three dimensional geometries, gaps between fibre tows can occur. This paper explores the interaction under compressive load of these tow gaps with impact damage. Two coupons with different distributions of tow-gaps were impacted. Results indicated that the area of delamination is smaller for an impact directly over a tow gap where the tow gap is situated close to the non-impact face. Subsequent Compression After Impact (CAI) testing demonstrated that both the formation of sublaminate buckles and subsequent growth of delaminations is inhibited by the presence of a tow gap near the nonimpact face. Non-destructive testing techniques and a computationally efficient infinite Strip model are used to analyse the damage resistance and damage tolerance of the coupons. A new validation of the Strip model is also presented.