AFP mandrel development for composite aircraft fuselage skin

Automatic fiber placement (AFP) has become a popular processing technique for composites in the aerospace industry, due to its ability to place prepregs or tapes precisely in the exact position when complex parts are being manufactured. This paper presents the design, analysis, and manufacture of an AFP mandrel for composite aircraft fuselage skin fabrication. According to the design requirements, an AFP mandrel was developed and a numerical study was performed through the finite element method. Linear static load analyses were performed considering the mandrel structure self-weight and a 2940 N load from the AFP machine head. Modal analysis was also performed to determine the mandrel's natural frequencies. These analyses confirmed that the proposed mandrel meets the design requirements. A prototype mandrel was then manufactured and used to fabricate a composite fuselage skin. Material load tests were conducted on the AFP fuselage skin curved laminates, equivalent flat AFP, and hand layup laminates. The flat AFP and hand layup laminates showed almost identical strength results in tension and compression. Compared to hand layup, the flat AFP laminate modulus was 5.2% higher in tension and 12.6% lower in compression. The AFP curved laminates had an ultimate compressive strength of 1.6% to 8.7% higher than flat laminates. The FEM simulation predicted strengths were 4% higher in tension and 11% higher in compression than the flat laminate test results.