• Jr., John W. Gillespie
• Cender, Thomas
• Tierney, John
• Füssel, Lukas
• Legenstein, Alexander
• Heider, Dirk

Abstract

Tailored universal Feedstock for Forming (TuFF) is a highly aligned discontinuous fiber composite material. A TuFF lamina can be stretched in the fiber direction at processing temperatures due to discontinuous fiber format. This deformation mode allows the production of complex shapes while maintaining high mechanical properties. Steering of continuous fiber materials are limited to a large minimum steering radius to minimize compression wrinkle defects. In-situ stretching of TuFF tape during Laser Assisted-Automated Fiber Placement (LA-AFP) has demonstrated tape steerability over an order of magnitude beyond the current state of the art. This paper develops a methodology to quantify the material strain and placement accuracy for stretch-steered TuFF tape to systematically optimize process variables. A methodology is developed for patterning TuFF tape (3 mm long IM7/PEI, 57% FVF) for reliably measuring the axial and transverse strain after tape placement using photogrammetry. The measurements also quantify the variability in strain components along the tape length. The results are shown to give good agreement with the theoretical prediction used to control the LA-AFP process. It is also shown that by optimally placing the center of rotation of the placement head at the nip-point (where tape is welded to the substrate) the placement accuracy and geometric conformity is two orders of magnitude beyond the current state of the art - 12.5 mm wide tape on a 50 mm radius of curvature - can be achieved without identifiable defects.

Topics

• impedance spectroscopy
• composite
• defect
• forming
• aligned