FEATURE / TuFF TECHNOLOGY Figure 3. TGA results of the furnace cycle show that most of the polymer residue degrades during the heat ramp (left), and SEM picture shows no coating left on fibers (right). Figure 4. Schematic and photo of the short fiber alignment process. surface and deposited on the porous belt. Fibers are highly aligned at the deposition belt surface, fluid is extracted through the porous belt using a vacuum, and the fiber material is stabilized. The deposition sheet can be rotated to position fibers at a wide range of widths and angles with respect to the belt travel direction to create tows, tapes and sheets. A schematic and a photo of the alignment process developed is shown in Figure 4. The pyrolyzed fiber material is dispersed in the mixing tank. Visual observation of the fiber sheet did not see any fiber clumps or agglomerations. The material behaved similar to virgin carbon fiber during the TuFF process and the aligned sheet (Figure 5) showed good quality without any agglomerates or other visual defects. This indicates that the pyrolysis cleaning step was successful in separating the material at the filament level. The aligned sheet is then further processed. In this case, 8 " by 6 " sections are cut and stacked into a 24-layer unidirectional layup. An epoxy resin film (Axiom AX5201 FR-1) is placed on the surface and the layup is bagged and processed per the manufacturer datasheet in the autoclave to manufacture a flat coupon for Figure 5. Picture of the aligned TuFF sheets with the pyrolyzed fibers showing good alignment quality. property evaluation. The fiber/resin areal weight ratio is selected to obtain a ~50% fiber volume fraction part. The resulting C-scan is very uniform with low attenuation similar to virgin fiber TuFF material indicating good quality. A cross-section of the panel is taken to identify the microstructure. Porosity levels are low (below 2%) meeting aerospace quality. 14 | SAMPE JOURNAL | SEPTEMBER OCTOBER 2022 www. sampe.orghttp://www.sampe.org