Examining the viability of carbon fiber reinforced three-dimensionally printed prosthetic feet created by composite filament fabrication.

BACKGROUND:: A low-cost, yet high-functioning, fabrication method for prosthetic components is needed to provide underserved amputee communities with quality mobility devices. Three-dimensional printing is a potential alternative, yet limitations in material characteristics have previously prevented the technology from emerging as a solution. OBJECTIVE:: To validate the application of a novel three-dimensional printing technique as a fabrication method for creating fiber composite patient end-use prosthetic feet. STUDY DESIGN:: Experimental designs were iterated upon throughout mechanical testing. METHODS:: A testing apparatus capable of loading prosthetic feet in dorsiflexion and plantarflexion was constructed. Load displacement data were gathered, and energy analyses were conducted. The three-dimensionally printed feet were compared to a Freedom Innovations Renegade® MX carbon fiber foot and a solid-ankle cushion heel foot. RESULTS:: The three-dimensionally printed feet achieved energy profiles that were similar, and in some cases preferable, to the energy profiles of the Renegade MX and solid-ankle cushion heel foot. The stiffness profiles of the three-dimensionally printed feet varied widely and depended greatly on the design of the feet, as well as the amount and location of the fiber reinforcement. CONCLUSION:: Composite filament fabrication three-dimensional printing has the potential to serve as a fabrication method for the production of energy returning prosthetic feet. CLINICAL RELEVANCE:: The results of this study indicate that carbon fiber reinforced three-dimensionally printed prosthetic feet have the potential to serve as a low-cost alternative to carbon fiber prosthetic feet and that three-dimensional printing has the capacity to function as a viable fabrication method for patient end-use prosthetic components.

Did a "lucky shot" sink the submarine H.L. Hunley?

The H.L. Hunley was the first submarine to be successful in combat, sinking the Union vessel Housatonic outside Charleston Harbor in 1864 during the Civil War. However, despite marking a milestone in military history, little is known about this vessel or why it sank. One popular theory is the "lucky shot" theory: the hypothesis that small arms fire from the crew of the Housatonic may have sufficiently damaged the submarine to sink it. However, ballistic experiments with cast iron samples, analysis of historical experiments firing Civil War-era projectiles at cast iron samples, and calculation of the tidal currents and sinking trajectory of the submarine indicate that this theory is not likely. Based on our results, the "lucky shot" theory does not explain the sinking of the world's first successful combat submarine.