查看更多>>摘要：SAMPE's conference events and activities always strive to bring our members, our technical community, and our global presence the most advanced technologies as they develop. There are many times that these developments in technology obviously start off with an idea of how to use a newly developed material in an application that has some promise downstream. Many such materials start off at Technology Readiness Levels (TRLs) in research labs and academia studies in efforts to further define the potential. Consequently, it is not unusual to see considerable initial research published in early TRL-1 through TRL-3 levels at conferences as the researcher pursues funding with future applications in mind. Manufacturing Readiness Levels (MRLs) are similar in which the material process goes through initial research effectively developing the "process engineering" limits of these new materials.
查看更多>>摘要：Stitched composites have been shown to exhibit damage tolerance and to reduce weight compared to traditional layered composites through unitization of the structure while eliminating fasteners. Stitching capabilities have been incorporated into the Integrated Structural Assembly of Advanced Composites (ISAAC) system at NASA Langley Research Center (LaRC) with the introduction of two stitching heads. Stitching path control was initially implemented as straight lines in space, as was done for previous stitching development in which LaRC was involved. However, more complex stitched structures, for applications such as a wind tunnel blades or around cutouts within a fuselage or wing skin, require that the stitching paths be implemented as three-dimensional (3D) stitching paths in space. Unfortunately, control programming output by an existing preprocessor program cannot stitch these curved paths. This is due to problems that arise in stitch formation and the introduction of side forces on the needles using the conventional programming approach, whereby the head is simultaneously controlled through translations and rotations. This lack of capability is most significant for the single-sided stitching head, where two needles are in the preform at the same time for the majority of the stitching process. A means to program 3D stitching paths in space was developed whereby the translation and rotation of each stitch were decoupled, thereby eliminating the problems associated with the current control programming approach. Using this newly developed stitching path definition and control programming, complex stitching paths have successfully been stitched at the ISAAC facility. The ability to stitch general 3D stitching paths using the developed approach opens up the design space and enables the use of stitching on more complex parts.
查看更多>>摘要：Fused Filament Fabrication is an Additive Manufacturing method where a thermoplastic filament is deposited layer-by-layer to create a three-dimensional part. The printed structures often demonstrate a high degree of mechanical anisotropy, leading to a drop in material strength when comparing structures along the disposition path (X and Y-Axis) to the build direction (Z-Axis). To reduce the mechanical isotropy, a z-pinning process was developed which deposited continuous pins in the build direction. This process demonstrated significant gains in inter-layer strength and toughness, especially for fiber-reinforced materials. However, the deposition of pins also created flaws in the structures that increased in severity and frequency as the pins grew in length and diameter. To mitigate these flaws, a penetrating nozzle has been proposed, in which a fine-tipped extrusion nozzle extends into the pin cavity and simultaneously extrudes z-pins as it retracts. By extending the extruder nozzle to a length that would permit it to penetrate the pin cavity heat loss through the nozzle, and therefor filament cooling, is going to become a major issue. To investigate the thermal properties of the penetrating nozzle, multiple finite element models were analyzed. The finite element analysis was conducted with a stock nozzle and 50.8 mm material nozzles extensions with two common extruder materials. The finite element analysis demonstrated that a 304 stainless-steel nozzle could be extended to a maximum length of 0.917 mm, which would allow the nozzle to penetrate 3 layers during the pinning process. Creating a brass penetrating nozzle would in turn, allow the penetrating nozzle to be extended to 2.205 mm, letting the nozzle to penetrate 8 layers into the pin cavity.
查看更多>>摘要：The National Aeronautics and Space Administration (NASA) initiated the Hi-Rate Composites Aircraft Manufacturing (HiCAM) project in 2021 with the goal of significantly increasing composite structures manufacturing rate in the commercial aircraft industry. The technologies currently under investigation include resin infusion and automated fiber placement (AFP) of novel thermoset materials and thermoplastic composites. Thermoplastic composites offer attractive solutions to rapid manufacturing due to their ability to be formed and consolidated quickly. NASA is particularly focused on assessing composite structure manufacturing utilizing an in-situ consolidation AFP of thermoplastics (ICAT) process employing a recently developed laser heating system. Two semi-crystalline Polyaryletherketone thermoplastic tape materials were characterized to ascertain the ICAT process parameters at AFP placement speeds approaching 423 mm/s. The required laser power settings were determined at Electroimpact, measuring material temperatures utilizing a forward looking infrared (FLIR) thermal imaging camera and thermocouples. The material temperature, tool temperature, and placement speed were varied for resulting consolidation quality assessment. The resulting temperature data were also utilized to calibrate thermal analysis models under development at NASA. The experimental temperature data confirmed analytical results. An overview of the HiCAM project as well as initial data from ICAT process characterizations are described.
查看更多>>摘要：Benzoxazine formulations are highly desirable with carbon-fiber reinforced thermoset manufacture for high temperature application in aerospace industry. Benzoxazines with additional unsaturated functional groups are the primary candidates for such application. A series of benzoxazines have been evaluated. Investigation has been carried out for the homo-polymerization of those benzoxazines, their copolymerization with other benzoxazines, epoxy resins, and bismaleimides, such as the Huntsman products MYO610 and Matrimid 5292A. Thermostabilities, thermo-mechanical properties, and possibility to improve the toughness of cured formulation are also studied, and with promising results.
查看更多>>摘要：Fiber Patch Placement is an advanced technology for automated fiber lay-up of geometrically complex composites and reinforcements. Patches are cut from a fiber reinforced tape and applied precisely on predetermined positions on a moid with a flexible patch gripper. The individual orientation of each patch along load paths opens new potential for automated fiber lay-up applications in aerospace. However, since the Fiber Patch Placement laminates uses discontinuous fibers, the question of material equivalency to classical laminates with continuous fibers arises. To investigate that question, a series of mechanical tests were conducted according to relevant aerospace testing standards. In screening characterization on unidirectional (UD) reinforced laminates, it can be shown that the stiffness of patched specimens is almost at level with continuously reinforced reference specimens. And although the static tensile strength shows a noticeable knockdown factor compared to a continuous fiber laminate, Fiber Patch Placement laminates feature design allowables based on open hole tension & compression, compressions after impact and bearing strength which are at level with the values of the conventional laminate. These results show the potential for Fiber Patch Placement to become a standard manufacturing technology for high performance aerospace composites while maintaining material equivalency.
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