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  • 1
    Publication Date: 2019-06-08
    Description: Approaches to optimize the adhesive joint strength between shape memory alloy ribbons and carbon fiber-reinforced epoxy composites were investigated for potential use as either an actuating structure or a dampening composite for structural applications. The interfacial bond strength between nickel-titanium (NiTi) and a polymer matrix composite (PMC) was measured by double lap shear testing as a function of NiTi surface treatment and adhesive material. The effect of NiTi surface treatment on damping was investigated using dynamic mechanical analysis. Lap shear data show that treating the surfaces of NiTi ribbons by light sandblasting and primer application increased the interfacial bond strength by 20 percent over the baseline composite structure. Lap shear data also reveal that out of three different film adhesives investigated, samples bonded with AF 191U and Hysol 9696U display the highest adhesive joint strengths. Optical microscopy reveals that most samples failed by either cohesive failure within the adhesive or by adhesive failure at either the adhesive/PMC or NiTi/adhesive interface. Adhering NiTi to the PMC did not appear to negatively impact damping performance; however, a more thorough examination into NiTi's role on vibration damping should be investigated.
    Keywords: Composite Materials
    Type: NASA/TM-2018-219906 , E-19523 , GRC-E-DAA-TN54786
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  • 2
    Publication Date: 2019-07-12
    Description: The effect of axial tow alignment within a laminate ply stack on the impact penetration threshold for a series of composite panels was evaluated; specifically, the effect of a lateral shift in alignment to induce fiber nesting. Panels were fabricated from braided T700S carbon fiber and TenCate Advanced Composites's TC275-1 epoxy resin prepreg. Axial tows in each ply were aligned, offset, or rotated to evaluate the influence of such parameters on impact penetration resistance. Panel-to-panel variation in thickness, resin content, and fiber volume ratio were measured. Ultimately, process-related deviations drove penetration limits on impact. Influence of axial tow alignment was difficult to discern outside of the processing-induced variations between panels.
    Keywords: Composite Materials
    Type: NASA/TM-2018-219881 , E-19504 , GRC-E-DAA-TN53689
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  • 3
    Publication Date: 2019-07-20
    Description: This project involves two separate processes for fabricating carbon fiber composite parts using Hexcels RTM6 resin system and Kanekas IR-6070 toughened resin system to impregnate carbon fiber tow and weave. These two resins were chosen to model microcracking in parts using RTM6 compared to parts using IR-6070. Plies of the composites were made by painting resin onto 8 harness satin weave or impregnating IM7 12k tow in a prepregging machine. Plies were consolidated using an out-of-autoclave oven or a heat press. Fabrication of the composite parts were conducted with the end goal of sending the composites to be tested and modeled for microcracking. The data will be used for computer modeling in the future.
    Keywords: Composite Materials
    Type: GRC-E-DAA-TN59122 , Annual Northeast Ohio Undergraduate Research Symposium (NOURS); Aug 02, 2018; Kent, OH; United States
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  • 4
    Publication Date: 2019-07-20
    Description: Carbon fiber composites are materials of great interest to the aerospace industry because of their light weight and high strength properties. Composite use in high load bearing applications such as roto-craft gearing requires manufacturing parts that are 1.5 inches thick and beyond. Very thick composite parts (laminates) produce thermal gradients and temperature spikes due to the heat released by resin polymerization and cross-linking during composite cure. It is believed that these thermal gradients will cause internal stresses to build-up inside these ultra-thick laminates during the cure-cycle, yielding parts with non-uniform mechanical properties throughout the thickness of the laminate. The goal of this study is to identify these thermal gradients and determine the magnitude of difference in mechanical properties generated by them.
    Keywords: Composite Materials
    Type: GRC-E-DAA-TN59121 , Northeast Ohio Undergraduate Research Symposium; Aug 02, 2018; Kent, OH; United States
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  • 5
    Publication Date: 2019-07-20
    Description: Computed Tomography (CT) is a useful tool for performing structural analysis on polymer based materials due to its high precision and accuracy. CT data was taken of two flared cones made from carbon fiber and fiberglass. One of the flared cones is pictured below. The variation in braid angle throughout the part was measured using Avizo 3D modelling software while the variation in thickness throughout the part was determined using MATLAB. Samples of pictures from the process of each of these analyses are shown below. The overall goal of this analysis was to collect structural data relevant to future testing of the parts.
    Keywords: Composite Materials
    Type: GRC-E-DAA-TN59080 , Research Experience for Undergraduates Symposium; Aug 02, 2018; Kent, OH; United States
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  • 6
    Publication Date: 2019-07-13
    Description: As a part of the NASA Composite Technology for Exploration project, eight different AS4 3D orthogonal woven composite panels were manufactured and were subjected to mechanical testing including uniaxial tension along the weaves' warp direction. Each set, with four different resin systems (KCR-IR6070, EP2400, RTM6, and RS-50), included weave architectures designed using 12K and 6K AS4 carbon fiber yarns. For the tension testing conducted at Room Temperature Ambient (RTA) conditions, the elastic modulus and strength of these eight panels (as-processed and thermally-cycled) were measured and compared while the potential evolution of micro-cracking before and after thermal cycling were monitored via optical microscopy and X-Ray Computed Tomography. The data set also included test results of the as-processed materials at Elevated Temperature Wet (ETW) conditions. In the second part of this study, efforts were made to compute elastic constants for AS4 6K/RTM6 and AS4 12K/RTM6 materials by implementing a finite element approach and the Multiscale Generalized Method of Cells (MSGMC) technique developed at NASA Glenn Research Center. Digimat-FE was used to model the weave architectures, assign properties, calculate yarn properties, create the finite element mesh, and compute the elastic properties by applying periodic boundary conditions to finite element models of each repeating unit cell. The required input data for MSGMC was generated using Matlab from Digimat exported weave information. Experimental and computational results were compared, and the differences and limitations in correlating to the test data were briefly discussed.
    Keywords: Composite Materials
    Type: GSFC-E-DAA-TN69072 , Composites and Advanced Materials Expo (CAMX 2019); Sep 23, 2019 - Sep 26, 2019; Anahem, CA; United States
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  • 7
    Publication Date: 2019-07-13
    Description: In 2015, the Composites for Exploration Upper Stage (CEUS) Project established an equivalency test program to reduce the scope of laminate coupon tests within the project. The material selected was IM7/8552-1, a variant of the IM7/8552 prepreg used to populate a National Center for Advanced Materials Performance (NCAMP) database. The CEUS successor program, Composites Technology for Exploration (CTE), kicked off in 2017 with the remaining CEUS prepreg planned for use. The IM7/8552-1 prepreg was recertified through an in-house defined set of pass/fail criteria then evaluated for equivalency to the NCAMP database. Over the course of recertification and equivalency panel fabrication, the time of freezer storage ranged from 19-23 months. Panels for recertification and equivalency tests were fiber placed at NASA Marshall Space Flight Center (MSFC) and NASA Langley Research Center (LARC).
    Keywords: Composite Materials
    Type: GRC-E-DAA-TN54537 , Advancement of Material and Process Engineering (SAMPE) Technical Conference and Exhibition; May 21, 2018 - May 24, 2018; Long Beach, CA; United States
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  • 8
    Publication Date: 2019-07-13
    Description: In 2015, the Composites for Exploration Upper Stage (CEUS) Project established an equivalency test program to reduce the scope of laminate coupon tests within the project. The material selected was IM7/8552-1, a variant of the IM7/8552 prepreg used to populate a National Center for Advanced Materials Performance (NCAMP) database. The CEUS successor program, Composites Technology for Exploration (CTE), kicked off in 2017 with the remaining CEUS prepreg planned for use. The IM7/8552-1 prepreg was recertified through an in-house defined set of pass/fail criteria then evaluated for equivalency to the NCAMP database. Over the course of recertification and equivalency panel fabrication, the time of freezer storage ranged from 19 - 22 months. Panels for recertification and equivalency tests were fiber placed at NASA Marshall Space Flight Center (MSFC) and NASA Langley Research Center (LARC).
    Keywords: Composite Materials
    Type: GRC-E-DAA-TN52622 , Society for the Advancement of Material and Process Engineering (SAMPE 2018) Technical Conference and Exhibition; May 21, 2018 - May 24, 2018; Long Beach, CA; United States
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  • 9
    Publication Date: 2019-11-01
    Description: In order to take full advantage of the weight savings and performance gains offered by the use of composite materials in large-scale space structures, adhesively bonded joints must be considered. While bonded joint manufacturing at laboratory scale can be straightforward, the same manufacturing processes are not trivial at full scale. Surface preparation becomes particularly challenging (a viable process must yield consistent results over a large application area and be repeatable for multiple application sites), as does the application of heat to cure the doublers and/or bond them to the primary structure (the nature and scale of assembled or partially assembled aerospace structures often necessitates an out-of-oven/out-of-autoclave approach). In this work, bonded joint manufacturing processes are adapted for a full-scale (approximately 30 feet in diameter at the aft end) composite payload adapter at the NASA Marshall Space Flight Center. By iterating across a range of variables, process parameters for adhesively bonded joints on a large-scale composite structure have been developed. Primary findings are presented with respect to overarching bonded joint manufacturing concepts so as to maximize the applicability of this work to similar material systems and structures.
    Keywords: Composite Materials
    Type: M19-7389 , The Composites and Advanced Materials Expo (CAMX) 2019; Sep 23, 2019 - Sep 26, 2019; Anaheim, CA; United States
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  • 10
    Publication Date: 2019-09-27
    Description: As a part of the NASA Composite Technology for Exploration project, eight different AS4 3D orthogonal woven composite panels were manufactured and were subjected to mechanical testing including uniaxial tension along the weaves' warp direction. Each set, with four different resin systems (KCR-IR6070, EP2400, RTM6, and RS-50), included weave architectures designed using 12K and 6K AS4 carbon fiber yarns. For the tension testing conducted at Room Temperature Ambient (RTA) conditions, the elastic modulus and strength of these eight panels (as-processed and thermally cycled) were measured and compared while the potential evolution of micro-cracking before and after thermal cycling were monitored via optical microscopy and X-Ray Computed Tomography. The data set also included test results of the as-processed materials at Elevated Temperature Wet (ETW) conditions. In the second part of this study, efforts were made to compute elastic constants for AS4 6K/RTM6 and AS4 12K/RTM6 materials by implementing a finite element approach and the Multiscale Generalized Method of Cells (MSGMC) technique developed at NASA Glenn Research Center. Digimat-FE was used to model the weave architectures, assign properties, calculate yarn properties, create the finite element mesh, and compute the elastic properties by applying periodic boundary conditions to finite element models of each repeating unit cell. The required input data for MSGMC was generated using Matlab from Digimat exported weave information. Experimental and computational results were compared, and the differences and limitations in correlating to the test data were briefly discussed.
    Keywords: Composite Materials
    Type: GSFC-E-DAA-TN73333 , Composites and Advanced Materials Expo (CAMX 2019); Sep 23, 2019 - Sep 26, 2019; Anahem, CA; United States
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