Engineering topics

Grenoble, Ray

Publications and source records attributed to Grenoble, Ray.

6 records

NASA NTRS2019

Automated Fiber Placement Manufactured Composites for Science Applications

Science instruments with large collecting areas that maintain dimensional stability, such as James Webb Space Telescope and Wide Field Space Telescope, help achieve next generation science advancements. Composite materials often used for science applications include high modulus fibers in cyanate ester matrices to result in dimensionally stable structures with low contamination. Hand lay-up fabrication is the most common approach for science instrument structures. Automated Fiber Placement (AFP) using intermediate modulus fibers is commonplace in aircraft production reducing manufacturing time and increasing quality and consistency. AFP manufacturing for future large science instruments can similarly reduce costs and increase reliability. However, high modulus fibers are more prone to damage than intermediate modulus fibers. This study investigates the manufacturing viability of M55J/RS3C (Tencate) slit tape material using AFP processing. Tencate provides slit tape materials. NASA Langley Research Center (LaRC) manufactured hand layup and AFP lay-up laminates under room temperature for initial trials, Marshall Space Flight Center (MSFC) manufactured AFP laminates under room temperature and elevated temperature conditions to evaluate processing affects. Goddard Space Flight Center (GSFC) tests and evaluates tension and Coefficient of Thermal Expansion (CTE) properties by hand lay-up and AFP slit tape automated manufacturing for large science applications. These results show processing material warm reduces process induced fiber fracture; leading to stiffness and CTE properties consistent with hand lay-up, while observing a slight degradation in tensile strength.

Segal, Kenneth N.↗

NASA NTRS2019

Automated Fiber Placement of Composite Wind Tunnel Blades: Process Planning and Manufacturing

The ability to accurately manufacture large complex shapes in a consistent and repeatable manner has led to Automated Fiber Placement (AFP) being the predominant mode of manufacturing for large composite aerospace structures today. Currently, AFP is being considered for medium- and small-scale parts. Composite wind tunnel blades have traditionally been fabricated by hand layup for pre-impregnated or dry fabrics with resin infusion. Though well proven, the traditional fabrication method is laborious and tedious, and hence expensive. The project described in this paper used the Integral Structural Assembly of Advanced Composites (ISAAC) facility at the NASA Langley Research Center to build a manufacturing demonstration unit (MDU) with a shape representative of a wind tunnel blade. This MDU is used to discuss tooling, process planning, and fabrication. Additionally, details of the generic manufacturing workflow are presented.

Harik, Ramy↗

NASA NTRS2019

Assessment of Automated Fiber Placement for the Fabrication of Composite Wind Tunnel Blades

Composite wind tunnel blades are frequently fabricated by hand layup of prepreg fabrics. Though well proven, this fabrication method is laborious and expensive. The study described in this paper used the Integrated Structural Assembly of Advanced Composites (ISAAC) facility at the NASA Langley Research Center to explore whether automated fiber placement (AFP) could reduce manufacturing time and cost for production of wind tunnel blades. Two blades, taken from two NASA wind tunnels, were investigated as representative geometries. Computer-aided design models of the blade surfaces were created, and AFP process planning and programming were employed to study the manufacturability of the shapes. A placement/cure tool was manufactured for the chosen blade surface from thermoplastic material using an additive manufacturing process. The present study revealed that the AFP head geometry, primarily the heater configuration of the ISAAC system, is the primary constraint that limits the ability to manufacture the selected wind tunnel fan blades using AFP.

Grenoble, Ray↗

NASA NTRS2018

Fabrication of a Composite Tow-Steered Structure for Air-Launch Vehicle Applications

Generation Orbit (GO) is developing the GO Launcher-1 (GO-1), a single stage liquid rocket that is launched from a Gulfstream III carrier aircraft platform. The vehicle is designed as the next generation platform for hypersonic flight testing and suborbital microgravity research. To reduce mass and increase payload, GO partnered with NASA Langley Research Center to design, analyze, optimize, and fabricate a tow-steered manufacturing development unit of a cylindrical section of a liquid oxygen tank. The fabrication process of using the ISAAC (Integrated Structural Assembly of Advanced Composites) system is described. The structural design challenges and the concept design solutions are also presented to provide the context for the fabrication process. The in-situ nondestructive evaluation supporting the effort is also described.

Grenoble, Ray↗

NASA NTRS2015

Test and Analysis Correlation for a Y-Joint Specimen for a Composite Cryotank

The Composite Cryotank Technology Demonstration (CCTD) project under NASA's Game Changing Development Program (GCDP) developed space technologies using advanced composite materials. Under CCTD, NASA funded the Boeing Company to design and test a number of element-level joint specimens as a precursor to a 2.4-m diameter composite cryotank. Preliminary analyses indicated that the y-joint in the cryotank had low margins of safety; hence the y-joint was considered to be a critical design region. The y-joint design includes a softening strip wedge to reduce localized shear stresses at the skirt/dome interface. In this paper, NASA-developed analytical models will be correlated with the experimental results of a series of positive-peel y-joint specimens from Boeing tests. Initial analytical models over-predicted the experimental strain gage readings in the far-field region by approximately 10%. The over-prediction was attributed to uncertainty in the elastic properties of the laminate and a mismatch between the thermal expansion of the strain gages and the laminate. The elastic properties of the analytical model were adjusted to account for the strain gage differences. The experimental strain gages also indicated a large non-linear effect in the softening strip region that was not predicted by the analytical model. This non-linear effect was attributed to delamination initiating in the softening strip region at below 20% of the failure load for the specimen. Because the specimen was contained in a thermally insulated box during cryogenic testing to failure, delamination initiation and progression was not visualized during the test. Several possible failure initiation locations were investigated, and a most likely failure scenario was determined that correlated well with the experimental data. The most likely failure scenario corresponded to damage initiating in the softening strip and delamination extending to the grips at final failure.

Mason, Brian H.↗

NASA NTRS2012

Sizing and Lifecycle Cost Analysis of an Ares V Composite Interstage

The Interstage Element of the Ares V launch vehicle was sized using a commercially available structural sizing software tool. Two different concepts were considered, a metallic design and a composite design. Both concepts were sized using similar levels of analysis fidelity and included the influence of design details on each concept. Additionally, the impact of the different manufacturing techniques and failure mechanisms for composite and metallic construction were considered. Significant details were included in analysis models of each concept, including penetrations for human access, joint connections, as well as secondary loading effects. The designs and results of the analysis were used to determine lifecycle cost estimates for the two Interstage designs. Lifecycle cost estimates were based on industry provided cost data for similar launch vehicle components. The results indicated that significant mass as well as cost savings are attainable for the chosen composite concept as compared with a metallic option.

Mann, Troy↗