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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Improved Method for Increased-Rate Stitched Composites Manufacturing

Stitched composites, as defined herein, are created by stitching a dry preform, infusing the preform with resin and curing the resin. Stitched composites have been shown to have benefits over unstitched composites for stiffened structures, including improved damage tolerance, reduced weight, and fewer fasteners. However, conventional stitched composite structure production is very time and manual-labor intensive, and therefore is not conducive for high-rate production of commercial aircraft main structure. The National Aeronautics and Space Administration (NASA) Hi-Rate Composite Aircraft Manufacturing (HiCAM) Project has the objective to increase the manufacturing rate for future composite aircraft. Stitched resin infused (SRI) composites are one of the technologies being considered under the HiCAM Project, but to be viable, production rates must be increased (i.e., production time reduced). Previous work has shown that it is possible to reduce the time required to stitch a dry composite preform, such as a skin with integral stiffeners, but the stitching process is a small portion of the total time required to produce a stitched preform. To significantly reduce overall stitched preform production time, a study was undertaken to examine a new stitching method that would yield time reduction in the pre- and post-stitching activities that include all portions of a stitched preform production with the exception of the actual stitching process. The new method resulted in significant reduction in production time, from 27% to 40%, while at the same time reducing the costs associated with fabricating a stitched preform by eliminating stations within the production line, simplifying tooling, reducing labor, and reducing consumables.

Stitching↗
NASA NTRSDate not supplied

Improved Method for Increased-Rate Stitched Composites Manufacturing

Stitched composites, as defined herein, are created by stitching a dry preform, infusing the preform with resin and curing the resin. Stitched composites have been shown to have benefits over unstitched composites for stiffened structures, including improved damage tolerance, reduced weight, and fewer fasteners. However, conventional stitched composite structure production is very time and manual-labor intensive, and therefore is not conducive for high-rate production of commercial aircraft main structure. The National Aeronautics and Space Administration (NASA) Hi-Rate Composite Aircraft Manufacturing (HiCAM) Project has the objective to increase the manufacturing rate for future composite aircraft. Stitched resin infused (SRI) composites are one of the technologies being considered under the HiCAM Project, but to be viable, production rates must be increased (i.e., production time reduced). Previous work has shown that it is possible to reduce the time required to stitch a dry composite preform, such as a skin with integral stiffeners, but the stitching process is a small portion of the total time required to produce a stitched preform. To significantly reduce overall stitched preform production time, a study was undertaken to examine a new stitching method that would yield time reduction in the pre- and post-stitching activities that include all portions of a stitched preform production with the exception of the actual stitching process. The new method resulted in significant reduction in production time, from 27% to 40%, while at the same time reducing the costs associated with fabricating a stitched preform by eliminating stations within the production line, simplifying tooling, reducing labor, and reducing consumables.

Stitching↗
NASA NTRS1993

Automated fiber placement composite manufacturing: The mission at MSFC's Productivity Enhancement Complex

Automated fiber placement is a manufacturing process used for producing complex composite structures. It is a notable leap to the state-of-the-art in technology for automated composite manufacturing. The fiber placement capability was established at the Marshall Space Flight Center's (MSFC) Productivity Enhancement Complex in 1992 in collaboration with Thiokol Corporation to provide materials and processes research and development, and to fabricate components for many of the Center's Programs. The Fiber Placement System (FPX) was developed as a distinct solution to problems inherent to other automated composite manufacturing systems. This equipment provides unique capabilities to build composite parts in complex 3-D shapes with concave and other asymmetrical configurations. Components with complex geometries and localized reinforcements usually require labor intensive efforts resulting in expensive, less reproducible components; the fiber placement system has the features necessary to overcome these conditions. The mechanical systems of the equipment have the motion characteristics of a filament winder and the fiber lay-up attributes of a tape laying machine, with the additional capabilities of differential tow payout speeds, compaction and cut-restart to selectively place the correct number of fibers where the design dictates. This capability will produce a repeatable process resulting in lower cost and improved quality and reliability.

Vickers, John H.↗
NASA NTRS2019

Automated Fiber Placement Manufactured Composites for Science Applications

What automated composite laminate manufacturing isWhy automation is of interest in science applicationsHow composite automation is being considered for science instrument applicationsAnd, about test data showing high stiffness materials processed with automation results in reduced material strength while stiffness and coefficient of thermal expansion are mostly unaffected.

Segal, Ken↗
NASA NTRS2012

Large Scale Composite Manufacturing for Heavy Lift Launch Vehicles

Risk reduction for the large scale composite manufacturing is an important goal to produce light weight components for heavy lift launch vehicles. NASA and an industry team successfully employed a building block approach using low-cost Automated Tape Layup (ATL) of autoclave and Out-of-Autoclave (OoA) prepregs. Several large, curved sandwich panels were fabricated at HITCO Carbon Composites. The aluminum honeycomb core sandwich panels are segments of a 1/16th arc from a 10 meter cylindrical barrel. Lessons learned highlight the manufacturing challenges required to produce light weight composite structures such as fairings for heavy lift launch vehicles.

Stavana, Jacob↗
NASA NTRS2004

Modeling the VARTM Composite Manufacturing Process

A comprehensive simulation model of the Vacuum Assisted Resin Transfer Modeling (VARTM) composite manufacturing process has been developed. For isothermal resin infiltration, the model incorporates submodels which describe cure of the resin and changes in resin viscosity due to cure, resin flow through the reinforcement preform and distribution medium and compaction of the preform during the infiltration. The accuracy of the model was validated by measuring the flow patterns during resin infiltration of flat preforms. The modeling software was used to evaluate the effects of the distribution medium on resin infiltration of a flat preform. Different distribution medium configurations were examined using the model and the results were compared with data collected during resin infiltration of a carbon fabric preform. The results of the simulations show that the approach used to model the distribution medium can significantly effect the predicted resin infiltration times. Resin infiltration into the preform can be accurately predicted only when the distribution medium is modeled correctly.

Song, Xiao-Lan↗
NASA NTRS2015

The Microwave Assisted Composite Manufacturing and Repair (MACMAR) Project

The inherent microwave property of carbon nanotubes (CNTs) generates the thermal energy required to induce reversible polymerization of the matrix in these self-healing composites. Microwaves will be used to demonstrate advanced composite manufacturing and repair using self-healing composites.

Falker, John↗
NASA NTRS2016

Ultrasonic NDE Simulation for Composite Manufacturing Defects

The increased use of composites in aerospace components is expected to continue into the future. The large scale use of composites in aerospace necessitates the development of composite-appropriate nondestructive evaluation (NDE) methods to quantitatively characterize defects in as-manufactured parts and damage incurred during or post manufacturing. Ultrasonic techniques are one of the most common approaches for defect/damage detection in composite materials. One key technical challenge area included in NASA's Advanced Composite's Project is to develop optimized rapid inspection methods for composite materials. Common manufacturing defects in carbon fiber reinforced polymer (CFRP) composites include fiber waviness (in-plane and out-of-plane), porosity, and disbonds; among others. This paper is an overview of ongoing work to develop ultrasonic wavefield based methods for characterizing manufacturing waviness defects. The paper describes the development and implementation of a custom ultrasound simulation tool that is used to model ultrasonic wave interaction with in-plane fiber waviness (also known as marcelling). Wavefield data processing methods are applied to the simulation data to explore possible routes for quantitative defect characterization.

Leckey, Cara A. C.↗
NASA NTRS1994

A neural network controller for automated composite manufacturing

At McDonnell Douglas Aerospace (MDA), an artificial neural network based control system has been developed and implemented to control laser heating for the fiber placement composite manufacturing process. This neurocontroller learns an approximate inverse model of the process on-line to provide performance that improves with experience and exceeds that of conventional feedback control techniques. When untrained, the control system behaves as a proportional plus integral (PI) controller. However after learning from experience, the neural network feedforward control module provides control signals that greatly improve temperature tracking performance. Faster convergence to new temperature set points and reduced temperature deviation due to changing feed rate have been demonstrated on the machine. A Cerebellar Model Articulation Controller (CMAC) network is used for inverse modeling because of its rapid learning performance. This control system is implemented in an IBM compatible 386 PC with an A/D board interface to the machine.

Lichtenwalner, Peter F.↗
NASA NTRS1992

Process and control systems for composites manufacturing

A precise control of composite material processing would not only improve part quality, but it would also directly reduce the overall manufacturing cost. The development and incorporation of sensors will help to generate real-time information for material processing relationships and equipment characteristics. In the present work, the thermocouple, pressure transducer, and dielectrometer technologies were investigated. The monitoring sensors were integrated with the computerized control system in three non-autoclave fabrication techniques: hot-press, self contained tool (self heating and pressurizing), and pressure vessel). The sensors were implemented in the parts and tools.

Tsiang, T. H.↗
NASA NTRS2015

Detection of CFRP Composite Manufacturing Defects Using a Guided Wave Approach

NASA Langley Research Center is investigating a guided-wave based defect detection technique for as-fabricated carbon fiber reinforced polymer (CFRP) composites. This technique will be extended to perform in-process cure monitoring, defect detection and size determination, and ultimately a closed-loop process control to maximize composite part quality and consistency. The overall objective of this work is to determine the capability and limitations of the proposed defect detection technique, as well as the number and types of sensors needed to identify the size, type, and location of the predominant types of manufacturing defects associated with laminate layup and cure. This includes, porosity, gaps, overlaps, through-the-thickness fiber waviness, and in-plane fiber waviness. The present study focuses on detection of the porosity formed from variations in the matrix curing process, and on local overlaps intentionally introduced during layup of the prepreg. By terminating the cycle prematurely, three 24-ply unidirectional composite panels were manufactured such that each subsequent panel had a higher final degree of cure, and lower level of porosity. It was demonstrated that the group velocity, normal to the fiber direction, of a guided wave mode increased by 5.52 percent from the first panel to the second panel and 1.26 percent from the second panel to the third panel. Therefore, group velocity was utilized as a metric for degree of cure and porosity measurements. A fully non-contact guided wave hybrid system composed of an air-coupled transducer and a laser Doppler vibrometer (LDV) was used for the detection and size determination of an overlap By transforming the plate response from the time-space domain to the frequency-wavenumber domain, the total wavefield was then separated into the incident and backscatter waves. The overlap region was accurately imaged by using a zero-lag cross-correlation (ZLCC) imaging condition, implying the incident and backscattered waves are in phase over the overlap boundaries.

Hudson, Tyler B.↗
NASA NTRS2007

Double Vacuum Bag Process for Resin Matrix Composite Manufacturing

A double vacuum bag molding assembly with improved void management and laminate net shape control which provides a double vacuum enviromnent for use in fabricating composites from prepregs containing air and/or volatiles such as reactive resin matrix composites or composites from solvent containing prepregs with non-reactive resins matrices. By using two vacuum environments during the curing process, a vacuum can be drawn during a B-stage of a two-step cycle without placing the composite under significant relative pressure. During the final cure stage, a significant pressure can be applied by releasing the vacuum in one of the two environments. Inner and outer bags are useful for creating the two vacuum environments with a perforated tool intermediate the two. The composite is placed intermediate a tool plate and a caul plate in the first environment with the inner bag and tool plate defining the first environment. The second environment is characterized by the outer bag which is placed over the inner bag and the tool plate.

Hou, Tan-Hung↗
NASA NTRS2012

Custom Machines Advance Composite Manufacturing

Here is a brief list of materials that NASA will not be using to construct spacecraft: wood, adobe, fiberglass, bone. While it might be obvious why these materials would not make for safe space travel, they do share a common characteristic with materials that may well be the future foundation of spacecraft design: They all are composites. Formed of two or more unlike materials - such as cellulose and lignin in the case of wood, or glass fibers and plastic resin in the case of fiberglass-composites provide enhanced mechanical and physical properties through the combination of their constituent materials. For this reason, composites are used in everything from buildings, bathtubs, and countertops to boats, racecars, and sports equipment. NASA continually works to develop new materials to enable future space missions - lighter, less expensive materials that can still withstand the extreme demands of space travel. Composites such as carbon fiber materials offer promising solutions in this regard, providing strength and stiffness comparable to metals like aluminum but with less weight, allowing for benefits like better fuel efficiency and simpler propulsion system design. Composites can also be made fatigue tolerant and thermally stable - useful in space where temperatures can swing hundreds of degrees. NASA has recently explored the use of composites for aerospace applications through projects like the Composite Crew Module (CCM), a composite-constructed version of the aluminum-lithium Multipurpose Crew Capsule. The CCM was designed to give NASA engineers a chance to gain valuable experience developing and testing composite aerospace structures.

Source record↗
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.↗