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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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NASA NTRS2018

Detection of Damage During Quasi-Static Loading of a Single Stringer Panel Using Passive Thermography and Acoustic Emission

The purpose of this paper is to describe the methodology of measuring damage onset and growth in a composite structure during quasi-static loading using passive thermography and acoustic emission. The early detection and measurement of damage progression is important to understand failure modes. A single stringer panel was subjected to quasi-static loading to induce deformation which resulted in the formation of damage between the stiffener flange and skin. The loading was stopped when damage growth was detected. Passive thermography and acoustic emission were used to detect damage in real-time as a function of the applied load. Of particular interest are the small transient thermographic signals resulting from damage formation which can be challenging to detect, as compared to the persistent passive thermography indications of cyclic fatigue loading. We describe a custom developed thermal inspection system for detection of composite damage during quasi-static loading. The thermal results are compared to a two-dimensional multi-layered thermal simulation based on the quadrupole method. Acoustic emission is used to further characterize the damage by comparing the acoustic emission events with the thermal imagery. Results are compared to ultrasonic measurements to document the damage through-the-thickness.

Zalameda, Joseph N.↗
NASA NTRS2019

New York City Panel on Climate Change 2019 Report Chapter 8: Indicators and Monitoring

The Indicators and Monitoring chapter of the first New York City Panel on Climate Change Report began with the paradigm: What cannot be measured cannot be managed (Rosenzweig et al., 2010). This statement is as valid today as it was then.The NPCC1 (2010) Indicators and Monitoring chapter addressed the need for assembling a suite of indicators to monitor climate change and adaptation in order to inform climate change decision making. It outlined criteria for selection of indicators (policy relevance, analytic soundness, measurability), defined categories of indicators (physical climate change; risk exposure, vulnerability, and impacts; adaptation; new research), and provided examples of specific indicators. Table 8.1 is a summary table of indicator development contribution from the NPCC1 I&M chapter (Jacob et al., 2011). The chapter explored the institutional requirements for indicator data availability, continuity, archiving, and public accessibility.

Blake, Reginald↗
NASA NTRS2019

New York City Panel on Climate Change 2019 Report Chapter 1: Introduction

While urban areas like New York City and its surrounding metropolitan region are key drivers of climate change through emissions of greenhouse gases, cities are also significantly impacted by climate shifts, both chronic changes and extreme events. These are already affecting the New York metropolitan region, including the five boroughs of New York City through higher temperatures, more intense precipitation, and higher sea levels, and will increasingly do so in the coming decades. The City of New York has embarked on a flexible adaptation pathway (i.e., strategies that can evolve through time as climate risk assessment, evaluation of adaptation strategies, and monitoring continues) to respond to climate change challenges. This entails significant programs to develop resilience in communities and critical infrastructure to observed and projected changes in temperature, precipitation, and sea level. The first NPCC Report laid out the risk management framing for the city and region via flexible adaptation pathways. The second New York City Panel on Climate Change Report (NPCC2) developed the “climate projections of record” that are currently being used by the City of New York in its resilience programs . The NPCC3 2019 Report co-generates new tools and methods for the next generation of climate risk assessments and implementation of region-wide resilience. Co-generation is an interactive process by which stakeholders and scientists work together to produce climate change information that is targeted to decision-making needs. These tools and methods can be used to observe, project, and map climate extremes; monitor risks and responses; and engage with communities to develop effective programs. They are especially important at “transformation points” in the adaptation process when large changes in the structure and function of physical, ecological, and social systems of the city and region are undertaken.

Rosenzweig, Cynthia↗
NASA NTRS2019

New York City Panel on Climate Change 2019 Report Chapter 3: Sea Level Rise

The New York City Panel on Climate Change (NPCC, 2015) sea level rise projections provide the current scientific basis for New York City scientific decision making and planning, as reflected in, for example, the City's Climate Resiliency Design Guidelines. However, since the IPCC (2013) and NPCC (2015) reports, recent observations show mounting glacier and ice sheet losses leading to rising sea levels. Furthermore, new developments in modeling interactions between oceans, atmosphere, and ice sheets suggest the possibility of a significantly higher global mean sea level rise (GMSLR) by 2100 than previously anticipated, particularly under elevated greenhouse gas emission scenarios.

Gornitz, Vivien M.↗
NASA NTRS2016

Electrostatic Discharge Testing of Carbon Composite Solar Array Panels for NASA's Planned Europa Mission to Jupiter

The next planned NASA mission to visit Jupiter is known as the Europa Mission. The objective of this mission concept is to enter orbit around Jupiter in order to conduct multiple close flybys of the icy moon Europa. After careful trade studies, the mission designers have selected solar arrays as the baseline power system for the proposed mission rather than more traditional radioisotope thermoelectric generators. In order to examine the risk of using solar arrays, a series of tests were devised to determine the response of a typical solar array coupon to energetic electrons. Test coupons were fabricated and exposed to electrons ranging from 10 keV to 100 keV, at 1 nA/cm2, while being held at both room and cryogenic temperatures and exposed to end of mission radiation levels. While under electron bombardment, electrical discharges were observed and recorded with the majority of discharges occurring with electron energies of 25 keV. The largest effects on discharge size and rate were the decrease in temperature and the reduction of dielectric material on the sample surface. These tests indicate that solar array panels could be used by the planned Europa Mission in the Jovian environment, but that electrostatic discharges could be expected on the carbon composite solar arrays.

carbon composite↗
NASA NTRS2016

Electrostatic Discharge Testing of Carbon Composite Solar Array Panels for the Europa Mission to Jupiter

Carbon composite solar array panel coupons similar to those considered for use on the planned NASA Europa Mission were exposed to energetic electrons to observe the size and rate of electrostatic discharge production. The discharge size and rate were found to be primarily dependent on the quantity of dielectric binder pooled on the surface of the sample. Cooling the samples to cryogenic temperatures increased the size of discharges but an end of mission radiation dose had only minimal effects. Samples were composed of M55J carbon composite impregnated with an RS3 binder. Additional samples tested included a co-cured Kapton surface.

Green, Nelson W.↗
NASA NTRS2019

Macro-Scale Findings of the DebriSat Debris Field Obtained from X-Rays of the Catch Panels

The DebriSat project analyzes the debris from a hypervelocity impact test conducted on a 56 kg-simulated satellite target in 2014. Its purpose is to generate a comprehensive database of the size, mass, material, shape, and the radar and optical properties of fragments generated from orbital collisions of modern-built spacecraft. Three hundred ninety-one foam catch panels from the DebriSat test have been X-rayed to locate the particles within them for subsequent extraction and assessment. The data from the tens of thousands of extracted particles has heretofore been the focus of the debris assessment. The work presented here connects the X-ray sample location images to reconstruct the 3D distribution of the entire fragment cloud. Although some errors are inherent to the process, this 3D database is valuable for qualitative studies of size and energy distributions. Further, the 3D database can indicate the extent of bending or breaking of the fragments as they decelerated to full capture. By virtue of its full sphere perspective, the 3D database allows graphical insight to the physics of the collision and breakup. This 3D representation has been developed as a “point and click” graphical interface to retrieve the full data set on individual recovered and assessed fragments within the growing database. Overall, this macro-level screening technique has added enormous insight to the experiment in unexpected ways.

Allen, Anthony↗
NASA NTRS2017

Medical Countermeasures for Radiation Induced Health Effects: Reports of an Interagency Panel Session Held at the NASA Human Research Program Investigator's Workshop, January 26, 2017

An Interagency Panel Session organized by the NASA Human Research Program Space Radiation Program Element (SRPE) was held during the NASA Human Research Program (HRP) Investigator’s Workshop (IWS) in Galveston, Texas on January 26, 2017 to identify complementary research areas that will advance the testing and development of medical countermeasures (MCM) in support of radioprotection and radiation mitigation on the ground and in space. There were several areas of common interest identified among the various participating agencies. This report provides a summary of the topics discussed by each agency along with potential areas of intersection for mutual collaboration opportunities. Common goals included repurposing of pharmaceuticals, neutraceuticals for use as radioprotectors and/or mitigators, low-dose/chronic exposure paradigms, late effects post-radiation exposure, mixed-field exposures of gamma-neutron, performance decrements, and methods to determine individual exposure levels.

Carnell, Lisa S.↗
NASA NTRSDate not supplied

Effect of Composite Stiffened Panel Design on Skin-Stringer Separation in Postbuckling

To design aeronautical composite multi-stringer panels that can safely operate in a postbuckled state, it is important to identify the parameters that can influence the different modes in which skin-stringer separation might occur. A methodology is under development to study the interaction between the skin-stringer separation and the postbuckling deformation. A simple criterion that can predict the initiation of skin-stringer separation is developed using the building block approach and single-stringer specimens. The criterion identifies whetherthe initiation is mainly due to bending or twisting deformations, so that these two possible modes can be studied separately. This procedure has the potential to reduce the overall development cost and allows the investigation of the design parameters that might precipitate or delay the skin-stringer separation.

Lucas J. Kootte↗
NASA NTRS2020

Quasi-Static and Dynamic Analysis of Composite Panels: Challenges in Engineering-Level Commercial Software

In engineering applications, where analysis time and efficiency are essential, analytical models and commercially available finite element (FE) material models are the two mainstream methods used to analyze composite crush scenarios. A reliable numerical model addressing the crushing response of composite materials requires a nonlinear progressive damage analysis which includes appropriate failure mechanisms such as matrix cracking, fragmentation, delamination, and fiber breakage. One might be able to address all these interacting failure responses through implementation/validation of a user defined material model or by utilization of a commercially available model, the latter being the most efficient engineering approach. In this paper, the quasi-static and dynamic crushing response of composite specimens, consisting of a C-channel and a corrugated geometry manufactured with carbon fiber/epoxy matrix fabric, are modeled using the progressive composite damage model within ABAQUS. The novel part of this work, which has not been previously addressed in the literature, is the utilization of a detailed parametric study to optimize composite damage model parameters for a given quasi-static crush simulation in ABAQUS. C-channel experiments were used to calibrate the model and then refine/optimize a set of material parameters that best fit the experimental results. These identical parameters were then used to simulate the crush response of the corrugated channel specimens, thereby making it a pure prediction and not a double recalibration. Next, the dynamic response of both panels were predicted, further confirming the predictive capability of the developed numerical model. The effect of parameter variation on the crush response is fully documented for future use in engineering applications utilizing this specific ABAQUS damage model.

Paria Naghipour↗
NASA NTRS2021

Modeling Laminar-to-Turbulent Transition in the Panel Test Facility Arcjet

A computational fluid dynamics (CFD) laminar-to-turbulence transition model was developed for the NASA Ames Research Center’s 20 MW Panel Test Facility (PTF). Surface pressure, heat flux to a water-cooled plate, and surface temperature on a tile plate coated with reaction-cured glass were measured across several conditions in the facility and compared with laminar and fully-turbulent CFD simulations. The potential for bypass transition in the PTF nozzle was assessed via application of the Langtry-Menter four-equation transitional shear-stress transport (SST) model. Results from the transition model were inconsistent with measurements. Flow interaction with a boundary conditioning plate feature inside the nozzle was also investigated as a potential source of laminar-to-turbulent transition using two turbulence models with specified transition locations. The Baldwin-Lomax turbulence model was configured to simulate a transition at the upstream edge of the boundary conditioning plate and produced results consistent with the surface pressure measurements but not the cold-wall heat flux. Finally, the SST turbulence model was calibrated to transition at the upstream edge of the boundary conditioning plate and produced results consistent with both the surface pressure and cold-wall heat flux measurements. The SST-based model demonstrated reasonable agreement with surface temperature measurements on the reaction-cured glass tile, albeit with some discrepancies.

Computational Fluid Dynamics↗
NASA NTRSDate not supplied

Effect of Composite Stiffened Panel Design on Skin-Stringer Separation in Postbuckling

To design aeronautical composite multi-stringer panels that can safely operate in a postbuckled state, it is important to identify the parameters that can influence the different modes in which skin-stringer separation might occur. A methodology is under development to study the interaction between the skin-stringer separation and the postbuckling deformation using the building block approach and single-stringer specimens. In particular, the methodology can identify whether the skin-stringer separation occurs due to bending or twisting, so that these two possible modes can be studied separately. For bending, a simple criterion that can predict the location of initiation is presented. This procedure has the potential to reduce the overall development cost and allows the investigation of the design parameters that influence the skin-stringer separation.

Lucas J. Koote↗
NASA NTRS2021

Testing of Composite Stiffened Panels with Mid-Length Lateral Notches

Two hat-stiffened carbon-epoxy panels were loaded to failure to determine their failure load and mode under the Advanced Composites Project (ACP) Rapid Design Tools activity. Each specimen contained a lateral notch located at the mid-length location which severed the central stiffener. A description of the specimens, instrumentation, test fixtures and procedures is presented, followed by the presentation of the experimental results.

Dawn C Jegley↗
NASA NTRSDate not supplied

Can Reflector Panel Technologies Tame Terrible Lunar Lighting Environments?

This project investigated the usage of reflector panel technology to redirect collimated sunlight to make it more usable for the lunar surface EVAs. When astronauts travel to the Moon’s South Pole, they will find a terrible exterior work environment to carry out EVA tasks. The location creates a situation where collimated light from the Sun illuminates the surface at low inclination angles, and the problem that the crew will often shadow their own workspace. Artificial lighting countermeasures will be marginally beneficial because the Sun’s illumination level is orders of magnitude higher than intensities possible from battery driven lighting systems. These conditions will persist because the latitude of the polar worksite, and the Moon’s orbit around the Earth. Photographers, on Earth, battle similar problems in their studios and outdoor worksites. To solve this problem, they use large portable reflectors to redirect light towards the object they are imaging.

Toni Anne Clark↗
NASA NTRSDate not supplied

Exploring Methods to Collect and Analyze Data on Human Contributions to Aviation Safety: A Panel Discussion

Focusing on undesired operator behaviors is pervasive in system design and safety management cultures in aviation. This focus limits the data that are collected, the questions that are asked during data analysis, and therefore our understanding of what operators do in everyday work. Human performance represents a significant source of aviation safety data that includes both desired and undesired actions. When safety is characterized only in terms of errors and failures, the vast majority of human impacts on system safety and performance are ignored. The outcomes of safety data analyses dictate what is learned from those data, which in turn informs safety policies and safety-related decision making. When learning opportunities are systematically restricted by focusing only on rare failure events, not only do we learn less (and less often), but we can draw misleading conclusions by relying on a non-representative sample of human performance data. Changes in how we define and think about safety can highlight new opportunities for collection and analysis of safety-relevant data. Developing an integrated safety picture to better inform safety-related decision making and policies depends upon identifying, collecting, and interpreting safety producing behaviors in addition to safety reducing behaviors. The panel will discuss opportunities and challenges in collecting and analyzing the largely unexploited data on desired, safety-producing operator behaviors.

aviation safety↗
NASA NTRS2021

Numerical Validation of Composite Panel Impact Tests

Researchers have met the challenge of modeling impact events involving composite targets for a variety of applications in a variety of ways. In this paper, the theory and implementation details of an orthotropic visco-elastic-visco-plastic material model with strain rate dependence are discussed. The model is driven by experimental data from quasi-static as well as high strain rate tests, and the data is used in defining the deformation, damage and failure sub-models. Validation data is generated by shooting a hollow 50 g Al-2024 projectile at different velocities against a flat panel target made of unidirectional composite material in a 16-ply [(0/90/45/-45)_(2)]_(S) layup. Explicit dynamic finite element analyses of four high speed tests involving one contained (projectile rebounded) and three uncontained (projectile penetrated) impact tests show that the developed material model and modeling techniques yield reasonable and acceptable predictions.

Orthotropic Composite↗

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