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NASA NTRS1986

Hidden impact damage in thick composites

NASA is developing light-weight graphite/epoxy filament-wound cases (FWC) for the solid rocket motors of the Space Shuttle. The 12-foot-diameter FWC's are about 1.4 inches or more thick. Tests were conducted to determine the tension strength of an FWC after low-velocity impact. Impactors of various kinetic energies, masses, and shapes were used. The conditions that give minimum visual evidence of damage were emphasized. The capability to characterize impact damage with radiography and ultrasonic attenuation was also evaluated. After impact, the specimens were loaded uniaxially in tension to determine residual strengths.

Poe, C. C., Jr.↗

NASA NTRS1994

Acoustic method of damage sensing in composite materials

The use of acoustic emission and acousto-ultrasonics to characterize impact damage in composite structures is being performed on both graphite epoxy and kevlar bottles. Further development of the acoustic emission methodology to include neural net analysis and/or other multivariate techniques will enhance the capability of the technique to identify failure mechanisms during fracture. The acousto-ultrasonics technique will be investigated to determine its ability to predict regions prone to failure prior to the burst tests. The combination of the two methods will allow for simple nondestructive tests to be capable of predicting the performance of a composite structure prior to being placed in service and during service.

Workman, Gary L.↗

NASA NTRS2010

Hypervelocity Impact Testing of IM7/977-3 with Micro-Sized Particles

Ground-based hypervelocity imapct testing was conducted on IM7/977-3 quasi-isotropic flat panels at normal incidence using micron-sized particles (i.e. less than or equal to 100 microns) of soda lime glass and olivine. Testing was performed at room temperature (RT) and 175 C with results from the 175 C test compared to those obtained at RT. Between 10 and 30 particles with velocities ranging from 5 to 13 km/s impacted each panel surface for each test temperature. Panels were ultrasonically scanned prior to and after impact testing to assess internal damage. Post-impact analysis included microscopic examination of the surface, determination of particle speed and location, and photomicroscopy for microcrack assessment. Internal damage was observed by ultrasonic inspection on panels impacted at 175 C, whereas damage for the RT impacted panels was confined to surface divets/craters as determined by microscopic analysis.

Smith, J. G.↗

NASA NTRS2004

Novel Horn Designs for Power Ultrasonics

Ultrasonic horns are used in a variety of industrial and medical applications. At JPL a rock-sampling tool based on an ultrasonic horn was developed to drill, abrade and core rock samples including hard basalts. This device is an impact device, which uses ultrasonic vibratlons that occur at the horn tip to produce a sonic resonance with the aid of a loosely connected mass. Although standard horns are found in many current industrial designs they suffer from a few key limitations when used for USDC applications. Manufacturing a horn requires turning down stock material (e.g. Titanium) from the larger outer diameter to the horn tip diameter, and this process is both time consuming and wasteful. In this paper, we present novel horn designs that are specifically designed for impact applications as the USDC. One such design addressed the excasive length that is involved with the use of the horn limiting its applications when system dimensions are constrained. For this purpose, a folded horn design was conceived that reduces the overall length of the resonator (physical length) but maintains or increases the acoustic length. Initial experiments with horns having such P design indicate that the tip displacement can be further adjusted by phasing the bending displacements and the extensional displacements. Another conceived horn design is the 'dog bone' horn that uses an end mass on the horn tip io increase the impact efficiency of the horn. In this paper, the experimental results for these novel born designs are presented and compared to the results predicted by theory.

acutators↗

NASA NTRS2010

TPSAS-NF1676L-11096-DND

A PRSEUS test article was subjected to controlled impact on the skin face followed by static and cyclic axial compressions. Phased array ultrasonic inspection was conducted before impact, and after each of the test conditions. A linear phased array probe with a manual X-Y scanner was used for interrogation. Ultrasound showed a delamination between the skin and stringer flange adjacent to the impact. As designed, the stitching in the flange arrested the lateral flaw formation. Subsequent ultrasonic data showed no delamination growth due to continued loading

Phased array↗

NASA NTRS2005

Ultrasonic Micro-Blades for the Rapid Extraction of Impact Tracks from Aerogel

The science return of NASA's Stardust Mission with its valuable cargo of cometary debris hinges on the ability to efficiently extract particles from silica aerogel collectors. The current method for extracting cosmic dust impact tracks is a mature procedure involving sequential perforation of the aerogel with glass needles on computer controlled micromanipulators. This method is highly successful at removing well-defined aerogel fragments of reasonable optical clarity while causing minimal damage to the surrounding aerogel collector tile. Such a system will be adopted by the JSC Astromaterials Curation Facility in anticipation of Stardust s arrival in early 2006. In addition to Stardust, aerogel is a possible collector for future sample return missions and is used for capture of hypervelocity ejecta in high power laser experiments of interest to LLNL. Researchers will be eager to obtain Stardust samples for study as quickly as possible, and rapid extraction tools requiring little construction, training, or investment would be an attractive asset. To this end, we have experimented with micro-blades for the Stardust impact track extraction process. Our ultimate goal is a rapid extraction system in a clean electron beam environment, such as an SEM or dual-beam FIB, for in situ sample preparation, mounting and analysis.

Ishii, H. A.↗

NASA NTRS1992

Rapid detection and quantification of impact damage in composite structures

It is shown that a multidisciplinary nondestructive evaluation approach for impact damage detection in composite structures can be used to produce a more efficient inspection. The multidisciplinary NDE approach relies on fast large area thermographic inspections along with detailed ultrasonic volumetric imaging. The thermal inspection technique rapidly identifies the impact damage. The ultrasonic volumetric imaging quantifies the impact generated delaminations through the volume of the structure.

Smith, Barry T.↗

NASA NTRS2006

Ultrasonic/Sonic Driller/Corer (USDC) as a Subsurface Sampler and Sensors Platform for Planetary Exploration Applications

The search for existing or past life in the Universe is one of the most important objectives of NASA's mission. For this purpose, effective instruments that can sample and conduct in-situ astrobiology analysis are being developed. In support of this objective, a series of novel mechanisms that are driven by an Ultrasonic/Sonic actuator have been developed to probe and sample rocks, ice and soil. This mechanism is driven by an ultrasonic piezoelectric actuator that impacts a bit at sonic frequencies through the use of an intermediate free-mass. Ultrasonic/Sonic Driller/Corer (USDC) devices were made that can produce both core and powdered cuttings, operate as a sounder to emit elastic waves and serve as a platform for sensors. For planetary exploration, this mechanism has the important advantage of requiring low axial force, virtually no torque, and can be duty cycled for operation at low average power. The advantage of requiring low axial load allows overcoming a major limitation of planetary sampling in low gravity environments or when operating from lightweight robots and rovers. The ability to operate at duty cycling with low average power produces a minimum temperature rise allowing for control of the sample integrity and preventing damage to potential biological markers in the acquired sample. The development of the USDC is being pursued on various fronts ranging from analytical modeling to mechanisms improvements while considering a wide range of potential applications. While developing the analytical capability to predict and optimize its performance, efforts are made to enhance its capability to drill at higher power and high speed. Taking advantage of the fact that the bit does not require rotation, sensors (e.g., thermocouple and fiberoptics) were integrated into the bit to examine the borehole during drilling. The sounding effect of the drill was used to emit elastic waves in order to evaluate the surface characteristics of rocks. Since the USDC is driven by piezoelectric actuation mechanism it can designed to operate at extreme temperature environments from very cold as on Titan and Europa to very hot as on Venus. In this paper, a review of the latest development and applications of the USDC will be given.

sampling↗

NASA NTRS1993

Effect of impact damage on the compression fatigue behavior of composite tubes

Experimental results are presented from an exploratory study to assess the effect of barely visible impact damage on the fatigue behavior of thin walled composite tubes. Undamaged composite tubes and tubes containing barely visible impact damage were tested in compression-compression fatigue. All tubes were inspected ultrasonically prior to testing. Tubes were outfitted with strain gages both in the damaged and far-field regions and an extensometer was utilized to measure axial displacements across the damaged region. Periodically, testing was halted and tubes were inspected ultrasonically and statically tested. In general, the impact damaged tubes exhibited a significantly shorter life than the undamaged tubes; however, there were considerable differences in the lives of the individual impact damaged tubes. No damage growth or stiffness loss was observed prior to failure. Failure of the impact damaged tubes was observed to occur in a combination of delamination buckling and shear crippling modes.

Krafchak, T. M.↗

NASA NTRS2010

Pulse-Echo Phased Array Ultrasonic Inspection of Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS)

Phased array↗

NASA NTRS1991

Rapid detection and quantification of impact damage in composite structures

NDE results from thermographic and volumetric ultrasonic techniques are presented to illustrate the multidisciplinary NDE approach to impact-damage detection in such composite structures as are increasingly prevalent in helicopters. Attention is given to both flat-panel and 'y-stiffened' panel specimens; these were fabricated either with kevlar or carbon fiber through-the-thickness reinforcements. While thermal inspection identifies impact damage, volumetric imaging quantifies the impact-generated delaminations through the volume of the structure.

Zalameda, Joseph N.↗

NASA NTRS1988

Nondestructive evaluation of advanced ceramics

A review is presented of Lewis Research Center efforts to develop nondestructive evaluation techniques for characterizing advanced ceramic materials. Various approaches involved the use of analytical ultrasonics to characterize monolythic ceramic microstructures, acousto-ultrasonics for characterizing ceramic matrix composites, damage monitoring in impact specimens by microfocus X-ray radiography and scanning ultrasonics, and high resolution computed X-ray tomography to identify structural features in fiber reinforced ceramics.

Klima, Stanley J.↗

NASA NTRS2023

Modeling of Response of Thermoplastic Composites Under High Energy Impact

This work investigates the response of a thermoplastic panel under high energy ballistic impact. The composite material system is a carbon fiber reinforced low melt semi-crystalline resin TC1225 LMPAEK T700G (T700/LMPAEK3). Several high energy dynamic impact tests were performed where an aluminum projectile impacted various panels at different impact velocities. For this work, the test performed at an impact velocity of 73.2 m/s was investigated. The projectile rebounded upon impact, and the damage to the panel was characterized through ultrasonic and CT-scanning. Response of the panel under impact and the associated damage is discussed. Numerical simulation of the impact process was performed using the LS-DYNA® computer code [1] with a new material model MAT_COMPOSITE_DAMAGE_DGD (MAT 299), a modification over MAT 261 material model in terms of an improved representation of damage coupling and additional capability for strain rate effects. Delaminations were modeled using cohesive zone contact formulation in LS-DYNA®, wherein the mixed-mode fracture is captured via the Benzegaggh-Kenane (B-K) mode-dependent fracture energy interpolation law. Simulation of this impact test demonstrates a good match of results in terms of panel deflection and panel-projectile interactions. The overall extent of delaminations was under-predicted by the simulation. This work forms the basis to model tests performed at higher velocities, involving projectile penetration of panel.

Composite Materials↗

NASA NTRS2007

Hypervelocity Impact (HVI): WLE High Fidelity Specimen RCC16R - Volume 7

During 2003 and 2004, the Johnson Space Center's White Sands Testing Facility in Las Cruces, New Mexico conducted hypervelocity impact tests on the space shuttle wing leading edge. Hypervelocity impact tests were conducted to determine if Micro-Meteoroid/Orbital Debris impacts could be reliably detected and located using simple passive ultrasonic methods. The objective of Target RCC16R was to study hypervelocity impacts through the reinforced carbon-carbon (RCC) panels of the Wing Leading Edge. Impact damage was detected using lightweight, low power instrumentation capable of being used in flight.

Gorman, Michael R.↗

NASA NTRS2007

Hypervelocity Impact (HVI): WLE Small-Scale Fiberglass Panel Flat Target C-2 - Volume 4

During 2003 and 2004, the Johnson Space Center's White Sands Testing Facility in Las Cruces, New Mexico conducted hypervelocity impact tests on the space shuttle wing leading edge. Hypervelocity impact tests were conducted to determine if Micro-Meteoroid/Orbital Debris impacts could be reliably detected and located using simple passive ultrasonic methods. The objective of Target C-2 was to study impacts through the reinforced carboncarbon (RCC) panels of the Wing Leading Edge. Fiberglass was used in place of RCC in the initial tests. Impact damage was detected using lightweight, low power instrumentation capable of being used in flight.

Gorman, Michael R.↗

NASA NTRS2007

Hypervelocity Impact (HVI): WLE Small-Scale Fiberglass Panel Flat Target C-1 - Volume 3

During 2003 and 2004, the Johnson Space Center's White Sands Testing Facility in Las Cruces, New Mexico conducted hypervelocity impact tests on the space shuttle wing leading edge. Hypervelocity impact tests were conducted to determine if Micro-Meteoroid/Orbital Debris impacts could be reliably detected and located using simple passive ultrasonic methods. The objective of Target C-1 was to study hypervelocity impacts on the reinforced carbon-carbon (RCC) panels of the Wing Leading Edge. Fiberglass was used in place of RCC in the initial tests. Impact damage was detected using lightweight, low power instrumentation capable of being used in flight.

Gorman, Michael R.↗

NASA NTRS1985

The influence of lay-up and thickness on composite impact damage and compression strength

The effects of composite stacking sequence, thickness, and percentage of zero-degree plies on the size, shape, and distribution of delamination through the laminate thickness and on residual compression strength following impact were studied. Graphite/epoxy laminates were impacted with an 0.5 inch diameter aluminum sphere at a specific low or high velocity. Impact damage was measured nondestructively by ultrasonic C-scans and X-radiography and destructively by the deply technique, and compression strength tests were performed. It was found that differences in compression failure strain due to stacking sequence were small, while laminates with very low percentages of zero-degree plies had similar failure loads but higher failure strains than laminates with higher percentages of zero-degree plies. Failure strain did not correlate with planar impact damage area, and delaminations in impact regions were associated with matrix cracking.

Guynn, E. G.↗

NASA NTRS2007

Hypervelocity Impact (HVI): WLE High Fidelity Specimen Fg(RCC)-1 - Volume 5

During 2003 and 2004, the Johnson Space Center's White Sands Testing Facility in Las Cruces, New Mexico conducted hypervelocity impact tests on the space shuttle wing leading edge. Hypervelocity impact tests were conducted to determine if Micro-Meteoroid/Orbital Debris impacts could be reliably detected and located using simple passive ultrasonic methods. The objective of Target Fg(RCC)-1 was to study hypervelocity impacts through the reinforced carbon-carbon (RCC) panels of the Wing Leading Edge. Fiberglass was used in place of RCC in the initial tests. Impact damage was detected using lightweight, low power instrumentation capable of being used in flight.

Gorman, Michael R.↗