Search NASA⌕ Search

SEARCH · Search NASA

Results for “IMPACT STRENGTH”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Mechanical property characterization and impact resistance of selected graphite/PEEK composite materials

To use graphite polyetheretherketone (PEEK) material on highly curved surfaces requires that the material be drapable and easily conformable to the surface. This paper presents the mechanical property characterization and impact resistance results for laminates made from two types of graphite/PEEK materials that will conform to a curved surface. These laminates were made from two different material forms. These forms are: (1) a fabric where each yarn is a co-mingled Celion G30-500 3K graphite fiber and PEEK thermoplastic fiber; and (2) an interleaved material of Celion G30-500 3K graphite fabric interleaved with PEEK thermoplastic film. The experimental results from the fabric laminates are compared with results for laminates made from AS4/PEEK unidirectional tape. The results indicate that the tension and compression moduli for quasi-isotropic and orthotropic laminates made from fabric materials are at least 79 percent of the modulus of equivalent laminates made from tape material. The strength of fabric material laminates is at least 80 percent of laminates made from tape material. The evaluation of fabric material for shear stiffness indicates that a tape material laminate could be replaced by a fabric material laminate and still maintain 89 percent of the shear stiffness of the tape material laminate. The notched quasi-isotropic compression panel failure strength is 42 to 46 percent of the unnotched quasi-isotropic laminate strength. Damage area after impact with 20 ft-lbs of impact energy is larger for the co-mingled panels than for the interleaved panels. The inerleaved panels have less damage than panels made from tape material. Residual compression strength of quasi-isotropic panels after impact of 20 ft-lbs of energy varies between 33 percent of the undamaged quasi-isotropic material strength for the tape material and 38 percent of the undamaged quasi-isotropic material strength for the co-mingled fabric material.

Baker, Donald J.↗
DOE OSTI2018

Investigation on Microstructural Evolutions and Mechanical Properties of P92 Steel During Thermal Processing

The evolution of the microstructure of P92 steel during heat processing has a significant effect on the final performance of steel products and is thus an area of critical interest. Accordingly, the grain growth behavior of austenite and δ-ferrite changes in P92 steel is comprehensively investigated in this study through thermodynamic calculations and physical simulation. The results show that the A{sub C1}, A{sub C3} and γ–δ transformation temperatures of P92 steel are 841 °C, 878 °C and 1095 °C, respectively, which are comparable to the measured values of 850 °C, 879 °C and 1175 °C, respectively. When the temperature exceeds the A{sub C1} temperature, the austenite grain size increases with increasing temperature and longer holding times, and the growth rate of austenite grains increases with higher temperatures but decreases with holding time at a certain temperature. A model that shows the austenite grain growth kinetics is established: D{sup n} − D{sub 0}{sup n} = 2.03 × 10{sup 16}exp(− 498,770/RT)t, in which the time exponent n decreases from 4.52 to 2.11 with an increase in temperature from 1000 °C to 1200 °C due to the reduced pinning effect resultant of the dissolution of precipitates, M{sub 23}C{sub 6}, VX and NbX at 887 °C, 1073 °C and 1200 °C, respectively. The formation of δ-ferrite at 1200 °C when held for 600 s and 1300 °C when held for 60 ~ 600 s causes a smaller austenite grain size. The relationship between the evolution of the microstructure of P92 steel and the mechanical properties is also studied. The results show that the prior austenite grain size has an inverse relationship with impact energy and ultimate tensile strength at 620 °C, while the presence of soft δ-ferrite leads to a reduction in the microhardness, impact energy and ultimate tensile strength at 620 °C.

36 MATERIALS SCIENCE↗
NASA NTRS2003

Effect of High Impact or Non-impact Loading Activity on Bone Bending Stiffness and Mineral Density

Material properties of conical bone, including mineral density (BMD) and its geometry is closely related to its load-carrying capacity. These two primary components determine the strength of conical bone. High impact loading involving acceleration and deceleration movements used in gymnastics induce higher BMD of the affected bone compared to the non-impact acceleration and deceleration movements used in swimming. Study of these two groups of athletes on bone bending stiffness has not been reported. The purpose of this study was to compare differences in bone bending stiffness and BMD between competitive female synchronized swimmers and female gymnasts. Thirteen world class female synchronized swimmers (SYN) and 8 female gymnasts (GYM), mean age 21 +/- 2.9 yr. were recruited for this study. We used a mechanical response tissue analyzer (Gaitscan, NJ) to calculate EI, where E is Young's modulus of elasticity and I is the cross-sectional moment of inertia. EI was obtained from tissue response to a vibration probe placed directly on the skin of the mid-region of tibia and ulna. BMD of the heel and wrist were measured with a probe densitometer (PIXI, Lunor, WI). The SYN were taller than (p < 0.05) the GYM but weighed the same as the GYM. EI obtained from tibia and ulna of the SYN (291 +/- 159 and 41 +/- 19.4, respectively) were not significantly different from thc GYM (285 +/- 140 and 44 +/- 18.3, respectively). BMD of the heel and wrist in GYM were higher than in SYN (p < 0.001). High impact weight-bearing activities promote similar bone strength but greater BMD response than non-impact activities performed in a buoyant environment.

Liang, Michael T. C.↗
NASA NTRS1990

Certification of damage tolerant composite structure

A reliability based certification testing methodology for impact damage tolerant composite structure was developed. Cocured, adhesively bonded, and impact damaged composite static strength and fatigue life data were statistically analyzed to determine the influence of test parameters on the data scatter. The impact damage resistance and damage tolerance of various structural configurations were characterized through the analysis of an industry wide database of impact test results. Realistic impact damage certification requirements were proposed based on actual fleet aircraft data. The capabilities of available impact damage analysis methods were determined through correlation with experimental data. Probabilistic methods were developed to estimate the reliability of impact damaged composite structures.

Rapoff, Andrew J.↗
NASA NTRS1994

Impact force as a scaling parameter

The Federal Aviation Administration (FAR PART 25) requires that a structure carry ultimate load with nonvisible impact damage and carry 70 percent of limit flight loads with discrete damage. The Air Force has similar criteria (MIL-STD-1530A). Both civilian and military structures are designed by a building block approach. First, critical areas of the structure are determined, and potential failure modes are identified. Then, a series of representative specimens are tested that will fail in those modes. The series begins with tests of simple coupons, progresses through larger and more complex subcomponents, and ends with a test on a full-scale component, hence the term 'building block.' In order to minimize testing, analytical models are needed to scale impact damage and residual strength from the simple coupons to the full-scale component. Using experiments and analysis, the present paper illustrates that impact damage can be better understood and scaled using impact force than just kinetic energy. The plate parameters considered are size and thickness, boundary conditions, and material, and the impact parameters are mass, shape, and velocity.

Poe, Clarence C., Jr.↗
NASA NTRS1991

Comparison of hand laid-up tape and filament wound composite cylinders and panels with and without impact damage

The results of this experimental comparison of filament wound control (unimpacted) cylinders loaded to failure in axial compression indicates that one fiber cross-over location has no effect on the failure mode or strain in thick walled filament wound graphite-epoxy specimens with stacking sequence (plus or minus 45/90) sub 3s. A comparison between filament wound and hand laid-up tape control cylinders indicates that there is little or no difference in the response of cylinders constructed by using two different fabrication methods, however, unimpacted panels with many fiber cross-overs fail at up to 15 percent lower strains than panels with no fiber cross-overs. A comparison of samples subjected to low speed impact damage prior to compressive loading indicates that impact damage reduces the strain at failure by over 60 percent in tape and filament wound graphite-epoxy cylinders and in tape flat panels. The presence of fiber cross-overs was observed to reduce the strength of filament wound impact-damaged panels, but to have no significant effect on the strength of filament wound impact-damaged cylinders.

Jegley, Dawn C.↗
NASA NTRS1971

Group theoretical selection rules for electron-impact spectroscopy.

Simple group theoretical principles are applied to the consideration of electron scattering off atoms and diatomic and polyatomic molecules. This approach is also used to estimate relative strengths of electron-impact-induced transitions of diatomic and polyatomic molecules.

Goddard, W. A., III↗
NASA NTRS1982

Impact resistance of fiber composites

Stress-strain curves are obtained for a variety of glass fiber and carbon fiber reinforced plastics in dynamic tension, over the stress-strain range of 0.00087-2070/sec. The test method is of the one-bar block-to-bar type, using a rotating disk or a pendulum as the loading apparatus and yielding accurate stress-strain curves up to the breaking strain. In the case of glass fiber reinforced plastic, the tensile strength, strain to peak impact stress, total strain and total absorbed energy all increase significantly as the strain rate increases. By contrast, carbon fiber reinforced plastics show lower rates of increase with strain rate. It is recommended that hybrid composites incorporating the high strength and rigidity of carbon fiber reinforced plastic with the high impact absorption of glass fiber reinforced plastics be developed for use in structures subjected to impact loading.

Chamis, C. C.↗
NASA NTRS1990

Surface crack analysis applied to impact damage in a thick graphite/epoxy composite

The residual tensile strength of a thick graphite/epoxy composite with impact damage was predicted using surface crack analysis. The damage was localized to a region directly beneath the impact site and extended only part way through the laminate. The damaged region contained broken fibers, and the locus of breaks in each layer resembled a crack perpendicular to the direction of the fibers. In some cases, the impacts broke fibers without making a visible crater. The impact damage was represented as a semi-elliptical surface crack with length and depth equal to that of the impact damage. The maximum length and depth of the damage were predicted with a stress analysis and a maximum shear stress criterion. The predictions and measurements of strength were in good agreement.

Poe, Clarence C., Jr.↗
NASA NTRS1997

Planetary and Primitive Object Strength Measurements and Sampling Apparatus

We present experimental data and a model for the low-velocity (subsonic, 0 - 1000 m/s) penetration of brittle materials by both solid and hollow (i.e., coring) penetrators. The experiments show that penetration is proportional to momentum/frontal area of the penetrator. Because of the buildup of a cap in front of blunt penetrators, the presence or absence of a streamlined or sharp front end usually has a negligible effect for impact into targets with strength. The model accurately predicts the dependence of penetration depth on the various parameters of the target-penetrator system, as well as the qualitative condition of the target material ingested by a corer. In particular, penetration depth is approximately inversely proportional to the static bearing strength of the target. The bulk density of the target material has only a small effect on penetration, whereas friction can be significant, especially at higher impact velocities, for consolidated materials. This trend is reversed for impacts into unconsolidated materials. The present results suggest that the depth of penetration is a good measure of the strength, but not the density, of a consolidated target. Both experiments and model results show that, if passage through the mouth of a coring penetrator requires initially porous target material to be compressed to less than 26% porosity, the sample collected by the corer will be highly fragmented. If the final porosity remains above 26%, then most materials, except cohesionless materials, such as dry sand, will be collected as a compressed slug of material.

Ahrens, Thomas J.↗
DOE OSTI2016

The Land Use Model Intercomparison Project (LUMIP) contribution to CMIP6: rationale and experimental design

Human land-use activities have resulted in large changes to the Earth's surface, with resulting implications for climate. In the future, land-use activities are likely to expand and intensify further to meet growing demands for food, fiber, and energy. The Land Use Model Intercomparison Project (LUMIP) aims to further advance understanding of the impacts of land-use and land-cover change (LULCC) on climate, specifically addressing the following questions. (1) What are the effects of LULCC on climate and biogeochemical cycling (past-future)? (2) What are the impacts of land management on surface fluxes of carbon, water, and energy, and are there regional land-management st rategies with the promise to help mitigate climate change? In addressing these questions, LUMIP will also address a range of more detailed science questions to get at process-level attribution, uncertainty, data requirements, and other related issues in more depth and sophistication than possible in a multi-model context to date. There will be particular focus on the separation and quantification of the effects on climate from LULCC relative to all forcings, separation of biogeochemical from biogeophysical effects of land use, the unique impacts of land-cover change vs. land-management change, modulation of land-use impact on climate by land-atmosphere coupling strength, and the extent to which impacts of enhanced CO 2 concentrations on plant photosynthesis are modulated by past and future land use.LUMIP involves three major sets of science activities: (1) development of an updated and expanded historical and future land-use data set, (2) an experimental protocol for specific LUMIP experiments for CMIP6, and (3) definition of metrics and diagnostic protocols that quantify model performance, and related sensitivities, with respect to LULCC. In this paper, we describe LUMIP activity (2), i.e., the LUMIP simulations that will formally be part of CMIP6. These experiments are explicitly designed to be complementary to simulations requested in the CMIP6 DECK and historical simulations and other CMIP6 MIPs including ScenarioMIP, C4MIP, LS3MIP, and DAMIP. LUMIP includes a two-phase experimental design. Phase one features idealized coupled and land-only model simulations designed to advance process-level understanding of LULCC impacts on climate, as well as to quantify model sensitivity to potential land-cover and land-use change. Phase two experiments focus on quantification of the historic impact of land use and the potential for future land management decisions to aid in mitigation of climate change. This paper documents these simulations in detail, explains their rationale, outlines plans for analysis, and describes a new subgrid land-use tile data request for selected variables (reporting model output data separately for primary and secondary land, crops, pasture, and urban land-use types). It is essential that modeling groups participating in LUMIP adhere to the experimental design as closely as possible and clearly report how the model experiments were executed.

58 GEOSCIENCES↗
NASA NTRS1985

Glass breaking strength: The role of surface flaws and treatments

Although the intrinsic strength of silicon dioxide glass is of the order of 10 to the 6th power lb/sq in, the practical strength is roughly two orders of magnitude below this theoretical limit, and depends almost entirely on the surface condition of the glass, that is, the number and size of flaws and the residual surface compression (temper) in the glass. Glass parts always fail in tension when these flaws grow under sustained loading to some critical size. Research associated with glass encapsulated crystalline-Si photovoltaic (PV) modules has greatly expanded our knowledge of glass breaking strength and developed sizeable data base for commercially available glass types. A detailed design algorithm is developed for thickness sizing of rectangular glass plates subject to pressure loads. Additional studies examine the strength of glass under impact loading conditions such as that caused by hail. Although the fundamentals of glass breakage are directly applicable to thin film modules, the fracture strength of typical numerical glass must be replaced with data that reflect the high temperature tin oxide processing, laser scribing, and edge processing peculiar to thin film modules. The fundamentals of glass breakage applicable to thin film modules and preliminary fracture strength data for a variety of 1 ft square glass specimens representing preprocessed and post processed sheets from current amorphous-Si module manufacturers are presented.

Moore, D.↗
DOE OSTI2018

Microstructure and property tailoring of castable nanostructured alloys through thermomechanical treatments

Three types of microstructures, i.e., tempered-martensite (TM), ferrite (F), and dual-phase (TM + F), were developed in a castable nanostructured alloy that favors a high density of nanoprecipitates compared with the precipitates in current reduced-activation ferritic-martensitic steels. The effect of the distinct microstructures on tensile properties, Charpy impact toughness, and thermal helium desorption behavior was investigated with the full TM structure as a reference. The results indicated that the F domain in the TM + F structure governed the strength and slightly impaired the impact toughness. The full F structure exhibited the highest strength without compromising ductility, but it noticeably diminished impact toughness. All microstructures had a dominant helium desorption peak at ~1070 °C. The higher density of nanoprecipitates and complex boundaries and dislocations in the TM + F structure enhanced the secondary helium desorption peak and extended the shoulder peak, in contrast to the full TM structure with an enlarged desorption peak associated with the ferrite-to-austenite transformation at ~810–850 °C and the full F structure with a dominant desorption peak related to bubble migration at ~1070 °C. These results suggest that components fabricated from functionally graded microstructures could be engineered to exploit the advantages of different microstructures for demanding application requirements.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Microstructures and mechanical properties of a modified 9Cr ferritic-martensitic steel in the as-built condition after additive manufacturing

A newly developed nano-structured high-Mn 9Cr ferritic-martensitic (FM) steel designed for additive manufacturing (Additive-manufactured Nanostructured Alloy, ANA) was fabricated via the direct energy deposition method. The as-printed ANA2 showed tensile properties (strength and elongation) and Charpy impact toughness (upper-shelf energy and ductile-brittle transition temperature) comparable to oxide-dispersion-strengthened (ODS) Eurofer and PM2000. Compared with wrought P91, the as-built ANA2 showed significantly higher yield strength but inferior Charpy impact toughness and ductility. Microstructural characterization revealed uniformly distributed sub-micron pores, an extremely high dislocation density, and a high density of ultrafine nano-structured precipitates in the matrix. The microstructures indicated the dislocations as the dominant strengthening element and the ultrafine precipitates as the primary contribution to estimated irradiation sink density. This work demonstrates the ability to exploit the unique consolidation properties of additive manufacturing to fabricate steels which marry the benefits of both ODS alloys and conventionally processed FM steels.

36 MATERIALS SCIENCE↗
NASA NTRS2024

Study on Near Edge Impact Behavior of Sandwich Panels in Support of the SLS Payload Adaptor Fitting (PAF)

This paper examines the effects of impacts near the edge of honeycomb sandwich panels compared to impacts at the center of the specimen. Instrumented impact data, NDE, cross-sectional photomicroscopy and Compression After Impact (CAI) testing were conducted. The key result is that for a given impact severity level, the CAI strength values are about the same regardless of how close the impact is to the edge of the panel.

Off Center Impacts↗
NASA NTRS1975

Impact fracture of composite sandwich structures

An experimental investigation of impact-initiated failures in high-strength graphite/epoxy and Kevlar-49/epoxy sandwich structures has been conducted. The tests consisted of firing small diameter aluminum projectiles with a velocity range of 16-67 meters/second (52-220 ft/sec) at preloaded sandwich specimens. These tests were intended to be representative of service conditions on materials and structures which might be used as secondary aircraft components. The preload and impact energy necessary to initiate catastrophic failure were determined. The residual strength of impact-damaged specimens was also measured. The results of these tests indicate that catastrophic failures in sandwich structures can be initiated at relatively low preloads by impact projectiles at energy levels well below that required to initiate visible damage.

Rhodes, M. D.↗
DOE OSTI2016

Radical Nature of C-Lignin

The recently discovered lignin composed of caffeoyl alcohol monolignols or C-lignin is particularly intriguing given its homogeneous, linear polymeric structure and exclusive benzodioxane linkage between monomers. By virtue of this simplified chemistry, the potential emerges for improved valorization strategies with C-lignin relative to other natural heterogeneous lignins. To better understand caffeoyl alcohol polymers, we characterize the thermodynamics of the radical recombination dimerization reactions forming the benzodioxane linkage and the bond dissociation into radical monolignol products. These properties are also predicted for the cross-coupling of caffeoyl alcohol with the natural monolignols, coniferyl alcohol, sinapyl alcohol, and p-coumaryl alcohol, in anticipation of polymers potentially enabled by genetic modification. The average BDEs for the C-lignin benzodioxane $\alpha$- and β-bonds are 56.5 and 63.4 kcal/mol, respectively, with similar enthalpies for heterodimers. The BDE of the $\alpha$-bond within the benzodioxane linkage is consistently greater than that of the β-bond in all dimers of each stereochemical arrangement, explained by the ability the $\alpha$-carbon radical generated to delocalize onto the adjacent phenyl ring. Relative thermodynamics of the heterodimers demonstrates that the substituents on the phenyl ring directly neighboring the bond coupling the monolignols more strongly impact the dimer bond strengths and product stability, compared to the substituents present on the terminal phenyl ring. Enthalpy comparisons furthermore demonstrate that the erythro stereochemical configurations of the benzodioxane bond are slightly less thermodynamically stable than the threo configurations. The overall differences in strength of bonds and reaction enthalpies between stereoisomers are generally found to be insignificant, supporting that postcoupling rearomatization is under kinetic control. Projecting the lowest-energy stereoisomer internal coordinates to longer polymer C-lignin strands highlights how significantly the stereochemical outcomes in polymerization may impact the macromolecular structure and in turn material and chemical properties. Lastly, through these comparisons of geometry, bond strengths, and reaction enthalpies, we shed light on the distinctive properties of C-lignin's radical recombination and decomposition chemistry, and its potential as a natural lignin solution for biorefinery feedstocks and unique materials science applications.

09 BIOMASS FUELS↗