14,553 research outputs found
High performance composites research at NASA-Langley
Barriers to the more extensive use of advanced composites in heavily loaded structures on commercial transports are discussed from a materials viewpoint. NASA-Langley matrix development activities designed to overcome these barriers are presented. These include the synthesis of processible, tough, durable matrices, the development of resin property/composite property relationships which help guide the synthesis program, and the exploitation of new processing technology to effectively combine reinforcement filament with polymer matrices. Examples of five classes of polymers being investigated as matrix resins at NASA Langley are presented, including amorphous and semicrystalline thermoplastics, lightly crosslinked thermoplastics, semi-interpenetrating networks and toughened thermosets. Relationships between neat resin modulus, resin fracture energy, interlaminar fracture energy, composite compression strength, and post-impact compression strength are shown. Powder and slurry processing techniques are discussed
On the rough Gronwall lemma and its applications
We present a rough path analog of the classical Gronwall Lemma introduced
recently by A. Deya, M. Gubinelli, M. Hofmanov\'a, S. Tindel in
[arXiv:1604.00437] and discuss two of its applications. First, it is applied in
the framework of rough path driven PDEs in order to establish energy estimates
for weak solutions. Second, it is used in order to prove uniqueness for
reflected rough differential equations
Preparing composite materials from matrices of processable aromatic polyimide thermoplastic blends
Composite materials with matrices of tough, thermoplastic aromatic polyimides are obtained by blending semi-crystalline polyimide powders with polyamic acid solutions to form slurries, which are used in turn to prepare prepregs, the consolidation of which into finished composites is characterized by excellent melt flow during processing
Wind-tunnel investigation of a flush airdata system at Mach numbers from 0.7 to 1.4
Flush pressure orifices installed on the nose section of a 1/7-scale model of the F-14 airplane were evaluated for use as a flush airdata system (FADS). Wing-tunnel tests were conducted in the 11- by 11-ft Unitary Wind Tunnel at NASA Ames Research Center. A full-scale FADS of the same configuration was previously tested using an F-14 aircraft at the Dryden Flight Research Facility of NASA Ames Research Center (Ames-Dryden). These tests, which were published, are part of a NASA program to assess accuracies of FADS for use on aircraft. The test program also provides data to validate algorithms for the shuttle entry airdata system developed at the NASA Langley Research Center. The wind-tunnel test Mach numbers were 0.73, 0.90, 1.05, 1.20, and 1.39. Angles of attack were varied in 2 deg increments from -4 deg to 20 deg. Sideslip angles were varied in 4 deg increments from -8 deg to 8 deg. Airdata parameters were evaluated for determination of free-stream values of stagnation pressure, static pressure, angle of attack, angle of sideslip, and Mach number. These parameters are, in most cases, the same as the parameters investigated in the flight test program. The basic FADS wind-tunnel data are presented in tabular form. A discussion of the more accurate parameters is included
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Adapting the International System of Units to the twenty-first century
We review the proposal of the International Committee for Weights and Measures
(Comité International des Poids et Mesures, CIPM), currently being considered by
the General Conference on Weights and Measures (Conférences Générales des Poids et
Mesures, CGPM), to revise the International System of Units (Le Système International
d’Unitès, SI). The proposal includes new definitions for four of the seven base units of
the SI, and a new form of words to present the definitions of all the units. The objective
of the proposed changes is to adopt definitions referenced to constants of nature, taken
in the widest sense, so that the definitions may be based on what are believed to be
true invariants. In particular, whereas in the current SI the kilogram, ampere, kelvin and
mole are linked to exact numerical values of the mass of the international prototype of the
kilogram, the magnetic constant (permeability of vacuum), the triple-point temperature
of water and the molar mass of carbon-12, respectively, in the new SI these units are linked
to exact numerical values of the Planck constant, the elementary charge, the Boltzmann
constant and the Avogadro constant, respectively. The new wording used expresses the
definitions in a simple and unambiguous manner without the need for the distinction
between base and derived units. The importance of relations among the fundamental
constants to the definitions, and the importance of establishing a mise en pratique for
the realization of each definition, are also discussed
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