USA As Represented by Secretary of the Navy

United States of America As Represented by the Administrator of Nasa

Liming W Salvino

Dale G Karr

Karin L Gipple

Norden E Huang

Robert Cawley

An apparatus, computer program product and method of analyzing structures. Intrinsic Mode Functions (IMFs) are extracted from the data and the most energetic IMF is selected. A spline is fit to the envelope for the selected IMF. The spline derivative is determined. A stability spectrum is developed by separating the positive and negative results into two different spectra representing stable (positive) and unstable (negative) damping factors. The stability spectrum and the non-linearity indicator are applied to the data to isolate unstable vibrations.

System and method of analyzing vibrations and identifying failure signatures in the vibrations

A metal mold is machined via a computer numerically controlled wire-cut electrical discharge technique so as to describe a fractally profiled parallel grooves-and-ridges configuration. Fibers are placed along the mold's grooves. Using the mold combined with the fibers situate in its grooves, a first composite portion is resin transfer molded so as as to describe a complementary fractally profiled parallel grooves-and-ridges configuration, and to include, in its ridges, the fibers situate in the mold's grooves. Fibers are placed along the first composite portion's grooves. Using the first composite portion combined with the fibers situate in its grooves, a second composite portion is resin transfer molded so as as to describe a complementary fractally profiled parallel grooves-and-ridges configuration, and to include, in its ridges, the fibers situate in the first composite portion's grooves, and to effect secondary bonding of the first and second composite portions.

Fabrication of a fractally attributively delamination resistive composite structure

The damping behavior of a physical system is evaluated by mapping of damping loss factors calculated from time-dependent amplitude and frequency functions to form a full time-frequency dependent damping spectrum. The time-dependent amplitude and frequency functions are formulated by calculations based on the intrinsic mode functions derived by empirical mode decomposition of the original time series dataset representing the system behavior. The amplitude and frequency functions for each intrinsic mode function are calculated from the polar representation of the Hilbert transform-based time-dependent complex function corresponding to the intrinsic mode function.

Time-frequency dependent damping via Hilbert damping spectrum

The inventive composite laminate has an interface profile which describes a fractally nonlinear contour. Inventive fabrication thereof typically includes computer numerically controlled wire-cut electrical discharge machining of a metal mold, resin transfer molding of a first composite portion using the metal mold, and resin transfer molding of a second composite portion using the first composite portion as a mold so that the interfacing surfaces of the composite portions are secondarily bonded to each other in conformal fashion. The interface surface of the second composite portion approximates the geometry of the metal mold surface, while the interface surface of the first composite portion approximates the inverted geometry of the metal mold surface. Each interface surface defines a multiplicity of lengthwise parallel grooves and ridges corresponding to the widthwise disordered undulations of the fractal interfacial profile. Both through-thickness strength and fracture toughness can be significantly increased by inventive practice of a composite laminate characterized by fractality of the interfacial profile.

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Rockville, MD, United States of America

Liming W Salvino