Analysis of Ultrasonic Backscatter for Porosity Characterization in Graphite-Epoxy Composites

This paper summarizes recent work on the use of ultrasonic back-scatter for the estimation of porosity levels in continuous-fiber-reinforced, layered graphite-epoxy composites. This work is a continuation of previous work described in Refs. 1–3, which addresses the effect of porosity on (1) azimuthal angle backscatter scans, and (2) the spectral characteristics of backscatter

Effect of Bottom-Surface Reflections on Backscatter from Porosity in a Composite Layer

Polar backscattering from a fiber-reinforced composite which contains regions of porosity, has been investigated in a number of papers [1]–[7]. Several scattering mechanisms appear to contribute to the backscattered signal. Roughly speaking the components of the backscattered signal can be attributed to effects of finite beam width, to the structuring of the material and to the existence of porosity

First record of Rhabdoceras suessi (Ammonoidea, Late Triassic) from the Transylvanian Triassic Series of the Eastern Carpathians (Romania) and a review of its biochronology, paleobiogeography and paleoecology

Abstract The occurrence of the heteromorphic ammonoid Rhabdoceras suessi Hauer, 1860, is recorded for the first time in the Upper Triassic limestone of the Timon-Ciungi olistolith in the Rarău Syncline, Eastern Carpathians. A single specimen of Rhabdoceras suessi co-occurs with Monotis (Monotis) salinaria that constrains its occurrence here to the Upper Norian (Sevatian 1). It is the only known heteromorphic ammonoid in the Upper Triassic of the Romanian Carpathians. Rhabdoceras suessi is a cosmopolitan species widely recorded in low and mid-paleolatitude faunas. It ranges from the Late Norian to the Rhaetian and is suitable for high-resolution worldwide correlations only when it co-occurs with shorter-ranging choristoceratids, monotid bivalves, or the hydrozoan Heterastridium. Formerly considered as the index fossil for the Upper Norian (Sevatian) Suessi Zone, by the latest 1970s this species lost its key biochronologic status among Late Triassic ammonoids, and it generated a controversy in the 1980s concerning the status of the Rhaetian stage. New stratigraphic data from North America and Europe in the subsequent decades resulted in a revised ammonoid biostratigraphy for the uppermost Triassic, the Rhaetian being reinstalled as the topmost stage in the current standard timescale of the Triassic. The geographic distribution of Rhabdoceras is compiled from published worldwide records, and its paleobiogeography and paleoecology are discussed

To understand the expression profile and function of heparanase in the adult spinal cord

The presence of porosity in a structural material generally has a detrimental effect on the strength and mechanical properties of the component [1]. Excessive porosity is especially undesirable in laminated composites such as graphite-epoxy as it substantially degrades the interlaminar shear strength, the compressive strength and the transverse flexural strength, Detailed morphological knowledge of the pores such as their geometrical shape, orientation and location of occurrence in the laminate is valuable in several areas. In the nondestructive evaluation of porosity in composites using ultrasound, such morphological data will aid the model development of the interaction of the ultrasonic field with the voids and help the interpretation of the ultrasonic measurement results. In the investigation of the effects of defects, data on the pore morphology serve as inputs to models of the stress distribution around the defects and the interaction between the defects

Utilization of Target-Specific, Hypersensitive Strains of Saccharomyces cerevisiae To Determine the Mode of Action of Antifungal Compounds

Target-specific hypersusceptible strains of Saccharomyces cerevisiae were used to screen antifungal compounds. Two novel Erg7p inhibitors were identified, providing proof of principle of the approach taken. However, observed hypersensitivities to antifungals acting via other targets imply that use of this tool to identify the mode of action requires significant deconvolution

Morphological science research: Where do we go from here?

The potential of ultrasonic polar backscatter measurements for detecting and characterizing porosity in composite laminates has been investigated in a number of laboratories[l–l1]. The objective of this study was to evaluate the influence of the nature of the composite’s surface on such measurements. The deleterious effects of bleeder cloth impressions, previously noted by Bar-Cohen[12], led to the hypothesis that the periodic surface features due to bleeder cloth impressions remaining after the cure process contribute significantly to the received backscattered signal, possibly masking the anisotropy of backscatter which is used to estimate porosity