Monitoring Damage in Non-Oxide Composites At High Temperatures Using Carbon-Containing CVD SiC Monofilament Fibers as Embedded Electrical Resistance Sensors

Electrical resistance has become a technique of interest for monitoring SiC-based ceramic composites. For aero engine applications, SiC fiber reinforced SiC matrix with a BN interphase are often the main constituents. For high temperature tests, electrical lead attachment must be in a cold region; however, there is interest in focusing the resistance measurement in the hot section where damage monitoring is desired. One approach considered here is to insert carbon "rods" in the form of CVD SiC monofilaments with a C core to try and better sense change in resistance as it pertains to matrix crack growth in an elevated temperature test condition. Two material systems were considered for this study. The first composite system consisted of a Hi-Nicalon woven fibers, a BN interphase and a matrix processed via polymer infiltration and pyrolysis (PIP) which had SCS-6 monofilaments providing the C core. The second composite system was a melt-infiltrated (MI) pre-preg laminate which contained Hi-Nicalon Type S fibers with BN interphases with SCS-Ultra monofilaments providing the C core. The two composite matrix systems represent two extremes in resistance, the PIP matrix being orders of magnitude higher in resistance than the Si-containing pre-preg MI matrix. Single notch tension-tension fatigue tests were performed at 815oC to stimulate crack growth. Acoustic emission (AE) was used along with electrical resistance (ER) to monitor the damage initiation and progression during the test.

Effects of Steel Slag on Durability Properties of Slurry Infiltrated Fibrous Concrete

Inthis research observed the properties of substitute of steel slag on slurry infiltrated fibrous concrete. Six series of test specimens were prepared using hook ended steel fibre with 0,2,3 and 4% volumes fractions along with 0 to 20 % steel slagsubstitute. All procedures on concrete subjected to fresh and hardened properties. For mechanical properties of concrete, compressive, splittingtingtensile and flexural tensile strength.Durability properties performed using the acidic attack test, sulfate attacktest and elevated temperature test. For workability properties to perform flowability, the passing abilitywas appraised using Slump flowand L-Boxtests. A fresh property depict the significant effect of changing steel slagsubstitute. Steel slag substitute along with 4% fibres showed that 25.73% compressive strength,20.34% splitting tensile strength,1.16% flexural strength improvement as compared to control specimen. Durability resultsuch as acid attack, sulfate attack for steel slag blend slurry infiltrated fibre concrete showed improvement over control specimen.

Overview of Experimental Study and Theoretical Analysis of Concrete Beams after High Temperature

After high temperature, mechanical properties and fire-resistant performance of concrete members has become one of the hotspots of study on fire resistance of structures. In this paper, the deficiencies of concrete beams at elevated temperature test and theoretical analysis are pointed out, the future prospects of concrete beams at elevated temperature is disscussed, some key problems are proposed to solve in the future.

Fecal Coliform Methods for Examination of Sea Water: Interlaboratory Evaluation of Split Sample Analysis

An interlaboratory study was conducted to compare the effectiveness of the following 3 multiple-tube fermentation methods for determining the most probable number (MPN) of Escherichia coli in a split artificial sea water sample: ( 1 ) the 72-hr standard methods procedure of the American Public Health Association, (2) a 24-hr elevated-temperature test using A-l medium, and (3) a 24-hr elevated temperature test modified to include an initial 3-hr resuscitation period using A-l medium. The capability of the laboratories to perform the 3 test procedures was also compared. Split sample replicates with low, medium, and high levels of E. coli were examined in 18 laboratories in the United States and Canada. Data indicate that the laboratories performed each test with equal capability, and all 3 procedures were equally effective in enumerating the strain of E. coli used in this investigation. By virtue of its homogeneity and stability, the split sample served as an appropriate specimen for this study and could probably be used as a proficiency test specimen for evaluating laboratory analyst performance in the bacteriological examination of sea water.