Development and experimental validation of a mathematical model for friction between fabrics and a volar forearm phantom.

An analytical mathematical model for friction between a fabric strip and the volar forearm has been developed and validated experimentally. The model generalizes the common assumption of a cylindrical arm to any convex prism, and makes predictions for pressure and tension based on Amontons' law. This includes a relationship between the coefficient of static friction (mu) and forces on either end of a fabric strip in contact with part of the surface of the arm and perpendicular to its axis. Coefficients of friction were determined from experiments between arm phantoms of circular and elliptical cross-section (made from Plaster of Paris covered in Neoprene) and a nonwoven fabric. As predicted by the model, all values of mu calculated from experimental results agreed within +/- 8 per cent, and showed very little systematic variation with the deadweight, geometry, or arc of contact used. With an appropriate choice of coordinates the relationship predicted by this model for forces on either end of a fabric strip reduces to the prediction from the common model for circular arms. This helps to explain the surprisingly accurate values of mu obtained by applying the cylindrical model to experimental data on real arms.

Determination of peptides and amino acids from wool and beer with sensitive fluorescent reagent 2-(9-carbazole)-ethyl chloroformate by reverse phase high-performance liquid chromotography and liquid chromotography mass spectrometry

A new method for the sensitive determination of amino acids and peptides using the tagging reagent 2-(9-carbazole)-ethyl chloroformate (CEOC) with fluorescence (FL) detection has been developed. Identification of derivatives was carried out by liquid chromotography mass spectrometry. The chromophore in the 2-(9-fluorenyl)-ethyl chloroformate (FMOC) reagent was replaced by carbazole, which resulted in a sensitive fluorescence lerivatizing agent CEOC. CEOC can easily and quickly label peptides and amino acids. Derivatives are stable enough to be efficiently analyzed by high-performance liquid chromatography. Studies on derivatization demonstrate excellent derivative yields over the pH range 8.8-10.0. Maximal yields close to 100% are observed with three- to fourfold molar reagent excess. Derivatives exhibit strong fluorescence and allow direct injection of the reaction mixture with no significant disturbance from the major fluorescent reagent degradation by-products, such as 2(9-carbazole)-ethanol and bis-(2-(9-carbazole)-ethyl) carbonate. In addition, the detection responses for CEOC derivatives are compared to those obtained with FMOC. The ratios AC(CEOC)/AC(FMOC) = 1.00-1.82 for fluorescence (FL) response and AC'(CEOC)/AC'(FMOC) = 1.00-1.21 for ultraviolet (UV) response are observed (here, AC and AC' are, respectively, FL and UV F response). Separation of the derivatized peptides and amino acids has been optimized on a Hypersil BDS C18 column. Excellent linear responses are observed. This method was used successfully to analyze protein hydrolysates from wool and from direct-derivatized beer. (C) 2003 Elsevier Science (USA). All rights reserved.

The effect of 3D weaving and consolidation on carbon fiber tows, fabrics, and composites

This article investigates the damage imparted on load-bearing carbon fibers during the 3D weaving process and the subsequent compaction behavior of 3D woven textile preforms. The 3D multi-layer reinforcements were manufactured on a textile loom with few mechanical modifications to produce preforms with fibers orientated in the warp, weft, and through-the-thickness directions. Tensile tests were conducted on three types of commercially available carbon fibers, 12k HTA, 6k HTS, and 3k HTS in an attempt to quantify the effect of fiber damage induced during the 3D weaving process on the mechanical and physical performance of the fiber tows in the woven composite. The tests were conducted on fiber tows sampled from different locations in the manufacturing process from the bobbin, through the creel and loom mechanism, to the final woven fabric. Mechanical and physical testing were then conducted to quantify the tow geometry, orientation and the effect of compaction during manufacture of two styles of 3D woven composite by vacuumassisted resin transfer molding (VaRTM).