Nonlinear analysis of laminated fibrous composites

A computerized analysis of the nonlinear behavior of fibrous composite laminates including axial loading, thermal loading, temperature dependent properties, and edge effects is presented. Ramberg-Osgood approximations are used to represent lamina stress-strain behavior and percent retention curves are employed to model the variation of properties with temperature. Balanced, symmetric laminates comprised of either boron/epoxy, graphite/epoxy, or borsic-aluminum are analyzed using a quasi-three-dimensional finite element analysis. Results are presented for the interlaminar stress distributions in cross-ply, angle-ply, and more complex laminates. Nonlinear stress-strain curves for a variety of composite laminates in tension and compression are obtained and compared to other existing theories and experimental results

Rate and time dependent behavior of structural adhesives

Studies on two adhesives (Metlbond 1113 and 1113-2) identified as having applications in the bonding of composite materials are presented. Constitutive equations capable of describing changes in material behavior with strain rate are derived from various theoretical approaches. It is shown that certain unique relationships exist between these approaches. It is also shown that the constitutive equation derived from mechanical models can be used for creep and relaxation loading. A creep to failure phenomenon is shown to exist and is correlated with a delayed yield equation proposed by Crochet. Loading-unloading results are presented and are shown to correlate well with the proposed form of the loading-unloading equations for the modified Bingham model. Experimental results obtained for relaxation tests above and below the glass transition temperature are presented. It is shown that the adhesives obey the time-temperature superposition principle

llama meat nutritional properties

The aim of this study was to determine the chemical composition of the muscle Longissimus thoracis taken from 20 llama males, reared in the Andean region, slaughtered at an age of 25 months and at a mean final body weight of 74kg. Llama meat showed a low fat (3.51%) and cholesterol content (58.16mg/100g), a good protein content (22.42%) and an ash content of 3.06%. The Warner-Bratzler shear force values determined in llama meat was 6.56 kg/cm2. This study confirmed that llama meat is healthy and nutritious, and represents a good source of proteins for Andean population

Wool quality in Gentile di Puglia sheep breed as measure of genetic integrity

The Gentile di Pugliais a breed created in the 15th century by crossing Merino Spanish rams and "gentile" ewes reared in some areas of Southern Italy, mainly Apulia and Basilicata. The crisis of the wool industry, the poor quantity of milk, the inadequacy of Gentile di Pugliato be milked by machine and the passage from transhumant to permanent rearing caused a dramatic reduction of this population, which was largely crossed with other breeds and declined from about one million heads in the sixties to 5,000 at the present time. In order to save the ancient typical Gentile di Pugliabreed, the aim of this work was to estimate the "genetic integrity" of the remaining Gentile di Pugliapopulation by means of an analysis of wool quality measured through the diameter of the fibre and the homogeneity of the fleece. Our hypothesis was that the animals originated from outcrosses to other Merino derived breeds specialised for meat would show larger diameters of the fibres and a reduced homogeneity of the fleece. The research was carried out using Herd Book registered animals from 9 farms: 1 from Isernia, 2 from Campobasso and 6 from Foggia province. The statistical analysis on the diameter of the fibre was carried out on a dataset of 38,200 observations (200 records x 191 animals) divided in four classes (ultrafine, fine, croisè, ordinary). The high frequencies of ultrafine and fine fibre classes show that the quality of the wool is still good in the population. This consideration can be extended to all the farms involved in the study that could therefore be suitable in the conservation programs for this breed. The homogeneity of the fleece was also good in provid- ing further evidence of the genetic integrity of the population. Other analysis carried out on the quality of the wool in relation to the body size confirmed that the observed Gentile di Pugliais well representative of the ancient breed

Preliminary study on MC1R polymorphism in some cattle breeds raised in Italy

Ricerche preliminari sul polimorfismo del gene MC1R in alcune razze bovine allevate in Italia – Il gene MC1R è stato analizzato in 193 soggetti appartenenti a 8 razze bovine, tramite PCR, per la presenza di due mutazioni ad effetto fenotipico noto sulla pigmentazione del mantello: la delezione G310 e la sostituzione T296C, associate rispettivamente al fenotipo feomelanico (e) ed eumelanico nero (Ed). Sessanta soggetti di razza Limousine e Pezzata Rossa Italiana presentano genotipo e/e; 27 soggetti di razza Frisona Italiana mostrano genotipo Ed/Ed mentre 2 genotipo Ed/e. Gli 84 soggetti appartenenti alle razze Cabannina, Chianina, Marchigiana e Piemontese non presentano tali mutazioni, analogamente a 18 soggetti di razza Romagnola, nella quale però si sono anche osservati 2 soggetti portatori dell’allele e allo stato eterozigote