Stress and failure analysis of composite materials using finite element method: a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology in Production Technology at Massey University

In early history, it was found that combinations of materials would produce properties in those materials that were superior to those of the separate components themselves. For instance, Damascus gun barrels combined layers of iron and steel and Mongols made bows from cattle tendons, wood, and silk bonded together. Most naturally occurring materials also derive their superb properties from combination of two or more components which can be distinguished readily when examined under optical or electron microscopes, like many tissues in the body, wood , bone, etc. A more useful definition of a composite would be: The combination of a reinforcement material (such as a particle or fibre) in a matrix or binder material. The principle materials used for composite matrices are polymers, ceramics, and metals, with polymers being the most common. Reinforcements are plastics, ceramics, or metals. The different kinds of reinforcements and matrices are shown in the following diagram. [FROM INTRODUCTION

National accounting statistics for the less developed economies (with special reference to Transkei)

Includes bibliographical references.Macroeconomics is that part of economics which studies the overall averages and aggregates of the economic system. It seeks to explain the causes and consequences of fluctuation in the general level of output, or prosperity and depression, the general price level, or inflation. and deflation, the general level of employment, which moves with the level of output, and the general level of interest rates, which is to some degree related to the phenomena above. It is evident therefore that macroeconomic analysis involves the measurement of macroeconomic activity. That branch of macroeconomics which is concerned with the measurement of macroeconomic activity is called national accounting, or national income accounting. Like all other branches of economics national accounting has evolved considerably over the past three centuries. Initially, different countries developed their own national accounting systems, depending mainly on the structure of their economies and the possibilities for data collection. Examples of developments in this direction are the French system of national accounts and the British system of national accounts. Later on, for the sake of international comparability, attempts were made to develop a standard pattern which would be employed by all countries. The results of these attempts were the 1953 and 1968 systems of National Accounts introduced by the United Nations (U.N.), referred to as the U.N. System of National Accounts. This thesis studies the underlying concepts and the general applicability of these two systems, the latter being a revised version of the former

Thermal stress analysis of unidirectional fiber reinforced composites

Composite materials are widely used in temperature fluctuating environments, which make these materials highly prone to cracking. The cracking phenomenon is a result of high thermal stresses that are generated by the mismatch in properties of the composite constituents, particularly the mismatch in the thermal expansion coefficient. The main objective of this study is to understand the micromechanics of such a phenomenon. The problem has been investigated using the finite element method (FEM). The analyses were performed utilizing 3-D prism and axisymmetric models. Hexagonal fiber packing of unidirectional composites was considered. The dimensions of the models were assumed such that the models could provide sufficient information on the behavior near the free surface as well as the interior of fiber composites. Properties of the constituents were considered to be temperature dependent. The elasto-plastic and visco-elastic characteristics of the materials were also included. The transient thermal analysis of the models showed that, for most practical applications, the temperature gradient in the composite constituents has minor effects on the stresses generated. Therefore, several stress analyses were performed assuming a uniformly changing temperature throughout the composite. The elastic analysis of thermal stresses and deformations showed high radial and hoop stress concentrations occurring at the fiber end on the free surface. This is contrary to the shear-lag theorem, which assumes that these stress components are negligible. An overlapping hypothesis, based on the deformation of the fiber and matrix, is proposed to explain such high radial and hoop stresses. Using regular FEM elements, it was concluded that the stresses are singular in nature. The stress singularity was numerically investigated and found to be of the type r -á with á being dependent on the material properties but having a value close to 1/3. The elasto-visco-plastic behavior of composites was also analyzed. Large plastic strains were localized at the fiber end even for a small temperature change. Creep effects that were significant at elevated temperatures brought about some stress relaxation during the manufacturing process. Thermally induced stress concentration in composites can be controlled, to some extent, by changing the geometry of the free surface. The analysis of such effects indicated that reduction of the contact angle between the fiber and the matrix on the fire surface reduced the high radial and hoop stress magnitudes. Also, the influence of covering the free surface of the composite with a thin layer of matrix-like material was studied. The magnitudes of the radial and hoop stress components were substantially reduced. The case when the cover and the composite are made in separate stages (two-stage covering), was also studied. Based on the analysis, effective and practical ways of applying the cover are recommended. To verify the effects of the covering process, experiments were conducted on large-scale laboratory-made composite samples. The samples with the free surface covered with a thin layer of matrix-like material showed no trace of cracking or fiber/matrix debonding even after 1000 thermal cycles. On the other hand, in the samples without cover, exposed to identical thermal cycling, numerous matrix cracks and extensive fiber/matrix debonding were observed

Motor simulation without motor expertise: enhanced corticospinal excitability in visually experienced dance spectators

The human “mirror-system” is suggested to play a crucial role in action observation and execution, and is characterized by activity in the premotor and parietal cortices during the passive observation of movements. The previous motor experience of the observer has been shown to enhance the activity in this network. Yet visual experience could also have a determinant influence when watching more complex actions, as in dance performances. Here we tested the impact visual experience has on motor simulation when watching dance, by measuring changes in corticospinal excitability. We also tested the effects of empathic abilities. To fully match the participants' long-term visual experience with the present experimental setting, we used three live solo dance performances: ballet, Indian dance, and non-dance. Participants were either frequent dance spectators of ballet or Indian dance, or “novices” who never watched dance. None of the spectators had been physically trained in these dance styles. Transcranial magnetic stimulation was used to measure corticospinal excitability by means of motor-evoked potentials (MEPs) in both the hand and the arm, because the hand is specifically used in Indian dance and the arm is frequently engaged in ballet dance movements. We observed that frequent ballet spectators showed larger MEP amplitudes in the arm muscles when watching ballet compared to when they watched other performances. We also found that the higher Indian dance spectators scored on the fantasy subscale of the Interpersonal Reactivity Index, the larger their MEPs were in the arms when watching Indian dance. Our results show that even without physical training, corticospinal excitability can be enhanced as a function of either visual experience or the tendency to imaginatively transpose oneself into fictional characters. We suggest that spectators covertly simulate the movements for which they have acquired visual experience, and that empathic abilities heighten motor resonance during dance observation

Production of single cell protein from stickwater of kilka fish meal factory using Lactobacillus acidophilus and Aspergillus niger

We investigated production of single cell protein (SCP) from stickwater of kilka fish meal factory as medium using Lactobacillus acidophilus and Aspergillus niger. Stickwater was used instead of the standard media of bacterium and fungus in a batch culture method. Amount of biomass, COD, RNA and protein in the bacterium and fungus in control and stickwater treatments were investigated. In maximum growth time, amino acids profile of the bacterium and fungus were measured and compared between treatments. Bacterial biomass production in the control and stickwater treatments were 3.16 and 5.12g/l, COD reduction was 33270 and 53330mg/l, the measured RNA were 15.27% and 15.04%, the amount of protein were 71.13% and 68.37%, respectively. The difference between bacterium and fungus biomass production was slight. We found that the amount of the fungus biomass in control and stickwater were 6.31 and 7.28g/l, COD reduction were 47800 and 55200mg/l, RNA was 9.36% and 9.09%, the amount of protein were 51.36% and 48.66%, respectively. In both bacterium and fungus, the maximum and minimum amount of amino acid of the control and stickwater was glutamic acid and methionin. The amount of methionin in bacterium was not different with fish meal and FAO reference and in fungus was a little lower than FAO reference. According to the results, application of pure stickwater was suitable for productionof Lactobacillus acidophilus and Aspergillus niger

Gelatine properties made from skin and bone of Lizard fish (Saurida tumbil)

Type-A gelatine was extracted from skins and bones of lizard fish and analysed for functional and chemical properties. Bloom gel strength was 159.14±14 and 135±7.9g, respectively, for skin and bone gelatines compared to 2243±7.7 for porcine gelatine (P<0.05). Gelatine from skin and bone exhibited higher viscosity and lower setting temperature than porcine gelatine. Skin gelatine had higher amino acid composition than bone gelatine, with a total amino acid content of about 21.71% and 19.83% for skin and bone respectively. Alpha chains were higher than pi and 6 components in skin and bone gelatine. Both bone and skin gelatines contained peptides with low molecular weight (<a). The differences in functional properties between the skin and bone gelatines appeared to be related to differences in amino acid composition and molecular weight distribution of the gelatines

Effects of using Artemia urmiana enriched with N-3 HUFA in first feeding of rainbow trout (Oncorhynchus mykiss) larvae

Effects of using n-3 HUFA-enriched Artemia and non-enriched Artemia as the starter food for growth and survival of rainbow trout larvae compared to commercial concentrated food were investigated in this study. The larvae with average weight of 92.9 mg were fed for 20 days with four food treatments included of commercial concentrated food, newly hatched Artemia, enriched Artemia, and mixture of enriched Artemia and concentrated food. At the end of experiment, the highest weight gain percentage was 104.4% in those larvae fed with enriched Artemia (p< 0.05). The highest survival rate was 96.5 % observed in larvae fed with mixture of enriched Artemia and commercial concentrated food (P<0.05). Larvae of third treatment that were fed with enriched Artemia with a survival rate of 98.9 %±1.9 under stress condition of low pH and survival rate of 66.5%±3.7 under stress condition of higher pH in rearing environment, were the most resistant larvae against stress resulting from pH fluctuation (P<0.05). Meanwhile the highest resistance against stress, resulting from temperature changes, was seen in larvae of the third and fourth treatment with survival rate of 77.8% at 24°C respectively

The effect of phytase enzyme on apparent digestibility of four plant feedstuffs fed to rainbow trout (Oncorhynchus mykiss)

This study was conducted to determine the effect of phytase enzyme on phosphorus, protein, fat, dry matter and energy digestibility of four practical plant feed stuffs wheat meal (WM), corn meal (CM), wheat bran (WB), rice bran (RB) in rainbow trout feeding. Five diets containing of one reference diet include of fish meal, soybean meal and meat flour, were prepared. Feed stuffs were mixing 75% of base diet with 25% of WM or CM and 85% of based diet with 15% of WB or RB with similar gross energy. Chromic oxide was added at 0.5% of the diet and used as an indigestible marker. A phytase solution was sprayed post pelleting on the all diets at minimum concentration of fat 1000 phytase units per Kg (FTU/Kg) dry diets. Experiment was done in two cubic metric tanks that were filled with 500 liters water. Maximum and minimum temperature, oxygen and pH were 15 and 18 degree C, 8 and 6.8 mg/l and 7.7 and 7.5 respectively. Results showed that phytase had not significantly effect on amount of bone phosphorus and protein digestibility (p>0.05), but the amount of these indexes were increased with phytase supplementation. Moreover phytase significantly improved digestibility of dry matter. Results also showed that kind of diets had different effects on the nutrition digestibility. diets had not significantly effects (p>0.05) on the amount of bone phosphorus and protein digestibility but totally diets containing of WM, CM, WB and RB had better nutrition digestibility respectively that can use them in Rainbow trout diet due to their availability

Effects of salinity on growth and survival of Indian white shrimp (Penaeus indicus)

This study was conducted the optimum salinity for culture of White Indian shrimp juvenile (Penaeus indicus) in Bandar Emam Khomeini fisheries research station in summer 2002. Five levels of salinity (10, 20, 30, 40 and 50 ppt) with four replicates were used in this trial. 35 specimen of White Indian shrimp juvenile (PL35) with mean weight of 0.26:t0.024g have been cultured for 60 days in 300 liter fiberglass tanks that each tank was filled with 200 liters water and stocked with 20 shrimp juveniles for estimating the growth and survival rates in different salinities. Results showed that salinity was significantly (P<0.05) affected on growth and survival of P. indicus juveniles. Highest increase in mean weight and the maximum final mean weight of juvenile, highest increase in carapace length and maximum C.L. and also the lowest FCR observed in 30 ppt salinity. According to the obtained results, it can be suggested that the optimal salinity for culture of White Indian shrimp is between 20 and 30ppm