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

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

Effect of diet composition on growth performance, hepatic metabolism and antioxidant activities in Siberian sturgeon (Acipenser baerii, Brandt, 1869) submitted to starvation and refeeding

Many fish species undergo natural starvation periods. Adaptation to starvation is possible through the activation of behavioral, biochemical and physiological mechanisms. Knowledge of the effect of dietary nutrients on the intermediary metabolism during starvation and refeeding can be useful to improve fish health and optimize aquaculture production. To analyze the effect of dietary nutrients on liver metabolism of Siberian sturgeon (Acipenser baerii) submitted to starvation and refeeding, four isoenergetic diets differing in nutrient composition were designed: LP-St (38 % protein, 12 % lipid, 36 % carbohydrate), HP-St (44 % protein, 10 % lipid, 30 % carbohydrate), LP-L (38 % protein, 18 % lipid, 25 % carbohydrate) and HP-L (44 % protein, 16 % lipid, 22 % carbohydrate). Four groups of fish were fed 3 weeks to satiety with the corresponding diet, starved for 2 weeks and then refed 5 weeks to satiety on the same diet. Starvation mobilized the hepatic lipid store to a greater extent than glycogen. Starvation increased superoxide dismutase activity irrespective of the diet, while low protein diets (LP-St and LP-L) increased catalase activity. The oxidative damage decreased after 5 weeks of refeeding. Refeeding the starved fish on the HP-St diet promoted the greatest growth performance. In addition to report for the first time the effect of diet composition on growth, liver composition and antioxidant activities in Siberian sturgeon submitted to starvation and refeeding, our findings suggest that refeeding on HP-St diet stimulated the use of dietary carbohydrates and allowed a protein sparing effect in Siberian sturgeon

Cerium oxide nanoparticle modulates hepatic damage, inflammatory and oxidative stress biomarkers in a dose-dependent manner: an in vivo study of rat liver

Objective (s): Cerium oxide nanoparticles nanoceria (CeNPs) is a novel nanoparticle that has great potential for the treatment of various diseases. This study aimed to investigate the effects of CeNPs on oxidative stress biomarkers in the liver of male rats. Materials and Methods: Twenty-four male Wistar rats were equally distributed into 4 groups (n=6/each). The first group was controlled and the next three groups received CeNPs (15, 30 and 60 mg/kg/day), with an intraperitoneal injection (IP) for 7 days. After treatment, serum and liver tissue was isolated. ALT and AST concentration, total antioxidant capacity (TAC), total thiol molecules (TTM), interleukin 17 (IL-17), nitric oxide (NO) and TNF-α were measured. Results: CeNPs 30, 60 mg/kg caused a significant increased NO (P=0.03, P=0.001), TNF-α (P=0.03, P=0.01) and IL-17 (P=0.04, P=0.01) levels, compared with the control group. Also CeNPs caused a decrease in the TTM (P=0.002) and increased MDA (P=0.04) in 60 mg/kg group compared to the control group. CeNPs 15 mg/kg significantly suppressed mainly the increase in plasma activities of aminotransferases (ALT (P=0.001), AST (P=0.01)), and liver IL-17 (P=0.01) and NO (P=0.02) concentrations compared to the control group. Conclusion: These results suggest that the effects of CeNPs are dose-dependent and at 15 mg/kg dose, it may have protective effects. Moreover, CeNPs in 30 and 60mg/kg doses showed immunotoxicity and oxidative effects in the liver

Anticancer properties of chitosan on osteocarcinoma , breast cancer and cervical cancer cell lines

Background: Cancer refers to the abnormal growth of cells and is still the most common cause of morbidity in world. The purpose of this study was to determine cytotoxicity effect of high molecular weight (HMWC) and low molecular weight of chitosan (LMWC) on three cancerous cell lines MCF-7, HeLa and Saos-2 with different histological origin. Methods: The anticancer property of two types of chitosan on three cancerous cell lines and human fibroblast as normal cell was evaluated by cytotoxic activity and apoptosis induction .The cells were treated by different concentration of chitosan and viability was determined by MTT assay after 24, 48 and 72 h .Mode of death was determined by Annexin V staining assay for apoptosis and analyzed by flow cytometry. Results: While both types of chitosan were more efficient in inhibiting cell proliferation of three cancerous cell lines, fibroblast cells showed somehow more compatibility with chitosan .Viability of cells was reduced concentration-dependently to 70-90 of the untreated cells as control. There were no significant differences between the effect of both types of chitosan on all cell lines. Flow cytometry analysis showed necrosis more observable with MCF7 while the apoptosis pattern of death was more in Saos-2 and HeLa. Also higher viability with both types of chitosan was seen in fibroblast as normal cells. Conclusion: While chitosan is compatible with normal diploid fibroblast cells, it shows anticancerous effect against 3 cancerous cell lines. Furthermore, it seems that the molecular weight of chitosan does not affect its anticancerous property

Effect of metabolic genetic variants on long-term disease comorbidity in patients with type 2 diabetes

Underlying genetic determinants contribute to developing type 2 diabetes (T2D) future diseases. The present study aimed to identify which genetic variants are associated with the incident of the major T2D co-morbid disease. First, we conducted a discovery study by investigating the genetic associations of comorbid diseases within the framework of the Utrecht Cardiovascular Pharmacogenetic studies by turning information of > 25 years follow-up data of 1237 subjects whom were genotyped and included in the discovery study. We performed Cox proportional-hazards regression to examine associations between genetic variants and comorbid diseases including cardiovascular diseases (CVD), chronic eye disease, cancer, neurologic diseases and chronic kidney disease. Secondly, we replicated our findings in two independent cohorts consisting of 1041 subjects. Finally, we performed a meta-analysis by combining the discovery and two replication cohorts. We ascertained 390 (39.7%) incident cases of CVD, 182 (16.2%) of chronic eye disease, 155 (13.8%) of cancer, 31 (2.7%) of neurologic disease and 13 (1.1%) of chronic kidney disease during a median follow-up of 10.2 years. In the discovery study, we identified a total of 39 Single Nucleotide Polymorphisms (SNPs) associated with comorbid diseases. The replication study, confirmed that rs1870849 and rs8051326 may play a role in the incidence of chronic eye disease in T2D patients. Half of patients developed at least one comorbid disease, with CVD occurring most often and earliest followed by chronic eye disease. Further research is needed to confirm the associations of two associated SNPs with chronic eye disease in T2D

Collection, identification of Iranian fish parasites for “Iranian parasitology Museum”

Abstract: Identification and classification of aquatic parasites are more important by the day. Aquaculture development are faced with parasites previously "not pathogenic in normal conditions, but under certain conditions bacame diseases and have caused heavy losses to the aquaculture farms. The results of these studies recognize the importance of parasites in fish production has clear economic value. Before any action for economic aquatic breeding the parasites that can infect the fish have been identified and methods of control will be drawn. The current project is a part (the fishes) of the project Parasitology Museum in the Faculty of Veterinary medicine of Tehran University. In the first phase of the project, it was planned the fish parasites from different regions of the country were collected and the Iranian Fish Parasites Data Base has also set up. Required experts and various specialties were organized for implementation an recognation of the collected parasitese. The province executive and coordination necessary and the methods of sampling were discussed after a day of training workshop was held at the Faculty of Veterinary medicine of Tehran University. Due to the lack of funds needed to coordinate the implementation, it was conducted that the parasite specimens collected from other projects. In the first phase of projects 261 parasites various have been sent. Collected samples received a temporary code and announced. In the laboratory the specimens categoried and the shape designed and finally the consultants send the final identification of the parasites. Posted parasites according to the latest international standards are maintained. Each parasite has a unique code that represents the name of the sender, verification of the final consultant, host and fishing region. Simultaneously, reported fish parasites from 1327 AD (1949 AD) were collected to create a database, they classified to be placed on the site inPersian and English. Fish parasites that have been reported are available in four types: final report of the research projects conducted at research centers and universities, student theses, abstracts published in scientific conferences and finally "published in national and international research journals. “Iranian fish parasitesd database” included: Founders and Pioneers Monument, Iranian fish parasite fauna, History, Search, Resources, Executive Committee, links, News. Researchers can search through the five “key words”: the name of the parasite, the parasite class branch, region or provincial fishing, infected of host organ. After achieving the desired list of parasites, descriptions, and specifications can be observe. The resource section lists some of the articles published and will be visible as a “pdf”

Effect of metabolic genetic variants on long-term disease comorbidity in patients with type 2 diabetes

Underlying genetic determinants contribute to developing type 2 diabetes (T2D) future diseases. The present study aimed to identify which genetic variants are associated with the incident of the major T2D co-morbid disease. First, we conducted a discovery study by investigating the genetic associations of comorbid diseases within the framework of the Utrecht Cardiovascular Pharmacogenetic studies by turning information of > 25 years follow-up data of 1237 subjects whom were genotyped and included in the discovery study. We performed Cox proportional-hazards regression to examine associations between genetic variants and comorbid diseases including cardiovascular diseases (CVD), chronic eye disease, cancer, neurologic diseases and chronic kidney disease. Secondly, we replicated our findings in two independent cohorts consisting of 1041 subjects. Finally, we performed a meta-analysis by combining the discovery and two replication cohorts. We ascertained 390 (39.7%) incident cases of CVD, 182 (16.2%) of chronic eye disease, 155 (13.8%) of cancer, 31 (2.7%) of neurologic disease and 13 (1.1%) of chronic kidney disease during a median follow-up of 10.2 years. In the discovery study, we identified a total of 39 Single Nucleotide Polymorphisms (SNPs) associated with comorbid diseases. The replication study, confirmed that rs1870849 and rs8051326 may play a role in the incidence of chronic eye disease in T2D patients. Half of patients developed at least one comorbid disease, with CVD occurring most often and earliest followed by chronic eye disease. Further research is needed to confirm the associations of two associated SNPs with chronic eye disease in T2D