In recent years, the application of composite materials in aircraft and space vehicle structural components has become increasingly popular. Preventing failure of composite structural systems has been an important issue in engineering design. Due to the lack of through-the-thickness reinforcement, structures made from laminated composite materials and adhesively bonded joints are highly susceptible to failure caused by interfacial crack initiation and growth. The delamination phenomenon in a laminated composite structure may reduce the structural stiffness and strength and redistribute the load in a way that the structural failure is delayed or may lead to structural collapse. As the most application of these materials is in space structures, the failure of a composite structure component can lead to a catastrophic failure of the structure as whole, thus, an accurate quantitative measurement and understanding of damage and determination of remaining useful service life plays a vital role in prediction of failure of such structures. To do so, first, the fracture properties of material should be determined. To calculate these properties, there are several experimental methods. Among them, the modified ARCAN test is one of the most apposite methods for in-plane mixed-mode loading condition. In this investigation, a new SPECIMEN has been introduced to reduce cost and problems concerning utilization of adhesively. The critical fracture parameters of carbon-epoxy woven laminated composite material, which is of paramount materials in industry, in room temperatures is calculated both with experimental and numerical methods. These parameters include the critical stress intensity factors and critical strain energy release rate on crack tip. The geometric correction factors for modified ARCAN test are calculated with a 2D finite element analysis. Finally, the values of critical fracture properties are calculated using these geometric modification factors and critical loads generated via experimental procedure.

ABS (Acrylonitrile butadiene styrene) polymeric material is widely used in different industries. The increasing demand of ABS for different applications has required a thorough understanding of its fracture behavior. This paper investigates mixed-mode fracture behavior of ABS polymeric material based on experimental and numerical analyses. Experiments were conducted on modified ARCAN set-up. By varying the loading angle from 0° to 90°, pure mode-I, pure mode-II and a wide range of mixed-mode data were obtained experimentally. Also, finite element analysis was carried out for different loading conditions in order to determine correction factors needed for fracture toughness calculations. In this study viscoelastic behavior was considered for ABS SPECIMENs. Therefore, it is expected that the values of stress intensity factors to be time (frequency) dependent. Consequently, based on correspondence principle and assuming linear elastic fracture mechanics, time dependent mixed-mode fracture toughness for ABS polymeric material was determined. Results indicated that in all loading conditions, values of fracture toughness decrease while time increases in stress relaxation test, until a specific time. Accordingly, it can be resulted that the minimum value of fracture toughness of ABS, which plays a crucial role in various applications, does not appear in the first instance of loading.

Eucalyptus globulus is one of the most important and fast growing species used in afforestation for wood and paper industries, essence and honey production. Due to the graft process incompatibility, as well as hard proliferation of roots in adult tissues, in this study the plant reproduction has been carried out through micropropagation methods Vegetative lateral buds were collected from selected adult and seedling in northern forests in different seasons and disinfected with seveal solutions of mercury chloride and sodium hypochlorite in different concentrations and times intervals depending on season and plant genotype. Then, the effects of five hormonal treatments, including different concentrations of cytokinins and auxines (0 to 1 mgl-1) on developing branches from micropropagation and seedling buds were studied in three replicated experiments with a statistical variance analysis based on a completely randomized design. Different characteristics such as shoot length, proliferation and greenish coefficient of shoot were measured. The most appropriate method of sterilization was immersion of buds in solution of 70% ethanol for 30 seconds and then in 0.5 % mercury chloride solution for 10 minutes in spring for mature SPECIMEN buds and 0.1 % mercuric chloride solution for 6 minutes in spring for seedling buds. The best proliferation of shoots from mature buds was achieved in MS medium (half strength Nitrate) containing 1 mgl-1 Zeatin and 0.2 mgl-1 IAA and for shoots from seedling buds was occurred at the same medium containing 0.5 mgl-1 BAP, 0.2 mgl-1 Kin, 0.1 mgl-1 GA3 and 0.01 mgl-1 IBA. Root germination in shoots with a length of 1.5 cm from the mature and seedling sources occurred in 1.4 concentration medium of MS macro elements and 0.5 mgl-1 of combined auxin hormones of NAA and IBA. After gradual adaptation of plantlets under greenhouse conditions, they were transferred and established successfully in soil.