Advanced Materials Research Vols. 264-265

Abstract: Composites based on polypropylene and glass fiber were prepared by melt mixing. The effect of magnesium hydroxide as a flame retardant on flammability and thermal behavior of glass fiber/polypropylene composites was studied. Ratio of glass fiber to magnesium hydroxide in each composite sample was varied. Maleic anhydride grafted polypropylene (MAPP) was used to improve the interfacial adhesion between polypropylene and fillers. Flammability and thermal behavior of the composites were examined using a horizontal burning test and a thermogravimetric analyzer, respectively. Morphology and mechanical properties of the composites were also investigated. Magnesium hydroxide reduced the flammability while improved thermal decomposition temperature of the polypropylene composites. However, magnesium hydroxide showed a negative impact on the tensile strength of the polypropylene composites.

Abstract: A computational approach based on finite element analysis (FEA) for integrated durability assessment in an automotive component is presented. For further time saving related durability evaluation, the objective of this research is to investigate how accurately a road data history can be edited. A road data has been collected using a fatigue data acquisition system. A substantial compression for automotive lower suspension arm fatigue damage was performed for the purpose of accelerated fatigue data analysis. FEA was then used to estimate the fatigue life for the original and the edited data using two different strain life models. The original road data has been successfully edited for the purpose of damage predicting using FEA with a big difference in the software spending time for the component fatigue life prediction. As a result, the editing method was shown to be useful for summarising long histories and resulting in significantly shorter analysis with presenting the predicted amount of the fatigue damage as the original histories. As a consequence of application for automotive lower suspension arm, this technique can be applied in performing a fatigue history editing, especially in compression of data set.

Abstract: The demand of today’s and future spacecrafts for a stable platform for critical payloads is the driving force behind the coefficient of thermal expansion (CTE) measurement of different aerospace materials. The CTE of a composite is different from that given by a simple rule of mixtures. This is because of the presence of reinforcement. The expansion coefficient of reinforcement is less than that of the matrix which introduces a mechanical constraint on the matrix. The degree of constraint is also dependent on the nature of the reinforcement. It is important to point out that interface can exert some influence on the value of CTE, especially for very small particle size. In addition to the interface, the CTE of particle reinforced metal matrix composites (MMCs) is affected by several other factors. To cater the needs of various requirements in a spacecraft making, a wide variety of materials are used. Besides, the indigenization efforts and development of new materials for space-use emphasizes the measurement of CTE before their actual use. Stir casting technique was used to fabricate composites containing Si Cp as reinforcements and special thermo physical properties of the material are found. CTE of the composites are measured by TMA. The experiments have been carried out in the temperature range -1400 C to 5750 C.

Abstract: Various materials are used to achieve a good “Thermal Control System” (TCS) of spacecraft. The performance of the TCS totally depends upon the thermal behaviour of the materials used in the elements of TCS. The measurements of the thermal properties of materials are fundamental for better understanding of the thermal design. Differential Scanning Calorimetry (DSC) is the most widely used thermal technique for obtaining a wealth of information about a material, especially for the specific heat measurement of a material. Stir casting technique was used to fabricate the 7075 aluminum alloy and 7075 Al / SiCp composites. The heat flow response is recorded as a function of actual sample temperature range from -1000 C to 4000 C. Specific heat characteristics of 7075 Al reinforced with different volume fraction of silicon carbide composites fabricated by stir casting method was analyzed.

Abstract: For producing high-quality components through a nanoimprint lithographic (NIL) process, it is important to measure quantitative properties about the behavior of polymers with regard to thermal-nano variation. NanoScale indents can be used as cells for molecular electronics and drug delivery and slots for integration into nanodevices; they can be used to detect defects for tailoring the structure and properties. This study evaluates the mechanical characteristics of polymers, such as Polymethylmetacrylate (PMMA) and COP (Cyclo-olefin Polymer), at high temperatures for the manufacture of nano/micro-sized polymers through thermal nanoindentation at high temperatures. At high temperatures, the mechanical properties of polymers exhibit extreme variation. When a polymer is heated, it becomes softer than at room temperature. In this regard, it is especially important to study the mechanical properties of polymers at high temperatures.

Abstract: At present, welding technology is not only emphasized in the development of manufacturing technology but also application is expanding. In these systems, application of SUS as high-temperature material which is used for special purposes is attempted, and improvement of manufacturing technologies bear watching together with increase of using rate. Specifically, Wings with surface of three-dimensional shape usually applied to Fastener with purpose of lightweight. However, due to development of welding technology, methods of existing assembly tend to be replaced by welding, recently. Specifically, if laser welding techniques is applied, it minimizes heat-affected zone than other welding techniques. However, in the case of these special welding, residual stress is raised, and it fatally affects fatigue life. In order to remove residual stress and delay effect of fatigue life, shot-peening is executed; it executes shot-peening and verifies delayed effects of fatigue life. The intention of this study is to obtain the optimal conditions of shot-peening

Abstract: The hybrid composites were fabricated by taking cheaply available empty fruit bunch fibers and jute fibers trilayers as reinforcement in epoxy matrix using simple hand lay-up-technique. Thermal, mechanical and morphological properties were characterized. The notched izod impact strength of most hybrids increased with respect to the virgin matrix. The laminates coupled with 2-Hydoxy ethyl acrylate (HEA) showed better impact properties than the one without coupling agent. The addition of fibers and coupling agent considerably improved the thermal stability (i.e., decomposition and residue content) of the hybrids. The thermal properties measured by thermogravimetric analysis (TGA) showed that fibres and coupling agents improved thermal properties. The impact fractured composite specimens were analyzed using field emission scanning electron microscopy (FESEM) to know the morphological behaviour.

Abstract: The solid I section beam with creating hexagonal cavities (openings) has numerous advantages over conventional rolled sections. As they are light weight, strong, cheap and elegant. The opening in the web simplifies the work of the installer and the electrician, since taking pipes across beams presents no problems. A cellular beam (circular openings) is the modern version of the traditional castellated beam. The beam comprises pronouncedly asymmetric cellular tees, to provide a wide bearing for either pre-cast units or a profiled metal deck. The elastic finite element analysis of castellated beam and cellular beam is carried out to understand its behaviour under load. The failure pattern and stresses developed under same loading condition are studied. Based on the various modes of failure, the applicable methods of analysis are studied which includes plastic analysis, mid post yielding and buckling analysis. From the previous experimental results, one beam is selected and analyzed. Then the no of openings is varied as 2, 4 and 6 in selected beam. The shape of opening is considered as hexagonal and circular of same cross sectional area. The support conditions are considered as fixed, hinged and roller. Overall 18 cases are studied for same central point load and span with change of spacing of openings. The maximum Deflection and the maximum VonMises stress are worked out. The comparative study is carried out using software for finite element analysis ANSYS.

Abstract: This work studied the theoretical solution for axisymmetric steady-state mechanical and thermal stresses in hollow functionally graded spheres with respect to heat source. The material properties of the FG sphere change continuously across the thickness direction according to the power functions of radial direction. The steady-state temperature, displacements, and stresses are derived due to the general mechanical and thermal boundary conditions as function of radial and circumferential directions. The temperature and Navier equations are solved analytically, using Taylor and Legendre series. With increasing the power law indices the temperature distribution due to heat source is decreased. Circumferential stress and radial displacement due to heat source are decreased as the power law index increases.

Abstract: An improved understanding of fatigue behavior of a cast aluminum alloy (2-AS5U3G-Y35) in very high cycle regime was developed through ultrasonic fatigue test in axial and torsion loading, cyclic loading in axial and torsion at 35 Hz and 20kHz with R=-1 was used respectively to demonstrate the effect of loading condition. S-N curves obtained show that fatigue failure occurred in range of 105 -1010 cycles in axial or torsion loading, the asymptote of S-N curve is inclined gently, but no fatigue limit under torsion and axial loading condition. Fatigue fracture surface shows fatigue crack essentially initiated from the surface of the specimens subjected to cyclic torsion load, it is different from the fatigue fracture characteristic in axial loading which fatigue crack initiate from subsurface defect in very high cycle regime. Fatigue initiation is on the maximum shear plane, the overall crack orientation is observed on a typical spiral 45° to the fracture plane, which is the maximum principle stress plane, however, shear strip are very clear in the torsion fatigue fracture surface, the torsion fracture is actually in shear fracture.