Development of Computer Models for the Assessment of Foreign Body Impact Events on Composite Structures

The objective of this project was to model the 5-3/4 inch pressure vessels used on the NASA RTOP program in an attempt to learn more about how impact damage forms and what are the residual effects of the resulting damage. A global-local finite element model was developed for the bottle and the states of stress in the bottles were determined down to the constituent level. The experimental data that was generated on the NASA RTOP program was not in a form that enabled the model developed under this grant to be correlated with the experimental data. As a result of this exercise it is recommended that an experimental program be designed using statistical design of experiment techniques to generate data that can be used to isolate the phenomenon that control the formation of impact damage. This data should include residual property determinations so that models for post impact structural integrity can be developed. It is also recommended that the global-local methodology be integrated directly into the finite element code. This will require considerable code development

Damage accumulation in closed cross-section, laminated, composite structures

The need for safe, lightweight, less expensive, and more reliable launch vehicle components is being driven by the competitiveness of the commercial launch market. The United States has lost 2/3 of the commercial lunch market to Europe. As low cost Russian and Chinese vehicles become available, the US market share could be reduced even further. This international climate is driving the Single Stage To Orbit (SSTO) program at NASA. The goal of the SSTO program is to radically reduce the cost of safe, routine transportation to and from space with a totally reusable launch vehicle designed for low-cost aircraft-like operations. Achieving this goal will require more efficient uses of materials. Composite materials can provide this program with the material and structural efficiencies needed to stay competitive in the international launch market place. In satellite systems the high specific properties, design flexibility, improved corrosion and wear resistance, increased fatigue life, and low coefficient of thermal expansion that are characteristic of composite materials can all be used to improve the overall satellite performance. Some of the satellites that may be able to take advantage of these performance characteristics are the Tethered Satellite Systems (TOSCIFER, AIRSEDS, TSS2, SEDS1, and SEDS2), AXAF, GRO, and the next generation Hubble Space Telescope. These materials can also be utilized in projects at the NASAIMSFC Space Optics Technology and System Center of Excellence. The successful implementation of composite materials requires accurate performance characterization. Materials characterization data for composite materials is typically generated using flat coupons of finite width. At the free edge of these coupons the stress state is exacerbated by the presence of stiffness and geometric discontinuities. The exacerbated stress state has been shown to dominate the damage accumulation in these materials and to have a profound affect on the material constants. Space structures typically have closed cross-sections, absent of free edges. As a result, composite material characterization data generated using finite width flat specimens does not accurately reflect the performance of the composite materials used in a closed cross-section structural configuration. Several investigators have recognized the need to develop characterization techniques for composite materials in closed cross-sectioned structures. In these investigations test methods were developed and cylindrical specimens were evaluated. The behavior of the cylindrical specimens were observed to depart from behavior typical of flat coupons. However, no attempts were made to identify and monitor the progression of damage in these cylindrical specimens during loading. The identification and monitoring of damage is fundamental to the characterization of composite materials in closed cross-section configurations. In the study reported here, a closed cross-sectioned test method was developed to monitor damage progression in 2 in. diameter cylindrical specimens and 1.5 in. finite width flat coupons subjected to quasi-static, tensile loading conditions. Damage in these specimen configurations was monitored using pulse echo ultrasonic, acoustic emission, and X-ray techniques

Finite Element Modeling of the Thermographic Inspection for Composite Materials

The performance of composite materials is dependent on the constituent materials selected, material structural geometry, and the fabrication process. Flaws can form in composite materials as a result of the fabrication process, handling in the manufacturing environment, and exposure in the service environment to anomalous activity. Often these flaws show no indication on the surface of the material while having the potential of substantially degrading the integrity of the composite structure. For this reason it is important to have available inspection techniques that can reliably detect sub-surface defects such as inter-ply disbonds, inter-ply cracks, porosity, and density changes caused by variations in fiber volume content. Many non-destructive evaluation techniques (NDE) are capable of detecting sub-surface flaws in composite materials. These include shearography, video image correlation, ultrasonic, acoustic emissions, and X-ray. The difficulty with most of these techniques is that they are time consuming and often difficult to apply to full scale structures. An NDE technique that appears to have the capability to quickly and easily detect flaws in composite structure is thermography. This technique uses heat to detect flaws. Heat is applied to the surface of a structure with the use of a heat lamp or heat gun. A thermographic camera is then pointed at the surface and records the surface temperature as the composite structure cools. Flaws in the material will cause the thermal-mechanical material response to change. Thus, the surface over an area where a flaw is present will cool differently than regions where flaws do not exist. This paper discusses the effort made to thermo-mechanically model the thermography process. First the material properties and physical parameters used in the model will be explained. This will be followed by a detailed discussion of the finite element model used. Finally, the result of the model will be summarized along with recommendations for future work

Foreign body impact event damage formation in composite structures

This report discusses a methodology that can be used to assess the effect of foreign body impacts on composite structural integrity. The described effort focuses on modeling the effect of a central impact on a 5 3/4 inch filament wound test article. The discussion will commence with details of the material modeling that was used to establish the input properties for the analytical model. This discussion is followed by an overview of the impact assessment methodology. The progress on this effort to date is reviewed along with a discussion of tasks that have yet to be completed

Environmental protection through nuclear energy

Environmental protection through implementation of green energies is progressively becoming a daily reality. Numerous sources of green energy were introduced in recent years. Although this process initially started with difficulties, it finally resulted in an acceleration and implementation of new green energy technologies. Nonetheless, new major obstacles are emerging. The most worldwide difficult obstacle encountered, especially for wind and photovoltaic electric power plants, is the not regular and predictable green energy production. This study proposes solutions designed to solve this unpleasant aspect of irregular production of green energy. The basic idea refers to the construction of specially designed nuclear power plants acting as energy buffers. Nuclear power plants, indeed, may behave as proper energy buffers able to work to a minimum capacity when the green energy (i.e., wind power or PV) is steadily produced (namely, when the energy generated by the turbines or PV panels is at full constant capacity) but that can also run at progressively increased capacities when the wind or solar energy production reduces or stops. The work get two major contributions: 1-propose to the achievement of an energy buffer using nuclear power plants (for the moment on nuclear fission); 2-shows some theoretical aspects important needed to carry out the reaction of the fusion

Something about the Balancing of Thermal Motors

Internal combustion engines in line (regardless of whether the work in four-stroke engines and two-stroke engines Otto cycle engines, diesel and Lenoir) are, in general, the most used. Their problem of balancing is extremely important for their operation is correct. There are two possible types of balancing: Static and dynamic balance. The total static to make sure that the sum of the forces of inertia of a mechanism to be zero. There are also a static balance partial. Dynamic balance means to cancel all the moments (load) inertia of the mechanism. A way of the design of an engine in a straight line is that the difference between the crank 180 [°] or 120 [°]. A different type of construction of the engine is the engine with the cylinders in the opposite line, called "cylinder sportsmen". In this type of engine (regardless of their position, which is most often vertical) for engines with two cylinders, one has a static balance total and an imbalance in the dynamic. Similar to the model of the earth concentrated in rotation movement are resolved and load balancing shafts rotating parts. An important way to reduce losses of heat engines is how to achieve a better balance. The methods may be used in equal measure and on engines with external combustion, type Stirling or Watt

corrigendum kinematics and forces to a new model forging manipulator

Correction to: American Journal of Applied Sciences http://doi.org/10.3844/10.3844/ajassp.2017.60.80, published online January 3, 2017; updated April 29, 2019 The original version of this Article contained Mr. MirMilad Mirsayar as a co-author. Mr. Mirsayar has not contributed to the preparation and publication of this manuscript. These errors have now been corrected in the HTML and PDF versions of the Article. http://doi.org/10.3844/10.3844/ajassp.2017.60.80

Something about the Balancing of Thermal Motors

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Using Al3+ to Tailor Graphene Oxide Nanochannels: Impact on Membrane Stability and Permeability

Graphene oxide (GO) membranes, which form from the lamination of GO sheets, attract much attention due to their unique nanochannels. There is much interest in controlling the nanochannel structures and improving the aqueous stability of GO membranes so they can be effectively used in separation and filtration applications. This study employed a simple yet effective method of introducing trivalent aluminum cations to a GO sheet solution through the oxidation of aluminum foil, which modifies the nanochannels in the self-assembled GO membrane by increasing the inter-sheet distance while decreasing intra-sheet spacing. The Al3+ modification resulted in an increase in membrane stability in water, methanol, ethanol, and propanol, yet decreased membrane permeability to water and propanol. These changes were attributed to strong interactions between Al3+ and the membrane oxygenated functional groups, which resulted in an increase in membrane hydrophobicity and a decrease in the intra-sheet spacing as supported by surface tension, contact angle, atomic force microscopy, and X-ray photoelectron spectroscopy measurements. Our approach for forming Al3+ modified GO membranes provides a method for improving the aqueous stability and tailoring the permeation selectivity of GO membranes, which have the potential to be implemented in vapor separation and fuel purification applications

Something about the V Engines Design

First time the corresponding author has studied these problems of motors in V, in the framework of some contracts made with the research collective of UPB and "Autobuzul" plant, in years 1980-1986. In the first phase, have been studied the vibrations and noises of an engine in V, their transmissibility from the engine to the chassis and the cab driver and the possibility of reducing vibration (of the engine or the submitted) by their insulation. Reducing the vibration transmitted, has taken place in various ways, but their level at the driver's seat and the passengers was still too large, much more than the allowed limits international. The vibrations were still more than the allowed limits, while in a similar engine Otto or diesel in a straight line, they were in line with the normal limits, until at last it was decided to change the type of the engine. The idea of the paper's authors was: "It can be synthesized one motor in V only by changing the alpha angle value (the constructive angle of a V engine)". By this method it is possible to change the kinematics of this motor and in the same time its dynamic work. Generally the constructive angle of an engine in V was calculated in function of the number of cylinders and by the engineering condition to achieve an ignition distributed uniformly to all cylinders. This paper try to solve the principal problem of any motor in V (noise and vibration) having in view that one motor in V is more dynamic, more powerful and has a higher yield than any other heat engine. The solution was found and it is very simple to be implemented. It needs only an angle value change. It's about the constructive angle, alpha. Calculations to demonstrate this fact and all the theory are very difficult and heavy. But the final result is very simple