scholarly journals Study of the samples of polymer composite materials with an uneven surface using hydrostatic weighing

2018 ◽  
Vol 84 (8) ◽  
pp. 32-35
Author(s):  
M. I. Dushin ◽  
K. I. Donetski ◽  
R. Yu. Karavaev ◽  
A. A. Platonov
Keyword(s):  
Composite Materials ◽  
Polymer Composite ◽  
Physical And Mechanical Properties ◽  
Binder Content ◽  
Polymer Composite Materials ◽  
Uneven Surface ◽  
Carbon Plastics ◽  
New Energy ◽  
Hydrostatic Weighing

An increase in the size and the number of the elements of the aircraft structures made of polymer composite materials (PCM) required the search for new energy-saving and less expensive non-autoclave technologies. The use of one of them, vacuum infusion, inevitably leads to formation of an uneven surface, thus inhibiting determination of the true thickness by standard methods, and, in turn, affects determination of the physical and mechanical properties of the material. The results of measuring density of carbon plastics by hydrostatic weighing are presented to calculate the true thickness of materials, volume content of binder and porosity. The developed method is also suitable for PCMs based on combustible reinforcing materials like organic plastics, hybrid and other materials that cannot be subjected to burning-off to determine the binder content.

scholarly journals METHOD OF SAMPLE MANUFACTURING FROM MULTILAYER COMPOSITE MATERIALS FOR STUDYING THEIR MECHANICAL PROPERTIES

2018 ◽  
pp. 16-23
Author(s):  
Alsaid Mazen ◽  
Ali Salamekh
Keyword(s):  
Mechanical Properties ◽  
Composite Materials ◽  
Polymer Composite ◽  
Testing Machine ◽  
Physical And Mechanical Properties ◽  
Polymer Composite Materials ◽  
Technological Parameters ◽  
Cutting Out ◽  
Method Of Production ◽  
Economic Considerations

In the last decades there is increasing the need to apply polymer composite materials in different industries, particularly in shipbuilding. There are developing single structures made from polymer composite materials to be used on board ships. The article focuses on technology of manufacturing slabs from polymer composite materials to carry out mechanical testing in the laboratory special standard units. Mechanical properties of polymer composite materials depend on molding technologies. There has been described a technology of sample manufacturing from polymer composite materials reinforced with glass fiber mat with fiberglass plastics. The technique of testing the specified samples for tensile strength has been considered. The sizes and shapes of the samples as well as the technological parameters of the manufacturing process have been validated, depending on the standard requirements and the technological features of the testing machine. The physical and mechanical properties of the components that make up the composite materials are considered. The sequence of stacking layers for preparation of plates from composite materials is indicated. The dimensions of the plates for cutting out finished samples are determined, depending on the method of production. The way of laying plates from composite materials has been chosen on the base of economic considerations and conditions of accessibility. The obtained results of mechanical properties can be used in solving problems of application of polymer composite materials in shipbuilding, for example, in manufacturing superstructures of some dry cargo vessels.

scholarly journals Determination of strength criteria on conditions of visual testability of impact damage in composite aircraft constructions

2019 ◽  
Vol 22 (6) ◽  
pp. 86-99
Author(s):  
S. V. Dubinskiy ◽  
Yu. M. Feygenbaum ◽  
V. Ya. Senik
Keyword(s):  
Composite Materials ◽  
Polymer Composite ◽  
Impact Damage ◽  
Bootstrap Method ◽  
Defect Size ◽  
Polymer Composite Materials ◽  
Composite Panel ◽  
Weibull Function ◽  
Operational Factors

One of the principal criteria of aircraft composite design strength on the conditions of damage tolerance is the minimum defect size of accidental impact damage that is sure to be located during regular maintenance checks. Construction strength with similar (BVID – Barely Visible Impact Damage) and smaller damages must be ensured under design load. The analysis of operational factors affecting the criterion value is conducted in the paper. The effects of personnel qualification, surface color, level of contamination, distance to the object as well as defect size variations during the time due to relaxation of inner strains in the damaged construction were studied.Research was carried out using 90 carbon fiber three stinger panels of different color and contamination levels which were subject to impact damages by a 25 mm spherical striker. Totally 80 blows were struck when applying energy within the range of 3–107 J. In the visual damage detectability test under different conditions 42 experts were participated including 25 airlines inspectors. For the statistical analysis of empirical data and determination of dependence for the damage detection probability on its size, the Weibull function was utilized. Determination of BVID size using "90/95" criterion was performed by means of the bootstrap method (95% of inspectors must detect not less than 90% of defects with the size not smaller than BVID). The results obtained in this study enabled to access the degree of various operational factors impact on reliability of damage detectability during the visual inspection and determine BVID values depending on the combination of the given factors. In particular, it was demonstrated that from all the viewing distances the defects in polymer composite materials are more detectable on the blue surface than on the gray and red ones. Conducted research demonstrated a significant effect of relaxation (the reduction effect of the surface defect sizes in the composite panel affected by different factors during time span) on the probability of defect detectability during operation. Also water saturation of the construction under excessive temperatures has the critical compared with other factors impact on relaxation of damages in polymer composite materials. The obtained results accord with the data in foreign publications making them more supplement and specific. On the basis of conducted research the entire range of recommendations for aircraft designers and operators utilizing composite constructions is formulated. 

Research of the Processes of Eliminating Warpage of Aviation Products Made of Polymer-Composite Materials Obtained by High-Temperature Molding

2021 ◽  
pp. 84-94
Author(s):  
V.I. Korolkov ◽  
E.N. Nekravtsev ◽  
K.S. Safonov ◽  
P.S. Ogurtsov ◽  
V.A. Oganesov ◽  
...  
Keyword(s):  
High Temperature ◽  
Composite Materials ◽  
Polymer Composite ◽  
Room Temperature ◽  
Binder Content ◽  
Polymer Composite Materials ◽  
Central Layer ◽  
Product Surface ◽  
Weaving Pattern ◽  
Significant Factors

The article considers issues of identifying the causes and factors that have a significant impact on the occurring and development of the warping process in monolithic products made of polymer — composite materials (PCM) obtained by the method of multidirectional layering of uncured PCM — semi-finished product (prepreg) and subsequent high-temperature molding in an autoclave. Warping is understood as a defect of a PCM product in the form of distortion of its configuration (deformation) under stresses arising during the polymerization of the binder prepreg at a high temperature (1800C) and cooling the product to room temperature. Flat samples made of glass-based prepregs have been researched. The selecting schemes of equilibrium stacking of samples of monolithic panels has been carried out. The influence of the binder content in the prepreg on the deformations in non-equilibrium layouts of the panel samples has been evaluated. It is shown that the most significant factors influencing the occurrence of warpage of monolithic PCM panels are: the weaving pattern of the prepreg reinforcing base, the amount of binder deposited in the prepreg, the direction of stacking monolayers in the panel, the edge effect and the shape of the product surface. It was found that the warpage of the sample occurs along the direction of unbalanced shrinkage of the binder. For balanced stacking, compensation in the direction of binder shrinkage and symmetry with respect to the central layer are necessary; more binder in the prepreg reduces the amount of warpage, but only slightly. The development of constructive and technological recommendations based on the results obtained will lead to a reduction in the terms of development of PCM products.

scholarly journals MODELLING OF CRACK DEVELOPMENT PROCESSES IN COMPOSITE ELEMENTS BASED ON VIRTUAL CRACK CLOSURE TECHNIQUE AND COHESIVE ZONE MODEL

2020 ◽  
Vol 17 (35) ◽  
pp. 591-599
Author(s):  
Yulong; ; LI ◽  
Vasiliy N. DOBRYANSKIY ◽  
Alexander A. OREKHOV
Keyword(s):  
Composite Materials ◽  
Polymer Composite ◽  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Fiber Composites ◽  
Polymer Composite Materials ◽  
Zone Model ◽  
Virtual Crack Closure Technique ◽  
Closure Technique

Fiber composites based on polymer matrices are promising structural materials that meet high requirements for strength, reliability, durability, and hardness. Therefore, composite materials are widely used as structural materials for aerospace products. The problems associated with the destruction of fiber composites were relevant at all stages of technology development. A variety of reinforcing fibers and polymer binders, as well as reinforcement schemes, allow directional control of strength, stiffness, level of working temperatures and other properties of polymer composite materials. This article discusses a methodology for experimental determination of the mechanical properties of carbon-based fiber-reinforced polymer composite materials, including the determination of the interlayer fracture toughness under loading under separation conditions using the doublecantilever beam method (DCB) and the fracture toughness under transverse shear conditions using the ENF (End-Notched Flexure) method and interlayer strength. The test results of samples of polymer composite materials with a carbon reinforcing filler with different surface densities are presented. The experimental data were used to identify the parameters of the VCCT (Virtual Crack Closure Technique) and CZM (Cohesive Zone Model) closure models used to describe the development of cracks in the composites under consideration. It was found that the parameters determining the strength of layered composites are such characteristics as interlayer strength and crack resistance. It was found that the decrease in the strength of individual layers of the composite does not always affect the current stress state of the entire structure, which is often difficult to detect experimentally, but can significantly affect the further behavior of the object under study provided that the crack develops further.

Investigation of a Suspension Bridge with Main Fiberglass Beams by Means of the Finite Element Method

2020 ◽  
pp. 58-71
Author(s):  
Ю. А. Гостеев ◽  
А. А. Лебедев ◽  
С. Д. Саленко ◽  
А. Н. Яшнов
Keyword(s):  
Finite Element ◽  
Composite Materials ◽  
Polymer Composite ◽  
Physical And Mechanical Properties ◽  
Suspension Bridge ◽  
Polymer Composite Materials ◽  
Main Beam ◽  
Suspension Bridges ◽  
Design Standards ◽  
Manufacturing Techniques

Постановка задачи. В настоящее время продолжается поиск конструктивных решений по применению полимерных композиционных материалов, в том числе стеклопластика, в несущих конструкциях мостов. Исследователи ведут работу по улучшению технологий изготовления данных материалов, их физико-механических свойств, а также совершенствованию методики расчета. Из этой проблематики в данной статье уделено внимание вопросам расчета висячего моста с балками жесткости из стеклопластика. Результаты. Созданы конечно-элементные модели висячих однопролетных пешеходных мостов. Проведены расчеты с учетом геометрической нелинейности. Предложен метод компенсации недостатков материала конструктивным способом для обеспечения требований норм проектирования по прогибам. Определен порядок регулирования усилий в элементах висячей системы повышенной жесткости (система С. А. Цаплина). Выводы. Расчет висячих мостов на воздействия основного сочетания нагрузок показал, что конструктивная компенсация недостатков материала обеспечивает выполнение требований норм проектирования по прочности и прогибам. На основе результатов проведенных исследований рассчитаны критические скорости ветрового резонанса для балки жесткости висячего моста длиной 60 м. Для ветра со скоростью 35 м/с минимальный запас для некоторых сечений составил 25 %. Полученные результаты свидетельствуют о необходимости продолжения аэродинамических исследований. Statement of the problem. Currently, the search for design solutions for the use of polymer composite materials, including fiberglass, in the load-bearing structures of bridges is ongoing. Researchers are working on improving the manufacturing techniques of these materials, their physical and mechanical properties as well as the method of calculating polymer composite materials. From this perspective, this article focuses on the calculation of a suspension bridge with main fiberglass beams. Results. Finite element models of suspension single-span pedestrian bridges were designed. They are calculated taking into account the geometric nonlinearity. The paper proposes a method for compensating material defects in a constructive way to meet the requirements of design standards for deflections. The procedure for regulating the forces in the elements of the suspended system of increased rigidity by S. A. Tsaplin is identified. Conclusions. The calculation of suspension bridges on the basis of the main combination of loads showed that the method of structural compensation of material disadvantages provides the requirements of design standards for strength and deflections. Based on the results of the study, the critical wind resonance speeds for the main beam of the suspension bridge with a length of 60 m was calculated. For a wind with a speed of 35 m/s, the minimum margin for some sections was 25 %. The results obtained indicate that it is necessary to continue aerodynamic research.

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