Introduction. Were investigated samples of fiberglass with the aim of its effective use in construction in the long term. Fiberglass is considered one of the most versatile and durable materials among polymer composite materials, however, and it is subject to destruction. It is known that one of the main reasons for reducing the specified characteristics and material properties is operational. At the design stage, it is necessary to determine the most reliable and economical materials used and, accordingly, be sufficiently aware of their strength and durability. Thus, in order to avoid the destruction of the material, as well as significantly enhance and prolong its service life, it is necessary to be aware of how exactly the properties of the material change over time. Regarding reinforced concrete, wood, brick and steel fiberglass is used in construction recently. This means that while the service life of the list of the most common materials in construction is known to a sufficient extent, manufacturers do not dare to use fiberglass as a material for critical structures. This occurs because changes in its characteristics, depending on operational factors, are not sufficiently studied for intervals exceeding 4-5 years of operation. Materials and methods. During the work, samples of fiberglass SPPS with a longitudinal and transverse arrangement of fiberglass were tested for climatic aging in a climatic chamber for 5 cycles simulating 5 years of material operation. All samples were subjected to tensile testing on a tensile testing machine R-5. Results. Destructive stresses were determined, calculations were carried out and elastic and strength characteristics of the samples were analyzed. On the basis of the obtained results, an analysis was carried out, conclusions were formulated about the use of fiberglass in the construction in the long term, as well as the influence of such operational factors as moisture, positive and negative temperatures, and ultraviolet radiation on the properties of fiberglass with a different arrangement of fiberglass. Conclusions. Found that the destructive stresses of fiberglass are significantly reduced during the first two years of operation, which must be considered when choosing fiberglass with the stated characteristics. Ultraviolet does not have a significant effect on the elastic-strength properties of the material, while during operat
Introduction. Pultruded fiberglass can be called the material of the future due to its properties — high strength, low weight, resistance to aggressive environment. Important aspects for the development of composite materials are surface treatment methods and methods of connecting structural elements. Glue compound has proven itself as the most effective, but there remains a need to conduct studies of its durability. The method of accelerated cyclic thermal tests allows to determine the expected changes in the strength of adhesive bonding in a short time. Materials and methods. Samples, which are three glued plates of SPPS fiberglass construction, were processed in a climate chamber and after each cycle they were tested on a GRM-1 machine. One climatic test cycle included being in a chamber with high humidity and temperature and then moving into the cold chamber. The specimens were tested prior to spalling, and the resulting disruptive stresses were recorded. The last test cycle corresponded to five years of operation of the structure. Results. The tests of the samples showed a significant change in the characteristics of the compounds over time. In the first two years of operation, a decrease in strength of 25 % is expected. The last characteristic test point, corresponding to five years, showed a drop to 60 % of the initial characteristics. Conclusions. The results should be considered at the design stage of supporting structures that are not protected from contact with the external environment. The factors of strength reduction after 100 years may be included in the regulatory documents for the calculation of especially important structures.
Experimental data supporting the feasibility of application of Poiseuille equation for determining the dimensions of the inner spinneret channel and the height of the hydrostatic melt column above the spinneret plate are reported. These data can be used to develop a method for calculating the strength and rigidity of the key components of the spinneret feeders.Over the recent decades of use of spinneret feeders (SF) and glass melting pots (GMP) for production of mineral fibres (glass, basalt, etc.), it has been established that one of the basic reasons for failure or scheduled suspension of operation of industrial spinneret feeders is high-temperature creep of their bottom [1].It is well known that the rate of deformation caused by creep depends on the nature and magnitude of the initial mechanical stresses developed at the bottom of the spinneret feeder (spinneret plate) under the impact of the pressure generated by the glass melt [2]. The pressure generated by the glass melt in the SF is expended for overcoming the local hydraulic resistances inside the SF or the GMP and the resistances at the spinneret inlet, for overcoming the forces of surface tension at the spinneret outlet, and, for the most part, for forcing (extruding) the melt through the spinneret.Specialists believe [3-5] that the major amount of the force (60-70%) is expended for forcing the melt through the spinneret. Currently, Poiseuille equation is used to determine these losses. Poiseuille equation is valid, however, only for laminar motion (flow) of incompressible Newtonian fluids, at constant viscosity of the melt, and under the condition that the length of the channel is greater than the length required for the development of the laminar flow in the channel. As calculations show [4], the melt flow in the spinneret feeder is laminar and the length of the channel in the spinneret ensures development of laminar flow. Glass melts, however, do not belong to Newtonian fluids, so experimental studies were carried out in this work to validate the feasibility of using Poiseuille equation for describing the motion of theses melts through spinneret channels.The experiment was performed in two industrial glass-melting pots (vessels) (Fig. 1) for two-stage production of fibres (threads) from the glass of the trademark VMP (S-type glass). One pot had 198 cylindrical spinnerets 1 and the other, the same number of combined cylindrical spinnerets with a conical (tapered) inlet (Fig. 2).During the experiment, heating up of the pot and fritting up of the level were carried out in accordance with the start-up procedure and technological schedule established for this production.Glass balls preheated to 450-500°C were loaded at the rate of two balls at a time into the loading holes 5 and one ball at a time into the central hole 7 in the top part of the pot (Fig. 1), which allowed them to be distributed evenly over the melting lattice. The next balls entered the pot only after complete melting of the preceding ones and restoration of the temperature to the original...
Introduction. With the use of prestressing, coatings are made for special-purpose buildings, requiring calculations for extreme impacts. Such impacts include an airplane strike. Modeling of prestressed structures and calculation of shock loads is difficult to implement in classical calculation programs. A universal tool for solving such problems is the PC SOFiSTIK. This software complex allows you to interact with the most modern software solutions. Materials and methods. For the description of the method, special-purpose coating was selected and the strike calculation of the Learjet 23 aircraft was performed. For modeling prestressing, the SOFIPLUS interface is used. To describe the impact, the internal programming language CADINP is used. Results. The nature of the change in the coating deformations in the first seconds of the aircraft crash is presented graphically. Also, iso-ares of internal bending moments of the coating were derived for the selection of reinforcement and the diagram of the moments of the beams from the action of prestressing, taking into account tension losses. Conclusions. SOFiSTIK PC allows you to solve complex engineering problems with a high degree of automation. Thanks to the open source code, it becomes possible to calculate atypical extreme effects. The obtained graphs and diagrams confirm the passage of checks on the limiting states of the coating, and can also be used to design and calculate similar special-purpose structures.