IntroductionThe widespread use of products made of polymer composite materials (PCM) in the field of shipbuilding is explained by their high mechanical characteristics compared to products made of steel, in particular, specific strength, as well as the possibility of obtaining finished products without the use of traditional expensive mechanical treatments, etc. [1].Fiberglass is a composite material consisting mainly of a fiberglass filler and a polymer matrix (binder) that combines the filler into a single homogeneous composition. Fiberglass based on polyester and vinyl ester resins is a structural material capable of withstanding all types of loads, including shock and vibration. According to its physical characteristics, fiberglass is considered resistant to many aggressive liquids, insoluble and non-melting, has high chemical resistance, low water absorption and an environmentally friendly product. One of the main advantages of composite materials is their minimal conductivity, which provides high protection against fire. Composite materials have high maintainability, low weight, biological resistance, structural rigidity, durability and impact resistance [2].The purpose of this study is to determine the effect of water on the weight and mechanical properties of samples made of PCM with treated and untreated edges with polyester resin when they are immersed in a liquid with a sustained period of time. Determination of the influence of the location of reinforcing layers (glass wool and roving fiberglass) on the ability of liquid penetration into the structure of the composite material. The object of the study is six layered samples with treated and untreated edges with polyester resin, made of composite materials using glass fabrics and with a different arrangement of reinforcing materials and a different quantitative ratio of layers. Methods of manufacturing and testing samples from PCMFor further experiments, plates were made of PCM of two different reinforcement schemes, from which samples were subsequently cut using a milling machine and a sawtooth disk made of hardened steel. The samples from the PCM were made for testing for three-point bending, compression and stretching.The pattern of reinforcement of the samples is as follows:– scheme I: glass wool, glass wool, roving fiberglass, roving fiberglass, glass wool, glass wool;– scheme II: roving fiberglass, roving fiberglass, glass wool, glass wool, roving fiberglass, roving fiberglass.The samples from each scheme were divided into two groups:– the first group, samples without edge treatment with polyester resin;– the second group, samples with polyester resin edge treatment.The edges of the samples of the second group are treated with polyester resin Yaropol 110, using a brush with natural bristles. After processing the edges of the samples, they must be left for 48 hours at normal room temperature, only after complete drying, the processed samples are weighed, immersed in water for 90 days at room temperature 23 °C and humidity 50%. Table 1 shows the weight characteristics of samples with different reinforcement schemes [3].Table 1Weight characteristics of samples before soaking in waterReinforcement scheme  Sample number Samples without edge treatment with polyester resinFor tensile testingFor compression testingFor bending testIIIIIIIIIWeight, g  154.1244.740.710.6834.7127.77  255.3742.550.640.6035.2627.79  350.9344.090.720.7435.5728.11  451.7142.240.700.5635.6530.76  554.3544.060.600.6335.3330.51Average values53.29643.5360.6740.64235.30428.988Samples with edge treatment with polyester resin  155.0643.980.850.8436.1131.11  254.8243.530.740.7936.3727.83  358.0945.190.760.7235.9430.63  459.3244.260.800.7735.6228.94  559.3243.290.890.8335.5829.51Average values57.32244.050.8080.7935.92429.604           Samples from PCM of different reinforcement schemes are weighed before immersion in water on certified equipment of the laboratory of Ship Mechanical Disciplines of the Caspian Institute of Marine and River Transport named after General-Admiral F. M. Apraksin.After the expiration of the specified period of time, samples of different reinforcement schemes are removed from the water, wiped dry with a cotton cleaning cloth and weighed (Table 2) on certified laboratory electronic scales of the VLTE-310T series [4].According to the measurement results of the average mass values of the samples of the two reinforcement schemes without edge treatment before and after soaking in water, it was found:– the increase in the masses of the samples intended for tensile tests of the I and II reinforcement schemes is 0.556 and 0.3 grams, respectively;– the increase in the mass of samples intended for compression tests of the I and II reinforcement schemes is 0.004 and 0.012 grams, respectively;– the increase in the mass of samples intended for bending tests of the I and II reinforcement schemes is 0.342 and 0.198 grams, respectively.The results of measuring the average mass values of samples of two reinforcement schemes with edge treatment with polyester resin before and after soaking in water showed that the average values of changes in the weight parameters of the samples increase, but at the same time:– for samples prepared for tensile tests, the increase in the average weight values of I and II reinforcement schemes is 1.084 and 0.654 grams, respectively;– for samples intended for compression tests, this increase is 0.0044 and 0.042 grams;– for samples intended for bending tests, the increase in the average values of weight characteristics is 0.966 and 0.39 grams.Table 2Weight characteristics of samples after soaking in waterReinforcement scheme  Sample number Samples without edge treatment with polyester resinFor tensile testingFor compression testingFor bending testI II I II I II Weight, g  154.5945.040.710.6935.0627.98  255.9342.830.650.6135.5927.97  351.4944.410.730.7535.9028.32  452.3642.530.700.5736.0230.96  554.8944.370.600.6535.6630.70Average values53.85243.8360.6780.65435.64629.186Samples with edge treatment with polyester resin  156.0544.590.890.8937.0831.40  255.7444.030.780.8337.2828.15  359.1745.910.800.7536.8431.02  460.4145.010.850.8136.6629.49  560.6643.980.940.8836.5929.91Average values58.40644.7040.8520.83236.8929.994 Based on the conducted studies, it follows (Fig. 1) that, lead has good penetrating abilities, causes swelling, accompanied by an increase in mass, volume, most noticeable on samples from PCM with treated edges with polyester resin [5].   Fig. 1. Samples from the PCM of two reinforcement schemes with treated edgeswith polyester resin after soaking in water Tests of samples from PCM in order to determine their mechanical characteristics after soaking in water were carried out on certified testing machines at the Department of Ship-Mechanical Disciplines of the Caspian Institute of Marine and River Transport named after General-Admiral F. M. Apraksin. Testing of samples from PCM for three-point bendingOn the basis of regulatory and technical documentation, test samples are produced. Testing of samples from PCM for static bending is carried out in accordance with USS 4648-2014, samples are made of rectangular shape with dimensions of length and width 200 × 20 mm (Fig. 2, 3) [6].   Fig. 2. Samples of two different reinforcement schemes without edge treatment with polyester resinfor the three-point bending test According to the average thickness of the samples according to the formula L = (16 ± 1)h, the distance between the supports is determined. The test samples are placed on supports and subjected to three-point bending at a constant loading rate until complete destruction, while measuring the destructive load applied to the sample [7]. The applied load is fixed at 10 mm/min. The bending strength of the PCM is calculated by the expression: where Fmax – is the value of the loading force, N; L – is the fixed distance between the installed supports, mm; b – is the size of the sample in width, mm; h – thickness of the sample, mm.The fixed distance between the installed supports is calculated using the formulaL = (16 ± 1)h.   Fig. 3. Samples of two different reinforcement schemes from the edge treatment with polyester resin to the three-point bending test Table 3 shows the results of testing samples from PCM for three-point bending.Table 3Test results of samples from PCM for three-point bendingSample numberReinforcement schemeIIIFmax, kgpσ, МРаFmax, kgpσ, МРаSamples without edge treatment with polyester resin  190177110275.8  2100200.695252.5  3105203.6105248.8  4110218.4120247  5115224115250.5Average values104204.72109254.92Samples with edge treatment with polyester resin  195175115304  290173.790243.6  385159.5125260  485164.8110250  5100200.5115261Average values91174.7111263.72         The results of the bending tests carried out show that the average value of the loading force on the samples of the first group (without processing the edges with polyester resin, Fig. 4) after soaking in water is greater than that of the second group (the edges of which are treated with polyester resin), but the average tensile strength of the samples of the second group (the edges of which are treated with polyester resin, Fig. 5) is an order of magnitude higher.                                                                                                 a                                                                                                                     b Fig. 4. Graphs of changes in the average values of the destructive forces (а) and strength limits (b)of samples without processing the edges with polyester resin during the bending test                                                                                                    a                                                                                                             b Fig. 5. Graphs of changes in the average values of destructive forces (a) and strength limits (b)of samples with edge treatment with polyester resin during bending testing Tensile testing of samples from PCMAccording to USS 11261-17, in order to determine the value of the tensile strength, the samples must have a flat shape with dimensions of 250 mm in length, 25 mm in width and 2 mm in thickness [8]. The tensile strength at PCM is determined by the formula:                                                                                                                                   (1) where A = bh – the cross-sectional area of the sample, mm2.The test samples (Fig. 6, 7) are stretched along their axis at the same speed of 5 mm/min, the tensile load is measured simultaneously and the breaking load and tensile strength are determined. Table 4 shows the results of tensile testing of samples from PCM.   Fig. 6. Samples of two different reinforcement schemes without edge treatment with polyester resinfor tensile testing   Fig. 7. Samples of two different reinforcement schemesfrom the edge treatment with polyester resinto the tensile test Table 4The results of tensile testing of samples from PCMSample numberReinforcement schemeIIIFmax, kgp σ, МРаFmax, kgpσ, МРаSamples without edge treatment with polyester resin  12 100147.62 700227.7  22 500164.42 100188.6  32 3501722 400205  41 900133.72 350222.5  52 600169.82 250198.8Average values2 290198.4442 360208.52Samples with edge treatment with polyester resin  12 700184.72 650181  22 2501522 300203  32 2001442 100177.5  42 1001302 250192.6  52 250138.72 500227Average values2 300149.882 360196.22              A comparative analysis of the results of the PCM tensile tests shows that the average applied load of the samples of the second group (the edges of which are treated with polyester resin, Fig. 8) after soaking in water is slightly greater or equal to the samples of the first group (without processing the edges with polyester resin, Fig. 9), and the average tensile strength of the samples of the first group (without processing the edges with polyester resin) is an order of magnitude higher. Compression testing of samples from PCMAccording to the requirements of USS 4651-2014, samples intended for compression tests (Fig. 10, 11) are made in a parallelepiped shape with dimensions l × b × h corresponding to 10 × 10 × 4 mm [9].The loading and compressive force is directed at the samples along the axes, perpendicular to the direction of the reinforcing layers and at a uniform rate until destruction or until the load decreases. It should be noted that the value of the compressive load on the samples is recorded during the entire course of the test. Table 5 shows the results of compression testing of samples from PCM.                                                                                                            a                                                                                                   b Fig. 8. Graphs of the dependence of the average values of destructive loads (a)and tensile strengths (b) during tensile testing of samples with edge treatment with polyester resin                                                                                                           a                                                                                                           b Fig. 9. Graphs of the dependence of the average values of destructive loads (a) and tensile strengths (b) during tensile testing of samples without edge treatment with polyester resin    Fig. 10. Samples of two different reinforcement schemes without edge treatmentwith polyester resin for compression testing   Fig. 11. Samples of two different reinforcement schemes from processingthe edges with polyester resin for compression testing Table 5The results of compression testing of samples from PCMSample numberReinforcement schemeIIIFmax, kgpσ, МРаFmax, kgpσ, МРаSamples without edge treatment with polyester resin  12 5004742 600551  22 9005472 900547  32 300433.52 900433.5  42 1003882 300388  52 350500.62 600500.6Average values2 430468.622 660484.02Samples with edge treatment with polyester resin  12 700482.42 750552.7  22 300437.62 350473  32 3004292 750562  42 600476.62 800568  52 900513.22 850578Average values2 560467.762 700546.74              Samples from the PCM are installed in the center of the support pads of the R-5 testing machine. The uniform speed of the applied load is fixed at a value of 1 mm/min.The values of the compressive strength of the samples are calculated according to the formula (1).A comparative analysis of the results of PCM tests for destructive compression load showed that the average values of the applied load and the tensile strength of the samples of the second group (whose edges are treated with polyester resin, Fig. 12) are higher than those of the samples of the first group (whose edges are not treated with polyester resin, Fig. 13).                                                                                                       a                                                                                                           b Fig. 12. Graphs of the dependence of the average values of destructive loads (a)and tensile strengths (b) during compression testing of samples with edge treatment with polyester resin                                                                                                    a                                                                                                                      b Fig. 13. Graphs of the dependence of the average values of destructive loads (a)and tensile strengths (b) during compression testing of samples without edge treatment with polyester resin ConclusionBased on the results obtained, it can be concluded that the ability of liquid penetration (in this case, water) into the structure of the PCM is influenced by the structure and location of the layers of the composite material, as well as its dimensions. The liquid has a better penetrating ability, especially for samples with small dimensions when the glass wool layer is located outside (scheme I), regardless of whether or not the edges are treated with resin.The penetration of liquid into the structure of PCM negatively affects their mechanical characteristics by reducing the values of tensile, compressive and bending strengths, while this decrease is less noticeable when the layers of roving fiberglass are located outside.