PSI - Issue 59

Bykiv N. et al. / Procedia Structural Integrity 59 (2024) 793–798 N.Bykiv et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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test was performed on a servo hydraulic machine STM 100 (Fig. 2). The loading speed was constant at 3.3 mm/s. The arithmetic mean value for each polymer is presented in the Table 1 and diagram (Fig. 3) and compared with the material characteristics according to the certificate.

Table 1. Characteristic data of polymers

Polymers

Bending strength, MPa

Tensile strength, MPa

Certified

Certified

Tested

PLA+ T-PLA

87 72 46

60 60 68

58 66

Elastan D100

-

The chart shows the average value for each type of polymer. Elastan D100 proved to be excessively elastic compared to PLA+ and T-PLA. Therefore, when the elongation value of the Elastan D100 specimens was 35%, the tensile test was stopped. The maximum stress obtained was 22 MPa.

Fig. 2. Testing polymer samples

According to the results obtained, PLA+ was chosen for the manufacturing and testing of the connecting element because its bending and tensile strengths are better than those of T-PLA and Elastan D100. The required cross-section of the connecting element was selected by finite element modelling using ANSYS software. This determines that the outer diameter of the connecting element must be at least 24 mm to ensure strength at the joint. These parameters apply to the connection of 400C rebar with a diameter of 12 mm. A tube of PLA+ polymer was printed on a 3D printer with the following dimensions: length L = 100 mm; diameters D = 24 mm and d 1 = 12 mm (Fig. 1). After printing, the tube cooled down and the actual dimensions were: L = 98 mm, D = 23 mm, d 1 = 11 mm. On the lathe, the rods are chamfered to 1×45°. One of the rods is fixed in a vice. Using a construction dryer, the polymer tube is exposed to a stream of hot air with an initial temperature of 140°C for 4 minutes. The crystallisation and melting points for this polymer are 105°C and 160°C by Lendvai, (2023); by Molnár et al., (2021). Under these conditions, the polymer crosses the crystallisation limit but does not yet begin to melt, which allows the tube to be inserted onto the rod from the side of the chamfer. After pushing the rod halfway through the tube 1 / 2 L = 50 mm , the polymer is again exposed to a stream of hot air with an initial temperature of 140°C for 4 minutes. The second rod, with the chamfered side, is pushed into the free end of the polymer tube until it touches the end of the first rod. The joint is allowed to cool in the air for 30 minutes.