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Parallel with the development of the pultrusion, also machines and technology for filament winding were introduced. Also this line of products was developed for antennas and antenna masts. Later the program was extended to other areas and production equipment was supplemented by new machines. So at present we are able to manufacture also cylinders for the electric power industry, pneumatic and hydraulic pressure vessels, tubes for motorcycle mufflers and many other special purpose products.
Filament wound products Trivavit are produced of glass, carbon, aramid and polyester fibres mostly in the form of rovings. For some product we use also veils and woven tapes. Various epoxy resin systems are used as matrix material.
Proper material selection and correct combination of covers with different winding angles is the basis for optimization of product properties to application requirements. In the next table a few characteristics of two filament wound tubes for high pressure purposes with different winding angles are presented.
| property | unit | round tube 60.0 mm / 63.2 mm E glass 75 degrees, double veil inside, epoxy resin |
round tube 85.0 mm / 90.0 mm E glass 55 degrees, double veil inside, epoxy resin |
| fibre content | vol % | 52 | 56 |
| density | Mg/m3 | 1.9 | 2.0 |
| specific heat | kJ/(kg*K) | 1.0 | 1.0 |
| elastic modulus | GPa | L: 10 C: 34 | L: 11 C: 19 |
| shear modulus | GPa | LC: 4 | LC: 12 |
| "open end" burst pressure and calculated stress by failure | bar GPa |
390 L: 0.0 C: 0.75 |
240 L: 0.0 C: 0.42 |
| "close end" burst pressure and calculated stress by failure | bar GPa |
320 L: 0.28 C: 0.56 |
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| dielectric strength | kV/mm | R: >8 | |
| specific el. resistivity | Ohm*cm | L,C,R: >10E10 | |
| dielectric constant | 5 |
| mandrel length | up to 3 m (conditionally up to 6 m) |
| mandrel diameter | 10 mm to 200 mm (conditionally up to 1 m) |
| winding angle | 8 to 88 degrees |
| mandrel length | up to 3 m |
| mandrel diameter | 10 mm to 200 mm |
| method of treatment |
tolerance |
| inner surface without treatment | ± 0.2 mm |
| outer surface as wound | ± 1.0 mm |
| outer surface overwound with polyester tape | ± 0.6 mm |
| outer surface centerless ground | ± 0.2 mm |
| outer surface turned on a lathe | ± 0.1 mm |
| method of cutting |
length |
tolerance |
| cutting with diamond saw | 50 mm to 3 m | ±0.5 mm to ±2 mm |
| turned on a lathe | 20 mm to 1 m | ±0.2 mm |
