PSI - Issue 59

Viktoriia Ihnatieva et al. / Procedia Structural Integrity 59 (2024) 487–493 Viktoriia Ihnatieva / Structural Integrity Procedia 00 (2019) 000 – 000

489

3

Fig. 1. Initial moulding of a profile strut 1 - mandrel; 2 - calibrating spinneret; 3 - moulded material; 4 - moulding device

The method of « wet » impregnation of the strut material also implies partial impregnation of the braiding layer. In this case the impregnation mechanism described in (Freger et al. (2004), Freger et al. (1998)) is carried out at pressure values c p , determined by the following formula

   

v R



k c D b

 

пр y

,

(2)

p

arctg



  

c

r

2

L

k

y

пр

where k D – diameter of the calibrating spinneret; c b – thickness of the profile strut;  – binder viscosity; np  – broaching speed; r np k – permeability coefficient in radial direction; y L – design parameter, which is equal to the distance along the product axis from the point where the semi-finished product comes off the mandrel to the point of contact with the sealing device. If prepreg is used, the binder is not extruded at this stage. The final moulding stage is the final stage of moulding the struts of a complex profile product. This stage can be carried out both together with the moulding of the shelves and separately. In the first case, the profile is moulded in a special spinneret. The dimensions of the spinneret ensure the specified geometric parameters of the product. In this spinneret, the final squeezing and redistribution of the binder over the profile cross-section takes place, the braiding layer is additionally impregnated and the product is hardened. For this purpose, the spinneret is heated to a temperature that corresponds to the polymerisation temperature of the binder. In the second case, the specified dimensions of the struts are ensured before the shelves are formed. This is done by passing the strut between two forming plates or rollers. The plates or rollers are heated to a temperature that provides the specified viscosity of the binder. The advantages of this method are that the pulling resistance forces can be reduced and this operation can be combined with broaching. This method is best used for the production of complex profile products with large dimensions. With this method, the forming spinneret not only forms the shelves, but also calibrates the dimensions of the strut. In addition, the braiding layer is additionally impregnated, if necessary. The braiding layer is impregnated by means of an external application of binder. The solidification of the product is also carried out in the spinneret. In both cases, significant pressures occur during the pressing of the product elements, and condition (2) is not fulfilled. As a result, the binder moves in the longitudinal direction. Thus, the process of binder filtration in the transverse direction is carried out both inside and outside the moulding devices.