PSI - Issue 50

V.G. Degtiar et al. / Procedia Structural Integrity 50 (2023) 40–49 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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radiation). The detector positional accuracy is 0.0001°. Interplanar distance d 002 and average distances of zones of coherent scattering L 002 were defined using the center-of-mass position and an integral width of diffraction peaks 002 with the standard methodology (the constant in computation of L 002 under Selyakov-Sherrer formula is equal to 0.9). The graphitation degree is estimated by the formula g = (3.44 – d 002 )/(3.44 – 3.354), where d 002 – interplanar distance of a considred sample. Table 1 summarizes data on the graphitation degree of different C-C composites.

Table 1. Graphitation degree of different C-C composites. C-C composite KIMF 4KMS-LG 4KMS-LB

4KMS-LU

4KMS-R

4KMP

MKU-4M-7

g

0.16

0.38

0.45

0.45

0.54

0.42

0.30…0.44

4. Accounting for misalignments of structure of a C-C composite frame when computing ablated shapes Average models of the distribution of density over volumes of C-C composite samples are formed on the basis of tomographic measurements. The tomographic data are averaged in small volumes, into which a sample is divided. The breakdown of density scatters of micro volumes (0.2 х 0.2 х 8.0) mm 3 in corresponding small volumes is featured by the presence of pores, shells, defects (cracks), t.i., fine-grained roughness. Taking into account the fact that in reality the distribution of density in composite samples differs from the average model, in each particular case in the same FV flight conditions different ablated shapes will be realized and different aerodynamic forces and moments, correspondingly. Consequently, the FV flight dynamic will also vary. Asymmetric distribution of density will cause asymmetry of ablated shapes and higher lateral moments implemented to the FV, correspondingly.

Fig. 6. A pattern of relative position of reinforcing elements.

A misalignment of the structure of a C-C composite frame, of which a TPS element is made, can cause the asymmetry of ablated shapes relative to the FV axis. Fig. 6 illustrates the relative position of C-C composite reinforcing elements, where i Α – direction vectors of reinforcing elements. Each reinforcing element outcrops as a roughness element, which geometrical parameters depends upon the relative orientation of its direction vector and the normal vector to surface. If the frame structure is declined from the nominal position by an angle, geometrical parameters of the roughness elements will also differ from the realized in nominal position. According to (7) the equivalent sandy-grained roughness will also differ. One of the most preferable geometry of C-C composite frames from the point of assurance of symmetry of ablated shapes is 4-directional geometry of materials of the 4KMS-L type, in which the structure is manifested as a