PSI - Issue 37
I. Shardakov et al. / Procedia Structural Integrity 37 (2022) 1065–1072 Author n me / Structural Integrity Procedia 00 (2019) 000 – 000
1067 3
Figure 1. Loading scheme for a film sample The value of the load P can be represented using the effective elastic modulus:
L
( ) 2 l P E F F = + ef s
(2)
L
Comparing (1) and (2) we obtain the expression for the elastic modulus of the carbonized layer:
( 2 )
1 1 h − − 2 s E h E h h ef
2
,
(3)
E
=
l
2
ef E is determined from (2):
where the expression
) 2 l F F L + s P L
(4)
E
=
(
ef
All uniaxial tensile experiments were performed using a Testometric FS100 testing machine. The following deformation mode was set: deformation up to 1% at a constant rate of 1% / min. This level of deformation ensures the elastic state of all layers of the sample. The longitudinal deformation of the sample was determined by the displacement of the crossheads of the testing machine. It was preliminarily found that the deformations calculated from the displacement of the traverses, and the same determined from the displacement of the marks on the sample,
coincide. The tensile force P was recorded using a force transducer. The sequence of experimental steps for one sample was as follows: 1) Measurement of the linear dimensions of the sample;
2) Uniaxial tension of the sample on a Testometric FS100 testing machine followed by complete unloading; the loading mode was as follows: the deformation rate 1% / min, maximum deformation 1%, cycle of loading-unloading was repeated 5 times; 3) Determination of the elastic modulus at each loading step and calculating the average value over 5 loading steps; 4) Ion-plasma treatment of two opposite surfaces of film sample with a given level of fluence; 5) Uniaxial tension of the treated sample in the above-described mode (5-fold loading-unloading) and determination of the elastic modulus of the carbonized layer based on the results of 5-fold repetition of the experiment using relations (1-4); The mentioned 5-fold repetition of the loading-unloading cycle was performed to obtain a statistical estimate of the accuracy of the obtained mechanical characteristics.
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