ANCOVA analysis of penetration force on Kevlar fabrics used for ballistic protective equipment

The paper aims to highlight the existence of significant differences between the variation of the penetration force of three groups of fabrics used for ballistic protective equipment in the function of the deformation arrow, using the ANCOVA mathematical model with a nominal independent variable and a quantitative independent variable. The model included: the dependent variable (Y) - the variation of the penetration force T (N); nominal independent variable - fabric group; quantitative independent variable - deformation arrow, Delta l (mm). This paper analyses the effect of the nominal independent variable and the quantitative independent variable on the penetration force variation, using the ANCOVA model. From the results obtained, through Tests of Be-tween-Subjects Effects, it is observed that the effect of the nominal independent variable "fabric group" is significant and also the effect of the covariate "deformation arrow" is significant. Interpreting the value of Sig < 0.05, it can be concluded that there are significant differences between the variation of the penetration force deformation (alternative hypothesis H1 is accepted). This technique can be used later to model the physical and mechanical properties of fabrics and to select the most appropriate fabrics to meet the requirements of a particular field of use.