Penetration depth, ballistic

Hardness is commonly defined as the resistance of a material to static penetration by a harder material [3]. The qualifier, static , excludes dynamic effects associated with erosion or ballistic penetration. Hardness can be quantified by determining the depth of penetration of a hard indentor, usually diamond, loaded perpendicular to a planar surface of the material under test [57]. The penetration depth is related to the contact area over which the load is transferred between the indentor and the sample. The hardness is equal to the load divided by the area of plastic contact. There is some ambiguity in ignoring recoverable, elastic penetration, but, apart from elastomeric materials, the effects of elastic recovery during unloading are usually small. The fixed load, P, applied to the indentor and the known indentor geometry are used to calculate the hardness from the contact area. A, between the indentor and the sample ... 

The manufactured 90 mm x 90 mm x 10 mm three-layered B4C/B4C-30wt%SiC tiles were tested as armor [67], The photographs of the experiment set-up of the ballistic test as well as a residual impression in the clay box that was used as one of the criteria in the ballistic performance of laminates are shown in Fig. 7.17. The ballistic penetration tests were performed to evaluate the ballistic performance of the laminates. Depth of penetration tests were used to evaluate the ballistic performance of the composite laminates. In addition, pure B4C monolithic ceramics were used as a standard for the test. Test panels were made using the three-layered B4C/B4C-SiC laminate and B4C monolithic ceramic material as the hard face. While the B4C monolithic tile had 100% of its theoretical density, the three-layered B4C/B4C-30wt%SiC laminates had about 3-4% of porosity. A commonly used Spectra fiber-reinforced polymer composite was used as backing plates. The targets were mounted on clay and the projectile was shot at the target at a specific velocity. 

The design of the test panels was selected to ensure defeat of the threat. The depth of penetration of the projectile into the backing was measured by peeling of the unpenetrated layers of the backing plate, and the diameter of the impression on the clay after the projectile had been shot was used to evaluate the ballistic performance of the laminate composites. The results of the ballistic performance evaluation are shown in Fig. 7.18. As one can see there was no significant difference in penetration of the projectile into pure B4C monolith ceramics and three-layered composite. 

The effect of the number of layers of laminated oriented PE film Tyvek for use in the development of light weight armor and the device for testing its ballistic characteristics were evaluated. The study shows that increasing the number of layers has a significant effect on the depth of penetration. Also how the layers are placed in relation to each other that is biaxial or parallel has an effect on the penetration and tensile properties of the laminate. Biaxial placement improves the tensile properties of the laminate in all directions. 

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