Impact force Bulk solid

A clearly visible application for the grafted from materials is also in ballistic protection. With a relatively low modulus (e.g., 148 MPa for polystyrene-crosslinked samples -Table 13.2) and bulk density (0.46 gcm ), it is calculated that the speed of sound (equal to [modulus/bulk density] ) is 635 m s This value is very low for a solid material and highly desirable because it will extend the duration of an impact reducing the effective force on the material. The relatively low yield stress (7.2 MPa) will allow early activation of the energy absorption mechanism, while the long stress plateau will allow for large energy absorption. 

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