This research aims to study some aspects and important properties in manufacturing of polymeric advanced composite materials reinforced by fibers will be studied ,these aspects show as introduction to some important properties of polymeric composite materials reinforced by fibers related with its composition and some mechanical properties (Tension ,Impact, Compression, Flexural, etc) .The objective of this research is to study the effect of using different reinforcement percentage of fibers on mechanical properties for composite material consist of vinyl ester resin reinforced by unidirectional Kevlar fibers with surface density (340 g/cm2) which included impact , tensile, compression , and flexural strength , where we extracted the mechanical properties for vinyl ester resin before reinforced by fibers, then we reinforced the resin by different weight percentage from kevlar Fibers (20%,40%,60%) and studied its effect on the above mechanical properties .