Nowadays, composite materials are widely used in the aeronautical industry to manufacture many different components. Development of composite materials has a very positive influence on the performance, reliability, weight and cost of modern aircraft. But composite material in practical use can be subjected to a wide variety of different loading conditions: mechanical stresses and environmental influence. In this case very important to know the mechanical properties of composite materials after effect of environment such as water. Water absorption and his effects on the mechanical properties of fiber composites is an important subject, because water absorption leads to change dimensions and reduce of mechanical properties. The objective of this work is development the influence of water absorption on mechanical properties of composite specimens. The material used in this study was manufactured in JSC “Voronezh Aircraft Manufacturing Company”. Test specimens were prepared according to procedure of GOST standard. Longitudinal tensile, transverse tensile and in-plane shear properties were studied.