An end connection for a shaft made of composite material, which accommodates for differences in stiffness, thermal expansion, chemical resistance between the shaft and the member connected thereto and operates under oscillating torque, thrust, and bending loads, and also provides for manufacturing flexibility in enabling the shaft and connection to be produced as separate parts which are formed when final assembly is to occur. The connection has a male insert which is inserted into the end of the composite shaft. Axial and circumferential grooves in the surfaces of the male insert and the shaft. These grooves are aligned to form circumferential and axial keyways which intersect each other. Material is injected into the keyway and polymerizes to form structural keys which transmit the thrust and torque, while locking the insert member and the shaft permanently together. The bending loads are transmitted through the tight fit extending axially between the shaft, insert member and keys. The radial thickness of the end of the shaft, the amount and orientation of the reinforcing fibers therein and the insert are matched so that their stiffness index approximately match. The composite shaft may be connected to a mixing impeller to provide a reliable support and drive therefor.