Structural response of a hybrid composite/aluminum strut assembly

This paper presents the structural response of a full-scale composite strut and a hybrid strut/ship connection. The strut is comprised of a pultruded E-glass/epoxy core, a filament wound carbon/epoxy structural section, and an E-glass/vinyl ester outer wrap used to protect the strut from the sea environment. The connection of the strut to the ship is made using an adhesively bonded aluminum boot that acts as the ship interface. A summary of the strut design, the experimental setup, and instrumentation details, is presented. Testing includes studies of the low-level cyclic flexural response about the weak axis, flexure about the strong axis, and combined weak axis flexure and torsion. A test to peak load was conducted about the strong axis and a high-displacement amplitude test was conducted about the weak axis. The predominant failure mode during the high-level strong axis test consisted of failure in the aluminum material at the base of the test article and failure in the aluminum flanges that mounted the boot to the test frame. No signs of distress were observed in the composite material, either visually or using the instrumentation. The peak load about the strong axis exceeds the design moment by a factor of 3.6. A finite element analysis of the strut is also provided along with a comparison to the test results and shows that the rotational stiffness of the hybrid connection considerably influences the overall response.