Development and manufacturing of flexible joints based on corrugated composite laminates

This paper investigates the exploitation of corrugated composite laminates to design flexible joints. The joint can sustain axial load using a flexible frame integrated into a composite tube, which transmits torque and supports the frame allowing significant bending deformations with low bending stiffness. The concept is explored numerically and applied to the design of a heavy-duty flexible joint for rotorcraft. The element is required to transmit torque, allow misalignments, and withstand high compressive forces in emergency landing conditions. After preliminary design, a manufacturing technique is developed to produce axisymmetric corrugated laminates. Technological demonstrators are produced and subjected to tests, investigating the failure modes, validating the numerical approach for predictions, and confirming the quality of manufacturing. Finally, a complete prototype is designed in detail, produced, and then tested in bending and compression. The results, in agreement with the numerical analyses, confirm the capability to withstand design limit loads without damage development.