Ultrasonic welding process and parameter optimization for wrapped nodes of CF/PEEK trusses in space environment

Aiming at the key issues of low connection efficiency and poor quality of CF/PEEK (Carbon Fiber/Polyether-Ether-Ketone) truss wrapped nodes in the on-orbit manufacturing of large space structures, an innovative truss node clad horn technology based on ultrasonic welding is proposed. Furthermore, by establishing a multi-field coupling model of heat generation-heat transfer-melt spreading for CF/PEEK ultrasonic welding in a vacuum environment. The interface friction-viscoelastic heat generation mechanism is revealed for the first time, which demonstrates the coupled heat generation effect of interface frictional dissipation and viscoelastic loss of the PEEK matrix during ultrasonic welding. and the welding temperature and liquid-phase spreading law are accurately predicted. The optimal design of the clad horn is completed; after optimization, the amplitude of the clad horn is 31.5 μm and the frequency is 28.11 kHz, which perfectly adapts to the welding requirements of truss nodes. A vacuum test under 10^-2 Pa is conducted to verify the validity of the model, and the optimal process parameters are determined. Compared with the atmospheric environment, the connection area and lap shear strength in the vacuum environment are increased by 44% and 60%, respectively. The technical system of "mechanism modeling-joint design-process matching" is constructed, which provides key theoretical basis and equipment support for the efficient on-orbit connection of large CF/PEEK trusses.