Experimental and computational study on flattening and punching of deployable composite shells for space applications

Bistable carbon fiber reinforced polymer (CFRP) shells have been successfully used in deployable space structures, where they generally undergo flattening and punching processes before assembly with the central hub in the housing mechanism, yet the damage and mechanical properties of continuous processes have not been well characterized. Mechanical response and damage evolution of CFRP shells during flattening and punching processes were analyzed experimentally and computationally in this paper. A finite element model employing continuum shell elements was established to obtain stress distribution and damage propagation during flattening of the CFRP shells. Subsequently, damage characteristics of the CFRP shells during punching holes were analyzed, followed by experimental validations of flattening and punching of CFRP shells. During the flattening process, the simulation results indicate that stress concentrates in the innermost and outermost plies, and the maximum flattening force yields a difference of 3.4% with respect to the experimentally measured value. During the punching process, the simulated maximum punching force considering initial stress was 320.5 N, yielding an error of 11.3% compared to the experimental measurement. In addition, the fiber compression damage and matrix cracking were shown around the hole edges in the simulation, which show great consistency with the scanning electron microscopy (SEM) observations.