Failure load prediction of anisogrid cylindrical composite lattice structures using failure criterion based on ratio of bending to compressive stress

This paper investigates the failure load prediction of anisogrid cylindrical composite lattice structures under axial compression. The failure criterion to predict compressive failure load of lattice structure is developed by using the compression test results of representative subelement specimens including several unit cells. Compression tests of subelement using two different fixture jigs which generate different ratio of bending to compressive stress in the knot region of lattice structures were performed. The critical stress function is introduced from the compression test results and is utilized in failure criterion. The finite element analysis is used to calculate the failure load with the proposed failure criterion and also the buckling load for the full-sized cylindrical lattice structures. The compression failure loads for two different full-sized cylindrical lattice structures agreed well with the predicted failure loads by using the failure criterion proposed in this paper. The results of these studies indicate that the proposed failure criterion for the cylindrical composite lattice structures under compressive load in this work can be applied to the stress analysis and optimization problem in the preliminary design phase.