Analysis Of Stiffness And Strength Of Two-Dimension Grid Composite Lattice Structures

Manufacturing and analysis method of stiffness and strength of two-dimension grid composite lattice structures (2D-GCLS) were studied in this paper. A model for predicting the in-plane stiffness and flexural stiffness of the 2D-GCLS was developed. Finite element models for analyzing stress distributions on local area of the rib-overlap and whole structures were built, respectively. Manufacturing of the 2D-GCLS by filament winding process was investigated and mechanical behavior of the structures under axial compression loading was evaluated.A repeat unit of the two-dimension grid composite lattice cylinder was used to simulate deformation of ribs of the 2D-GCLS, and equivalent in-plane stiffness and flexural stiffness of the repeat unit were obtained. Effects of the geometrical parameters of the ribs on the stiffness were further investigated. Simulated results show that under same weight conditions, width of helical rib b_h, height of the ribs H and spacing of the helical rib a_h have significant effects on the in-plane and flexural stiffness.A finite element model for the whole cylinder was built. Difference of the plies of fiber and geometrical shape of the overlap area of ribs were eliminated at this moment for purpose of getting distributions of stress and strain over the whole structures. Numerical results show that stress concentration on the overlap area of the ribs can be observed. Effects of curvature of rib at the overlap area on bulking of the ribs were investigated and a critical curvature of the ribs was obtained. According to the results a finite element model for the repeat unit of the cylinder was built and the difference of the plies of fiber at the overlap area of the ribs was involved in the finite element model. Numerical results show that stress concentration on the overlap area of the ribs can be observed.A glass fiber reinforced epoxy matrix composite grid cylinder structure was fabricated successfully by filament winding process. A wooden mould and a silicon rubber mould were designed and fabricated firstly, and the grid cylinder was obtained by filament winding process. Volume fractions of fiber at the rib overlap area and ribs of the grid cylinder are 59.2% and 36%, respectively. Mechanical properties of the cylinder structures with different dimensions of the ribs were examined under axial compression loading.Looking at the broken area of the tested structures the fiber bond fracture and squeezes can be observed. Further observation with SEM shows that fiber broken and delaminated cracks between fibers and epoxy matrix can also be observed.Comparison with experimental results the predicted stiffness of the grid structure cylinders is quite good and the relative error between them is less than 3%.