Experimental Analysis of Low-Velocity Impact and CAI Properties of 3D four-directional Braided Composites after Hygrothermal Aging

Abstract

Abstract In this paper, 3D four-directional braided composites(3D4d-BC) materials with different braiding angles (15°and 30°) were subjected to hygrothermal aging treatment under different conditions, and then low-velocity impact and post-impact compression experiments were conducted to record the changes of relevant parameters. Through experiments, the temperature has an important effect on the increase of water absorption of the epoxy resin matrix. Higher water absorption results in better energy absorption for 3D4d-BC, but it is less integrated and therefore has lower residual compression properties. Although the intervention of oxygen molecules has little effect on the water absorption of the matrix, it has the degraded interface property between the matrix and the composite material, so it will further reduce its compression strength. The smaller the braiding Angle, the lower the water absorption efficiency and the lower the impact peak load during the hygrothermal aging process. In the compression process, H15 occurs mainly along the lateral side, and the failure form is buckling failure. H30 fractures along the 45° direction, and the failure form is a shear failure.