Residual Strength Analysis Of Damaged Composite Honeycomb Plate In Hot And Humid Environment

The proportion of composite materials in the structural weight of the B787 has reached 50%,and that of the C919 composite materials in the domestic civil aircraft accounts for about 25%.The mechanical properties of composite materials are especially sensitive to the humid and thermal environment.However,most studies on honeycomb sandwich materials in our country and abroad do not consider the influence of the environment on the materials.Honeycomb core layer was assumed as a uniform entity by sandwich equivalent theory,the wet stress in hygrothermal environment is equivalent to the thermal stress,and the constitutive equation of honeycomb sandwich material under hot and humid environment was established,improved Hashin criteria and Besant criterion were used as the failure criterion of honeycomb sandwich material,which was realized by writing VUMAT subroutine.The Cohesive element simulation panel and connection between the core layer to establish finite element model of honeycomb sandwich plates under hygrothermal environment,hygrothermal environment will effect the performance of the honeycomb sandwich materials bending.By removing some of the Cohesive zone model panel and core layer debonding phenomena to establish finite element model under the debonding damage debonding location,zthe debonding area,number of debonding and debonding area,the relative position between bending the influence of the residual strength of honeycomb sandwich material.The results showed that the ultimate bearing capacity of the material decreased by 1.6% in the humid and thermal environment and decreased with the increase of humidity and temperature.The debonding phenomenon will accelerate the separation between the panel and the core layer,and the debonding position will affect the damage spreading property of the material and reduce the bending strength of the material.Edge debonding can reduce the maximum stress that the honeycomb sandwich material can bear more than the center debonding and can aggravate the separation between the panel and the core layer.Hot and humid environment more than the relative position between the debonding area for bearing the regularity of the symmetric point distribution for honeycomb sandwich materials contribute less residual strength,panel on symmetry material area debonding stress value decline rate is 31.04%,symmetric debonding of the region under the panel material maximum stress value of 95.73%,asymmetric debonding of the region on the panel material maximum stress value of the decline rate is 99.39%.