Study On The Open-hole Compression Properties Of Carbon/epoxy Fabric-unidirectional Tape Hybrid Laminates

With the rapid development of aerospace science and technology,higher requirements have been placed on the properties of materials.Composite materials have been widely used in aerospace and other engineering fields because of their excellent properties such as high strength and specific stiffness,become the fourth important and more promising structural material.Compared with conventional single fiber reinforced composites,hybrid fiber composites refer to the composite materials made of two or more kinds of fibers.Different types of fibers can complement each other and match each other to produce a synergistic effect.Through reasonable design,a structural form with lighter weight and satisfactory mechanical properties can be obtained.When these hybrid laminates are in use,due to the structural needs such as mechanical connection,it is inevitable to make opening treatment,resulting in the structural load bearing capacity decline.Therefore,studying the bearing characteristics of hybrid laminates with open holes has important reference value for the safety design of composite laminates.This paper chooses to conduct research on the compression characteristics of openings of carbon/epoxy fabric-unidirectional tape hybrid laminates and the influence of wet and hot environment.It mainly includes two aspects:First,through experiments,the influence of temperature and humidity environment and hybrid layer ratio on hole compression strength and failure mode are studied;Secondly,the ABAQUS finite element analysis software is used to simulate the opening compression process of woven laminates and hybrid laminates,establish a progressive damage model,study the damage evolution process of the composite material at the edge of the hole,and study the compression damage mechanism and failure mode of the laminated plate.Experimental investigation shows that the compression failure process of the opening is divided into two stages.In the first stage,the load increases linearly with the increase of displacement.In the second stage,when the load reaches the limit load,the test piece is crushed and the test is stopped.Under the same conditions,the pore compression strength of hybrid laminates is significantly higher than that of woven laminates.The temperature and humidity environment has a great influence on the hole compression performance of composite laminates.Under the high temperature and humidity environment,the moisture absorption softening of the resin base decreases the bearing capacity,but the compression strength retention rate of the hybrid laminates is high.The retention rate of M3-H6 laminate test specimens was as high as 92.5%,and that of M3-H5 laminate test specimens with the lowest compression strength retention rate also reached 86.7%;With the increase of 0° layering ratio,the hole compression strength of laminate increased nonlinearly.The compressive strength of openings in laminates is mainly referred to the ultimate load.The failure mode of laminates is mainly the lateral horizontal failure along the middle of laminates;The damage part is mainly concentrated around the hole,and the damage area spreads from the periphery of the hole to the surroundings.Comparing the woven structure with the hybrid structure,it is found that the damage load of the hybrid structure is significantly higher than that of the woven structure,which has a stronger bearing capacity.Numerical simulations show that in simulating the damage initiation,evolution and failure of hybrid laminates,the modified Hashin-Puck failure criterion is used to write the user subroutine VUMAT.It was found that during the compression failure of the openings of the hybrid laminate,the damage expanded in the direction of 0 degrees and the shape expanded in a strip shape.The damage expansion rate of the 0°direction layer is the fastest,which is the main bearing capacity layer.