Research on stratified evolution of composite materials under four-point bending loading

Abstract

Abstract:In order to explore the effect of stratified evolution and delamination on the load capacity and service life of the composite materials under the four-point bending loading, the artificial tectonic defects of the different positions were set up. The four-point bending test was carried out, and the whole process was recorded by acoustic emission, and the damage degree of the composite layer was judged by the impact accumulation of the specimen -time-amplitude history chart, load-time-relative energy history chart, acoustic emission impact signal positioning map. The results show that the stratified defects near the surface of the specimen accelerate the process of material failure and expansion. The location of the delamination defects changes the bending performance of the composites to a great extent. The closer the stratification defects are to the surface of the specimen, the greater the damage, the worse the service capacity of the specimen. IntroductionGlass fiber reinforced composite materials have excellent plasticity, fatigue resistance, and durability. Therefore, they are widely used in aerospace, shipbuilding, military equipment, sports equipment, water conservancy, infrastructure, and many other areas [1][2][3][4][5]. However, during their operation, sub-layer damage may enhance the composite material stratification, which issue becomes more and more topical.Some scholars and experts have made a study of composite materials. Huget et al [6] used the acoustic emission (AE) method to monitor the AE signal of polyester / GF composites during static tensile loading. By analyzing the data on duration, the two types of failure modes of fracture and debonding were found and the neural network was used to identify the damage. Alander et al [7] performed a three-point load loading test on composite specimens and found that the damage of the specimen occurred at 19% -32% of the failure load. Wu [8] used the Weibull function to describe the composite layer by the material damage mode and found that the tensile strength of the material with the number of layers is gradually decreased. The tensile strength values of the two-, three-and four-layer fiber reinforced composites were lower that of single-layer ones by 10, 20, and 25%, respectively. However, there is scarce research on the stratified damage evolution behavior of glass fiber reinforced composites, which is critical to the bearing capacity and service life of composite materials.