Delamination Damage Defect Detection Of Composite Materials Based On Vibration Modal Analysis

With the improvement of science and technology,"lightweight"has become the goal pursued in the fields of aerospace,automobiles,ships,and daily necessities.Carbon fiber composite laminates rely on their excellent properties-low density,high specific modulus,and high specific strength.High pressure resistance,high temperature resistance,corrosion resistance and other advantages are widely used.In the process of material use and service,the structure itself will inevitably undergo fiber fracture,impact,delamination and other different modes of damage.Long-term use will also seriously affect the stability of the structure and reduce the safety of the use of materials.This project uses a combination of finite element simulation and experimental verification to carry out damage detection on carbon fiber composite laminates,and conducts research on the impact of circular delamination damage on the modal frequency and mode shape of laminates based on vibration modal analysis.Analyze the effect of the delamination damage of the laminate on the modal characteristics of the laminate,and use the Rayleigh-Ritz method to calculate the effect of the delamination damage on the frequency properties of the laminate,laying a foundation for improving the convenience of detection.The DH5927 dynamic signal test system was used to establish a vibration test platform for four-corner fixed-supported carbon fiber laminates.The modal characteristics of non-damaged laminates and laminates with varying degrees of delamination damage were experimentally studied.The difference between the third-order vibration mode frequency and the mode shape is analyzed for the damage of different sizes,and the influence of different types of laminate structures on the vibration mode characteristics of the laminate.Use the ABAQUS finite element analysis software to perform three typical laminate structures:[0°]₁₆,[0°/90°]_4s,[0°/90°/±45°]_2sModeling,using Cohesive adhesive layer to simulate delamination damage,designing laminates with circular damages of 3mm,6mm,and 9mm in radius,analyzing and comparing the first three-order modal frequencies of laminates,and extracting them through secondary development Vibration shape and MATLAB fitting to get the vibration shape curve.The study found that different ply structures of the same material have a greater impact on the modal frequency;damage will reduce the modal frequency of the material,and the second-order modal frequency of the material has the greatest impact.2%of the damage area has a significant impact on the modal frequency.The rate of change has reached 2.5%;the modal shape has a large gap between different ply structures,and the exchange of peaks and troughs generated by the laminated plate modal shape of the same ply structure with different damage areas and the modal shape Quantitative analysis of the area ratio can be used to evaluate damage prediction for material damage.Based on the vibration modal analysis method,the damage degree of the composite laminate can be detected during service,and a reasonable inspection method is provided to improve the safety of the material.If necessary,it can be replaced in time to reduce the risk of use and improve the safety.