湿热环境对挖补修理后复合材料层合板振动特性的影响

通过对湿热环境下阶梯挖补胶接修理后碳纤维/双马树脂(T300/QY8911)层合板振动特性的分析,探究了挖补修理后碳纤维/双马树脂层合板在不同湿热效应下的振动特性。基于Mindlin-Reissner板理论与最小势能变分原理,在考虑湿热效应前提下,推导了正交各向异性复合材料层合板的本构关系及四边简支条件下的自由振动控制方程;其次,利用ABAQUS软件建立了三维黏弹性有限元挖补修理模型,应用Fortran语言将湿热耦合下的应力-应变本构关系编入UMAT二次开发文件中,采用三维八节点五自由度等参单元进行了离散。通过与参考文献对照,验证了胶接修理后T300/QY8911层合板有限元模型和编译的湿热环境下UMAT子程序的合理性与有效性。算例结果表明:湿热环境对挖补修理后层合板固有频率的影响比对完整层合板严重;温度对材料性能的影响大于湿度;相比于材料性能变化对振动特性的影响,湿热残余应力对胶接修理后层合板振动特性的影响占主导;参考环境下,胶接修理后层合板的固有频率增大;湿应力对层合板固有频率的影响大于热应力。

Effects of vibration characteristics of step repaired laminated composites under hygrothermal environment

Through the analysis of the vibration characteristics of T300/QY8911 step repaired laminated composites under hygrothermal environment,the vibration characteristic of T300/QY8911 step repaired composite plate under different hygrothermal effects are explored.Firstly,based on Mindlin-Reissner plate theory and the variational principle of minimum potential energy,considering hygrothermal environment factors,this paper derives the orthotropic composite material plates of constitutive relation and the free vibration governing equation sunder four end sclamped.Secondly,by using ABAQUS software to establish three-dimensional finite element model of step repaired laminate,the software uses UMAT subroutine interface to bring the refactor hygrothermal material stress-strain constitutive relation to it by using Fortran language.The vibration characteristics are analyzed by using the isoparametric element with eight nodes and five degrees of freedom.The UMAT subroutine and the model are verified by comparing with the reference literature.The numerical results show that the natural frequency of composite plate increases more severely after being step repaired than intact composite laminate.The influence of temperature on the properties of materials is greater than that of moisture rate,the influence of residual stress on the vibration characteristics of step repaired composite laminate is dominant.The influence of wet stress is greater than that of thermal stress under reference environment.