Free edge stress analysis of laminated structures with arbitrary cross sections using mechanics of structure genome

Lingxuan Zhou, Purdue University

Abstract

Composite laminates have been increasingly used in advanced structural applications, due to their excellent strength-to-weight properties and considerable flexibility on designing with respect to the laminate layup. However, the heterogeneity and anisotropy of composite laminates have brought many challenges for analysis and numerous researches have been devoted in this field. A well known problem which has been studied intensively is the so-called free-edge problem. It states that due to the mismatch in elastic properties of adjacent layers, full-scale three-dimensional (3D) and highly concentrated stress fields will occur in the vicinity of the free edges. The interlaminar stresses grow very rapidly at the layer interface over a small boundary region and decay quickly toward the inner laminate region at the free edges. As the transverse normal and shear strength of interfaces are usually very low, these interlaminar stresses may cause initiation of delamination. Therefore, it is important to obtain the accurate 3D stress field of the free-edge problem. In the present study, free-edge stress analysis of composite laminated structures with arbitrary cross sections is dealt with mechanics of structure genome (MSG). MSG is a unified theory that links the original heterogeneous structures with microscopic details and the hypothetical homogeneous continuum used in the macroscopic structural analysis. A cross-sectional analysis specialized from MSG is formulated to solve the free-edge problem of composite laminates with arbitrary cross sections. In contrast to the existing methods, MSG cross-sectional analysis is applicable to laminates of general layups under general loads. In this thesis, MSG based free-edge stress analysis has been further explored to analyze composite laminated structures with arbitrary cross sections and arbitrary layup under general loads. An I-beam laminate and a curved beam laminate subjected to extension, bending and twisting are analyzed separately by MSG to study the distributions of interlaminar stresses. The results successfully capture the stress singularity at the free edge and are in excellent agreement with 3D finite element analysis (FEA) results. Moreover, MSG shows significant advantages in efficiency while accuracy is maintained by comparing to 3D FEA results.

Degree

M.S.A.A.

Advisors

Yu, Purdue University.

Subject Area

Aerospace engineering|Mechanical engineering

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