Influence of stacking sequence and interlaminar layer on stress singularities at free edge of composite laminates

Meccanica ◽  
1990 ◽  
Vol 25 (1) ◽  
pp. 32-39 ◽  
Author(s):  
Gian Luca Ghiringhelli ◽  
Giuseppe Sala
Keyword(s):  
Composite Laminates ◽  
Free Edge ◽  
Stacking Sequence ◽  
Stress Singularities

Hypersingularities in Three-Dimensional Crack Configurations in Composite Laminates

2013 ◽  
Vol 577-578 ◽  
pp. 209-212
Author(s):  
Sascha Hell ◽  
Wilfried Becker
Keyword(s):  
Composite Laminates ◽  
Three Dimensional ◽  
Free Edge ◽  
Aerospace Engineering ◽  
Stress Singularities ◽  
Infinite Domains ◽  
Failure Tolerance ◽  
Failure Risk ◽  
Elasticity Problems ◽  
Scaled Boundary Finite Element

Composite laminates meanwhile are of common use, especially in aerospace engineering. Inter-fiber cracks within a laminate ply are often accepted in practice to be still within failure tolerance, although the structural mechanics of this situation is not fully understood. The situation gets even more complex when the interaction of inter-fiber cracks in neighboring plies is considered. In this work, such three-dimensional crack configurations in composite laminates involving inter-fiber cracks and the influence of the laminate free-edge effect are studied by means of the Scaled Boundary Finite Element Method (SBFEM). The SBFEM is an efficient semi-analytical method that permits the analysis of linear elasticity problems including stress singularities or infinite domains. It is shown that in crack configurations in composite laminates so-called hypersingularities (or supersingularities) can occur, i.e. stress singularities which are of higher order than the classical crack singularity. This indicates that the laminate failure risk induced by certain considered crack configurations is not to be underestimated.

Boundary-Layer Effects in Composite Laminates: Part 1—Free-Edge Stress Singularities

1982 ◽  
Vol 49 (3) ◽  
pp. 541-548 ◽  
Author(s):  
S. S. Wang ◽  
I. Choi
Keyword(s):  
Boundary Layer ◽  
Composite Laminates ◽  
Stress Singularity ◽  
Homogeneous Solution ◽  
Expansion Method ◽  
Free Edge ◽  
Anisotropic Elasticity ◽  
Stress Singularities ◽  
Eigenfunction Expansion Method ◽  
Reinforced Composite

A study of boundary-layer stress singularities in multilayered fiber-reinforced composite laminates is presented. Based on Lekhnitskii’s stress potentials and the theory of anisotropic elasticity, formulation of the problem leads to a pair of coupled governing partial differential equations (P.D.E.’s). An eigenfunction expansion method is developed to obtain the homogeneous solution for the governing P.D.E. ’s. The order or strength of boundary-layer stress singularity is determined by solving the transcendental characteristic equation obtained from the homogeneous solution for the problem. Numerical examples of the singular strength (or singular eigenvalues) of boundary-layer stresses are given for angle-ply and cross-ply composites as well as the cases of more general composite lamination.

A General Ply Design for Aero Engine Composite Fan Blade

2017 ◽  
Author(s):  
Jiaguangyi Xiao ◽  
Yong Chen ◽  
Qichen Zhu ◽  
Jun Lee ◽  
Tingting Ma
Keyword(s):  
Composite Laminates ◽  
Composite Structures ◽  
Stacking Sequence ◽  
Composite Blade ◽  
Arduous Task ◽  
Aero Engine ◽  
Margin Of Safety ◽  
Fan Blade ◽  
The Impact ◽  
Ply Orientation

Composite fan blade ply lay-up design, which includes ply drop-off/shuffle design and stacking sequence design, makes fan blade structures different from traditional composite structures. It gives designers more freedom to construct high-quality fan blades. However, contemporary fan blade profiles are quite complex and twisted, and fan blade structures are quite different from regular composite structures such as composite laminates and composite wings. The ply drop-off design of a fan blade, especially for a fully 3D fan blade, is still an arduous task. To meet this challenge, this paper develops a ply lay-up way with the help of a software called Fibersim. The fully 3D fan blade is cut into ply pieces in Fibersim. As a result, an initial ply sequence is created and ply shuffle could revise it. Because of the complexity of ply shuffling, the ply shuffle table developed in this paper mainly refers to the design experience gained from simple plate-like laminate structures and some criterion. Besides, the impact of different ply orientation patterns on the reliability of composite fan blade is studied through static and modal numerical analysis. The results show that this ply lay-up idea is feasible for aero engine composite fan blade. Under the calculated rotating speeds, the ply stacking sequence 4 (i.e.[−45°/0°/+45°/0°] with the outer seven groups are [−45°/0°/−45°/0°]) shows the greatest margin of safety compared with other stacking sequences. Modal analysis shows that plies with different angles could have relatively big different impacts on blades vibration characteristics. The composite fan blade ply design route this paper presents has gain its initial success and the results in this paper might be used as basic references for composite blade initial structural design.

Stacking sequence blending of multiple composite laminates using genetic algorithms

2001 ◽  
Author(s):  
Grant Soremekun ◽  
Zafer Gurdal ◽  
Christos Kassapoglou ◽  
Darryl Toni
Keyword(s):  
Genetic Algorithms ◽  
Composite Laminates ◽  
Stacking Sequence
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