Interlaminar Stress Concentrations in Layered Structures: Part I - A Selective Literature Survey on the Free-Edge Effect since 1967

Mittelstedt, Christian; Becker, Wilfried

doi:10.1177/0021998304040566

Cited by 119 publications

(60 citation statements)

References 113 publications

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“…three-dimensional crack [1][2][3] or notch [4] situations as well as stress ÿelds in the vicinity of free edges [5] and corners [6-8] of layered structures-by means of standard ÿnite element method (FEM) analyses is computationally quite involved. Thus, there is a particular interest in introducing new and e cient analysis methods like e.g.…”

Section: The Boundary Finite Element Methods (Bfem)mentioning

confidence: 99%

Semi‐analytical computation of 3D stress singularities in linear elasticity

Mittelstedt

Becker

2005

Commun. Numer. Meth. Engng.

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SUMMARYThe boundary ÿnite element method (BFEM (Finite-Element Modelling of Unbounded Structures. Wiley: Chichester, England, 1996, The Scaled Boundary Finite Element Method. Wiley: Chichester, England, 2003) is employed for the investigation of the order of stress singularities for several classes of three-dimensional singular stress concentration problems, namely notch, crack and laminate freeedge situations. In all cases, the BFEM results agree excellently with reference results. The required computational e ort is considerably lower compared to e.g. standard ÿnite element computations and thus establishes the BFEM as a powerful tool for the semi-analytical modelling of linear elastic solids. KEY WORDS: stress singularities; boundary ÿnite element method; cracks; notches; free-edge e ects THE BOUNDARY FINITE ELEMENT METHOD (BFEM)The purely numerical analysis of singular elasticity problems-e.g. three-dimensional crack [1][2][3] or notch [4] situations as well as stress ÿelds in the vicinity of free edges [5] and corners [6-8] of layered structures-by means of standard ÿnite element method (FEM) analyses is computationally quite involved. Thus, there is a particular interest in introducing new and e cient analysis methods like e.g. the boundary ÿnite element method (BFEM) (BFEM, see e.g. References [9, 10], also known as scaled BFEM or consistent inÿnitesimal ÿnite element cell method), especially when detailed information on the asymptotic behaviour of the state variables-displacements, strains and stresses-in the vicinity of the singularity is desired. The BFEM combines the advantages of the FEM and the boundary element method (BEM) to a new and e cient procedure. The BFEM applies for the investigation of unbounded as well as bounded structures and as a prerequisite assumes a certain scalability of the given

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Section: The Boundary Finite Element Methods (Bfem)mentioning

confidence: 99%

Semi‐analytical computation of 3D stress singularities in linear elasticity

Mittelstedt

Becker

2005

Commun. Numer. Meth. Engng.

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“…The fracture mechanism of the joint is controlled by the stress concentration due to the contact angle and fiber compaction at the joint interface. It has been shown that all mechanical and adhesive composite joining methods impart some degree of stress concentration in the material [27,28]. Crack initiation and failure mechanisms at joint locations govern the macroscopic strength and failure of the composite [28,29].…”

Section: Bundle Joint Strengthmentioning

confidence: 99%

“…Examples of possible joining candidates include composite free edges [27], internal ply drop offs [29,31], holes [32] and between layers of lamina [33]. The potential for joining damaged fibers may also be of interest in the repair of composite structures after low velocity impacts [34].…”

Section: Seam Joint Strengthmentioning

confidence: 99%

Laser Joining of Continuous Glass Fiber Composite Pre-Forms

Tan

Yao

2012

ASME 2012 International Manufacturing Science and Engineering Conference

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A laser fusion joining method is investigated for the purpose of through thickness strengthening of fiber pre-forms used in the vacuum infusion fabrication of thick composite structures. Laser joining is achieved without filler materials to replace adhesives, pins or stitches used in conventional composite fabrication.A two step joining process is developed to fuse fibers within a single bundle and between multiple fiber bundles. Finite element analysis is used to investigate the joint strength with respect to joint morphology. Joint strength is found to be a function of the fiber contact angle and packing density at the joint interface. Tensile tests show that laser joined fiber bundles exhibit higher strength than comparable fastening methods. Lessons learned from the axial joining of fiber bundles are applied to joining in the radial and thickness directions of 3d pre-form architectures. Flow induced joint morphology and densification effects observed in the axial direction indicate the need for a two step joining process in the thickness direction. Fiber compaction effects on joint strength in the axial direction motivate the need for high fiber packing fraction at joint interfaces in the thickness direction. INTRODUCTIONComposite pre-preg fabrication involves placing densely packed resin infused tapes of reinforcement fibers in layers (laminates) and then curing to produce thin shell structures. Composite components manufactured from pre-preg processes exhibit high fiber packing fraction and high strength along the fiber directions, but offer little strength perpendicular to the fiber directions. Laminates of pre-preg construction contain no fiber reinforcements aligned in the thickness direction due to the layer by layer assembly process. Thus, pre-preg fabrication is undesirable for making composite parts requiring high through thickness strength and fracture toughness. One method for improving the through thickness strength of pre-preg constructed components is to insert metal pins through layers of pre-preg prior to curing [1,2]. Mechanical pinning increases through thickness strength, relying on matrix load transfer mechanisms between the fibers and pins. The insertion of metal pins into a stack of pre-preg lamina displaces the fibers in the lamina and introduces

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“…[3]. Furthermore, we mention a general survey on the computation of interlaminar stress concentrations, see Mittelstedt and Becker [4]. In the following we would like to concentrate on the question how to calculate interlaminar stresses.…”

Section: Introductionmentioning

confidence: 99%

An enhanced FSDT model for the calculation of interlaminar shear stresses in composite plate structures

2009

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Summary In this paper a procedure is proposed to calculate the interlaminar shear stresses in layered composite plates. The transverse shear stresses are obtained via the constitutive law and derivatives of some warping functions. For 4-node elements the derivatives of curvatures and strains of the reference surface with respect to the in-plane coordinates are determined through a system of four equations. Hence the equilibrium equations lead to a coupled system of ordinary differential equations, which are solved applying a displacement method. The resulting interlaminar shear stresses are continuous at the layer boundaries. The quality of the obtained results is demonstrated within several plate examples with symmetric and unsymmetric lay-ups. Comparisons with two other approaches using 9-node elements and a solid shell formulation together with a three-dimensional material law show good accuracy and efficiency of the proposed algorithm.

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Interlaminar Stress Concentrations in Layered Structures: Part I - A Selective Literature Survey on the Free-Edge Effect since 1967

Cited by 119 publications

References 113 publications

Semi‐analytical computation of 3D stress singularities in linear elasticity

Semi‐analytical computation of 3D stress singularities in linear elasticity

Laser Joining of Continuous Glass Fiber Composite Pre-Forms

An enhanced FSDT model for the calculation of interlaminar shear stresses in composite plate structures

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