Influence of the Free Edge upon the Strength of Angle-Ply Laminates

Pipes, R. Byron; Kaminski, B.; Pagano, N. J.

doi:10.1520/stp36487s

Cited by 37 publications

(7 citation statements)

References 6 publications

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“…These are predicted to be the locations of greatest susceptibility to delamination when AWJ cutting. The interlaminar stresses are highly sensitive to the stacking sequence [193][194][195] and are largest near free edges [196,197] and decrease rapidly with distance from free boundaries [128]. This is consistent with the numerical results of Fig.…”

Section: Delamination Onset When Awj Cuttingsupporting

confidence: 83%

Predicting Surface Roughness and Delamination When Abrasive Waterjet Machining Fiber Reinforced Polymer Composites

Schwartzentruber¹

2023

Preprint

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The machining of composite materials is difficult because of their non-homogenous structure and their constituents commonly possess a high resistance to cutting. Abrasive waterjet machining (AWJM) is more attractive for composite substrates than conventional machining techniques because of its ability to rapidly machine a wide variety of materials with low reactionary forces on the workpiece, and without creating a heat-affected zone. However, AWJM is prone to producing variable surface roughness and delamination. This dissertation aimed to model these surface roughness and delamination mechanisms. The thesis presents 2D and 3D roughness models capable of predicting the surface roughness during abrasive waterjet (AWJ) trimming of composite substrates. The models were able to predict the measured surface roughness with an average error of 10% and 16%, for the 2D and 3D models, respectively. The thesis also presents experimental and numerical results characterizing the delamination when AWJ piercing and cutting a carbon-fiber/epoxy laminate. Fluid-structure interaction (FSI) models created to simulate the piercing process showed that interlaminar delamination was due to the hydraulic shock (‘water hammer’) associated with liquid jet impact. As expected, increased pressure and nozzle size resulted in ply debonding, and was experimentally verified using 3D x-ray micro-tomography. The composite anisotropy was found to produce an asymmetric shock loading along the liquid-solid interface, which contributed to the asymmetric delamination. The FSI model showed that delamination when cutting carbon-fiber/epoxy depended primarily on the normal interlaminar stress, with relatively large damage zones occurring ahead of the cutting front. This trend was also observed in x-ray micro-tomographs of an AWJ cut. The amount of delamination across different process parameters was also measured using a moisture uptake methodology, and showed that increase traverse speed, increased nozzle size, and decreased abrasive flow rate, increased delamination. Prediction and characterization of surface roughness and delamination when AWJM will allow further improvement of cut-surface finish and structural integrity of composite materials, respectively

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Section: Delamination Onset When Awj Cuttingsupporting

confidence: 83%

Predicting Surface Roughness and Delamination When Abrasive Waterjet Machining Fiber Reinforced Polymer Composites

Schwartzentruber¹

2023

Preprint

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“…Since it is felt that the experimental observation of free-edge effects and the conduction of corresponding failure analyses is a very special field and worth a separate review work, we will only cite some references on this topic, yet we will not go into more details. The interested reader may refer to some experimental studies reported in for example [4][5][6]10,12,37,58,68,72,81,87,88,120,[124][125][126] and may consult further references cited therein.…”

Section: Experimental Investigationsmentioning

confidence: 99%

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

Mittelstedt

Becker

2004

Journal of Composite Materials

119

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Stress concentration phenomena in composite laminates are technically important situations. A well-known problem of this class is the free-edge effect in composite laminates or as a superordinated example the stress concentrations in the vicinity of free laminate corners (so-called free-corner effect). The present work is split into two parts. In the present contribution, after a short introduction to the given stress concentration problems in general we will survey relevant selected literature on the classical free-edge effect dating from 1967 until today. Beside accentuation on approximate closed-form analytic methods for the stress analysis in the free-edge effect situation, numerous references on numerical methods and investigations on the occurring stress singularities are also cited. In a subsequent paper we will present a simple closed-form method for the analysis of the stress fields in the vicinity of free laminate corners with arbitrary layup. The method is based on adequate stress shape assumptions and a variational principle. The present article contains 136 references.

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“…Experimental investigations are reported in e.g. [68][69][70][71][72][73]. The interested reader may refer to various available detailed surveys on this topic, see e.g.…”

Section: Introductionmentioning

confidence: 99%

Free-corner Effects in Cross-ply Laminates: An Approximate Higher-order Theory Solution

Mittelstedt¹,

Becker

2003

Journal of Composite Materials

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Like in the well-known free-edge effect situation, stress fields in the vicinity of free corners of layered plates exhibit a distinct three-dimensional and singular behavior and thus represent an important technical situation. Nevertheless, there are only few thorough investigations available concerning stress concentrations near free laminate corners. Since numerical analyses of stress concentration phenomena in composite laminates are computationally expensive, the present contribution is devoted to a simple closed-form higher-order theory approach for the calculation of displacements, strains, and stresses in the vicinity of a rectangular corner of a symmetric cross-ply laminate under thermal load. Appropriate representations for the displacement field in the manner of a single-layer theory with unknown inplane components and assumed trigonometric functions through the thickness yield closed-form expressions for the strains and stresses throughout the whole laminate. The inplane displacement functions are determined by equilibrium considerations in an integrated form with the solution of some resultant characteristic equations. Boundary conditions are fulfilled in an integral sense. The present approach can be applied easily, requires little computational effort and is in good conformity with comparative finite-element calculations and other closed-form analyses.

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Influence of the Free Edge upon the Strength of Angle-Ply Laminates

Cited by 37 publications

References 6 publications

Predicting Surface Roughness and Delamination When Abrasive Waterjet Machining Fiber Reinforced Polymer Composites

Predicting Surface Roughness and Delamination When Abrasive Waterjet Machining Fiber Reinforced Polymer Composites

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

Free-corner Effects in Cross-ply Laminates: An Approximate Higher-order Theory Solution

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