scholarly journals Free Edge Strain Concentrations in Real Composite Laminates: Experimental-Theoretical Correlation

1985 ◽  
Vol 52 (4) ◽  
pp. 787-793 ◽  
Author(s):  
C. T. Herakovich ◽  
D. Post ◽  
M. B. Buczek ◽  
R. Czarnek
Keyword(s):  
Finite Element ◽  
Shear Strain ◽  
Composite Laminates ◽  
Critical Angle ◽  
Axial Strain ◽  
Free Edge ◽  
Experimental Results ◽  
Resin Matrix ◽  
Maximum Shear Strain ◽  
Isoparametric Finite Element

The magnitude of the maximum shear strain at the free edge of axially loaded [θ2/–θ2]s and [(± θ)2]s composite laminates was investigated experimentally and numerically to ascertain the actual value of strain concentration in resin matrix laminates and to determine the accuracy of finite element results. Experimental results using moire´ interferometry show large, but finite, shear strain concentrations at the free edge of graphite-epoxy and graphite-polyimide laminates. Comparison of the experimental results with those obtained using several different finite element representations showed that a four-node isoparametric finite element provided the best and most trouble-free numerical results. The results indicate that the ratio of maximum shear strain at the free edge to applied axial strain varies with fiber orientation and does not exceed nine for the most critical angle which is 15 deg.

Progressive Damage Analyses of Composite Laminates Exhibiting Free Edge Effects Using a New Micro-Meso Approach

2011 ◽  
Vol 471-472 ◽  
pp. 263-267
Author(s):  
Hossein Hosseini-Toudeshky ◽  
Amin Farrokhabadi ◽  
Bijan Mohammadi
Keyword(s):  
Edge Effects ◽  
Composite Laminates ◽  
Free Edge ◽  
Experimental Results ◽  
Progressive Damage ◽  
Stress Strain ◽  
Laminate Thickness ◽  
Stress Variations ◽  
Angle Ply Laminates ◽  
Free Edges

In this paper, the developed new micro-meso method by the authors is used for the edge-effects analyses of various angle-ply laminates such as [10/-10]2s and [30/-30]2s. It is shown that the obtained stress-strain behaviors of laminates are in well agreement with the available experimental results. The stress variations through the laminate thickness and near the free edges are also computed and compared with the available CDM results.

Finite Element Analysis of Dynamics of Human Muscle Compressed by Fabric Sleeve

2018 ◽  
Author(s):  
Shodai Ueda ◽  
Atsushi Sakuma
Keyword(s):  
Finite Element ◽  
Shear Strain ◽  
Athletic Performance ◽  
Optimal Level ◽  
The Body ◽  
Moderate Pressure ◽  
Maximum Shear Strain ◽  
Element Analysis ◽  
Analysis Of Dynamics ◽  
Method Model

Recently, compression wear has become the preferred performance material for many athletes, where it has the effect of reducing the burden on the body by suppressing muscle vibrations and improves athletic performance by providing the body with suitable moderate pressure. This study concerns thigh sleeves formed of compression wear. The optimal level of compression is studied in order to improve athletic performance and reduce muscular strain. Subsequently, the mechanics of the thigh compression sleeve are discussed. Here, the optimal tensile rigidity of the sleeve, which is calculated using the Young’s modulus of the sleeve in the circumferential direction, is discussed with the aim of reducing muscular strain. The finite element method model is adopted to represent the thigh, which commonly experiences muscle strain during running. The model is constructed using a semi-circular shape, which represents the thigh cut in the transverse plane. The model consists of two solid components, which reflect the muscle (outer) and femur (inner), as well as a shell that covers the thigh. The model generates sinusoidal vibrations, which reflect human behavior when running in a uniaxial direction. The maximum shear strain is approximately half of the tensile rigidity of the sleeve. Indeed, the muscle is sufficiently soft that the tensile rigidity of the sleeve is generally smaller when there is little shear strain on the muscle. From these results, it is concluded that the maximum shear strain of the muscle decreases by almost half when covered by the thigh compression sleeve compared to when no thigh compression sleeve is worn. Furthermore, the shear strain of the muscle can be reduced by varying the tensile rigidity of the sleeve when the human is running. Finally, the tensile rigidity of the sleeve can be decreased to reduce the shear strain of the muscle as it softens.

Implementation of an Efficient Description of Elastic Properties of a Layered Composite in a Finite Element

1992 ◽  
Author(s):  
Edward M. Patton
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Free Edge ◽  
Layered Composite ◽  
Single Element ◽  
Isoparametric Finite Element ◽  
Interlaminar Shear ◽  
Displacement Based ◽  
Constitutive Formulation ◽  
Good Agreement

Abstract A constitutive formulation for a layered composite originally proposed by Christensen (1) is implemented in a displacement-based three dimensional isoparametric finite element. The element is tested against the much studied free-edge stress problem, and is found, in general, to have good agreement with published results using a single element through the thickness of the laminate, even in the vicinity of the free edge. In-plane stresses and through thickness normal stresses agree extremely well with previous results. The results for interlaminar shear stress are, however, somewhat lower than previously published. Reasons for this discrepancy are discussed.

Multiaxial Stress Concentration in an Externally Pressurized Cylinder With an External Circumferential Groove

1995 ◽  
Vol 117 (4) ◽  
pp. 404-409
Author(s):  
S. M. Tipton ◽  
K. A. Hickey ◽  
M. S. Rawson ◽  
J. R. Sorem
Keyword(s):  
Finite Element ◽  
Stress Concentration ◽  
Axial Strain ◽  
Radial Strain ◽  
Strain Ratio ◽  
Experimental Results ◽  
Stress Strain ◽  
Elastic Plastic ◽  
Circumferential Groove ◽  
Neuber's Rule

A thick-walled cylindrical specimen containing an external circumferential groove was subjected to external pressure. To investigate the maximum pressure sustainable by the reduced wall thickness, strain gage measurements were taken during external pressurization tests. For comparison to experimental results, an elastic-plastic notch stress-strain analysis was conducted based on Neuber’s rule. The analysis utilized multiaxial elastic finite element results along with elastic-plastic tensile test data for the cylinder material. Based on experimental observations, it was necessary to supplement the approach with an additional relation between elastic and elastic-plastic multiaxial strains for the axisymmetric geometry under investigation. Assuming an invariant hoop to radial strain ratio rather than an invariant hoop to axial strain ratio provided better agreement with experimental results. It is demonstrated that the boundary conditions used to model the specimen had a substantial effect on the finite element results, even though the boundary was somewhat removed from the region of concentrated stress. Biaxial strain measurements are presented versus pressure over the elastic and into the plastic regime, and deformation plasticity theory was used to compute stress and radial strain components corresponding to measured strains. It is demonstrated that in order to apply a multiaxial Neuber’s rule to accurately estimate the elastic-plastic stress-strain response (using elastic stress concentration information and elastic-plastic material data), it is necessary to utilize an experimental observation that the ratio of the hoop to radial strain remains invariant from the elastic to the elastic-plastic regime. This differs from published assumptions about invariant hoop-to-axial strain ratios based on analysis of circumferentially grooved solid shafts. The predictions are accurate for moderate plastic strains, but correlation breaks down for bulk plastic deformation.

scholarly journals Investigation of the Free Edge Interlaminar Stresses Dependence on the PLY Thickness and Orientation

2006 ◽  
Vol 15 (1) ◽  
pp. 096369350601500
Author(s):  
Dionisios T. G. Katerelos
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Composite Laminates ◽  
Free Edge ◽  
Thermomechanical Loading ◽  
Interlaminar Stresses ◽  
Element Analysis ◽  
3 Dimensional ◽  
Out Of Plane ◽  
Dimensional Finite Element

Among the principal damage modes in composite laminates, is delamination. Design details, such as free, straight or curved, edges, induce large local out-of-plane loads, generating interlaminar stresses. In the present work, the effect of ply thickness and the angle between two adjacent layers on the interlaminar stresses developed at the vicinity of straight and curved free edges in composite laminates under thermomechanical loading is examined. The results are obtained by the application of a 3-dimensional Finite Element Analysis.

Thermal-Mechanical Response of Stiffened Composite Cylinders

1997 ◽  
Vol 50 (11S) ◽  
pp. S87-S92
Author(s):  
Carl T. Herakovich ◽  
Farshad Mirzadeh
Keyword(s):  
Thermal Effects ◽  
Mechanical Response ◽  
Axial Strain ◽  
Free Edge ◽  
Interlaminar Stresses ◽  
Stress Concentrations ◽  
Isoparametric Finite Element ◽  
Layer Analysis ◽  
Composite Cylinders ◽  
Discrete Layer

A two-dimensional, curvilinear, isoparametric finite element is used to provide a discrete layer analysis of deformations and stresses in stiffened composite cylinders subjected to thermal-mechanical loading. Individual layers of the cylinder and the stiffener are modeled explicitly, providing an accurate and detailed representation of deformations and stresses including interlaminar stresses. Several skin and stiffener laminates are studied for fabrication induced residual thermal effects, applied axial strain, and internal pressure loadings. The analysis shows that local curvatures and interlaminar stress concentrations are present near the skin/stiffener joint. Interlaminar stresses are also present along the free edge of the stiffener.

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