scholarly journals Effect of Defects Part II: Multiscale Effect of Microvoids, Orientation of Rivet Holes on the Damage Propagation, and Ultimate Failure Strength of Composites

2021 ◽  
Vol 5 (4) ◽  
pp. 112
Author(s):  
Vahid Tavaf ◽  
Mohammadsadegh Saadatzi ◽  
Sourav Banerjee
Keyword(s):  
Ultimate Strength ◽  
Composite Plates ◽  
Unidirectional Composite ◽  
Numerical Results ◽  
Image Correlation ◽  
Damage Analysis ◽  
Damage Propagation ◽  
Ultimate Failure ◽  
Square Configuration ◽  
Diamond Configuration

Material properties at the vicinity of the cut-outs in composites are not entirely defect-free. The nteraction of multiple cutouts like rivet holes, the repercussion of their configuration on crack propagation, and ultimate strength were predicted using Peridynamic method and the results are reported in this article. The effect of microscale defects at the vicinity of the cutouts on macroscale damage propagation were shown to have quantifiable manifestation. This study focused on two to four holes in unidirectional composite plates with 0°, 45°, and 90° fiber directions, while the vicinity of a hole was considered degraded. Numerical results were validated using quantitative ultrasonic image correlation (QUIC) and the tensile test. Both the experimental and numerical results confirmed that the strength of the horizontal configuration is higher than the vertical in the plates with two holes. Furthermore, the square configuration was found to be stronger than the diamond configuration with four holes. When the effect of microscale defects was considered, the prediction of ultimate strength was better compared to the experimental results. The predictive model could be reliably used for progressive damage analysis.

The Mechanical Behavior of Short-Fiber-Elastomer Composites

1976 ◽  
Vol 49 (5) ◽  
pp. 1167-1181 ◽  
Author(s):  
A. Y. Coran ◽  
P. Hamed ◽  
L. A. Goettler
Keyword(s):  
Test Piece ◽  
Composite Plates ◽  
Short Fiber ◽  
Strength Properties ◽  
Unidirectional Composite ◽  
Short Fibers ◽  
Principal Stresses ◽  
Elastomer Composites ◽  
Ultimate Limit ◽  
Time Of Failure

Abstract The measured elastic and strength properties of angle-ply composites of short fibers and rubber depend on test-piece geometry. In general, higher tensile moduli and strengths are obtained when plies are both thin and wide. Once the effects of test-piece geometry are taken into account, elastic properties can be calculated as functions of the properties of a single ply. Classical compliance transformation equations can be used. However, because of the invariance of shear modulus in aligned composites, the tensor transformation equations are somewhat simplified. Tensile strengths of off-axis unidirectional composite plates and balanced-angle plies can be fitted by Hill's criterion. Unidirectional composites tend to fail in the weakest mode, depending on the angle of stress, but laminating causes all principal stresses in a ply to be near their ultimate limit at the time of failure.

Nonlinear Free and Forced Vibrations of Symmetric Laminated Panels

2011 ◽  
Vol 471-472 ◽  
pp. 616-621 ◽  
Author(s):  
Alireza Shooshtari ◽  
Soheil Razavi ◽  
Hadi Ghashochi Bargh ◽  
Mohammad Homayoun Sadr-Lahidjani
Keyword(s):  
Perturbation Method ◽  
External Force ◽  
Laminated Composite ◽  
Composite Plates ◽  
Forced Vibrations ◽  
Numerical Results ◽  
Transverse Displacement ◽  
Laminated Composite Plates ◽  
Free And Forced Vibrations ◽  
Laminated Panels

In this paper, free and forced vibrations of symmetric laminated composite plates are studied analytically by using a perturbation method where the analytical results for transverse displacement are compared with the numerical results. The external force is taken to be harmonic in time and having uniform amplitude.

scholarly journals Numerical Modeling and Digital Image Correlation Strain Measurements of Coated Metal Sheets Submitted to Large Bending Deformation

2013 ◽  
Vol 554-557 ◽  
pp. 2424-2431
Author(s):  
Laurent Duchêne ◽  
Amine Ben Bettaieb ◽  
Victor Tuninetti ◽  
Anne Marie Habraken
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Shell Element ◽  
Numerical Results ◽  
Image Correlation ◽  
Integration Scheme ◽  
Forming Process ◽  
Coated Metal ◽  
Assumed Strain ◽  
Assumed Natural Strain

The recently developed SSH3D solid-shell element [1], which is based on the Enhanced Assumed Strain (EAS) and the Assumed Natural Strain (ANS) techniques, is utilized for the modeling of a severe bending sheet forming process. To improve the element's ability to capture the through thickness gradients, a specific integration scheme was developed. In this paper, the performances of this element for the modeling of the T-bent process were assessed thanks to comparison between experimental and numerical results in terms of the strain field at the outer surface of the sheet. The experimental results were obtained by Digital Image Correlation. It is shown that a qualitative agreement between experimental and numerical results is obtained but some numerical parameters should be optimized to improve the accuracy of the simulation predictions. In this respect, the influence of the penalty coefficient of the contact modeling was analyzed.

Analysis of Stresses in CFRP Composite Plates Drilled with Conventional and Abrasive Water Jet Machining

2013 ◽  
Vol 763 ◽  
pp. 127-143 ◽  
Author(s):  
M. Saleem ◽  
Habiba Bougherara ◽  
L. Toubal ◽  
F. Cénac ◽  
Redouane Zitoune
Keyword(s):  
Fatigue Testing ◽  
Composite Plates ◽  
Water Jet ◽  
Image Correlation ◽  
Initial Surface ◽  
Abrasive Water Jet ◽  
Machining Processes ◽  
Static Tests ◽  
The Difference ◽  
Conventional Machining

The aim of this paper is to analyze the influence of two machining processes on the mechanical behaviour of composite plates under cyclic loading. For this purpose, an experimental study using several CFRP plates drilled with conventional machining and non-conventional machining (abrasive water jet) was carried out. Digital image correlation and static tests using an Instron 4206 tester were performed. In addition, infrared thermography (IR) and fatigue tests were also performed to assess temperature and damage evolutions and also the stiffness degradation. Fatigue results have shown that the damage accumulation in specimens drilled with conventional machining was higher than the abrasive water jet ones. Furthermore, the endurance limit for plates drilled conventionally was approximately 10% higher than those drilled with abrasive water jet. This difference was related to the initial surface integrity after machining induced by the difference in the mechanism of material's removal between the two processes. The difference in surface texture was responsible for the initiation of stress concentration sites as evident from IR camera’s stress analysis. This was confirmed by SEM tests conducted after a destructive sectioning of the specimens before fatigue testing.

Inhomogeneous Strain Distribution in SiCf/SiC Coupons Under Tensile Loading

2017 ◽  
Author(s):  
Christopher D. Newton ◽  
Jonathan P. Jones ◽  
Adam L. Chamberlain ◽  
Martin R. Bache
Keyword(s):  
Mechanical Testing ◽  
Room Temperature ◽  
Ceramic Matrix Composites ◽  
Tensile Tests ◽  
Image Correlation ◽  
Failure Data ◽  
Inhomogeneous Strain ◽  
Ultimate Failure ◽  
Complex Structural ◽  
Structural Architecture

The complex structural architecture and inherent processing artefacts within ceramic matrix composites combine to induce inhomogeneous deformation and damage prior to ultimate failure. Bulk measurements of strain via extensometry or even localised strain gauging will fail to characterise such inhomogeneity when performing conventional mechanical testing on laboratory scaled coupons. The current research project has, therefore, applied digital image correlation (DIC) techniques to the room temperature axial assessment of a SiCf/SiC composite under static and ratchetted loading. As processed SiCf/SiC panels were subjected to detailed X-ray computed tomography (XCT) inspection prior to specimen extraction and subsequent mechanical testing. In situ DIC strain measurements were taken throughout the period of room temperature monotonic and ratchet style tensile tests. Contemporary acoustic emission (AE) signals were also recorded to indicate significant damage events and the onset of ultimate failure. Data from these separate monitoring techniques were correlated to indicate the sensitivity or otherwise to pre-existing artefacts within the as received CMC panels.

Progressive Fatigue Damage Simulation in Laminated Composites Based on Explicit Finite Element Formulation

2019 ◽  
Vol 64 (2) ◽  
pp. 1-12
Author(s):  
Yuri Nikishkov ◽  
Guillaume Seon ◽  
Andrew Makeev
Keyword(s):  
Finite Element ◽  
Laminated Composites ◽  
Test Methods ◽  
Remaining Useful Life ◽  
Image Correlation ◽  
Progressive Damage ◽  
Damage Analysis ◽  
Explicit Finite Element ◽  
Analysis Methods ◽  
Open Hole

Advanced polymeric composites are playing a major role in designing high-performance and lightweight vertical lift structures. However, uncertain residual strength and remaining useful life of the composite rotor and airframe structures due to complexity of failure mechanisms and susceptibility to manufacturing irregularities, which may be precursors to structural damage, impose risks that cannot be mitigated exclusively by time-consuming and costly experimental iterations. Validated analysis techniques accelerating design, certification, and qualification of composite structures are needed. Our team has been taking essential steps toward improving confidence in material qualification for laminated composites. The first step started with our reduced lamina test methods, short-beam shear, and small-plate twist based on digital image correlation measuring as a subset the standard material properties and, in addition, key properties that cannot be currently measured using any standard test methods. The lamina properties provide essential material input data for laminate analysis. The laminate analysis was the second step increasing confidence in material qualification. A known weakness of the existing progressive damage analysis methods is the lack of effective techniques to predict ultimate failure. The newly developed methodology relies on explicit finite element modeling and eliminates convergence issues in the ply-level progressive damage analysis methods due to severe nonlinear discontinuities after propagation of damage beyond detectable size. This work shows results of applying this methodology to nanosilica-toughened IM7/PMT-F3GHT open-hole tension strength/fatigue, open-hole compression strength/fatigue, and bearing strength multidirectional laminate configurations. The ability to predict progression of damage from initiation to ultimate strength and fatigue for advanced material systems including IM7/PMT-F3GHT carbon/epoxy reinforced by nanosilica has been demonstrated for the first time.

Thermoelastic Bending Response of Angel-Ply Composite Plates Resting on Elastic Foundations

2013 ◽  
Vol 22 (2) ◽  
pp. 096369351302200
Author(s):  
Ashraf M. Zenkour ◽  
Ibrahim A. Abbas
Keyword(s):  
Composite Plate ◽  
Composite Plates ◽  
Numerical Results ◽  
Elastic Foundations ◽  
Different Types ◽  
Thermoelastic Response ◽  
Pasternak’S Model ◽  
Sinusoidal Temperature ◽  
Bending Response ◽  
Thermoelastic Bending

Different plate theories are presented to study the thermoelastic response of a multilayered angle-ply composite plate. The plate is subjected to a sinusoidal temperature and resting on different types of elastic foundations. The effects due to thermal loads and elastic foundations parameters as well as the variation of lamination angle are studied. Numerical results suggest that Pasternak's model should be used for such plates resting on elastic foundations.

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