EFFECT OF MICROSTRUCTURE ON INITIATION OF DELAMINATION IN CROSS PLY LAMINATES FROM A TRANSVERSE CRACK

2021 ◽  
Author(s):  
LINQI ZHUANG ◽  
LUCIO MARAGONI ◽  
RAMESH TALREJA
Keyword(s):  
Transverse Crack ◽  
Crack Path ◽  
Crack Tip ◽  
Matrix Crack ◽  
Equal Length ◽  
Damage Mode ◽  
Fiber Distribution ◽  
Interface Cracks ◽  
Modeling Studies ◽  
Effect Of Microstructure

Transverse crack propagating towards a cross-ply interface is investigated in this study. The non-uniform fiber distribution near ply interface is modelled explicitly in order to study the effect of microstructure on crack path and initiation of delamination. The growth of fiber/matrix interfacial debond and debond kinking out of interface are analyzed based on a combination of energy and stress-based approach, which is convenient in predicting matrix crack path. Kinking of transverse crack tip when it approaches ply interface is investigated using an energy-based approach. It is found that predicted matrix crack path and crack tip kinking behavior near interface is strongly influenced by the local microstructure. The obtained results indicate that an induced symmetrical delamination, i.e., interface cracks of equal length on either side of the transverse ply crack, as often assumed in modeling studies, is not always a favorable damage mode.

Crack-Path Effect on Material Toughness

1990 ◽  
Vol 57 (1) ◽  
pp. 97-103 ◽  
Author(s):  
Asher A. Rubinstein
Keyword(s):  
Crack Path ◽  
Numerical Procedure ◽  
Crack Tip ◽  
Elastic Solid ◽  
Singular Integral Equations ◽  
Length Change ◽  
Curvilinear Crack ◽  
Linear Elastic ◽  
System Of Cracks ◽  
Remote Stress

The material-toughening mechanism based on the crack-path deflection is studied. This investigation is based on a model which consists of a macrocrack (semi-infinite crack), with a curvilinear segment at the crack tip, situated in a brittle solid. The effect of material toughening is evaluated by comparison of the remote stress field parameters, such as the stress intensity factors (controlled by a loading on a macroscale), to effective values of these parameters acting in the vicinity of a crack tip (microscale). The effects of the curvilinear crack path are separated into three groups: crack-tip direction, crack-tip geometry pattern-shielding, and crack-path length change. These effects are analyzed by investigation of selected curvilinear crack patterns such as a macrocrack with simple crack-tip kink in the form of a circular arc and a macrocrack with a segment at the crack tip in the form of a sinusoidal wave. In conjunction with this investigation, a numerical procedure has been developed for the analysis of curvilinear cracks (or a system of cracks) in a two-dimensional linear elastic solid. The formulation is based on the solution of a system of singular integral equations. This numerical scheme was applied to the cases of finite and semi-infinite cracks.

Characterization of Crack Tip Damage Zone Formation on Alloy 625 During Fatigue Crack Growth at 750°C by Transmission EBSD Method

2017 ◽  
Author(s):  
Yuji Ozawa ◽  
Tatsuya Ishikawa ◽  
Yoichi Takeda
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Power Plants ◽  
Crack Path ◽  
Damage Zone ◽  
Crack Tip ◽  
Loading Frequency ◽  
Zone Formation ◽  
Alloy 625

In order to clarify the mechanism of fatigue crack growth in alloy 625, which is a candidate material for use in advanced ultra supercritical power plants, the crack tip damage zone formation after a crack growth test conducted in high temperature steam was investigated. It was observed that the oxide thickness at the crack tip tended to increase with decreasing cyclic loading frequency. The crack path was a mix of transgranular and intergranular fractures. According to the grain reference orientation deviation (GROD) maps, it was revealed that the density of geometrically necessary dislocations (GNDs) in the matrix along the crack path and ahead of crack tip increased with an increase in the fatigue crack growth rate (FCGR) due to environmental effects. It was observed that (1) mobile dislocations at the crack surface were blocked due to the thick oxide layer, resulting in an increase in the density of GNDs, and (2) an increase in the density of GNDs might induce stress concentration at the crack tip, deformation twinning, and the acceleration of FCGRs.

Effect of inhomogeneous distribution of non-metallic inclusions on crack path deflection in G42CrMo4 steel at different loading rates

2015 ◽  
Author(s):  
S. Henschel ◽  
L. Krüger
Keyword(s):  
Fracture Mechanics ◽  
Crack Growth ◽  
Crack Path ◽  
Testing Machine ◽  
Crack Tip ◽  
Crack Growth Resistance ◽  
Impact Testing ◽  
Inhomogeneous Distribution ◽  
Metallic Inclusions ◽  
Crack Tip Blunting

An inhomogeneous distribution of non-metallic inclusions can result from the steel casting process. The aim of the present study was to investigate the damaging effect of an inhomogeneous distribution of nonmetallic inclusions on the crack extension behavior. To this end, the fracture toughness behavior in terms of quasi-static J-?a curves was determined at room temperature. Additionally, dynamic fracture mechanics tests in an instrumented Charpy impact-testing machine were performed. The fracture surface of fracture mechanics specimens was analyzed by means of scanning electron microscopy. It was shown that an inhomogeneous distribution significantly affected the path and, therefore, the plane of crack growth. Especially clusters of non-metallic inclusions with a size of up to 200 ?m exhibited a very low crack growth resistance. Due to the damaging effect of the clusters, the growing crack was strongly deflected towards the cluster. Furthermore, crack tip blunting was completely inhibited when inclusions were located at the fatigue precrack tip. Due to the large size of the non-metallic inclusion clusters, the height difference introduced by crack path deflection was significantly larger than the stretch zone height due to the crack tip blunting. However, the crack path deflection introduced by a cluster was not associated with a toughness increasing mechanism. The dynamic loading ( 1 0.5 5 s MPam 10 ? ? K? ) did not result in a transition from ductile fracture to brittle fracture. However, the crack growth resistance decreased with increased loading rate. This was attributed to the higher portion of relatively flat regions where the dimples were less distinct.

Mixed Mode Loading of an Interface Crack Subjected to Creep Conditions

2003 ◽  
Author(s):  
Ali P. Gordon ◽  
David L. McDowell
Keyword(s):  
Transition Layer ◽  
Mixed Mode ◽  
Elevated Temperatures ◽  
Numerical Solutions ◽  
Crack Tip ◽  
Functionally Graded ◽  
Pure Mode ◽  
Mixed Mode Loading ◽  
Creep Ductility ◽  
Interface Cracks

Interface cracks are seldom subjected to pure Mode I or pure Mode II conditions. Stationary interface cracks between two distinct, bonded elastic-creep materials subjected to remotely applied mixed mode loading are simulated. The finite element method (FEM) is used to examine crack tip fields and candidate driving force parameters for crack growth. Plane strain conditions are assumed. In most cases a functionally graded transition layer is included between the two materials. Examples of such systems include weld metal (WM) and base metal (BM) interfaces in welded or repaired boiler components subjected to elevated temperatures. Numerical solutions based on the asymptotic fields of the homogeneous and heterogeneous Arcan-type specimens are presented. Creep ductility-based damage models are used to predict the initial crack propagation trajectory. The incorporation of functionally graded transition layer regions affects the evolution of time-dependent stress components in the vicinity of the crack tip. The magnitude and direction of crack tip propagation can then be optimized with respect to interface properties.

A transverse crack tip field in bimaterial

1994 ◽  
Vol 10 (3) ◽  
pp. 267-272 ◽  
Author(s):  
Du Shanyi ◽  
Shi Zhifei ◽  
Wu Linzhi
Keyword(s):  
Transverse Crack ◽  
Crack Tip ◽  
Crack Tip Field

Analysis of Composite Plates Containing Cracks

1992 ◽  
Vol 114 (3) ◽  
pp. 358-363 ◽  
Author(s):  
Y. W. Kwon
Keyword(s):  
Stress Intensity Factor ◽  
Material Properties ◽  
Composite Plate ◽  
Crack Tip ◽  
Composite Plates ◽  
Unidirectional Composite ◽  
Matrix Crack ◽  
Fiber Breakage ◽  
Fiber Volume ◽  
Element Analysis

Effect of microcracks, such as local matrix crack and fiber breakage, on a macroscale crack in a unidirectional composite plate was studied for various fiber volume fractions, as well as different material properties of fiber and matrix materials. A finite element analysis was performed for this study. It showed that microcracks, located near a macroscale crack tip, resulted in a significant increase of stress intensity factor at the crack tip.

scholarly journals Effect of microstructure on fatigue crack tip field of laser melting deposited Ti–5Al–5Mo–5V–1Cr–1Fe titanium alloy

2018 ◽  
Vol 165 ◽  
pp. 02009
Author(s):  
Kai Wang ◽  
Rui Bao ◽  
Siyuan Ren ◽  
Dong Liu ◽  
Chuliang Yan
Keyword(s):  
Titanium Alloy ◽  
Fatigue Crack ◽  
Strain Field ◽  
Crack Tip ◽  
Image Correlation ◽  
Laser Melting ◽  
Crack Tip Field ◽  
Significant Difference ◽  
Microstructure Effect ◽  
Effect Of Microstructure

In this paper, experimental and simulated investigations were carried out to understand the effect of microstructure on the fatigue crack tip strain field of laser melting deposited Ti–5Al–5Mo–5V–1Cr–1Fe titanium alloy. The mechanical properties of the laser melting deposited material corresponding to different microstructure zones were measured by digital image correlation method under in-situ static stretching, and the results indicate that the direction of primary α lamellas has great influence on the mechanical property of each grain. The crack tip strain fields considering the influence of material microstructure under constant amplitude conditions were measured, and the strain field of plastic zone has significant difference. Crystal plasticity finite element simulation of the static tensile and crack tip field considering the microstructure effect had been conducted and compare with experiment results. The simulation results are in good agreement with the test results in both the static tension strain field and crack tip strain field.

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