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Fracture Behaviour (fracture + behaviour)

Distribution by Scientific Domains

Polymers and Materials Science	92%

Selected Abstracts

Fracture behaviour of cracked carbon nanotube-based polymer composites: Experiments and finite element simulations

FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 2 2010
Y. KURONUMA
ABSTRACT This paper studies the fracture behaviour of cracked carbon nanotube (CNT)-based polymer composites by a combined numerical,experimental approach. Tensile tests were conducted on single-edge cracked plate specimens of CNT/polycarbonate composites at room temperature and liquid nitrogen temperature (77 K), and the critical loads for fracture instabilities were determined. Elastic,plastic finite element simulations of the tests were then performed to evaluate the,J -integrals corresponding to the experimentally determined critical loads. Scanning electron microscopy examinations were also made on the specimen fracture surfaces, and the fracture mechanisms of the CNT-based composites were discussed. [source]

Fracture behaviour of maraging steel tensile specimens and pressurized cylindrical vessels

FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 3 2004
T. CHRISTOPHER
ABSTRACT A three-parameter fracture criterion is applied for the development of a failure assessment diagram to maraging steels and its validity verified by considering the maraging steel fracture data of surface crack tension specimens (SCT) and pressure vessels having axial surface cracks. Fracture-strength/failure-pressure estimates based on this criterion are found to be in reasonably good agreement with test results. [source]

Fracture behaviour of PC/ABS resin under mixed-mode loading

FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 12 2001
Husaini
Fracture behaviour of polycarbonate (PC)/acrylonitrile-butadiene-styrene (ABS) under mixed-mode loading conditions was studied for several weight fractions of PC and ABS. Mode I and mixed-mode fracture tests were carried out by using compact,tension,shear specimens. At a certain value of mixed-mode loading ratio KII,/KI, a crack of the shear type will initiates at the initial crack tip. Fracture toughness increases under mixed-mode loading with an increase in the mode II component, whereas it reduces with the appearance of a shear-type fracture. Fracture toughness and the appearance of a shear-type fracture depends on the blending ratio of PC and ABS. The transition to shear-type fracture occurs at lower value of KII,/KI for resins with higher fracture toughness. [source]

Acrylic Nanocomposite Resins for Use in Stereolithography and Structural Light Modulation Based Rapid Prototyping and Rapid Manufacturing Technologies,

ADVANCED FUNCTIONAL MATERIALS, Issue 16 2008
Matthias Gurr
Abstract A novel family of optically transparent acrylic nanocomposites containing up to 30,wt,% silica nanoparticles with an average diameter of 20,nm was developed for application in structural light modulation (SLM) and stereolithography (SL) technologies. The uniform dispersion of nanoparticles affords a significantly improved toughness/stiffness-balance of the photopolymerized and postcured nanocomposites. It is possible to increase stiffness, as expressed by Young's modulus, from 1290 to 1700,MPa without encountering the embrittlement typical for many other conventional filled polymers. Fracture behaviour is examined by means of fracture mechanics investigation and SEM analyses of fracture surfaces. According to TEM analyses and measurement of optical transmittance remarkable uniform dispersion of silica nanoparticles was achieved. The silica nanoparticle concentrations up to 17,wt,% give only marginally higher viscosities and do not affect transmittance, while slightly increasing the exposure times needed in photopolymerization. Moreover, the silica nanoparticles afford materials with reduced shrinkage and improved properties. The green effective ankle splay out (EASO) measured on H-shaped diagnostic specimens, is significantly reduced for the nanocomposite materials from 1.38,mm for the unfilled material to 0.82,mm for nanocomposites containing 30,wt,% nanosilica. The building accuracy is increased significantly with increasing content of silica nanofillers. [source]

Fracture behaviour of cracked carbon nanotube-based polymer composites: Experiments and finite element simulations

Study of influence of notch root radius on fracture behaviour of extra deep drawn steel sheets

FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 12 2009
V. V. CHAUDHARI
ABSTRACT Fracture tests are carried out on extra deep drawn steel CT specimens containing notches with different values of notch root radius (,= 0.07,0.75 mm). Experimental findings clearly show a critical notch root radius (,c) below which the fracture toughness remains independent of , and above which it varies linearly with ,. The 3D finite element analysis shows that the location of maximum stress level causing crack initiation is in the vicinity of notch tip. The maximum stress level is independent of ,; however, its location is shifted away from notch tip along unbroken ligament length with increase in ,. [source]

Modelling ductile fracture behaviour from deformation parameters in HSLA steels

FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 10 2004
S. SIVAPRASAD
ABSTRACT In this work, an attempt is made to model the ductile fracture behaviour of two Cu-strengthened high strength low alloy (HSLA) steels through the understanding of their deformation behaviour. The variations in deformation behaviour are imparted by prior deformation of steels to various predetermined strains. The variations in parameters such as yield strength and true uniform elongation with prior deformation is studied and was found to be analogous to that of initiation fracture toughness determined by independent method. A unique method is used to measure the crack tip deformation characterized by stretch zone depth that also depicted a similar trend. Fracture toughness values derived from the stretch zone depth measurements were found to vary in the same fashion as the experimental values. A semiempirical relationship for obtaining ductile fracture toughness from basic deformation parameters is derived and model is demonstrated to estimate initiation ductile fracture toughness accurately. [source]

Ductile fracture of commercial purity titanium at room temperature

FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 10 2000
G. Shatil
An experimental and numerical program was carried out to examine and assess the deformation and fracture behaviour of alloys of commercial purity (CP) titanium. The material rate-dependent deformation under constant displacement rates and under sustained loads was directly simulated in finite element analyses using an implemented unified material model. The simulations predicted the fracture of compact tension specimens subjected to J,R tests and sustained load tests employing a dimensional analysis and strain-hardening approach. Differences between two batches with different oxygen contents were examined and the limitation of the material model was investigated. [source]

A framework for fracture modelling based on the material forces concept with XFEM kinematics

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 13 2005
Ragnar Larsson
Abstract A theoretical and computational framework which covers both linear and non-linear fracture behaviour is presented. As a basis for the formulation, we use the material forces concept due to the close relation between on one hand the Eshelby energy,momentum tensor and on the other hand material defects like cracks and material inhomogeneities. By separating the discontinuous displacement from the continuous counterpart in line with the eXtended finite element method (XFEM), we are able to formulate the weak equilibrium in two coupled problems representing the total deformation. However, in contrast to standard XFEM, where the direct motion discontinuity is used to model the crack, we rather formulate an inverse motion discontinuity to model crack development. The resulting formulation thus couples the continuous direct motion to the inverse discontinuous motion, which may be used to simulate linear as well as non-linear fracture in one and the same formulation. In fact, the linear fracture formulation can be retrieved from the non-linear cohesive zone formulation simply by confining the cohesive zone to the crack tip. These features are clarified in the two numerical examples which conclude the paper. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Crack Toughness Behaviour of Multiwalled Carbon Nanotube (MWNT)/Polycarbonate Nanocomposites

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 15 2005
Bhabani K. Satapathy
Abstract Summary: The morphology and fracture behaviour of polycarbonate (PC)/multiwalled carbon nanotube (MWNT) composites have been studied by AFM and post-yield fracture mechanics. The essential work of fracture (EWF) method has been used to distinguish between two terms representing the resistance to crack initiation and crack propagation. A maximum in the non-essential work of fracture was observed at 2 wt.-% MWNT, demonstrating enhanced resistance to crack propagation compared to pure PC. At 4 wt.-% MWNT, a tough-to-brittle transition has been observed. The time-resolved in-situ strain field analysis revealed that the onset of crack initiation was shifted to a shorter time for nanocomposites with 4 wt.-% MWNT compared to that with 2 wt.-%, and thus explained the existence of a tough-to-brittle transition in these nanocomposites. [source]

Mechanical and dynamic mechanical properties of nylon 66/montmorillonite nanocomposites fabricated by melt compounding

POLYMER INTERNATIONAL, Issue 8 2004
Zhong-Zhen Yu
Abstract Nylon 66 nanocomposites were prepared by melt compounding of nylon 66 with organically modified montmorillonite (MMT). The organic MMT was pre-modified with about 14 wt% of ammonium surfactant, much lower than the 35,46 wt% in most commercial organic MMT powders. Transmission electron microscope observation indicated that the MMT layers were well exfoliated in nylon 66 matrix. Dynamic mechanical analysis confirmed the constraint effect of exfoliated MMT layers on nylon 66 chains, which benefited the increased storage modulus, increased glass transition temperature and reduced magnitude of alpha relaxation peak. The effects of organic MMT loading levels on reinforcement and fracture behaviour of the nanocomposites were evaluated using tensile and three-point bending tests. The addition of the organic MMT clearly increased Young's modulus and tensile strength but decreased ductility and fracture toughness of nylon 66. Copyright © 2004 Society of Chemical Industry [source]