scholarly journals Determination of Single Parameter for Serviceability Requirements of Fibre Reinforced Concrete: Study of Fracture Characteristics

2021 ◽  
Vol 9 (11) ◽  
pp. 108-115
Author(s):  
Umar Islam Wani
Keyword(s):  
Fracture Toughness ◽  
Crack Growth ◽  
Continuous System ◽  
Fibre Volume ◽  
Steel Fibers ◽  
Fibre Content ◽  
Fibre Reinforcement ◽  
Fibre Glass ◽  
Steel Fibres

Abstract: This The influence of fibre reinforcement on crack propagation in concrete was studied . Thirty-five double torsion specimens, made with three types of fibres (fibre glass , straight steel fibres and deformed steel fibres ) were tested . The variables were the fibre volume and size of the fibres. The test results indicated that the resistance to rapid crack growth increased somewhat with increasing fibre content up to about 1.25% - 1.5% by volume. The degree of compaction had an enormous effect on the fracture properties .The fracture toughness increased with fibre content up to about 1.25% by volume, and then decreased , due to incomplete compaction. It was found that in this test geometry, fibres did not significantly restrain crack growth. It was also observed that once the crack had propagated down the full length of the specimen, the system changed from a continuous system to a discontinuous system, consisting of two separate plates held together by the fibre reinforcement. Different types of fibres did not significantly affect the fracture toughness. Keywords: Fibre glass, straight steel fibers, deformed steel fibers, fracture toughness.

Determination of J Resistance Curves From CWP Specimens

2012 ◽  
Author(s):  
Fan Zhang ◽  
Honggang Zhou ◽  
Yong-Yi Wang ◽  
Ming Liu ◽  
Yaxin Song
Keyword(s):  
Fracture Toughness ◽  
Crack Growth ◽  
J Integral ◽  
Resistance Curve ◽  
Constraint Condition ◽  
Longitudinal Loading ◽  
Resistance Curves ◽  
Unloading Compliance ◽  
Girth Welds

A crack is highly constrained in traditional toughness tests, e.g., CVN and SE(B). However, a crack in the girth welds of pipelines under longitudinal loading is low constrained. Curved wide plate (CWP) test provides similar constraint condition as that of pipeline girth weld. CWP tests are being used recently for strain-based design. One of the desirable outcomes from those tests is fracture toughness resistance curves. The resistance curve consists of two components, the crack growth and the toughness measure, such as J-integral or CTOD. The paper describes the development of procedures for the determination of those two components. A normalized equation was developed to estimate the crack growth from the experimentally measured unloading compliance. The equation was verified by multiple FEA simulations with different pipe geometries and materials. The second set of equations was developed to evaluate the J-integral through an incremental frame based on the instantaneous crack growth and the load-CMOD record. The application of the resistance curve procedures was demonstrated through CWP tests of X80 and X100 welds.

Determination of fracture toughness for carbon fiber reinforced plastics free of the crack initiator using the acoustic microscopy

2020 ◽  
Vol 86 (8) ◽  
pp. 58-65
Author(s):  
A. V. Pankov ◽  
V. L. Tokar ◽  
Yu. S. Petronyuk ◽  
V. M. Levin ◽  
E. S. Morokov ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Carbon Fiber ◽  
Crack Initiation ◽  
Crack Growth ◽  
Crack Front ◽  
Flaw Detection ◽  
Acoustic Microscopy ◽  
Shear Mode ◽  
Ultrasonic Ndt

The fracture toughness which reflects change in the elastic deformation energy of the structural element with an increase in the crack area per unit at the onset of straining is one of the crack resistance parameters of carbon fiber plastics (CFRPs). When studying the fracture toughness, the position of the crack front is determined: both the initial one and that obtained as a result of crack growth. Currently existing test standards (STO TsAGI, ASTM D7905) determine the viscosity by the shear mode GIIc using the samples with a crack initiator. However, the method does not reflect the real conditions of crack initiation in CFRPs structures and can lead to a decrease in the accuracy of determining the load of crack initiation. A new technique of the fracture viscosity determination free of the standard delamination initiator has been developed in TsAGI. We present the results of developing the proposed methodology. The GIIc values were determined for a shear crack under three-point bending conditions after wedging. To determine the position and shape of the crack front, as well as to assess the dynamics of its propagation under subsequent loads, we used ultrasonic methods — ultrasonic flaw detection (ultrasonic NDT) and acoustic microscopy instead of the standard visual observation of the crack boundaries from the end surface of the samples. It is shown that acoustic microscopy at a frequency of 50 MHz provides determination of the crack front position in CFRP samples at a depth of 3.0 – 3.5 mm with a high resolution about 100 μm. The features of the crack growth under shear conditions are discussed. The results of the study show that high accuracy of acoustic microscopy in comparison with traditional ultrasonic NDT diagnostics is strongly sought for determining the shape of the cracks, as well as for analyzing the dynamics of crack growth and revealing the mechanisms of interlayer crack propagation in a composite material.

scholarly journals Determination of Static Fracture Toughness of Nettle Fibre (Urtica Dioica)/Polymethyl-methacrylate Composites Using Different Fracture Methods

Mechanika ◽  
2020 ◽  
Vol 26 (2) ◽  
pp. 95-102
Author(s):  
Kenan Büyükkaya ◽  
Faruk Güner
Keyword(s):  
Fracture Toughness ◽  
Bending Strength ◽  
Tensile Tests ◽  
Compact Tension ◽  
Fibre Reinforcement ◽  
Bending Stresses ◽  
Static Fracture ◽  
Compact Tension Test ◽  
Point Bend

In this study, the breaking behaviour of polymethylmethacrylate reinforced with nettle fibre was investigated experimentally. Single edge notched bending (SENB) and compact test(CT)  specimens were produced to include notches in various ratios. The Mode I fracture behaviour of samples were determined utilizing static frac-ture toughness experiments such as the Three Point Bend-ing (TPB) and Compact Tensile tests. The fracture tough-ness (KIC) was investigated using the TPB Test (Compli-ance and Initial notch method), and Compact Tension test. The bending module and bending stresses were also determined. It was found that nettle-fibre reinforcement improves the bending strength of the composite by 60% and improves the fracture toughness more than two-fold.

Influence of subcritical crack growth on the determination of fracture toughness in brittle materials

2016 ◽  
Vol 36 (5) ◽  
pp. 1307-1312 ◽  
Author(s):  
C. Krautgasser ◽  
Z. Chlup ◽  
P. Supancic ◽  
R. Danzer ◽  
R. Bermejo
Keyword(s):  
Fracture Toughness ◽  
Crack Growth ◽  
Subcritical Crack Growth ◽  
Brittle Materials
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