The Use of Acoustic Emission to Detect the Onset of Interlaminar Shear Failure in Short Beam Fatigue Specimens

2009 ◽  
pp. 369-369-11 ◽  
Author(s):  
JH Edwards
Keyword(s):  
Acoustic Emission ◽  
Shear Failure ◽  
Short Beam ◽  
Interlaminar Shear

Failure mechanisms in three and four point short beam bending tests of unidirectional glass/epoxy

1992 ◽  
Vol 27 (4) ◽  
pp. 235-243 ◽  
Author(s):  
W C Cui ◽  
M R Wisnom ◽  
M Jones
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Shear Failure ◽  
Beam Theory ◽  
Interlaminar Shear Strength ◽  
Bending Test ◽  
Bending Tests ◽  
Four Point Bending ◽  
Short Beam ◽  
Interlaminar Shear

Three and four point bending tests are compared both analytically and experimentally. In all the three point bending tests, damage was observed under the loading roller in addition to the interlaminar shear failure, while in the four point bending tests, only interlaminar shear failure was observed. Therefore, this four point bending test is valid for measuring the interlaminar shear strength. From the finite element analysis, it is found that the roller diameter is a critical parameter in determining the stress concentrations in short beam tests. In order to avoid damage under the roller and thus to make the short beam test a valid means for measuring the interlaminar shear strength, the appropriate roller diameters should be chosen. The damage under the loading roller in the three point bending test basically reduces the effective specimen thickness and thus this test underestimates the interlaminar shear strength. The interlaminar shear cracks in the short beam tests were found to be randomly distributed in a region between 30 percent and 70 percent through the thickness from the top surface. This is due to the non-linear shear response which means that the shear stress distribution is more uniform near the middle of the section. Also the maximum value of the shear stress is lower than the maximum value given by beam theory. A non-linear shear correction factor is suggested to account for this effect and for the glass/epoxy composite tested here, the actual interlaminar shear strength is only about 83 percent of the apparent value from classical beam theory. The interlaminar shear crack does not occur at the location of maximum shear stress. This may be because there is insufficient energy to propagate a crack at this location.

Apparent Interlaminar Shear Strength Measurement by Four Point Short Beam Test

2015 ◽  
Vol 24 (2) ◽  
pp. 096369351502400 ◽  
Author(s):  
Züleyha Aslan
Keyword(s):  
Shear Strength ◽  
Load Distribution ◽  
Shear Failure ◽  
Strength Test ◽  
Interlaminar Shear Strength ◽  
Thickness Ratio ◽  
Test Results ◽  
Beam Test ◽  
Short Beam ◽  
Interlaminar Shear

The main purpose of this investigation is to characterize experimentally the interlaminar shear strength of cross-ply and quasi-isotropic E-glass/epoxy composites by the four point short beam test. ASTM D2344-three point short beam strength test results and the four point short beam strength test results are compared. To determine the details of the four point short beam test, the effects of support span to thickness ratio, load span, ply number, width and fibre orientation on the interlaminar shear strength are investigated. According to the test results the four point short beam test is more advantageous and more convenient than the three point short beam test because of the better load distribution and higher support span to thickness ratio. It is concluded that the support span to thickness ratio should be 8 to obtain pure interlaminar shear failure. The distance between the two loading cylinders should be one half of the support span instead of one third of the support span. When measuring the interlaminar shear strength for E-glass/epoxy laminates, the ply number and the width of the specimen should be chosen carefully.

Interlaminar shear properties of nanostitched/nanoprepreg aramid/phenolic composites by short beam method

2018 ◽  
Vol 53 (21) ◽  
pp. 2941-2957
Author(s):  
Kadir Bilisik ◽  
Gulhan Erdogan ◽  
Erdal Sapanci
Keyword(s):  
Shear Failure ◽  
Fiber Type ◽  
Multiwall Carbon Nanotubes ◽  
Plane Failure ◽  
Short Beam ◽  
Out Of Plane ◽  
Nanotube Composites ◽  
Failure Properties ◽  
Interlaminar Shear ◽  
Multiwall Carbon

The interlaminar shear strengths of nanostitched 3D aramid/phenolic composites were studied. Stitching slightly improved the interlaminar strength of the z-stitching/nanotube composites. In addition, the stitching fiber type influenced the interlaminar strength of the z-stitching/nanotube aramid/phenolic composites. The failures of all structures in the compression and tensile sides were almost negligible. However, all structures had interlaminar shear failure where delamination in z-stitching/nanotube composites was arrested. The introduction of the stitching yarn in the baseline structure improved its out-of-plane failure properties without reducing the in-plane properties. The effects of stitching and multiwall carbon nanotubes on the 3D aramid/phenolic composite were encouraging and the nanostitched para-aramid/phenolic nanocomposite could be considered as damage tolerance material.

scholarly journals Influence of preliminary thermal aging on the residual interlayer strength and staging of damage accumulation in structural carbon plastic

2021 ◽  
pp. 41-51
Author(s):  
D. S Lobanov ◽  
E. M Lunegova ◽  
A. I Mugatarov
Keyword(s):  
Mechanical Properties ◽  
Acoustic Emission ◽  
Damage Accumulation ◽  
Elevated Temperatures ◽  
Energy Parameter ◽  
Carbon Plastic ◽  
Diagnostic Systems ◽  
Static Tests ◽  
Interlayer Shear ◽  
Short Beam

Aging of composites is a pervasive problem that leads to mechanical properties degradation, reduced design life of a structure and premature accidental failure. The work is devoted to an experimental study of the preliminary temperature aging effect on the residual mechanical properties of structural CFRP. The joint use of test systems and systems for registration and analysis of acoustic emission signals was applied. The Short Beam Shear Test of CFRP specimens were carried out using the short beam method. The tests were carried out on universal electromechanical systems Instron 5882 and Instron 5965 in accordance with the recommendations of ASTM D2344. In the process of loading the samples were continuously recorded by using the acoustic emission signals system AMSY-6. A piezoelectric sensor with a frequency range of 300-800 kHz was used. The test and diagnostic systems were synchronized during the tests. In the course of the work the values of the interlayer shear strength were determined for the samples of CFRP. Typical types of the sample destruction are illustrated. When analyzing the change in the mechanical properties of the carbon fiber reinforced plastic from a temperature increase the critical values of temperatures were established in which a sharp decline in the strength and elastic characteristics of materials occurs due to an active destruction of the binder. The graphs of the energy parameter dependence and frequency characteristics of acoustic emission signals on time have been constructed and analyzed. The estimate of the processes of damage accumulation in composites is carried out. The change of the damage accumulation mechanisms was illustrated. The obtained results illustrate the effect of elevated temperatures and the duration of their impact on the mechanical behavior of structural CFRP specimens during the static tests for the interlayer shear.

Modified Short Beam Shear Test for Measuring Interlaminar Shear Strength of Composites

AIAA Journal ◽  
2002 ◽  
Vol 40 (11) ◽  
pp. 2368-2370
Author(s):  
Kunigal Shivakumar ◽  
Felix Abali ◽  
Adrian Pora
Keyword(s):  
Shear Strength ◽  
Shear Test ◽  
Interlaminar Shear Strength ◽  
Short Beam ◽  
Beam Shear ◽  
Interlaminar Shear

Microstructure optimizations for improving interlaminar shear strength and self-healing efficiency of spread carbon fiber/epoxy laminates containing microcapsules

2020 ◽  
Vol 55 (1) ◽  
pp. 27-38
Author(s):  
Yasuka Nassho ◽  
Kazuaki Sanada
Keyword(s):  
Shear Strength ◽  
Carbon Fiber ◽  
Optical Microscope ◽  
Interlaminar Shear Strength ◽  
Self Healing ◽  
Short Beam ◽  
Healing Efficiency ◽  
Beam Shear ◽  
Interlaminar Shear ◽  
Carbon Fiber Epoxy

The purpose of this study is to improve interlaminar shear strength and self-healing efficiency of spread carbon fiber (SCF)/epoxy (EP) laminates containing microcapsules. Microencapsulated healing agents were embedded within the laminates to impart a self-healing functionality. Self-healing was demonstrated on short beam shear specimens, and the healing efficiency was evaluated by strain energies of virgin and healed specimens. The effects of microcapsule concentration and diameter on apparent interlaminar shear strength and healing efficiency were discussed. Moreover, damaged areas after short beam shear tests were examined by an optical microscope to investigate the relation between the microstructure and the healing efficiency of the laminates. The results showed that the stiffness and the apparent interlaminar shear strength of the laminates increased as the microcapsule concentration and diameter decreased. However, the healing efficiency decreased with decreasing the microcapsule concentration and diameter.

scholarly journals Investigation for Influences of Seepage on Mechanical Properties of Rocks Using Acoustic Emission Technique

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Saisai Wu ◽  
Xiaohan Zhang ◽  
Junping Li ◽  
Zhao Wang
Keyword(s):  
Mechanical Properties ◽  
Acoustic Emission ◽  
Rock Mass ◽  
Shear Failure ◽  
Great Influence ◽  
Average Energy ◽  
Acoustic Emission Technique ◽  
Failure Patterns ◽  
Initial Rupture ◽  
Emission System

The behavior of rock mass is governed by the properties of both the rock material and discontinuities in the rock mass. Surrounding environments including the existence of water also have a great influence on the behavior and mechanical properties of rocks. In this study, a novel-designed compression and seepage testing system, associated with an acoustic emission system, was designed and constructed. The changes in the specimens resulting from the uniaxial compression were monitored by an acoustic emission technique. The characteristics of the acoustic emission parameters at different stages including compaction and crack initiation, crack propagation, and catastrophic failure were analyzed. The existence of seepage had direct influences on the mechanical properties and failure patterns of the specimens. The specimens tested in pure compression conditions demonstrated strong burst proneness and ruptured into separate pieces, while for the specimens with seepage, no burst proneness was observed and the specimens tended to fail along a macroscopic shear failure plane. The highest average energy of the acoustic signal occurred at the stage of initial rupture of rock specimens, rather than at the stage of widespread rupture. The studies explored the possibilities of using the acoustic emission technique to investigate the problems associated with the seepage in geotechnical and rock engineering and provided meaningful results for further research in this field.

scholarly journals Effects of Piezoceramic Particle Addition on the Fracture Toughness Behaviour of CF/EP – Composites

2005 ◽  
Vol 14 (4) ◽  
pp. 096369350501400
Author(s):  
Patrick Rosso ◽  
T. Tanimoto ◽  
Klaus Friedrich
Keyword(s):  
Fracture Toughness ◽  
Piezoelectric Ceramic ◽  
Tensile Tests ◽  
Interlaminar Shear Strength ◽  
Interlaminar Fracture Toughness ◽  
Short Beam ◽  
Beam Shear ◽  
Fracture Surface Analysis ◽  
Interlaminar Shear ◽  
Particle Addition

In this study, the influence of piezoelectric ceramic particles (PZT) on a continuous carbon fibre (CF) reinforced epoxy was investigated. Therefore, unidirectional laminates were produced via film stacking in an autoclave. Mode-I interlaminar fracture toughness tests were carried out as well as tensile tests and short beam shear test to evaluate E-modulus and interlaminar shear strength (ILSS), respectively. The amount of PZT was varied and additional fracture surface analysis by scanning electron microscopy (SEM) clarified how the PZT affects the GIC of the particular laminates. It was found, that the addition of the PZT-particles caused a significant decrease in fracture toughness, whereas stiffness and ILSS were effected only marginally.

scholarly journals Mechanical Properties and Acoustic Emission Characteristics of Karst Limestone under Uniaxial Compression

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Jianxun Chen ◽  
Qingsong Wang ◽  
Jiaqi Guo ◽  
Yanbin Luo ◽  
Yao Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Acoustic Emission ◽  
Water Content ◽  
Uniaxial Compression ◽  
Wave Velocity ◽  
Brittle Failure ◽  
Shear Failure ◽  
Testing Machine ◽  
Natural State ◽  
Saturated State

Firstly, I-RPT ultrasonic detector was used to test the wave velocity of karst limestone with different initial microstructure and water content. Then, RMT-150B rock testing machine and DS2-16B acoustic emission system were used to test the acoustic emission (AE) under uniaxial compression. Mechanical properties and AE characteristics were obtained during rock failure. The detailed relationship between stress-strain and AE characteristics was studied in this paper. Research results indicated the following: (1) For samples with many primary fissures and defects, wave velocity in dry state was larger than that in its natural state. From natural state to saturated state, the wave velocity tended to increase. For samples with good integrity, wave velocity increased with increasing of water content. (2) In the dry state, the samples presented tension failure. In saturated state, the samples presented tension-shear failure. For samples with cracks and good integrity, samples showed brittle failure. For samples with many corrosion pores which showed ductile damage under natural and saturated state, the spalling phenomenon was enhanced under saturated state. (3) With increasing of water content, the peak stress and AE peak reduced dramatically. In brittle failure, AE peak could be considered a sign of failure. In ductile failure, AE activity decreased gradually with the decrease of stress. (4) The mechanical properties and AE characteristics corresponding to four main fracture propagation types were also discussed.

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