scholarly journals Guiding and Trapping Cracks With Compliant Inclusions for Enhancing Toughness of Brittle Composite Materials

2020 ◽  
Vol 87 (3) ◽  
Author(s):  
Neal R. Brodnik ◽  
Chun-Jen Hsueh ◽  
Katherine T. Faber ◽  
Blaise Bourdin ◽  
Guruswami Ravichandran ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Elastic Modulus ◽  
Heterogeneous Material ◽  
Effective Elastic Modulus ◽  
Elastic Compliance ◽  
Field Approach ◽  
Numerical Predictions ◽  
The Matrix ◽  
3D Printed ◽  
Square Array

Abstract The problem of toughening heterogeneous materials with a stiff matrix and compliant inclusions is investigated through numerical simulations and experiments. Specifically, the problem of optimizing a combination of effective toughness and effective elastic modulus in the context of a square array of compliant inclusions in a stiff matrix is explored. Crack propagation in the heterogeneous material is simulated using a variational phase-field approach. It is found that the crack can meander between or get attracted to and trapped in the inclusions. Composite specimens with a stiff matrix and compliant circular inclusions were 3D printed, and their fracture toughness was measured using a specially designed loading fixture. The experimental results show agreement with the numerical predictions by demonstrating the attraction and trapping of cracks in the inclusions. This study demonstrates the potential for significant enhancement of toughness through elastic compliance contrast between the matrix and the inclusion without notably compromising the effective elastic modulus of the composite material.

A Method to Determine Fracture Toughness Using Berkovich Indenter for Bulk Materials

2013 ◽  
Vol 331 ◽  
pp. 456-460
Author(s):  
Min He ◽  
Duan Hu Shi ◽  
Feng Yang ◽  
Ning Zhang ◽  
Hua Feng Guo
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Elastic Modulus ◽  
Penetration Depth ◽  
Effective Elastic Modulus ◽  
Berkovich Indenter ◽  
Bulk Materials ◽  
Ductile Materials ◽  
Penetration Depths ◽  
Determine Fracture Toughness

An indentation approach with Berkovich indenter is proposed to determine fracture toughness for ductile materials. With decrease of effective elastic modulus, an approximate linear relationship between logarithmic plastic penetration depth and logarithmic effective elastic modulus, and a quadratic polynomial relationship between the plastic penetration depths and penetration loads are exhibited by indentation investigation with Berkovich indenter. The damage constructive equation of effective elastic modulus is proposed to determine the critical effective elastic modulus at the fracture point, which is the key problem to calculate the indentation energy to fracture. The critical plastic penetration depth is identified after the critical effective elastic modulus can be predicted by conventional mechanical properties. The fracture toughness is calculated according to the equation of penetration load, plastic penetration depth and the critical plastic penetration depth.

Magnetorheological Elastomers With Increased Structural Integrity for Multifunction Applications

2007 ◽  
Author(s):  
Zelalem Aga ◽  
Dan Feimster ◽  
LeAnn Faidley
Keyword(s):  
Elastic Modulus ◽  
Vibration Isolation ◽  
Structural Integrity ◽  
Effective Elastic Modulus ◽  
Zero Field ◽  
Magnetorheological Elastomers ◽  
The Matrix ◽  
Cure Temperature ◽  
Vibration Tests ◽  
Novel Applications

Magnetorheological Elastomers (MREs) are composite materials formed of a soft elastomer matrix and a magnetic-powder filler. The interaction of the matrix and filler in a magnetic field causes the effective elastic modulus of the MRE to be controllable by an external field. In previous studies the applications of MREs have been severely limited by their lack of structural integrity, forcing them to be applied only as soft pads or as the filler in sandwich beams. This study represents initial steps towards improving the structural integrity of MREs while retaining some level of modulus variability. Specimens are made from Sylgard 184 Silicone with a variety of cure temperatures and filler volume percentages. Longitudinal swept-sine vibration tests are performed to measure the dependence of elastic modulus on applied fields of up to 40 kA/m. It is found that the softer specimen (ie: the lowest cure temperature) with 27% percent filler exhibits the largest percent change in effective modulus of almost 40%. The zero-field modulus for this specimen is 5.7 MPa giving it the structural integrity needed for multifunction applications in which the material is both active and load bearing. Many novel applications exist including active modulus control of sound radiating plates, novel design of vibration isolation tables, and more.

scholarly journals SIZE-DEPENDENT ELASTIC MODULUS AND FRACTURE TOUGHNESS OF THE NANOFILM WITH SURFACE EFFECTS

2008 ◽  
Vol 15 (05) ◽  
pp. 599-603 ◽  
Author(s):  
JIAN-GANG GUO ◽  
LI-JUN ZHOU ◽  
YA-PU ZHAO
Keyword(s):  
Fracture Toughness ◽  
Elastic Modulus ◽  
Surface Energy ◽  
Size Effects ◽  
Interatomic Potential ◽  
Effective Elastic Modulus ◽  
Surface Effects ◽  
Surface Relaxation ◽  
Ideal Crystal ◽  
Size Dependent

The effective elastic modulus and fracture toughness of the nanofilm were derived with the surface relaxation and the surface energy taken into consideration by means of the interatomic potential of an ideal crystal. The size effects of the effective elastic modulus and fracture toughness were discussed when the thickness of the nanofilm was reduced. And the dependence of the size effects on the surface relaxation and surface energy was also analyzed.

scholarly journals Simulation on the Effect of Porosity in the Elastic Modulus of SiC Particle Reinforced Al Matrix Composites

Metals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 391 ◽  
Author(s):  
Jorge E. Rivera-Salinas ◽  
Karla M. Gregorio-Jáuregui ◽  
José A. Romero-Serrano ◽  
Alejandro Cruz-Ramírez ◽  
Ernesto Hernández-Hernández ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Aluminum Matrix ◽  
Stress Transfer ◽  
Effective Elastic Modulus ◽  
High Volume ◽  
Aluminum Matrix Composites ◽  
Matrix Composites ◽  
Element Analysis ◽  
Soft Matrix ◽  
Numerical Predictions

Although the porosity in Al-SiC metal matrix composites (MMC) can be diminished; its existence is unavoidable. The purpose of this work is to study the effect of porosity on Young’s modulus of SiC reinforced aluminum matrix composites. Finite element analysis is performed based on the unit cell and the representative volume element approaches. The reliability of the models is validated by comparing the numerical predictions against several experimental data ranging in low- and high-volume fractions and good agreement is found. It is found that despite the stress transfer from the soft matrix to the reinforcement remains effective in the presence of pores, there is a drop in the stress gathering capability of the particles and thus, the resulting effective elastic modulus of composite decreases. The elastic property of the composite is more sensitive to pores away the reinforcement. It is confirmed, qualitatively, that the experimentally reported in the literature decrease in the elastic modulus is caused by the presence of pores.

Fracture Toughness of a Silica-Doped Cubic Zirconia (8Y-CSZ)

2010 ◽  
Vol 638-642 ◽  
pp. 3846-3851 ◽  
Author(s):  
Keijiro Hiraga ◽  
Koji Morita ◽  
Byung Nam Kim ◽  
Hidehiro Yoshida
Keyword(s):  
Fracture Toughness ◽  
Elastic Modulus ◽  
Crack Propagation ◽  
Glass Phase ◽  
Indentation Method ◽  
Grain Sizes ◽  
Pure Silica ◽  
Beam Method ◽  
The Matrix ◽  
A Site

In a high-purity 8Y-CSZ, the doping of 0.15 - 5 mass% pure silica introduces a glass phase dispersing uniformly along grain-boundary facets and at multiple junctions. For materials with grain sizes of 0.75 - 2.4 m, the dispersion of the glass phase decreases the elastic modulus, the Vickers hardness and the elastic modulus-to-hardness ratio, whereas it affects little in the fracture toughness measured by a Vickers-indentation method and a single-crack-precracked-beam method. Inspection of crack propagation paths shows that the glass phase with sizes smaller than those of the matrix grains is not a site for easy crack-propagation, but provides a site for a crack-deflection mechanism.

Machinability Evaluation of Ce-ZrO2/CePO4 Ceramics with Digraph Method

2007 ◽  
Vol 280-283 ◽  
pp. 1079-1082
Author(s):  
Ai Bing Yu ◽  
L.J. Zhong ◽  
Xin Li Tian ◽  
F. Zou
Keyword(s):  
Mechanical Property ◽  
Fracture Toughness ◽  
Elastic Modulus ◽  
Vickers Hardness ◽  
Material Removal ◽  
Ceramic Materials ◽  
Experimental Results ◽  
The Matrix ◽  
Machinability Index ◽  
Machinable Ceramic

A new method is proposed for machinability evaluation of machinable ceramic materials. The relation of machinability attributes is modeled as a digraph, and machinability attribute matrix is defined. Machinability indexes are calculated with permanent function of the matrix, and machinabilities of machinable ceramics are ranked. Five composites consisting of CePO4 and zirconia were fabricated, measured and drilled with tungsten-cobalt carbide bits. Mechanical property parameters of Ce-ZrO2/CePO4 composites, including Vickers hardness, fracture toughness and Elastic modulus, are selected as machinability attributes. The experimental results of material removal rates are consistent with the ranking of machinability index values of Ce-ZrO2/CePO4 ceramics. The machinabilities of Ce-ZrO2/CePO4 ceramics improve with the increase of CePO4 proportions. Machinability of machinable ceramics can be evaluated with digraph method.

scholarly journals 3D-Printed vs. Heat-Polymerizing and Autopolymerizing Denture Base Acrylic Resins

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5781
Author(s):  
Leila Perea-Lowery ◽  
Mona Gibreel ◽  
Pekka K. Vallittu ◽  
Lippo V. Lassila
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Elastic Modulus ◽  
Flexural Strength ◽  
Water Solubility ◽  
Base Material ◽  
Acrylic Resin ◽  
Denture Base ◽  
3D Printed ◽  
Work Of Fracture

The aim of this work was to investigate the effect of two post-curing methods on the mechanical properties of a 3D-printed denture base material. Additionally, to compare the mechanical properties of that 3D-printed material with those of conventional autopolymerizing and a heat-cured denture base material. A resin for 3D-printing denture base (Imprimo®), a heat-polymerizing acrylic resin (Paladon® 65), and an autopolymerizing acrylic resin (Palapress®) were investigated. Flexural strength, elastic modulus, fracture toughness, work of fracture, water sorption, and water solubility were evaluated. The 3D-printed test specimens were post-cured using two different units (Imprimo Cure® and Form Cure®). The tests were carried out after both dry and 30 days water storage. Data were collected and statistically analyzed. Resin type had a significant effect on the flexural strength, elastic modulus, fracture toughness, and work of fracture (p < 0.001). The flexural strength and elastic modulus for the heat-cured polymer were significantly the highest among all investigated groups regardless of the storage condition (p < 0.001). The fracture toughness and work of fracture of the 3D-printed material were significantly the lowest (p < 0.001). The heat-cured polymer had the lowest significant water solubility (p < 0.001). The post-curing method had an impact on the flexural strength of the investigated 3D-printed denture base material. The flexural strength, elastic modulus, fracture toughness, work of fracture of the 3D-printed material were inferior to those of the heat-cured one. Increased post-curing temperature may enhance the flexural properties of resin monomers used for 3D-printing dental appliances.

scholarly journals Self-Reinforced Nylon 6 Composite for Smart Vibration Damping

Polymers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1235
Author(s):  
Bidita Salahuddin ◽  
Rahim Mutlu ◽  
Tajwar A. Baigh ◽  
Mohammed N. Alghamdi ◽  
Shazed Aziz
Keyword(s):  
Matrix Material ◽  
Nylon 6 ◽  
Vibration Damping ◽  
Vibration Energy ◽  
Damping Factor ◽  
Passive Vibration Control ◽  
Reinforced Composite ◽  
Coiled Structure ◽  
The Matrix ◽  
3D Printed

Passive vibration control using polymer composites has been extensively investigated by the engineering community. In this paper, a new kind of vibration dampening polymer composite was developed where oriented nylon 6 fibres were used as the reinforcement, and 3D printed unoriented nylon 6 was used as the matrix material. The shape of the reinforcing fibres was modified to a coiled structure which transformed the fibres into a smart thermoresponsive actuator. This novel self-reinforced composite was of high mechanical robustness and its efficacy was demonstrated as an active dampening system for oscillatory vibration of a heated vibrating system. The blocking force generated within the reinforcing coiled actuator was responsible for dissipating vibration energy and increase the magnitude of the damping factor compared to samples made of non-reinforced nylon 6. Further study shows that the appropriate annealing of coiled actuators provides an enhanced dampening capability to the composite structure. The extent of crystallinity of the reinforcing actuators is found to directly influence the vibration dampening capacity.

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