Search results for "Toughness"
showing 10 items of 105 documents
Coating Toughness Estimation through a Laser Shock Testing in Ni-Cr-B-Si-C Coatings
2018
In the nuclear field, efforts are made to find substitutes to cobalt hardfacing alloys since these alloys have a principal drawback, the transmutation from stable 59Co to 60Co under neutron irradiation. In case of wear, fragments could be deposed on the surface of primary circuit and thus contaminate it, causing a real issue for deconstruction.
Photoelastic stress analysis assisted evaluation of fracture toughness in hydrothermally aged epoxies
2014
The present work has investigated the fracture toughness of a model DGEBA epoxy system subject to Hidro-Thermal aging. A Photoelastic Stress Analysis technique has been implemented, showing the evolution of stresses arising throughout the water uptake process due to the non-uniform swelling of the material. Gravimetric and Dynamic Mechanical Thermal Analyses have further complemented the characterization, showing the onset of plasticization effects with aging. The correlation of all previous characterizations has allowed to conclude that an increase of KIC fracture toughness is obtained at the fully saturated condition. In particular Photoelasticity has also revealed the onset of relevant s…
Enhancement of Static and Fatigue Strength of Short Sisal Fiber Biocomposites by Low Fraction Nanotubes
2021
AbstractThanks to good mechanical performances, high availability, low cost and low weight, the agave sisalana fiber allows to obtain biocomposites characterised by high specific properties, potentially very attractive for the replacement of synthetic materials in various industrial fields. Unfortunately, due to the low strength versus transversal damage processes mainly related to the matrix brittleness and/or to the low fiber/matrix adhesion, the tensile performance of random short fiber biocomposites are quite low, and to date most of the fiber treatments proposed in literature to improve the fiber-matrix adhesion, have not led to very satisfactory results. In order to overcome such a dr…
The performance of molybdenum toughened alumina cutting tools in turning a particulate metal matrix composite
2003
In this paper, a study of the tool wear mechanism in turning aluminium alloy reinforced with alumina using molybdenum-toughened alumina tools is presented. Alumina tools with three different amounts (15, 20 and 25 vol.%) of molybdenum were prepared and tested. The wear type was identified and its evolution with cutting time was measured. The results show that the main mechanism of tool wear is abrasion and not heat. The best overall performance was achieved, as far as flank wear is concerned, using the tool with 20 vol.% of molybdenum added. This has been explained using some of the composites intrinsic properties. SEM examination revealed that molybdenum particles are easily torn from the …
Wear mechanisms and residual stresses in alumina-based laminated cutting tools
2005
Abstract The outstanding performances of the Al2O3 cutting tools in terms of potential cutting speed can lead to substantial economies in the machining of metallic materials. Nevertheless, their widespread use is limited by some drawbacks such as the tendency to edge chipping and to the propagation of microcracks, which can lead to premature failures. These shortcomings are due to the intrinsic low toughness of the ceramic material, which is in turn related to its characteristics non-metallic bonds. A well-recognised method of increasing the toughness of brittle materials is the introduction of surface compressive stresses, which can be obtained through a suitable lamination geometry of the…
Non associative damage interface model for mixed mode delamination and frictional contact
2019
Abstract The present paper proposes a new interface constitutive model based on the non-associative damage mechanics and frictional plasticity. The model is developed in a thermodynamically consistent framework, with three independent damage variables. The non associative flow rules drive the concurrent evolution of the three damage variables. The interface model provides two independent values for the mode I fracture energy and the mode II fracture energy and it is able to accurately reproduce arbitrary mixed mode fracture conditions. The model can also take into account the presence of frictional effects both at the fully debonded zones and at the partially debonded ones. The experimental…
Mode I translaminar fracture toughness of high performance laminated biocomposites reinforced by sisal fibers: Accurate measurement approach and lay-…
2022
Abstract The present work performs a systematic experimental analysis of the translaminar fracture behavior of high performance biocomposites constituted by green epoxy reinforced by sisal fibers, by varying the main influence parameters as fiber concentration and lay-up. Despite the corrective function properly introduced to take into account the anisotropy as well as the use of the equivalent crack length, the study shows that the LEFM does not give accurate estimations of the fracture toughness, because the extension of the near tip damaged zone is higher than the singular dominated one. Accurate estimations can be obtained instead by the proposed modified area method that takes into acc…
Biomimetic composites with enhanced toughening using silk-inspired triblock proteins and aligned nanocellulose reinforcements
2019
Silk-like proteins produced in bacteria are used as adhesives for cellulose nanofibrils to make a new biological material.
Analytical Solution of the 4ENF Test with Interlaminar Frictional Effects and Evaluation of Mode II Delamination Toughness
2018
The present paper proposes an analytical solution of the four points bend end-notched flexure test (4ENF) with frictional contact between the delamination surfaces. The analytical solution was developed in the framework of the classic Euler-Bernoulli bending beam theory with orthotropic linear elastic constitutive behavior. The frictional contact was modeled as rigid-perfectly plastic with the Mohr-Coulomb activation function and the nonassociative flow rule. The elastic solution of the partially cracked beam subjected to the four points bending test with frictional contact was developed, and the Mode II delamination toughness was analytically determined by means of the Griffith approach, a…
Recyclable and Light-Adaptive Vitrimer-Based Nacre-Mimetic Nanocomposites.
2021
Nacre's natural design consists of a perfect hierarchical assembly that resembles a brick-and-mortar structure with synergistic stiffness and toughness. The field of bioinspired materials often provides attractive architecture and engineering pathways which allow to explore outstanding property areas. However, the study of nacre-mimetic materials should not be limited to the design of its architecture but ought to include the understanding, operation, and improvement of internal interactions between their components. Here, we introduce a vitrimer prepolymer system that, once integrated into the nacre-mimetic nanocomposites, cures and cross-links with the presence of Lewis acid catalyst and …