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"Materials Testing"
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Toughened composites : micro and macro systems
\"This book covers micro and macro aspects of toughened composites covering polymer matrix, metal matrix, ceramic matrix and nanomatrix. It gives the reader understanding of composites fabrication, construction, and light weight yet high crack - resistance performance, macroscopic testing supported by microscopic bonding and debonding features, models of stress transfer, and commercial features of developing cheaper yet high quality materials. Features: Focuses on micro/macro aspects of toughening methods and principles of composite materials. Includes all types of composites including polymer matrix, metal matrix, ceramic matrix and nanomatrix. Covers corrosion resistance and oxidation resistance as well as solubility resistance. Discusses use of recycled materials. Provides good balance of long fiber, short fiber, nanoparticle, and particulate modifiers. This book aims at Researchers and professionals in Materials Science, Composite materials, Fracture mechanics, Materials Characterization & Testing, Properties and Mechanics, Nanomaterials, Aerospace and Automotive Engineering, and Structural Engineering\"-- Provided by publisher.
BOOK
A unified in vitro evaluation for apatite-forming ability of bioactive glasses and their variants
The aim of this study was to propose and validate a new unified method for testing dissolution rates of bioactive glasses and their variants, and the formation of calcium phosphate layer formation on their surface, which is an indicator of bioactivity. At present, comparison in the literature is difficult as many groups use different testing protocols. An ISO standard covers the use of simulated body fluid on standard shape materials but it does not take into account that bioactive glasses can have very different specific surface areas, as for glass powders. Validation of the proposed modified test was through round robin testing and comparison to the ISO standard where appropriate. The proposed test uses fixed mass per solution volume ratio and agitated solution. The round robin study showed differences in hydroxyapatite nucleation on glasses of different composition and between glasses of the same composition but different particle size. The results were reproducible between research facilities. Researchers should use this method when testing new glasses, or their variants, to enable comparison between the literature in the future.
Journal Article
Fracture toughness of graphene
Perfect graphene is believed to be the strongest material. However, the useful strength of large-area graphene with engineering relevance is usually determined by its fracture toughness, rather than the intrinsic strength that governs a uniform breaking of atomic bonds in perfect graphene. To date, the fracture toughness of graphene has not been measured. Here we report an
in situ
tensile testing of suspended graphene using a nanomechanical device in a scanning electron microscope. During tensile loading, the pre-cracked graphene sample fractures in a brittle manner with sharp edges, at a breaking stress substantially lower than the intrinsic strength of graphene. Our combined experiment and modelling verify the applicability of the classic Griffith theory of brittle fracture to graphene. The fracture toughness of graphene is measured as the critical stress intensity factor of
and the equivalent critical strain energy release rate of 15.9 J m
−2
. Our work quantifies the essential fracture properties of graphene and provides mechanistic insights into the mechanical failure of graphene.
While the intrinsic strength of graphene has previously been demonstrated to be high, the fracture toughness remains unknown. Here, the authors perform
in situ
testing of graphene in a scanning electron microscope and report a critical stress intensity factor of ~4.0 MPa√m.
Journal Article
Smart cement : development, testing, modeling and real-time monitoring
\"Smart cement is a chemo-thermo-piezoresistive material that functions as a highly sensing 3-dimensional bulk sensor. It can be used for monitoring changes oflectrical resistivity in concrete by the addition of 0.03% of selected conductive or semi-conductive fibers are added to the bulk cement\"-- Provided by publisher.
BOOK
Flexible high-performance carbon nanotube integrated circuits
Carbon nanotube thin-film transistors
1
are expected to enable the fabrication of high-performance
2
, flexible
3
and transparent
4
devices using relatively simple techniques. However, as-grown nanotube networks usually contain both metallic and semiconducting nanotubes, which leads to a trade-off between charge-carrier mobility (which increases with greater metallic tube content) and on/off ratio (which decreases)
5
. Many approaches to separating metallic nanotubes from semiconducting nanotubes have been investigated
6
,
7
,
8
,
9
,
10
,
11
, but most lead to contamination and shortening of the nanotubes, thus reducing performance. Here, we report the fabrication of high-performance thin-film transistors and integrated circuits on flexible and transparent substrates using floating-catalyst chemical vapour deposition followed by a simple gas-phase filtration and transfer process. The resulting nanotube network has a well-controlled density and a unique morphology, consisting of long (~10 µm) nanotubes connected by low-resistance Y-shaped junctions. The transistors simultaneously demonstrate a mobility of 35 cm
2
V
–1
s
–1
and an on/off ratio of 6 × 10
6
. We also demonstrate flexible integrated circuits, including a 21-stage ring oscillator and master–slave delay flip-flops that are capable of sequential logic. Our fabrication procedure should prove to be scalable, for example, by using high-throughput printing techniques.
Carbon nanotube transistors with high mobilities and high on/off ratios are demonstrated, along with flexible nanotube-based integrated circuits that are capable of sequential logic.
Journal Article
Artificial intelligence in biomaterials: a call for unified biocompatibility standards
A standardized definition of biocompatibility is essential for advancing biomaterials research. This letter emphasizes the need for clear guidelines and interdisciplinary frameworks in assessing biocompatibility, with artificial intelligence (AI) playing a pivotal role. Such an approach will facilitate research efforts and strengthen regulatory processes to develop next-generation biomaterials.
A standardized definition of biocompatibility is essential for advancing biomaterials research. This letter emphasizes the need for clear guidelines and interdisciplinary frameworks in assessing biocompatibility, with artificial intelligence (AI) playing a pivotal role. Such an approach will facilitate research efforts and strengthen regulatory processes to develop next-generation biomaterials.
Journal Article
Successful reading assessments and interventions for struggling readers : lessons from literacy space
\"Each struggling reader has a unique combination of strengths and areas that require targeted instruction. Through their work with teachers and children in an after school tutoring program, the authors have identified six types of struggling readers and offer suggestions for assessment and instruction for each type of struggling reader. The book shares lessons learned from the tutoring program that are applicable to the classroom. Suggestions of how teachers can outreach and involve parents, caregivers, and families is included\"-- Provided by publisher.
Book
A novel true triaxial apparatus for high-stress low-frequency disturbance in hard rocks: Development, validation, and application
A novel true triaxial apparatus (TTA) has been designed and fabricated to investigate the mechanical behavior of deep underground engineering under high-stress conditions and low-frequency disturbance loads. This apparatus features a two-rigid, one-flexible loading system, with rigid loading applied along the directions of the maximum and intermediate principal stresses, offering maximum load capacities of 2000 kN and 4000 kN, respectively. The direction of the maximum principal stress is also equipped with dynamic loading capabilities, enabling low-frequency disturbance loads with frequencies up to 20 Hz and amplitudes of 0.5 mm. The minimum principal stress direction utilizes flexible loading, with pressure capabilities of up to 120 MPa. Moreover, the integration of a high-rigidity loading frame and high-precision servo control systems has significantly enhanced the apparatus’s performance and data accuracy, particularly in small-scale deformation tests. Additionally, a dual-actuator, dual-loop servo control mode is employed to effectively suppress eccentric loading effects in true triaxial tests. To validate the reliability of the TTA and to preliminarily explore the effects of stress paths and disturbances on deep rock mechanical properties, true triaxial tests were conducted using granite. The results demonstrate that both the intermediate principal stress and disturbance frequency significantly influence the strength and failure modes of the rock. Static and disturbance tests exhibited excellent high repeatability and consistency, further confirming the accuracy and reliability of the apparatus. Overall, the TTA provides a novel methodology for investigating the mechanical properties of deep rock masses under high-stress and low-frequency disturbance conditions, making it an effective tool for addressing related scientific and engineering challenges.
Journal Article