Interfaces in Fibre Reinforced Cements

1987 ◽  
Vol 114 ◽  
Author(s):  
A. Bentur
Keyword(s):  
Mechanical Performance ◽  
Fibre Surface ◽  
Special Structure ◽  
Analytical Models ◽  
The Matrix

ABSTRACTThe microstructure of the matrix in the vicinity of the fibre surface is quite different from the microstructure of the bulk paste matrix. This can have an important effect on the processes that take place at the interface, such as crack-fibre interaction and debonding. The present paper describes the special structure of this zone, in monofilament and bundled fibre reinforced cements, and discusses its effects on some characteristics of the mechanical performance of the composites, which cannot be predicted by analytical models assuming a uniform matrix up to the fibre surface. The modification of the microstructure at the interface as a means for improving properties in some composites is described.

scholarly journals Thermo-Mechanical Properties of PLA/Short Flax Fiber Biocomposites

2019 ◽  
Vol 9 (18) ◽  
pp. 3797 ◽  
Author(s):  
Laura Aliotta ◽  
Vito Gigante ◽  
Maria-Beatrice Coltelli ◽  
Patrizia Cinelli ◽  
Andrea Lazzeri ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Load Transfer ◽  
Mechanical Performance ◽  
Nucleating Agent ◽  
Flax Fiber ◽  
Analytical Models ◽  
Poly Lactic Acid ◽  
Flax Fibers ◽  
The Matrix

In this work, biocomposites based on poly(lactic acid) (PLA) and short flax fibers (10–40 wt.%) were produced by extrusion and characterized in terms of thermal, mechanical, morphological, and thermo-mechanical properties. Analytical models were adopted to predict the tensile properties (stress at break and elastic modulus) of the composites, and to assess the matrix/fiber interface adhesion. The resulting composites were easily processable by extrusion and injection molding up to 40 wt.% of flax fibers. It was observed that despite any superficial treatment of fibers, the matrix/fiber adhesion was found to be sufficiently strong to ensure an efficient load transfer between the two components obtaining composites with good mechanical properties. The best mechanical performance, in terms of break stress (66 MPa), was obtained with 20 wt.% of flax fibers. The flax fiber acted also as nucleating agent for PLA, leading to an increment of the composite stiffness and, at 40 wt.% of flax fibers, improving the elastic modulus decay near the PLA glass transition temperature.

scholarly journals Ligno-Cellulosic Fibre Sized with Nucleating Agents Promoting Transcrystallinity in Isotactic Polypropylene Composites

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1259 ◽  
Author(s):  
Armin Thumm ◽  
Regis Risani ◽  
Alan Dickson ◽  
Mathias Sorieul
Keyword(s):  
Isotactic Polypropylene ◽  
Mechanical Performance ◽  
Fibre Surface ◽  
Regenerated Cellulose ◽  
Nucleating Agents ◽  
Scanning Calorimetry ◽  
Mechanical Pulp ◽  
Polypropylene Composites ◽  
The Matrix ◽  
Final Composite

The mechanical performance of composites made from isotactic polypropylene reinforced with natural fibres depends on the interface between fibre and matrix, as well as matrix crystallinity. Sizing the fibre surface with nucleating agents to promote transcrystallinity is a potential route to improve the mechanical properties. The sizing of thermo-mechanical pulp and regenerated cellulose (Tencel™) fibres with α- and β-nucleating agents, to improve tensile strength and impact strength respectively, was assessed in this study. Polarised microscopy, electron microscopy and differential scanning calorimetry (DSC) showed that transcrystallinity was achieved and that the bulk crystallinity of the matrix was affected during processing (compounding and injection moulding). However, despite substantial changes in crystal structure in the final composite, the sizing method used did not lead to significant changes regarding the overall composite mechanical performance.

Investigation on Shear Strength of Steel-Polymer Interface in Plastic Pipe Reinforced by Cross Helically Wound Steel Wires

2013 ◽  
Author(s):  
Jun Shi ◽  
Jianfeng Shi ◽  
Jinyang Zheng
Keyword(s):  
Shear Strength ◽  
Load Transfer ◽  
Mechanical Performance ◽  
Analytical Models ◽  
Polymer Interface ◽  
Pull Out ◽  
Steel Wires ◽  
Reinforced Plastic ◽  
The Matrix ◽  
Fibre Matrix

Shear strength of fibre-matrix adhesive interface is crucial important to the mechanical performance of fibre-reinforced plastic pipes and fittings, due to its function for load transfer between the fibre and the matrix. In this study, pull-out tests of steel-polymer specimens were carried out with different embedded lengths. Ultrasonic scanning was adopted to monitor the failure procedure of the interface. From the analysis of UT scanning graphs, it could be determined that the studied steel-polymer interface failed rapidly on the whole embedded length under the maximal pull-out force, but not in the manner that crack initiated from a stress concentration point under a relatively small pull-out force and then propagated gradually. Different kinds of pull-out analytical models were discussed. Finally the analytical model of yielding interface was applied to characterize the steel-polymer interfacial adhesive property. Combing with experimental results of pull-out tests of different embedded lengths, the nominal bond shear strength was calculated out.

scholarly journals Preparation of Long Sisal Fiber-Reinforced Polylactic Acid Biocomposites with Highly Improved Mechanical Performance

Polymers ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1124
Author(s):  
Zhifang Liang ◽  
Hongwu Wu ◽  
Ruipu Liu ◽  
Caiquan Wu
Keyword(s):  
Mechanical Properties ◽  
Polylactic Acid ◽  
Mechanical Performance ◽  
Tensile Elongation ◽  
Sisal Fiber ◽  
Fiber Reinforced ◽  
Impact Performance ◽  
The Matrix ◽  
Blending Process ◽  
Extension Direction

Green biodegradable plastics have come into focus as an alternative to restricted plastic products. In this paper, continuous long sisal fiber (SF)/polylactic acid (PLA) premixes were prepared by an extrusion-rolling blending process, and then unidirectional continuous long sisal fiber-reinforced PLA composites (LSFCs) were prepared by compression molding to explore the effect of long fiber on the mechanical properties of sisal fiber-reinforced composites. As a comparison, random short sisal fiber-reinforced PLA composites (SSFCs) were prepared by open milling and molding. The experimental results show that continuous long sisal fiber/PLA premixes could be successfully obtained from this pre-blending process. It was found that the presence of long sisal fibers could greatly improve the tensile strength of LSFC material along the fiber extension direction and slightly increase its tensile elongation. Continuous long fibers in LSFCs could greatly participate in supporting the load applied to the composite material. However, when comparing the mechanical properties of the two composite materials, the poor compatibility between the fiber and the matrix made fiber’s reinforcement effect not well reflected in SSFCs. Similarly, the flexural performance and impact performance of LSFCs had been improved considerably versus SSFCs.

scholarly journals Nanocomposites Materials of PLA Reinforced with Nanoclays Using a Masterbatch Technology: A Study of the Mechanical Performance and Its Sustainability

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2133
Author(s):  
Helena Oliver-Ortega ◽  
Josep Tresserras ◽  
Fernando Julian ◽  
Manel Alcalà ◽  
Alba Bala ◽  
...  
Keyword(s):  
Food Packaging ◽  
Mechanical Performance ◽  
Polymeric Materials ◽  
Barrier Properties ◽  
Food Tray ◽  
Environmental Concerns ◽  
Poly Lactic Acid ◽  
The Matrix ◽  
Surface Modified ◽  
Being Moved

Packaging consumes around 40% of the total plastic production. One of the most important fields with high requirements is food packaging. Food packaging products have been commonly produced with petrol polymers, but due to environmental concerns, the market is being moved to biopolymers. Poly (lactic acid) (PLA) is the most promising biopolymer, as it is bio-based and biodegradable, and it is well established in the market. Nonetheless, its barrier properties need to be enhanced to be competitive with other polymers such as polyethylene terephthalate (PET). Nanoclays improve the barrier properties of polymeric materials if correct dispersion and exfoliation are obtained. Thus, it marks a milestone to obtain an appropriate dispersion. A predispersed methodology is proposed as a compounding process to improve the dispersion of these composites instead of common melt procedures. Afterwards, the effect of the polarity of the matrix was analyzing using polar and surface modified nanoclays with contents ranging from 2 to 8% w/w. The results showed the suitability of the predispersed and concentrated compound, technically named masterbatch, to obtain intercalated structures and the higher dispersion of polar nanoclays. Finally, the mechanical performance and sustainability of the prepared materials were simulated in a food tray, showing the best assessment of these materials and their lower fingerprint.

Design of composite lattice materials combined with fabrication approaches

2018 ◽  
Vol 53 (3) ◽  
pp. 393-404 ◽  
Author(s):  
Jun Xu ◽  
Yaobo Wu ◽  
Xiang Gao ◽  
Huaping Wu ◽  
Steven Nutt ◽  
...  
Keyword(s):  
Shear Strength ◽  
Mechanical Performance ◽  
Analytical Models ◽  
Core Material ◽  
Foam Core ◽  
Hierarchical Lattice ◽  
Bottom Up ◽  
Lattice Materials ◽  
Assembly Technique ◽  
Composite Lattice

Lattice materials can be designed through their microstructure while concurrently considering fabrication feasibility. Here, we propose two types of composite lattice materials with enhanced resistance to buckling: (a) hollow lattice materials fabricated by a newly developed bottom-up assembly technique and the previously developed thermal expansion molding technique and (b) hierarchical lattice materials with foam core sandwich trusses fabricated by interlocking assembly process. The mechanical performance of sandwich structures featuring the two types of lattice cores was tested and analyzed theoretically. For hollow lattice core material, samples from two different fabrication processes were compared and both failed by nodal rupture or debonding. In contrast, hierarchical lattice structures failed by shear buckling without interfacial failure in the sandwich struts. Calculations using established analytical models indicated that the shear strength of hollow lattice cores could be optimized by judicious selection of the thickness of patterned plates. Likewise, the shear strength of hierarchical foam core truss cores could be maximized (with minimal weight) through design of truss geometry. The bottom-up assembly technique could provide a feasible way for mass production of lattice cores, but the design about how to assembly is critical. Hierarchical lattice cores with foam sandwich trusses should be a suitable choice for future lightweight material application.

Properties of a Dielectric Elastomer Actuator Modified by Dispersion of Functionalised Carbon Nanotubes

2012 ◽  
Vol 79 ◽  
pp. 41-46 ◽  
Author(s):  
Fabia Galantini ◽  
Sabrina Bianchi ◽  
Valter Castelvetro ◽  
Irene Anguillesi ◽  
Giuseppe Gallone
Keyword(s):  
Carbon Nanotubes ◽  
Dielectric Constant ◽  
Mechanical Performance ◽  
Broad Class ◽  
Dielectric Elastomer ◽  
Low Dielectric ◽  
Dielectric Elastomer Actuators ◽  
Electromechanical Transduction ◽  
The Matrix ◽  
Simple Matrix

Among the broad class of electro-active polymers, dielectric elastomer actuators represent a rapidly growing technology for electromechanical transduction. In order to further develop this applied science, the high driving voltages currently needed must be reduced. For this purpose, one of the most promising and adopted approach is to increase the dielectric constant while maintaining both low dielectric losses and high mechanical compliance. In this work, a dielectric elastomer was prepared by dispersing functionalised carbon nanotubes into a polyurethane matrix and the effects of filler dispersion into the matrix were studied in terms of dielectric, mechanical and electro-mechanical performance. An interesting increment of the dielectric constant was observed throughout the collected spectrum while the loss factor remained almost unchanged with respect to the simple matrix, indicating that conductive percolation paths did not arise in such a system. Consequences of the chemical functionalisation of carbon nanotubes with respect to the use of unmodified filler were also studied and discussed along with rising benefits and drawbacks for the whole composite material.

scholarly journals Utilization of vegetable fibers for production of reinforced cementitious materials

2018 ◽  
Vol 2 ◽  
pp. 145-154 ◽  
Author(s):  
Viviane Costa Correia ◽  
Sergio Francisco Santos ◽  
Holmer Savastano Jr ◽  
Vanderley Moacyr John
Keyword(s):  
Mechanical Performance ◽  
Stress Transfer ◽  
Cost Effective ◽  
Nanofibrillated Cellulose ◽  
Cementitious Materials ◽  
Vegetable Fibers ◽  
The Matrix ◽  
As Stress ◽  
Hybrid Reinforcement ◽  
Cellulosic Pulp

Vegetable fibers produced from agroindustrial resources in the macro, micro and nanometric scales have been used as reinforcement in cementitious materials. The cellulosic pulp, besides being used as the reinforcing element, is also the processing fiber that is responsible for the filtration system in the Hatcheck method. On the other hand, the nanofibrillated cellulose has the advantage of having good mechanical performance and high specific surface, which contributes to improve the adhesion between fiber and matrix. In the hybrid reinforcement, with micro and nanofibers, the cellulose performs bonding elements with the matrix and acts as stress transfer bridges in the micro and nano-cracking network with the corresponding strengthening and toughening of the cementitious composite. Some strategies are studied to mitigate the degradation of the vegetable fibers used in cost-effective and non-conventional fiber cement, as well as to reach a sustainable fiber cement production. As a practical example, the accelerated carbonation curing at early age is a developing technology to increase the durability of composite materials: it decreases porosity, promotes a higher density in the interface generating a good fiber–matrix adhesion and a better mechanical behavior. Thus, the vegetable fibers are potentially applicable to produce high mechanical performance and sustainable cementitious materials for use in the Civil Construction.

Microstructure and Mechanical Performance of AZ31-1.7 Wt.% Si Alloy Processed by Cyclic Channel Die Compression

2010 ◽  
Vol 667-669 ◽  
pp. 457-461
Author(s):  
Wei Guo ◽  
Qu Dong Wang ◽  
Man Ping Liu ◽  
Tao Peng ◽  
Xin Tao Liu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Tensile Strength ◽  
Mechanical Performance ◽  
Chinese Script ◽  
Cast State ◽  
Microstructure And Mechanical Properties ◽  
Mean Grain Size ◽  
The Matrix ◽  
The Mean

Cyclic channel die compression (CCDC) of AZ31-1.7 wt.% Si alloy was performed up to 5 passes at 623 K in order to investigate the microstructure and mechanical properties of compressed alloys. The results show that multi-pass CCDC is very effective to refine the matrix grain and Mg2Si phases. After the alloy is processed for 5 passes, the mean grain size decreases from 300 μm of as-cast to 8 μm. Both dendritic and Chinese script type Mg2Si phases break into small polygonal pieces and distribute uniformly in the matrix. The tensile strength increases prominently from 118 MPa to 216 MPa, whereas the hardness of alloy deformed 5 passes only increase by 8.4% compared with as-cast state.

scholarly journals Biocomposites from Rice Straw Nanofibers: Morphology, Thermal and Mechanical Properties

Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2138 ◽  
Author(s):  
José Carlos Alcántara ◽  
Israel González ◽  
M. Mercè Pareta ◽  
Fabiola Vilaseca
Keyword(s):  
Rice Straw ◽  
Mechanical Performance ◽  
Cellulose Nanofibers ◽  
Nucleating Agent ◽  
Mechanical Analysis ◽  
Nanocomposite Films ◽  
Chemical Extraction ◽  
Poly Vinyl Alcohol ◽  
Scanning Calorimetry ◽  
The Matrix

Agricultural residues are major potential resources for biomass and for material production. In this work, rice straw residues were used to isolate cellulose nanofibers of different degree of oxidation. Firstly, bleached rice fibers were produced from the rice straw residues following chemical extraction and bleaching processes. Oxidation of rice fibers mediated by radical 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) at pH 10 was then applied to extract rice cellulose nanofibers, with diameters of 3–11 nm from morphological analysis. The strengthening capacity of rice nanofibers was tested by casting nanocomposite films with poly(vinyl alcohol) polymer. The same formulations with eucalyptus nanofibers were produced as comparison. Their thermal and mechanical performance was evaluated using thermogravimetry, differential scanning calorimetry, dynamic mechanical analysis and tensile testing. The glass transition of nanocomposites was shifted to higher temperatures with respect to the pure polymer by the addition of rice cellulose nanofibers. Rice nanofibers also acted as a nucleating agent for the polymer matrix. More flexible eucalyptus nanofibers did not show these two phenomena on the matrix. Instead, both types of nanofibers gave similar stiffening (as Young’s modulus) to the matrix reinforced up to 5 wt.%. The ultimate tensile strength of nanocomposite films revealed significant enhancing capacity for rice nanofibers, although this effect was somehow higher for eucalyptus nanofibers.

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