In addition, technologies for the integration of active materials such as shape memory alloys are discussed. The following ISBNs are associated with this title:. ISBN - Use of special fillers in polymer composite parts with multifunctional properties 4. Multi- functional polymer composites using natural fiber reinforcements 7.
Multi-functionality of polymer nanocomposites for aerospace applications Multi-Functional Adhesives for Aerospace Applications Friction Composites Multi-Functional Polymer Nanocomposite Coating Multi-Functional Composites for load bearing and electrical power storage Multifunctional Polymer Composites for Intellectual' Structures Electrodes using Electrospun Composite Fibres Light-weight radar transparent composites for structural applications Multi-Functional Polymer materials for medical stents and scaffolds Composite Materiomics: Multi Length scale self-assembly of hierarchical composites for structural and tissue engineering applications Self-sending carbon nanotube composites Then, in ene and Diels—Alder reactions, three-dimensional cross-linked structures were formed between the derivative and the other two BMI components [ 97 , 98 ].
The covalent bonding between CNT and BMI dramatically enhanced the interfacial adhesion, and thus, the improved load transfer was achieved by the functionalization. After the functionalization to for interfacial covalent bonds, the mechanical properties of the resultant film were further improved. Schematics of carbon fiber-reinforced polymer, composite structure with aggregated CNTs, and ideal structure containing unaggregated CNTs, respectively .
Recent Overviews in Functional Polymer Composites for Biomedical Applications
The high-volume fraction CNT composites have exhibited exciting advantages in achieving high mechanical and electrical performances. However, due to the aggregation of nanometer-sized components, there is still a severe problem in paving the way to stronger materials [ 99 ]. The large specific surface area is one important advantage of CNT. When the aggregated CNTs were used to replace solid carbon fibers, as observed in many reports [ 12 , 82 , 87 , 93 , 95 ], larger interfacial contact area was formed, and tensile strengths of the CNT composites range from 2.
However, in the aggregation phase, the load transfer is not as efficient as at the interface. Thus, such aggregation phase might become the weak parts in the composites and hinders further reinforcement. In an ideal structure, the nanometer-sized components should be uniformly distributed in the matrix without formation of any aggregation phases.
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Therefore, all the interfaces can play roles in shear load transfer. The situation becomes very severe in the layer-by-layer stacking of aligned CNT sheets with the aid of solution spray [ 12 , 82 , 87 ], where the CNTs or more commonly, small-sized CNT bundles usually aggregate first into large-sized bundles and then are surrounded by polymer matrix.
Usually, the CNT aggregation was observed in a scale of hundreds of nanometer. Nevertheless, due to the entanglement, the preformed CNT webs were found to be more optimal than the forest-based CNT sheets in realizing the aggregation control. C Acetone-densified CNT webs maintained the feature of entanglement.
As-inspired by the natural composite structures, the entanglement was utilized to produce the optimal composite structure where the CNTs and polymer matrix co-existed and uniformly distributed among each other. This is reminiscent of the formation process of biological composites. During the formation, the matrix and the major components are simultaneously grown from stem cells at the optimized fractions to maximize the interfacial stress transfer.
Bio-inspired aggregation control showed great advantages in realizing super-strong CNT composites . The entangled CNTs can be re-assembled and aligned by a high level of stretching. This requires the CNT film to possess high plasticity.
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After the stretching, the tensile strength was improved from — to — MPa owing to the improved alignment. This means that the impregnation prior to stretching also resulted in improved processability.
After 8 or 10 steps, the total stretching magnitude was 1. In this multi-step way, the CNTs were fully aligned and the packing density during the hot-pressing was also improved. At this stage, the small-sized CNT bundles were well surrounded by the BMI resin molecules and maintained unaggregated phases. At the same time, the elastic modulus was up to — GPa. Based on the aggregation control and high CNT alignment, a big step has been realized towards the ideal composite structure.
Although individual CNTs were difficult to distinguish, CNT bundles with small size were found perpendicular to the cross section and their surfaces were all surrounded by BMI resins. Obviously, the maximized interface contacts can allow the most efficient interfacial stress transfer.
Notice that the level of CNT aggregation was within 20—50 nm. This means that there is still a big challenge to obtain the ideal composite structure where individual CNTs are aligned, highly packed, and unaggregated.
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The square resistance of the as-produced CNT web was 1. After being impregnated with BMI resins, the resistance decreased to 0.http://checkout.midtrans.com/sada-grupos-para-conocer-gente.php
Multifunctionality Of Polymer Composites: Challenges And New Solutions
As a result, the resistance increased to 1. The layer-by-layer stacking of aligned CNT sheets and the stretching of entangled CNT webs have provided two different solutions to realize the high-strength CNT composite films. Considering the easy aggregation between CNTs, the bio-inspired aggregation control makes a big step to approach the ideal composite structure where the CNTs are highly packed, aligned, and unaggregated. We anticipate that the present fabrication method can be generalized for developing multifunctional and smart nanocomposites.
The authors thank financial supports from the National Natural Science Foundation of China , , , , , and the Youth Innovation Promotion Association of the Chinese Academy of Sciences , Grant to X.
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Edited by Sergey Mikhailov. We are IntechOpen, the world's leading publisher of Open Access books. Built by scientists, for scientists. Our readership spans scientists, professors, researchers, librarians, and students, as well as business professionals. Downloaded: Keywords carbon nanotube composite high volume fraction super-strong multifunctionality bio-inspired.
Introduction Since their discovery in [ 1 ], carbon nanotubes CNTs have generated huge activity in most areas of science and engineering due to their unprecedented mechanical, electrical, and thermal properties. Conventional composite processing Solution processing and melt processing have been widely used to prepare composites, where CNTs and polymer matrix can be well mixed together. Super-strong CNT assembly film As inspired by the forest-based fiber spinning where macroscopic one-dimensional assembly fiber with pure neat CNTs can be produced [ 75 , 76 ], the layer-by-layer stacking can be also used to fabricate pure CNT films with high mechanical performances.
Stretching on entangled CNT webs As the CNT length can only reach several hundred micrometers for the forest-based spinning, the aspect ratio of the CNTs is thus limited to be in the range of 10 4. Direct stretching A simple mechanical-stretch method can be used to align the CNTs in the entangled webs [ 93 ].
CNT functionalization Although the improvement in CNT alignment benefited the mechanical properties, substantial CNT pull-outs were observed at the fracture of the composites [ 93 ], corresponding to weak interfacial bonding. Bio-inspired aggregation control. Impregnation without introducing aggregation As-inspired by the natural composite structures, the entanglement was utilized to produce the optimal composite structure where the CNTs and polymer matrix co-existed and uniformly distributed among each other.
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