Whiskers are defect free and hence more stronger and stiffer than fibers. But why they are not used widely? what exactly makes their production difficult ?
Hello,
A whisker is a single crystal in the form of a fiber. Whiskers can be considered as a sub-group of fibers possessing shorter lengths compared to conventional fibers. They are among the strongest materials that we know of. Whiskers can be produced from materials like graphite, silicon carbide, aluminum oxide, iron, and alike as well as hydroxyapatite, dicalcium phosphate anhydrous, cellulose whiskers and other biomaterials.
As you mentioned whiskers are with nearly zero defects exhibiting extraordinary strengths. Engineering materials in whisker form can possess strength and modulus as high as 25000 MPa and 1000 GPa (based on the mateiral type) far exceeding those in their bulk form.
However, whiskers are not without drawbacks.
They are easily damaged, i.e. break to shorter lengths, during processing. They also tend to get oriented leading to unwanted anisotropy in composites. It is also very difficult to carry out large-scale manufacturing of whiskers that are defect-free. Thus, they are very expensive. Whiskers also pose difficulty in packing compared to particulates; hence, it is not possible to achieve high reinforcement-to-matrix ratios.
These are the disadvantages that should be overcome to broaden the use of whiskers in composite reinforcement applications.
Best Regards.
For a general outlook you may refer to the followng links:
http://www.ae.iitkgp.ernet.in/ebooks/chapter2.html
https://www.princeton.edu/~ota/disk2/1988/8801/880107.PDF
http://in.bgu.ac.il/engn/mater/Documents/LaboratoryBriefings/4/Materials%20Science%20and%20Engineering%20introduction%20Chapter%2015%20Composites%207th%20ed.pdfx
https://www.ncbi.nlm.nih.gov/pubmed/19113881
https://www.hindawi.com/journals/amse/2016/2172365/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2423228/
Hello,
A whisker is a single crystal in the form of a fiber. Whiskers can be considered as a sub-group of fibers possessing shorter lengths compared to conventional fibers. They are among the strongest materials that we know of. Whiskers can be produced from materials like graphite, silicon carbide, aluminum oxide, iron, and alike as well as hydroxyapatite, dicalcium phosphate anhydrous, cellulose whiskers and other biomaterials.
As you mentioned whiskers are with nearly zero defects exhibiting extraordinary strengths. Engineering materials in whisker form can possess strength and modulus as high as 25000 MPa and 1000 GPa (based on the mateiral type) far exceeding those in their bulk form.
However, whiskers are not without drawbacks.
They are easily damaged, i.e. break to shorter lengths, during processing. They also tend to get oriented leading to unwanted anisotropy in composites. It is also very difficult to carry out large-scale manufacturing of whiskers that are defect-free. Thus, they are very expensive. Whiskers also pose difficulty in packing compared to particulates; hence, it is not possible to achieve high reinforcement-to-matrix ratios.
These are the disadvantages that should be overcome to broaden the use of whiskers in composite reinforcement applications.
Best Regards.
For a general outlook you may refer to the followng links:
http://www.ae.iitkgp.ernet.in/ebooks/chapter2.html
https://www.princeton.edu/~ota/disk2/1988/8801/880107.PDF
http://in.bgu.ac.il/engn/mater/Documents/LaboratoryBriefings/4/Materials%20Science%20and%20Engineering%20introduction%20Chapter%2015%20Composites%207th%20ed.pdfx
https://www.ncbi.nlm.nih.gov/pubmed/19113881
https://www.hindawi.com/journals/amse/2016/2172365/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2423228/
Hi Murali
By default, whisker reinforcements are more expensive than fiber reinforcements.
The physical properties of the whisker are closely matched to their theoretical physical properties. This is because whiskers are single crystals free of defects ,i.e. point defects ,dislocations, stacking faults, and so on. The processes of manufacturing whiskers are very expensive when it comes to produce whiskers in a bulk amount. Therefore, by default, whisker reinforcements are more expensive than fiber reinforcements.
Whisker reinforcement is random orientation of short fibers.
Fibers are long filaments which can be oriented They are easier to process in the composite (as a matrix material). Offer less wear and tear on processing equipment.
Besides that the fiber strengths are far larger than polymer strengths. One may not gain a lot more for the composite strength from the defect free whiskers and their higher strength
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