How the diameter of the fiber plays a role in interfacial bonding? If the dia of Fiber is small, we assume the matrix will completely adhere to the fiber. If the dia is larger, the same matrix covers the fiber. Whatever the surface area might be. It depends on how good it binds the fibers. But how this dia play a role in that?
Generally in my point of view when diameter of fiber increases , distribution of fiber in fabricated plate is not even ( for best example palmyra fiber is large diameter) then automatically gap between the fiber and matrix will increases and finally while on testing the specimens it reduce mechanical properties.
Dear all, generally it is the aspect ratio is used instead of the diameter solely. Anyway, the importance of low diameter compared to higher one resids in the fact that even if the binding is not strong, reducing the diameter increases specific surface area, hence, increasing contact or interface between the different phases, this will enhance binding points which means binding energy. Other thing to consider is stress transfer is more efficient with low dimensions fibers. My Regards
Moon, C.K., Lee, J.O., Cho, H.H. and Kim, K.S., 1992. Effect of diameter and surface treatment of fiber on interfacial shear strength in glass fiber/epoxy and HDPE. Journal of applied polymer science, 45(3), pp.443-450.
coarseness of fiber is affected. Higher length to diameter ratio gives better flexibility and leading to better interaction and bonding.
Fine
Increase duration of surface treatment and reduce the fibre dia that geve better mechanical property and interfacial bonding With matrix.
Warm Regards
Dear Rajendra Kumar, if reinforcement is the main goal, fiber length is more influencing since it inbicates the number of fiber ends which usually considered as the starting of failure (stress concentration, defects). So, long fibers have less fiber ends comparer to shorter once. Telling this without neglecting the other parameters such as fiber orientation.
The aspect ratio in fact reflects the influence of number of fiber ends (fonction of length) to the contact interface or specific surface area (size). My Regards
Yes, even specific surface area is fonction of the geometrical parameters, length and diameter, in addition to porosity if any. My Regards
In summary mechanical properties of thermoplastic fiber reinforced compounds are largely influenced by fiber orientation and fiber length retention ( shorter ones result in higher number of fiber ends, where premature failure of polymer matrix usually occurs) , that reflects low fiber breakages during processing and good fiber wetting ( to promote a continuous phase) . However these are opposing factors as good fiber orientation and wetting requires higher shear that causes fiber breakages. Thus to get a more appropriate balance one has to choose an appropriate screw configuration , and paly around extrusion residence time.
Other points to consider are :
. fiber properties
. fiber sizing ( that will react with adhesion promoters / coupling agents to result in a stronger interface between fiber and polymer matrix)
. type and amount of coupling agent
. kind of extruder used and screw configuration
. location of fiber let down in extruder
. extrusion residence time
. polymer viscosity ( will tend to affect wetting performance as well)
. the diameter of the fiber will affect the critical fiber length , defined as the minimum length required for the maximum fiber stress to achieve the ultimate fiber strength at its mid-length , estimated by :
*Lc = (Ultimate fiber tensile strength X fiber diameter )/ ( 2 x interfacial shear between the fiber and the matrix), under the assumption that both matrix and fibers show a linearly elastic responses.
* more details can be found :
. Kelly, A. and Tyson , W. R., J. Med. Phys. Solids, 13, 329 - 350 / 1965
. R.A. Malloy , plastic Part Design for Injection Molding , Hanser Publishers, New York, 1994, page 265.
A great deal of the final strength of a fiber based "construction" is a result of either the friction between the surfaces of fibers (e.g., in a yarn) or the area of contact between a resin and a fiber surface. In both cases, the amount of fiber surface areas relative to the weight of the fiber is a very important parameter in explaining the "potential strength imparting ability" of a given sample of fiber. Fibers, and especially natural fibers, are not perfectly round in cross-section, however, if we think of their cross-sections as squished circles, we can estimate their average perimeters by knowing their average diameters. If we have an optical scanning system (e.g., FibreShape) that creates discrete ranges of fiber diameters we can also estimate a range of discrete perimeters and areas of the fibers in each range by assuming these fibers are circular in cross-section. If the fibers are all made from similar material, the percentage of total area in each discrete range will correspond to the percentage of weight (i.e., mass) of each discrete fiber diameter range. If all fibers are the same length, then the amount of total fiber surface area is directly proportional to the total amount of perimeters (in percentage terms) of each fiber diameter range. When the above numbers and percentages are calculated, we can then estimate a fiber strength imparting ability for a sample of fibers with the smallest diameter fibers having the greatest surface area for their weight and hence the highest strength imparting ability. Unfortunately fibers are not equal in length and the smallest diameter fibers are often, but not always, also the shortest. Hence, the strength imparting ability of fibers estimated in the manner above should be further modified to take into account factors like fiber length, fiber stiffness and fiber surface slipperyness.
The diameter of fiber when it is used as a reinforced agent plays an important role in enhancing the mechanical and the physical properties of the composite. For example in the cementitious matrix, nanofibrillated cellulose (small diameter) fit well in the close packaging structure of the matrix and provide a satisfactory balance on the mechanical performance (crack bridging on the nanoscale) and the physical performance ( reduction of the porosity, and water absorption, with increasing of the density).
I addition, if the length to diameter ratio is high, the reinforcement efficiency will more important.
Dear Mahaboob Subhani
I suggest you follow and read carefully these two promising articles, which describe in detail enhancing the mechanical properties as well as the interfacial performance of specific fibers (including the average diameter "d" of the utilized fibers).
You can find your target within the calculation of the interface shear strength (IFSS), dynamic contact angle (θ), surface energy (γf ), and surface tension (ST), which lie in equations 1, 2, 3 & 4, respectively. Best Wishes
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If Fibre and Matrix have very strong compatibility, this may not be significant. But, with the decreasing compatibility, the aspect ratio becomes important. Further, in your case if you are focussing on single fiber properties you are right. But if you take equal weight% of variable diameter fibres in two or more matrix, the reinforcement is more in case of less dia fibers.
Diameter of a fiber is an important factor that describes the strength of a composite. High Aspect ratio (length/diameter) means that the fiber is lengthy and the diameter is less. This causes more fibers to get restrained and covered by matrix resulting in increased surface area, as against a large diameter fiber that are less in count. Fibers that are well restrained and covered by matrix can withstand more loads. Lumen, a small cavity inside a fiber and the cell wall thickness too plays a vital role in mechanical strength of the fiber. Hence fiber architecture important in governing the mechanical properties.
The following research article is recommended for this "Intrinsic fiber architecture and their influence on the mechanical properties of hybrid composites".
The link for the above specified article is https://doi.org/10.1007/s43452-020-00125-y.
Small diameter fibres have a high surface area compared to their volume, which helps improve fiber-matrix bonding. Increased surface area provides for more effective load transmission between fibres and matrix and more points of contact. Matrix material may attach to fibres better, resulting to stronger interfacial bonding.
When the fibres' diameter is bigger, their surface area is less compared to their volume, which might weaken interfacial bonding. The matrix material may not adequately cling to the fibres, reducing interfacial bonding strength.
Interfacial bonding between fibres and matrix material in a composite is regulated by fibre and matrix characteristics, fibre surface roughness, and processing conditions. Diameter of fibres is one element that affects composite interfacial bonding strength.
Hello Dr./Mr. Subhani,
Please refer to this paper.
Article Effect of diameter and surface treatment of fiber on interfa...
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