Hi all,
I am testing CF/clay/Epoxy bend bar composites using 3pt-bending. The strength of these composites will be used to compare with a model that predict the composite strength based on fiber length distribution. However, the model consider predicting the ultimate tensile strength, so how can I correlate them with each other?
Thanks in advance,
-Nadim
check my publications about strength of undidirectional fiber composites. Or best my dissertation (it is in Germnan)
The condition of this correlation must be homogenous distribution of fiber
Really, the case of uniform distribution of fibers allow us to simplify the correlation dependence under discussion.
Dear Nadim Hmeidat, these links may be helpful
http://digitalcommons.calpoly.edu/cgi/viewcontent.cgi?article=1036&context=matesp
http://www.sciencedirect.com/science/article/pii/S1359835X14003510
https://www.hindawi.com/journals/jnm/2013/565401/
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-73862000000200006
http://iccm-central.org/Proceedings/ICCM17proceedings/Themes/Materials/HIGH%20PERFORMANCE%20FIBRES/D6.3%20Naito.pdf
https://web.anl.gov/PCS/acsfuel/preprint%20archive/Files/41_1_NEW%20ORLEANS_03-96_0354.pdf
Numerical Relationship
It is expected that these two types of strengths are closely related, but there is no direct proportionality. It is noticed that with the increment of compressive strength, the tensile strength is also increased but at a decreasing rate.
A better correlation is found between the various measures of tensile strength and the square root of the compressive strength. A number of empirical formulae connecting ft and fc´ have been suggested, many of them of the following type:
ft = k (fc)n
where k and n are co-efficients. Values of n between ½ and ¾ have been suggested. The former value is used by the American Concrete Institute, but Gardner and Poon found a value near the later, cylinders being used in both cases. Probably the best fit overall is given by the expression:
ft = 0.3 (fc)2/3
where, ft is the splitting strength, and fc´is the compressive strength of cylinders, both in megapascal. If the stress is expressed in pounds per square inch the co-efficient is replaced by 1.7. The above expression was suggested by Raphael. A modification of Oluokun is
ft = 0.2 (fc)0.7
where the strength are in megapascals; the co-efficient becomes 1.4 in psi.
An expression used in British Code of practice BS 8007:1987 is similar, namely
ft = 0.12 (fc)0.7
Bearing in mind that the compressive strength is determined on cubes( in megapascals); ft represents the direct tensile strength.
The difference between the various expressions are not large. What is important, however, is that the power exponent used in the ACI Building Code 318-89( revised 1992) is too low so that the splitting strength is overestimated at low compressive strengths and underestimated at high compressive strength.
These approximate expressions show that tension and compression strength are by no means proportional, and trhat any incrase in compression strength, such as that achieved by lowering the water- cement ration, is accompanied by a much smaller percentage increase in tension strength.
You are welcome, I'm glad I was able to help. Good luck with your research!
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