If I prepare a composite where the strength and elongation increases. Since the hardness increases with the increase in strength and increase in hardness led to increase in brittleness. As we see in many cases the strength and elongation increases with reinforcement. How it is possible? Increase in strength shows the increase in brittleness and increase in elongation shows the increase in ductility of the material. Both are contradicting with each other.
With composites you must apply other concepts than with bulk materials. Composites are not only a mixture of two bulk materials, but the shape of the reinforcing phase as well as the structure of the reinforced matrix contribute significantly to the physical properties, leave alone interaction at the interfaces! If you reinforce a stiffer matrix material with a more elastic phase (e.g. long or endless fibers), you will obtain a "mixed" elasticity/ductility, hence the "elongation" of the composite will be higher than for the pure bulk matrix. When adherence of fiber and matrix as well as the difference between elastic moduli of both phases are properly combined, the composite will have a higher yield strength.
When talking about composites, the usual trade between tensile strength and elongation is that one grows while the other decreases. There are some ways to increase both -like crosslinking-, however this are the exceptions rather than the rule. Also remember that when tensile strength and elongation are efectively increased, total toughness is growth, also known as tenacity.
Strength and elongation are not directly related to each other. These are material properties. For each material, they need to be evaluated independently. Elongation can not be predicted if strength is known for a specific material.
Do you have any reference that we can cite for this kind of behaviour? Thanks !
You are interested in the hardness or strength of material? Strength will obviously grow with a growth of limit deformation, but you write that the tvenrdost grows too. But it is impossible to understand as you have measured it statically (on a print of HRC, HRB) or dynamically on a curve?
Dear S Arun
This depends on type of material to be tested and its mechanicsl propeerties
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