SHEAR OF EPOXY RESIN
SHEAR OF EPOXY RESIN
(OP)
Hello everybody,
I am currently studying the behavior of composite plates in 4 points bending and in-plane shear and especially the strain in the panel depending on the fiber orientation.
Let’s take a plate with a fiber orientation 0/90 degree (weave fabric) subjected to a 4 points bending loads and the same plate -45/45 fiber orientation.
In term of strain it is the configuration two that would give the maximum strain allowable because it is the matrix that “works” which much more ductile than the fiber.
If I take the same panel working in in-plane shear I would obtain an even greater results (strain before failure) knowing that shear modulus of the Epoxy is about 3 times lower than the E modulus. Correct ?
Is there any other explanation to these results? I have read that a resin like the Epoxy works better in shear than flexure but with no explanation.
Thanks,
I am currently studying the behavior of composite plates in 4 points bending and in-plane shear and especially the strain in the panel depending on the fiber orientation.
Let’s take a plate with a fiber orientation 0/90 degree (weave fabric) subjected to a 4 points bending loads and the same plate -45/45 fiber orientation.
In term of strain it is the configuration two that would give the maximum strain allowable because it is the matrix that “works” which much more ductile than the fiber.
If I take the same panel working in in-plane shear I would obtain an even greater results (strain before failure) knowing that shear modulus of the Epoxy is about 3 times lower than the E modulus. Correct ?
Is there any other explanation to these results? I have read that a resin like the Epoxy works better in shear than flexure but with no explanation.
Thanks,





RE: SHEAR OF EPOXY RESIN
At failure, shear strains do tend to be greater than direct strains at tensile failure. However, this depends a lot on the strain after yield, which it is hard to generalise about.
Shear strain at failure often seems to be above 0.5 even for the brittle-ish epoxy matrix resins (I'm basing this on remembered in-plane shear test stress/strain data; I'll have to look the data out, if I can find it, to be sure), and often above 1.0 for the softened epoxy film adhesives. Epoxy resins do yield but rarely seem to deform more than six or seven percent in tension (often only two or three). Just finding a shear strain to failure and a tensile strain to failure for the same material is quite hard, even for metals.
I would guess that this dearth of information is partly because we rarely need it. What do you want it for? Just curious.