force-displacement diagram of a sandwich
force-displacement diagram of a sandwich
(OP)
Hi,
that's force-displacement diagram of a sandwich,
Sandwich consists of pulp foam and flax laminate
The aim of the sandwich is to absorb energy, which can later be used in a crush box.
How do the results look like?
Are there any remarks?
I also have pictures for each sample, I can upload it here if someone needed to see it.
Thank you
that's force-displacement diagram of a sandwich,
Sandwich consists of pulp foam and flax laminate
The aim of the sandwich is to absorb energy, which can later be used in a crush box.
How do the results look like?
Are there any remarks?
I also have pictures for each sample, I can upload it here if someone needed to see it.
Thank you





RE: force-displacement diagram of a sandwich
RE: force-displacement diagram of a sandwich
RE: force-displacement diagram of a sandwich
The test is 3 point flexure test
in all samples, this kind of failure has occurred:
core failure
adhesive failure
usually fails glue first.
the adhesive used is polyurethane in pasty form.
would it be better if I used glue in liquid form?
core consists of pulp and Faces of flax fibre laminate (see attachment)
During the experiment.
End of the experiment
RE: force-displacement diagram of a sandwich
RE: force-displacement diagram of a sandwich
B.E.
You are judged not by what you know, but by what you can do.
RE: force-displacement diagram of a sandwich
Adhesive bond is left on both surfaces, but mostly on the skin.
Flax has been in the laboratory for 2 years.
can you please name some glues that are good for sandwiches?
I have noticed that the surface of the core is very dry and quickly absorbs moisture. and glue do not uniformly spread on the surface of the core.
it's a good idea that I vary a little bit the viscosity of the paste polyurethane?
The goal of these tests is to determine the failure modes of this new sandwich,and evaluate the different failure modes and their causes.
RE: force-displacement diagram of a sandwich
For more streght bond between core and skin try to apply epoxy resins such as EA9396, EY3804 or Epocast 50A.
For example, they are used to repair disbond between skin and core of composite material parts on aircrafts Boeing and Embraer.
EA9396 and EY3804 usually are used to repair of exterior parts, but Epocast 50A for interior parts and it has good properties of resistance to flame iaw FAR 25.853a.
They are room temperature cured, as well you can accelerate curing process using heat sources.
ATACS 4103/5103 and DP100 are fast curing adhesives and using to bond different materials.
Anyway find in google and check datasheets of materials for properties and applying before use them.
Best regards
CRM
RE: force-displacement diagram of a sandwich
RE: force-displacement diagram of a sandwich
Thank you for your suggestion for adhesive.
yes, the costs in this project are also important, so we try out cheap materials.
Thank you very much for pointing out that the surface layer is brittle.
this is another photo, where I have marked is core shear yield strength Fyield and facing yield stress
RE: force-displacement diagram of a sandwich
RE: force-displacement diagram of a sandwich
Mixture is:
- 200 g paper fibres, 800 ml water (ratio 1:4)
- 9 % binder (CMC), based on the dry matter pulp = 18 g
- 3 % raising agent (NaHCO3), based on the dry matter pulp = 6 g
- Microwave drying process
yes, the weight is also important in this work.
Epoxy resin is used as a matrix for the Skin.
The Fiber volume ratio is 45%.
RE: force-displacement diagram of a sandwich
the support bars and loading bar are not equal in size!
that will lead to different pressures on both sides.
RE: force-displacement diagram of a sandwich
RE: force-displacement diagram of a sandwich
my supervisor advised me not to put many adhesives on the core, he said that they are evenly distributed under pressure on their own.
the problem is the core is too dry and not quite flat