sandwich composite panel
I am trying to simulate the standard ASTM 393 flat compression test on a composite panel with honeycomb structure at its core.
I modelled the facesheets in two ACPs and honeycomb geometry in design modular. For meshing i used quad dominant method ( SHELL 181 i guess) and for facesheets i used automatic meshing(solid 181 i guess). After importing these geometries in the static structure i do defined the contact - bonded between the honeycomb and facesheets.
To simulate the test i fixed the lower face and then applied a remote displacement on the upper face (0.5mm/min).
Then i used stress probe to find out the compressive stress in the core, force reaction on the lower face sheet & stress probe in the upper facesheet.
The compressive strength of core is minimum and i assumed the sandwich will fail when the compressive stress in the core reaches the compressive strength.
the bare compressive strength of the core as given by the manufacturer is 2.85 MPa . And i was expecting compressive strength for the whole sandwich is greater than the sole core . But the results doesn't validated that.
The compressive stress in the core is about 3 Mpa at 1.25 sec , so it fails before that.
The force reaction in the lower face sheet at 1.25 sec is about 330 N. Dividing it by the surface area of the facesheet (50X105) will give the compressive strength of the whole sandwich panel=0.058 Mpa.
So why is the compressive strength of panel is less than core?
Is there any mistake in my meshing, constraints ,method or the values i used to define the honeycomb core under orthotropic materiel is wrong?