How to reduce fiber damage

[vikram manoj]

Hi,


I’m doing a simulation of low-velocity impact on a composite laminate (32 layers, each 0.12 mm thick) using 15 J impact energy. I'm using a 3D Hashin failure model in my VUMAT. But I’m getting very high fiber damage (around 0.9), while the experimental paper I’m comparing with shows almost no fiber damage. I already tried increasing the fiber strength values and reducing the cohesive (interface) strength, but it didn’t help much. Here’s what could be going wrong and how to improve it:

c -- ---------------------------Fiber Mode-----------------------------------
if ( s11 .gt. zero ) then
rft = (s11/f1t*1.0d0 )**2 +(s12/f12*1.0d0)**2+(s13/f13*1.0d0)**2
c write(*,*),rft
if (rft .ge. one) then
dft=1.d0-exp((1.d0/(2.7182818d0*cmft))*
* (1.d0-(rft)**cmft))
else
dft =0
end if
if (dft .ge. 0.9) then
dft = 0.9d0
end if
else if ( s11 .lt. zero ) then
rfc = (s11/(f1c*1.0d0))**2
if (rfc.gt.one) then
dfc=1.d0-exp((1.d0/(2.7182818d0*cmfc))*
* (1.d0-(rfc)**cmfc))
else
dfc =0
end if
if (dfc .ge. 0.9) then
dfc = 0.9d0
end if
end if
c --------------------------Matrix mode--------------------------------------
if((s22+s33).gt.zero) then
rmt = ((s12**2+s13**2)/f12**2) +((s23**2 -s22*s33)/f23**2)
* +(s22/f2t)**2 +(s33/f2t)**2
if(rmt.gt.one) then
dmt=1.d0-exp((1.d0/(2.7182818d0*cmmt))*
* (1.d0-(rmt)**cmmt))
else
dmt=0
end if
if (dmt .ge. 0.9) then
dmt = 0.9d0
end if
else if ((s22+s33).lt.zero) then
rmc =(B/(D+(E*A)))**2+(C/(f12+(F*A)))**2
if(rmc.gt.one) then
dmc=1.d0-exp((1.d0/(2.7182818d0*cmmc))*
* (1.d0-(rmc)**cmmc))
else
dmc=0
end if
if (dmc .ge. 0.9) then
dmc = 0.9d0
end if
end if

 

[FEA way]

Have you seen the DS Knowledge Base article "Abaqus/Explicit VUMAT for the simulation of damage and failure in unidirectional fiber composite materials" ?

You should make sure your setup doesn’t differ significantly from the reference experiment. Some calibration of material data might be necessary to achieve reasonable fit. Also, check all the relevant energies.