Changing axes linewidth on a stacked plot

I cannot change the axes linewidth on a stacked plot, at least in the way that I am able to change the axes linewidth in other types of plots. For example, I have tried the following with no change to the axes linewidth:

figure(1)
stackedplot(time_axis, testdata)
hAx=gca;    
hAx.LineWidth=2;

Answer 1

[Adam Danz]

You have to access the axis handles first.

h = stackedplot(rand(10,4)); 
ax = findobj(h.NodeChildren, 'Type','Axes'); % use flipud to puts axes in order. 
set(ax,'LineWidth',2)

[Elliot Tseng]

Thanks Adam, works great.