Sorry, my example is the same nested loop, just using a more compact syntax. Rewritten with your loop structure,
DatArr = [ElasticMatrix{Float64}(undef, 3, 0) for j = 1:Nj, k = 1:Nk]
for i in 1:5
for j in 1:Nj
for k in 1:Nk
Nrand = rand(1:10)
xyzVect = ElasticArray{Float64}(undef, 3, 0)
for n in 1:Nrand
append!(xyzVect,rand(3))
end
append!(DatArr[j,k], xyzVect)
end
end
end