Using eval is a misdirection that forces you into writing slow, inefficient, complex code:
It is much simpler and more efficient to use basic indexing, just like MATLAB was designed for:
C = {cell array of the five table variable names};
V = 0:10:50; % those square brackets were superfluous.
N = numel(V)
T = cell(1,N); % preallocate cell array.
for k = 1:N
fnm = sprintf('UCS_stress_%d.txt',V(k));
tmp = readtable(fnm);
tmp.Properties.VariableNames = C;
T{k} = tmp; % basic indexing.
end
