FCLoopPropagatorPowersExpand[exp] rewrites propagators
raised to integer powers as products.
Overview, FCLoopPropagatorPowersCombine.
SFAD[{q, m, 2}]
ex = FCLoopPropagatorPowersExpand[%]\frac{1}{(q^2-m+i \eta )^2}
\frac{1}{(q^2-m+i \eta )^2}
ex // StandardForm
(*FeynAmpDenominator[StandardPropagatorDenominator[Momentum[q, D], 0, -m, {1, 1}], StandardPropagatorDenominator[Momentum[q, D], 0, -m, {1, 1}]]*)SFAD[{q, m, 2}, q + p]
ex = FCLoopPropagatorPowersExpand[%]\frac{1}{(q^2-m+i \eta )^2.((p+q)^2+i \eta )}
\frac{1}{(q^2-m+i \eta )^2.((p+q)^2+i \eta )}
ex // StandardForm
(*FeynAmpDenominator[StandardPropagatorDenominator[Momentum[q, D], 0, -m, {1, 1}], StandardPropagatorDenominator[Momentum[q, D], 0, -m, {1, 1}], StandardPropagatorDenominator[Momentum[p, D] + Momentum[q, D], 0, 0, {1, 1}]]*)