The present disclosure is directed to a curable composition comprising: a) an epoxy resin; b) an epoxy curing agent comprising at least one cycloaliphatic amine; c) at least 3 wt % of a metal triflate catalyst; d) optionally, a fatty acid polyamide; and e) optionally, a filler material. The compositions of the present disclosure are particularly suitable for use in structural assembly, in particular for potting and filling operations in sandwich structures. The present disclosure also relates to a composite assembly and to methods of using such epoxy resin based curable compositions.