The present invention provides a composite muffler for use with an auxiliary power unit. The composite muffler comprises a composite outer can, an annular baffle, an acoustic liner, and a thermal barrier. The composite outer can is disposed substantially symmetrically about a longitudinal axis and has an inner peripheral surface defining a cavity. The annular baffle is disposed within the composite outer can cavity, has an opening formed therein, and extends radially outwardly from the opening toward the composite outer can inner peripheral surface. The acoustic liner extends through the annular baffle opening. The thermal barrier is coupled between the annular baffle and the outer can inner peripheral surface.