In an example, a method for accelerated conditioning of a composite core sandwich coupon is described. The method includes setting a first temperature and a first relative humidity level of the conditioning apparatus, wherein a combination of the first temperature and the first relative humidity level correspond to a desired relative humidity level of the plurality of cells of the core layer at room temperature. The method includes maintaining the first temperature and the first relative humidity for a first period, wherein during the first period a core humidity of the plurality of cells in the core layer approaches the first relative humidity level. The method includes determining that the core humidity has reached the first relative humidity level. The method includes, based on determining that the core humidity has reached the first relative humidity level, adjusting the first temperature to a second temperature.