Abstract: In this paper the authors proposed that the term of "design allowables" should be replaced by "design values" and "allowables" as composites were used in aircraft structures. The relationship between design values and allowables was discussed. The determination of compressive design values for composite structures was based mainly on impact damage tolerance allowables. The impact damage failure curve of typical laminates was defined as the impact damage tolerance allowable and the reasonableness of this definition was discussed. The principle and method for determining this allowable were proveded. The suggestion to develop the compressive design value for aircraft components based on this allowable was made as well.

Key words: composite structure, impact damage, damage tolerance, design value, allowable