A method and apparatus for fabricating a composite part, such as a fuselage or internal stiffener, with a shape memory polymer (SMP) apparatus usable as both a rigid lay-up tool and a bladder. The SMP apparatus may be heated until malleable, shaped, and then cooled in a desired rigid tool configuration. For example, cavities may be formed into the SMP apparatus for nesting components therein to co-bond or co-cure with the composite part. Next, composite material may be applied onto the SMP apparatus and then placed into a rigid external tool and heated to composite cure temperatures at which the SMP apparatus is malleable. A pressure differential may be induced which urges the SMP apparatus to compress the composite material against the rigid external tool.; When the composite material is cured, the SMP apparatus may be urged away from the cured composite material and removed from within the composite part.