From the Rules.. I have no idea what this bit in bold means - cant find any mention of limb construction so I guess you can make them from what you like?
22.4.1.
A bow of any type, which complies with the common meaning of the word bow as used in target archery, consisting of a handle/riser and grip (no shoot-through type) and two flexible limbs each ending in a tip with a string nock. The riser is produced of a natural or resin based material (e.g.wood, bamboo, horn, cloth, fibreglass, and a portion of the riser may include carbon/graphite or metal). The riser must be of laminated construction or one piece of wood. The bow may be of a take-down type and may incorporate factory installed metal fittings in the riser for limb attachment, sight mount inserts, cushion plunger insert and stabilizer bushings only. The bow may include a single adjustable limb for tiller adjustment only, but may not have adjustable limb pockets for bow weight adjustment. The riser may include thin synthetic laminates up to 6 mm in width to use for limb/pocket protection for structural use within the riser, but no more than one quarter of the riser's construction may be produced of metal or synthetic material. The riser must contain some wood or bamboo. For non-takedown bows, limb laminates of any material that fade into the riser section are permitted. The bow is braced for use by a single string attached directly between the two string nocks, and in operation is held in one hand by its handle (grip) while the fingers of the other hand draw and release the string.
The bow as described above shall be bare, except for an arrow rest as described in 22.4.3. and free from protrusions, sights or sight marks, marks or blemishes or laminated pieces (within the bow window area) which could be of use in aiming. Weights inside the bow riser are permitted if installed during the manufacturing process of the bow and not post construction. Any such weights shall be completely invisible on the exterior of the riser and be covered by laminates applied during the initial construction with no visible holes, plugged holes, covers or caps with the exception of the original manufacturer's inlay or insert logo.