Composite repairing is an issue because of the size of the parts, the cost of the production equipment and the poor consolidation between the parent part and the repairing patches. In this study an out-of-autoclave procedure is proposed where the agglomeration pressure is provided by shape memory foams. These foams can be shaped in the desired form by means of a thermos-mechanical cycle, and provide additional pressure if constrained during recovery. Shape recovery is achieved by using the same thermal cycle which is necessary for the cure of the patches. In this study, thermoplastic shape memory foams have been characterized to evaluate the agglomeration pressure they can provide as a function of the compression strain. In order to show the feasibility of their application, the cure of a composite laminate has been performed by using pre-shaped shape memory foams. Results show that a good consolidation is achieved despite of the absence of a vacuum bag.

No abstract

Anisogrid lattice cylinders have been produced by means of an innovative out-of-autoclave (OOA) process by using thermoplastic prepreg. Unidirectional thermoplastic tapes with polypropylene matrix and glass fibers were wound on cylindrical mandrels at room temperature. Composite consolidation was achieved by using the compression of a heat-shrink tube during its shape recovery in oven. A cylindrical anisogrid lattice structure was manufactured and mechanically tested under vertical loading. Results from the buckling test revealed the optimal adhesion between prepreg layers after the out-of-autoclave molding. Numerical modelling of buckling has been performed to correlate the structural behavior of the anisogrid lattice cylinder with composite material properties and geometrical features. A parametric model of the lattice structure has been defined for this aim. The proposed manufacturing technology combines the advantages of thermoplastic composites (reparability, easy handling, easy storage, long prepreg life, productivity) with the designing potential of anisogrid lattice structures in terms of lightness and stiffness.

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