Shape Memory Composite Structures for Space Debris Removal
Creators: name:  L. SANTO 
name:   F. QUADRINI 
name:   L. IORIO 
name:   M. HOLYNSKA 
Publisher: name: Proceedings of  the 9th European Conference for Aerospace Sciences. Lille, France, 27 June - 1 July, 2022
Year: 2022
Subjects: SPACE DEBRIS
OBSERVATION
ORBIT DETERMINATION
ACTIVE DEBRIS REMOVAL

description: Shape memory polymer composites (SMPC) are structural laminates with additional morphing functionalities. Their unique properties make them optimal candidates for Space structures, when structural requirements are combined with self-adapting capabilities or actuation. Best examples are composite booms for solar or drag sails, self-deploying systems, debris capturing devices. In fact, SMPCs are able to freeze a non-equilibrium shape by a thermo-mechanical cycle. The composite structure is softened by heating over a characteristic temperature, deformed, and left to cool below the characteristic temperature, without removing the constraints. After cooling, the constraints can be released, and the frozen shape is preserved with a minimal elastic recovery. In order to recover the initial equilibrium shape, re-heating over the characteristic temperature is necessary in absence of constraints. This SM behavior is defined one way, as a new thermo-mechanical cycle is necessary to freeze again the non-equilibrium shape. Even if two-way actuation systems may be preferred for such uses, there are many important cases where only one shape change is necessary during the operating life of the structure. In particular, for space debris removal, SMPCs provide low actuation with additional damping for a soft interaction with debris. In this study, the use of carbon fiber reinforced (CFR) SMPCs is discussed for Space debris grabbing. A prototype of a 1 U device has been designed, in the shape of a smart composite hand, and manufactured by using conventional technologies for CFR laminates. This hand has separate fingers, which consist, in turn, of a chain of two main elements, one active (the SMPC hinge) and one passive. This kind of grabbing geometry is able to capture an object of undefined shape, avoiding its escape. Moreover, fragmentation of the debris is prevented thanks to the intrinsic damping behavior of SMPCs after transition. In fact, SMPCs are soft during shape recovery and object grabbing, and they become rigid only when the debris is fully confined. The passive elements of the smart fingers were manufactured by compression molding of commercial aeronautic CFR prepregs. The SMPC hinges were produced by using the same prepregs with SMP interlayers. The interlayers were inserted in the shape of an uncured SM epoxy resin during composite lamination. Both passive elements and SMPC hinges were 4-ply laminates. The single SMPC hinge has a mass of about 2 g. After SMPC and CFRP laminate molding, the sub-components have been assembled into the smart finger, and tested together with the single hinge, alone. In particular, the actuation load exerted by the SMPC hinge has been evaluated through an instrumented test. In this study, the tested SMPC hinge had an opening angle of 75 deg, thus requiring 105 deg of angle change to reach the flat temporary configuration. The actuation load has been extracted from the plateau region of the recovery load, and it is of about 8 N. The recovery load has been measured also on the assembled finger but, in this case, the heating stage was made by an external micro-heater. Because of the lower heating rate, lower recovery loads have been measured down to 1 N. In the case of free recovery, a time about 2 min is necessary for full shape change of the smart finger with 2 SMPC hinges.