|Authors: (Guoqiang Li and Manu John, Department of Mechanical Engineering Louisiana State University, Baton Rouge, LA, and others)
Thermoset polymer based syntactic foams have been widely used in high
performance foam cored sandwich structures such as auto, ship, aircraft, train, tank,
pressure vessel, etc. due to their high specific strength and stiffness, corrosion resistance,
and tailor-ability. It is well known that foreign object impact is not uncommon for
composite sandwich structures. Subjected to an impact load, the thermoset syntactic foam
core would be significantly damaged in the form of macro-cracking, microballoon
crushing, microcracking, etc., leading to a considerable reduction in residual load
carrying capacity. This cannot be avoided because of the brittleness of the thermoset
polymer and the lack of ability to self-heal internal damage. In order to maintain the
structural capacity under impact, it is desired to develop a new syntactic foam which is
able to absorb more impact energy and to repair internal damage autonomously,
repeatedly, efficiently, and at molecular length-scale.
In this chapter, we propose to develop a novel shape memory polymer based
syntactic foam as the composite sandwich core. Our goal is to utilize the shape recovery
functionality of the shape memory polymer for the purpose of self-repairing impact
damage. In this chapter, the state-of-the-art of syntactic foams and shape memory
polymers will be reviewed. The underlying principle for self-healing will be analyzed.
Raw materials selection, fabrication, characterization, and testing of the smart foam and
foam cored sandwich will be presented. It is found that this novel syntactic foam is able
to repair impact damage up to 7 impact-healing cycles with almost 100% capacity to
maintain its original load carrying capacity.