Composites processed by RTM using self-healing agents dispersed into the matrix: viscoelastic behavior and interlaminar fracture in mode II

Abstract

It is well known that epoxy resin reinforced with carbon fibers, is used in the aeronautical industries due to its light weight, however has high tendency to nucleate microcracks, which, under applied loading, progress to delamination and possible structural failure. The traditional procedure to minimize the possibility of fracture is during maintenance schedule when inspecting to remove or repair the damaged region for example by thermoplastic welding under a vacuum bag but will lead to reduction in mechanical strength and also in the useful operational life of the component. The scientific and industry interests are increasingly gravitating towards use of self-healing material technology, which has the ability to repairs microcracks continuously during the operation without much knock down in properties. However, considering safety is the main concern in the aeronautical field, the question how to disperse this material in the appropriate way in the composite, need to be addressed. The understanding of healing mechanism and the influence on physical properties of polymer composites is of fundamental importance because, from the literature, it is well known that the self-repair agent often acts to change the material stiffness as well as viscoelasticity and, as consequence, the relaxation phenomena. The objective of this research project is to understand the significant contribution of the self-healing technology to repair failure damage in carbon/epoxy composite loaded with 5% self-healing microcapsule processed by resin transfer molding (RTM). Mechanical dynamic analysis in small strain regime that provide significant deformation, will be conducted to determine the relaxation times in terms of fragility index (variation of properties as and from Tg). An analytical study of how macromolecules relaxation phenomena changes in the presence of microparticles and, consequently, the mechanism by which self-repair occurs, will be performed. The development of the project at the center for composite material (CCM) in the University of Delaware is justified as it is an internationally recognized institute which has been named several times as the center of excellence in technology transfer in the area of processing science, materials and mechanical performance. In particular, prof. Suresh Advani, with whom the fatigue and aeronautical materials group has been collaborating since 2017, has over 3 decades of experience in the area of rheology and composite processing and, mainly, in the analytical study of phenomena that occur in these anisotropic materials published in over 350 publications, as can be seen from his CV. (AU)