Showing papers by "Ajit Mal published in 2010"

Smart Self-Healing Material Systems Using Inductive and Resistive Heating

Abstract: Based on the metric of "healing window", the ionomer composite containing 2-3% nano iron oxide particles and heated at induction frequencies between 250 and 300 kHz yields the most favorable results. The metric of healing window is defined as the time difference between initiation of healing (melting) and onset of deformation. At this aforementioned ideal volume fraction, composition and induction frequency range, healing of a damaged thick film of ionomeric polymer occurs between 5 and 10 seconds. In this study, both compliant and structural remendable polymers are combined with a small amount of heating material (<5% volume fraction) to facilitate site-specific healing and facilitate future active self-healing. The compliant remenable polymer is an ionomer. The structural remendable polymer is a highly cross-linked polymers called "Mendomer." The heating materials include nanoscale and microscale magnetic particles used with induction heating and carbon fibers used with resistive heating. The inductive heating approach compared to the resistive heating approach has the advantage of being non-contact. Current approaches describe in-situ healing where external power is delivered to generate heating. Active self-healing will be made possible by coupling the healing mechanism with a damage event. Remending polymers can be layered or combined with conventional materials to yield a multifunctional solution offering both a conventional function plus the added remendable feature. One application combines ionomeric remendable polymers layered with polyimide and polytetrafluoroethylene to form remendable wire insulation multilayer composites. Another application uses the Mendomer as the matrix for conventional carbon-fiber composite fabrication to mitigate damage from matrix cracking and subsequent delamination. Preliminary and quantitative results are given and discussed for ionomers, ionomers combined with magnetic particles, ionomers combined with carbon fiber, Mendomers, and Mendomers combined with magnetic particles. For the case of magnetic particles used with induction heating, optimal volume fractions are between 2 and 3%.