A Multi-Scale Approach for Understanding the Role of the Interphase in Polymer Matrix Composites

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The focus of the research is a multi-scale(molecular-nanometer-micrometer) investigation of the interphase and itsrelationship to polymer matrix composite (PMC) performance. The firstobjective of the research is to monitor the chemistry of the interphaseregion in situ, and in real-time during the polymer curing cycle. Thesecond objective is to measure the size and the mechanical properties of theinterphases that result as a function of silane coupling agent surfacetreatments. The third objective is the measurement of the micromechanicalperformance of a model PMC system. Several tasks are involved to meet the research objectives. Thefirst task will involve in situ reaction monitoring of a model polymer usinga novel Fourier transform infrared fiber optic sensor system which allowsdirect monitoring of interphase chemistry. Experiments will be performedusing polymer/curing agent mixtures on unmodified glass fibers, and polymercuring followed as a function of time at elevated temperature. Next, silanecoupling agent surface treatments will be performed on the glass fibers andthe organofunctional reactivity determined simultaneously with curingagent/polymer reactivity. The second task in the proposed research will be the nano-mechanicalproperty characterization after surface treatment and polymer curing.Atomic force microscopy and nanoindentation will be used to characterize theinterphase region. These results will be correlated with the in situinfrared data from the first task, in particular, the role oforganofunctional reactivity and polymer curing on the resultant interphaseproperties. The third task will involve measurement of the micromechanicalbehavior of the model PMC through the use of the microbond test method.Results obtained during this portion of the research will be correlated withthe first two tasks mentioned above.