Impact Studies in Elastomer, Fly Ash, and Hybrid-filled Epoxy Composites: Part II - Comparison of Data and Fracture Features of the Samples Cured via a Single Room Temperature and Multiple High Temperatures

Abstract

Epoxy composites reinforced with CTBN, fly ash as individual and hybrid fillers, are fabricated for various compositions of the fillers, viz., 1, 2, 3, 5,10, and 20 by weight. Two routes are adopted for making the composites. In one, a single room temperature curing (abbreviated with an ending letter ‘R’) is adopted while in the other multiple higher temperatures (designated with an ending letter ‘H’) are followed. How this differing curing program affects the impact properties of the different fillers and/or compositions-bearing composites is looked into in this work using drop weight instrumented impact tests. When samples cured corresponding to ‘H’ designation are compared with those with ‘R’, an increase in impact energy is noticed for all combinations of fillers and compositions. Significant increase (almost 50%) in total energy is noted in the case of the 3% CTBN-bearing sample. Similarly, 60% increase in impact energy is noticed in the 20% fly ash-bearing composite. In the case of hybrids, it is again the 20% composition-bearing system that exhibits the maximum increase. Also the ductility index (DI) values are studied for all the samples. For rubber bearing samples, the DI value is more in ‘R’ when rubber concentration is 5% or higher. Twenty percent shows the maximum DI value. Similar trend was noticed for the fly ash-bearing samples. For the 20% fly ash-bearing sample, the DI recorded is high. For hybrids, the DI was higher for the ‘H’ samples for all concentrations with maximum noticed for 20% composition for the fillers. The results obtained are analyzed in the light of their postfailure fracture surface features seen in a scanning electron microscope (SEM). In case of ‘H’ samples, increased number of cleavage paths are seen compared to ‘R’ cases.