Influence of processing rate and formulation on the interface strength of vinyl ester/E‐glass composites

Abstract The single fiber fragmentation test was used to investigate the effect of gelation time on interfacial shear properties of fast reacting resin systems. We developed a processing system capable of producing single fiber fragmentation samples with gelation times that ranged from 2 min to 45 min. The interfacial properties of E‐glass fibers in vinyl ester resin were measured with single fiber fragmentation tests using a manual and an automated testing machine. We found that vinyl ester resins catalyzed with methyl ethyl ketone peroxide and promoted with cobalt naphthenate and dimethylaniline gelled in less than two minutes and had an estimated interfacial shear strength of 105 MPa. Specimens cured without the promoter gelled in 45 min and had an interfacial shear strength of 72 MPa. Further curing of the unpromoted specimens resulted in an increase in shear strength to 96 MPa. We have demonstrated the ability to make and test rapidly cured specimens, thus expanding the range of materials that can be tested using the single fiber fragmentation testing technique.