PSI - Issue 14

M.K. Singh et al. / Procedia Structural Integrity 14 (2019) 475–481 M. K. Singh, R. Kitey / Structural Integrity Procedia 00 (2018) 000 – 000

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5. Conclusion The epoxy matrix is prepared by mixing DGEBA (Diglycidyl Ether of Bisphenol-A) resin and MTHPA (Methyltetrahydrophthalic Anhydride) hardener in equal proportion by weight. A small amount of 2,4,5 tris[(dimethylamino) methyl] Phenol is used to accelerate the polymerization process. Three different sizes of 1 6 μm diameter milled glass fibers , 1/4”, 1/8” and 1/32” long, are reinforced into the epoxy matrix with 3% volume fraction. The fracture tests are conducted by following ASTM D5045-14 standards. The composites exhibit monotonically increasing flexural modulus and fracture toughness with the increasing reinforced filler size. While the 1/32” filler composite shows only a marginal increase in the K IC value at 3% V f , the 1/4” reinforcement enhances the K IC more than 3.5 times when compared with neat epoxy case. Even the post crack initiation area under the load vs. deflection curve, indicating the composites’ resistance to crack propagation, increa ses with increasing filler size . It is suggested that in the presence of large slender fillers fiber fracture is the dominant toughening mechanism whereas the smaller size fibers are subjected to pull-out in the fracture process. References A.L. Yesgat and R. Kitey, 2016. Effect of filler geometry on fracture mechanisms in glass particle filled epoxy composites. Engineering Fracture Mechanics, 160, 22 – 41. ASTM D5045-14. Standard test methods for plane strain fracture toughness and strain energy release rate of plastic materials. ASTM D790-17. Standard test method for Flexural properties of unreinforced and reinforced plastics and electrical insulating materials. Fu, S.Y., Lauke, B., Mader, E., Yue, C. Y. and Hu, X., 2000. Tensile properties of short-glass-fiber-and short-carbon-fiber-reinforced polypropylene composites. Composite Part A: Applied Science and manufacturing, 31(10), 1117-1125. Kitey R and Tippur HV, 2005. Role of particle size and filler-matrix adhesion on dynamic fracture of glass-filled epoxy. I. Macro measurements. Acta Mater, 53,1153 – 65. Nam, S., Yu, Y.H., Choi, I. and Bang, C.S., 2014. Fracture toughness improvement of polyurethane adhesive joints with chopped glass fibers at cryogenic tempratures. Composite Structure, 107, 522-527. R. Rahul and R. Kitey, 2016. Effect of cross-linking on dynamic mechanical and fracture behaviour of epoxy variants, Composites Part B, 85, 336-342.