Fracture behaviour of liquid crystal epoxy resin systems based on diglycidyl ether of 4,4'-dihydroxy-alpha-methylstilbene .2. Effect due to blending with TACTIX* 556 epoxy resin and phenolic monomers
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The mechanical behaviours of unoriented, poured resin castings based on formulated blends containing the diglycidyl ether of 4,4-dihydroxy--methylstilbene monomer are studied. It is found that the mechanical and fracture behaviours of these liquid crystalline epoxy (LCE) blends vary significantly. In general, the LCE blends possess much higher fracture toughness and fatigue crack resistance than conventional epoxy resins. At low temperatures (-40C), the KIC values of the LCE blends are slightly higher than those measured at room temperature. The common fracture mechanisms observed in the ductile LCE blends are crack segmentation, crack branching, crack bridging and crack blunting. The fracture surfaces of the tougher LCE blends only exhibit limited ductile drawing (furrow pattern) at the slow crack growth region; no signs of shear lips on the edges of the starter crack region are observed. The optical microscopy and transmission electron microscopy work suggests that orientation and/or transformation toughening may be the source for such high fracture toughness of the LCE blends. The possible cause(s) of the unusual fracture behaviour of the LCEs is discussed. Approaches for making high performance LCE blends are also addressed.
JOURNAL OF MATERIALS SCIENCE
author list (cited authors)
Sue, H. J., Earls, J. D., & Hefner, R. E.
complete list of authors
Sue, HJ||Earls, JD||Hefner, RE