Mode I and mode II delamination properties of glass/vinyl-ester composite toughened by particulate modified interlayers

Various vinyl-ester (VE)/poly(acrylonitrile-butadiene-styrene) (ABS) blends were used for interlayer-toughening of a glass/VE composite to increase delamination resistance of the base material under mode I and mode II loading. Dry ABS powder was mixed with the liquid resin in four weight ratios: 3.5, 7, 11 and 15 phr (parts per hundred parts of resin) while the layer thickness was varied within the range of 150-500 μm. Firstly, mode I fracture toughness and tensile properties of the VE/ABS blends were assessed. By using the Raman Spectroscopy technique a chemical reaction was discovered which occurred during ABS-VE mixing: i.e. butadiene transition from the ABS particles to the VE. A butadiene saturation was discovered to occur in the VE beyond 7% ABS particle content. Both mode I and mode II fracture toughness were significantly improved with application of the interlayers. Mode I fracture toughness was found to be a function of layer thickness and particle content variations. The latter dominated G Ic after the saturation point. On the other hand mode II fracture toughness was found to be independent of the layer thickness (within the used layer thickness range) and only moderately influenced by the particle content. Important Toughening mechanisms were plastic deformation and micro-cracking of the layer materials. Evidence of both mechanisms has been found using optical and scanning electron microscopy (SEM).