Alpha-alumina is known to exhibit photo-luminescent (PL) properties, mainly characteristic R-lines that shift according to applied stress. In addition to showing excellent PL properties, polymers with embedded alumina nanoparticles have been shown to improve the overall composite mechanical properties. While the use of the PL properties to develop stress-sensing materials using an alumina-epoxy material has been success- fully shown in compression, the properties have not been developed for tension. In this study, the PL response of variable volume fraction alumina-epoxy composites will be determined under tensile conditions. It is expected that increasing the volume fraction of alumina nanoparticles will increase the sensitivity of the particles PL emission shift to applied stress. Three tensile alumina-epoxy specimens of 21.0%, 31.2%, and 34.5% volume fractions were manufactured and tested under tensile static loads. The results of this experiment will determine the piezospectroscopic (PS) coeffi cient and calibration of bulk alumina nanocomposites in tension. A linear region was identified in the PS response of the nanocomposite to the applied tensile load. The PS coeffi cient of this linear region increased as the volume fraction of the nanocomposite increased. To demonstrate the application of structural composites with stress sensing capabilities, alumina nanoparticles were integrated in the manufacturing of a carbon fiber composite specimen. The results of the stress-sensing composite mechanical experiment showed that alumina nanoparticles were able to detect changes in stress. The results for both the bulk nanocomposite calibrations and the application of stress-sensing alumina nanoparticles in a carbon-fiber composite will advance the development of this novel stress-sensing method.

Yes / Thermal degradation of polyamide 6 (PA6)/organoclay nanocomposites is a serious impediment to wider applications of these nanocomposites. In this study, a solution is proposed based on the well‐established use of chain extenders. As in PA6, thermal degradation, in the absence of moisture, produces broken polymer chains with amide end groups, a chain extender with anhydride functionalities, known to be strongly reactive with amide groups, was used to reconnect the chains. Experiments conducted using a laboratory twin‐screw extruder were first checked, through transmission electron microscopy observations, to have produced good organoclay intercalation and exfoliation into PA6. Following from this, samples with the chain extender added were produced and characterized. The data obtained were conclusive in the effectiveness of the chain extender: for the chain extended nanocomposites, there is an enhancement in the value of the complex viscosity by 7 times and in the storage modulus by 88 times, while the tensile modulus increased by 57% compared with the neat PA6. The nonchain extended nanocomposite achieved in comparison an enhancement of 2 times the value of the complex viscosity and 19 times the storage modulus while the tensile modulus increased by 53% compared to the neat PA6. These data provide conclusive proof on the rationale that anhydride functionalities should be sought when developing chain extenders for PA6 nanocomposites. / Government of Turkey

Cyanate ester (PT-15, Lonza Corp) composites containing the inorganic-organic hybrid polyhedral oligomeric silsesquioxanes (POSS), octaaminophenyl(T8)POSS (C6H4NH2)8(SiO1.5)8, cyanopropylheptacyclopentyl(T8)POSS, (C5H9)7(SiO1.5)8(CH2) 3CN or TriSilanolPhenylPOSS (C42H38O12Si7), were synthesized respectively. These PT-15/POSS composites were characterized by FT-IR, X-ray diffraction (XRD), small-angle neutron scattering (SANS), scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (X-EDS), transmission electron microscopy (TEM), dynamic mechanical thermal analysis (DMTA) and three-point bending flexural tests. XRD, TEM and IR data are all consistent with molecular dispersion of octaaminophenyl(T8)POSS and TriSilanolPhenylPOSS due to the chemical bonding of the POSS macromer into the continuous cyanate ester network phase. In contrast to octaaminophenyl(T8) POSS and TriSilanolPhenylPOSS, cyanopropylheptacyclopentyl (T8)POSS has a low solubility in PT-15 and does not react with the resin before or during the cure. The TriSilanolPhenylPOSS (C42H38O12Si7) was incorporated into the aliphatic epoxy (Epoxy 9000, Clearstream Products, Inc.) in 99/1, 97/3, 95/5, 90/10 and 85/15 w/w ratios and cured. This same epoxy resin was also blended with an equal weight (50/50 w/w) of cyanate ester resin (PT-15, Lonza Corp) and TriSilanolPhenylPOSS was added in resin/POSS weight ratios of 99/1, 97/3, 95/5, 90/10 and 85/15 and cured. Both sets of composites were characterized by FT-IR, X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (X-EDS), dynamic mechanical thermal analysis (DMTA) and three-point bending flexural tests. TriSilanolPhenyl-POSS was first thoroughly dispersed into the uncured liquid epoxy resin or the epoxy/PT-15 blend. XRD and X-EDS measurements after curing were consistent with partial molecular dispersion of the POSS units in the continuous matrix phase, while the remainder forms POSS aggregates. TEM and SEM show that POSS?enriched nanoparticles are present in the matrix resins of both the epoxy/POSS and epoxy-PT-15/POSS composites.

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