Characterization of Ice Adhesion: Approaches and Modes of Loading

Airborne structures are vulnerable to atmospheric icing in cold weather operation conditions. Most of the ice adhesion-related works have focused on mechanical ice removal strategies because of practical considerations, while limited literature is available for a fundamental understanding of the ice adhesion process. Here, we present fracture mechanics-based approaches to characterize interfacial fracture parameters for the tensile and shear behavior of a typical ice/aluminum interface. An experimental framework employing single cantilever beam, direct shear, and push-out shear tests were developed to achieve near mode-I and near mode-II fracture conditions at the interface. Both analytical (beam bending and shear-lag analysis), and numerical (finite element analysis incorporating cohesive zone method) models were used to extract mode-I and II interfacial fracture parameters. The combined experimental and numerical results, as well as surveying published results for the direct shear and push-out shear tests, showed that mode-II interfacial strength and toughness could be significantly affected by the test method due to geometrically induced interfacial residual stress. As a result, the apparent toughness of the zero-angle push-out test could reach an order of magnitude higher than those derived from direct shear tests. Moreover, it was found that the interfacial ice adhesion is fracture mode insensitive and roughness insensitive for tensile and shear modes, for the observed modes of failures in this stud

The microstructural and hardening behaviour of tricalcium silicate pastes in the presence of calcium chloride

A sequential examination of strength development in terms of microhardness was studied during paste hydration of C[3]S in the presence of 2 and 5% CaCl[2] and at w/s ratios of 0.3 or 0.5. An attempt has been made to relate strength with microstructural features studied by means of Scanning Electron Microscopy. Generally, at earlier periods it was found that the 2% addition of CaCl[2] gave the strongest material; the effect was most pronounced in the 6-month sample of the series with 0.3 w/s. The high strength for the sample prepared at a w/s ratio of 0.3 may be related to a high CaO/SiO[2] C-S-H phase, low porosity, and possibly a hydrated calcium hydroxy chloride complex. The pore size distribution was also measured. In general, the higher the porosity the lower the strengths but the relationship was not perfectly linear even on the semi-logarithmic plot.On a effectu\ue9 un examen s\ue9quentiel du d\ue9veloppement de la r\ue9sistance en termes de microduret\ue9 au cours de l'hydratation de la p\ue2te de C[3]S en pr\ue9sence de 2 et de 5 pour cent de CaCl[2] \ue0 un rapport eau/solide de 0.3 ou de 0.5. On a tent\ue9 de relier la r\ue9sistance aux aspects microstructuraux \ue9tudi\ue9s au moyen de microscope \ue9lectronique \ue0 grille. En g\ue9n\ue9ral, l'addition de 2 pour cent de CaCl[2] produit le mat\ue9riau le plus r\ue9sistant. L'\ue9chantillon de six mois de la s\ue9rie, avec un rapport eau/solide de 0.3, produit l'effet le plus prononc\ue9. La r\ue9sistance \ue9lev\ue9e de cet \ue9chantillon est peut-\ueatre li\ue9e \ue0 une phase C-S-H CaO/SiO[2] \ue9lev\ue9e, \ue0 une faible porosit\ue9 et m\ueame \ue0 un complexe de chlorure en hydratation. On mesure \ue9galement la r\ue9partition du diam\ue8tre des pores. R\ue8gle g\ue9n\ue9rale, plus la porosit\ue9 est \ue9lev\ue9e, plus la r\ue9sistance est faible, mais le rapport n'est pas parfaitement lin\ue9aire m\ueame pour le diagramme semi- logarithmique.Peer reviewed: YesNRC publication: Ye

Stability tests of the Europoort breakwater

This paper deals with model tests conducted at the Delft Hydraulics Laboratory (DHL) and the River and Harbour Laboratory at the Technical University of Norway (RHL) for the design of the Europoort Breakwater. A series of tests with regular waves was conducted at the DHL from which the design of the breakwater was decided. The chosen design was tested with irregular waves based on in situ observations. Wave spectra, wave height distributions and the joint distribution of wave height and period were specified. These tests were conducted at the RHL, and some tests were repeated at the DHL. It has been commonly assumed that the destructive effect of a train of regular waves on a breakwater in model is equal to the effect of irregular waves with a significant wave height corresponding to the height of the regular waves. The tests showed that for this particular breakwater the irregular waves represented a more severe wave attack than the regular waves

Strength of C3A paste containing gypsum and CaCI2

A study has been made of the strength of 3CaO.Al[2]O[3] and 3CaO.Al[2]O[3] + gypsum pastes as well as of the influence of the admixture CaCl[2] on these pastes. The methods employed were microhardness indentation and cone penetration. With 16 per cent CaCl[2] added to the 3CaO.Al[ 2]O[3] paste a significant gain in strength was obtained after 3 months, while an 8 per cent CaCl[2] addition to the 3CaO.Al[2]O[3] + gypsum system gave the highest strength at the same age. Morphological changes in the pastes were found to be related to changes in hardness. From a comparison of the two methods it was concluded that cone penetration measurements are useful up to a certain hardness level.On a fait une \ue9tude de la r\ue9sistance des p\ue2tes de 3CaO.Al[2] O[3] et de 3CaO.Al[2]O[3] plus gypse ainsi que de l'effet de l'addition de CaCl[2] \ue0 ces m\ueames p\ue2tes. On a utilis\ue9 les m\ue9 thodes de la microduret\ue9 par indentation et de la p\ue9n\ue9 tration d'un c\uf4ne. Lorsqu'on ajoute 16 pour cent de CaCl[ 2] \ue0 la p\ue2te de 3CaO.Al[2]O[3], la r\ue9sistance augmente consid\ue9rablement en trois mois, tandis que l'addition de 8 pour cent de CaCl[2] au syst\ue8me 3CaO.Al[2]O[3] plus gypse produit la r\ue9sistance la plus \ue9lev\ue9e pour cette m\ueame p\ue9 riode. Les changements morphologiques de la p\ue2te sont li\ue9 s \ue0 des changements de duret\ue9. Une comparaison des deux m\ue9 thodes indique que les mesures de la p\ue9n\ue9tration d'un c\uf4ne sont utiles jusqu'\ue0 un certain degr\ue9 de duret\ue9.Peer reviewed: YesNRC publication: Ye

Hydration of 3CAOA12O3 and 3CAOA12O3 + gypsum with and without CAC12

Paste samples of tricalcium aluminate alone, with CaCl[2], with gypsum, and with gypsum and CaCl[2] were hydrated for up to 6 months and the hydration products characterized by SEM, XRD, and DTA. Tricalcium aluminate hydrated initially to a hexagonal hydroaluminate phase which then changed to the cubic form; the transformation rate depended on the size and shape of the sample and on temperature. The addition of CaCl[2] to tricalcium aluminate resulted in the formation of 3CaO.Al[2]O[3].CaCl[2].10H[2]O and 4CaO.Al[2]O[3].13H[2]O, or a solid solution of the two. The chloride retarded the formation of the cubic phase 3CaO.Al[2]O[3].6H[2]O; the addition of gypsum resulted in the formation of monosulfoaluminate with a minor amount of ettringite. When chloride was added to tricalcium aluminate and gypsum, more ettringite was formed, although 3CaO.Al[2]O[3].CaSO[4].12H[2] O and 3CaO.Al[2]O[3].CaCl[2].10H[2]O were the main hydration products.Des \ue9chantillons de p\ue2te d'aluminate tricalcique seul, avec du chlorure de calcium, avec du gypse, puis avec du gypse et du chlorure de calcium sont hydrat\ue9s pendant jusqu'\ue0 six mois et les produits d'hydratation sont caract\ue9ris\ue9s \ue0 l'aide de la spectroscopie \ue9lectronique \ue0 grille, de la diffraction des rayons X et de l'analyse thermique diff\ue9rentielle. L'hydratation de l'aluminate tricalcique donne d'abord une phase hexagonale d'hydroaluminate qui prend ensuite la forme cubique, la vitesse de la transformation \ue9tant fonction des dimensions et de la forme de l'\ue9chantillon ainsi que de la temp\ue9rature. L'addition de chlorure de calcium \ue0 l'aluminate tricalcique entra\ueene la formation de 3CaO.Al[2]O[3].CaCl[2].10H[2]O et de 4CaO.Al[2]O[3].13H[2]O ou d'une solution solide des deux \ue0 fois. La pr\ue9sence de chlorure retarde la formation de la phase cubique 3CaO.Al[2] O[3].6H[2]O; l'addition de gypse entra\ueene la formation de monosulfoaluminate avec une faible quantit\ue9 d'ettringite. L'addition de chlorure \ue0 l'aluminate tricalcique plus gypse produit d'autre ettringite bien que les principaux produits d'hydratation soient 3CaO.Al[2]O[3].CaSO[4].12H[2]O et 3CaO. Al[2]O[3].CaCl[2].10H[2]O.Peer reviewed: YesNRC publication: Ye

A study of the microstructure and hydration characteristics of tricalcium silicate in the presence of calcium chloride

The morphological and hydration characteristics of tricalcium silicate treated with 0, 2 and 5 per cent calcium chloride were followed by employing Scanning Electron Microscopy (SEM), Differential Thermal Analysis (DTA), and X- ray diffraction techniques. The water:solid ratios used were either 0.5 or 0.3. In terms of Ca(OH)[2] estimation CaCl[2] accelerated hydration, except with 5 per cent CaCl[ 2] at a 0.3 w/s ratio. The maximum amount of Ca(OH)[2] and calcium silicate hydrate was formed at 2 per cent CaCl[2] and a w/s ratio of 0.5. Except at very early times, the rate of reaction was slower at 0.3 w/s with or without CaCl[ 2] compared with the corresponding samples at 0.5 w/s.On observe les caract\ue9ristiques morphologiques et d'hydratation du silicate tricalcique en pr\ue9sence de 0 pour cent, 2 pour cent et 5 pour cent de chlorure de calcium au moyen de la microscopie \ue9lectronique \ue0 grille, de l'analyse thermique diff\ue9rentielle et de techniques de diffraction de rayons X. Le rapport eau/solide est de 0.5 ou de 0.3. En termes d'\ue9valuation de Ca(OH)[2], le CaCl[2] acc\ue9l\ue8re l'hydratation, sauf pour 5 pour cent de CaCl[2] et un rapport eau/solide de 0.3. La formation maximale de Ca(OH)[2] et d' hydrate de silicate de calcium r\ue9sulte de 2 pour cent de CaCl[2] et d'un rapport eau/solide de 0.5. Apr\ue8s trois mois, le degr\ue9 d'hydratation, en termes de formation d'hydrate de silicate de calcium, est tr\ue8s semblable dans p\ue2tes lorsque le rapport eau/solide est de 0.3. En comparaison des \ue9chantillons correspondants lorsque le rapport eau/solide est de 0.5, la r\ue9action est plus lente pour un rapport eau/solide de 0.3 avec ou sans CaCl[2], sauf au tout d\ue9but.Peer reviewed: YesNRC publication: Ye

The strain rate and temperature dependence of Young's modulus of ice

Measurements were made of Young's modulus of polycrystalline ice over the strain rate range of 10[-8] to 5 x 10[-3] s[-1] at temperatures of -10, -19.3, -29 and -39.5 degrees C on two types of ice: naturally formed granular ice and laboratory grown columnar-grained ice. Load was applied at constant rate of cross-head movement until the stress was about 5 kg/cm[2], and then removed immediately at the same rate. Young's moduli were determined from the linear portion of the stress-strain curve during loading. The modulus for both types of ice increased with increasing strain rate over the full range of strain rate covered in the investigation.Les auteurs mesurent le module de Young de la glace polycristalline \ue0 des viteses de d\ue9formation entre 10[-8] et 5 x 10[-3] s[-1] et \ue0 des temp\ue9ratures de -10, -19.3, -29 et -39.5 degr\ue9s C pour deux genres de glace: la glace granulaire naturelle et la glace colonnaire obtenue en laboratoire. La charge est appliqu\ue9e \ue0 une vitesse de traverse constante jusqu'\ue0 une contrainte d'environ 5 kg/cm[ 2], puis enlev\ue9e imm\ue9diatement \ue0 la m\ueame vitesse. On d\ue9 termine le module de Young d'apr\ue8s la partie lin\ue9aire de la courbe contrainte/d\ue9formation durant le chargement. Le module des deux genres de glace augmente en m\ueame temps que la vitesse de d\ue9formation augmente \ue0 toutes les vitesses de d\ue9formation \ue9tudi\ue9es.Peer reviewed: NoNRC publication: Ye