Durability study of CFRP strengthened steel circular hollow section members under marine environment

Galvanic corrosion is a common phenomenon in Carbon Fibre Reinforced Polymer (CFRP) strengthened steel structures in wet environments and submerged conditions, which reduces durability by weakening the bond between the CFRP and steel substrate. CFRP materials have already been proven to have superior resistance to corrosion and chemical attacks but the adhesive and steel are generally affected by long-term exposure to moisture, especially in conjunction with salts resulting from deicing of ocean spray. This paper presents the results of a research program to improve the durability of CFRP strengthened steel circular hollow section (CHS) members by treating the steel surface with an epoxy based adhesion promoter and inserting Glass Fibre Reinforced Polymer (GFRP) as a galvanic corrosion barrier against simulated sea water. It also presents the effects of accelerated corrosion on the bond of CFRP strengthened hollow steel members. The program consisted of four CFRP strengthened steel beams and one unstrengthened steel beam. Two strengthened beams were used as control while the other two beams were exposed to a highly corrosive environment to induce accelerated corrosion. The corrosion rate was considered 10% which represents a moderate level of loss in the cross-sectional area of the steel tube throughout its intended service life. The beams were then loaded to failure under four-point bending. The research findings indicate that the accelerated corrosion adversely affected the ultimate strength of the conditioned beams and the embedded glass fibre enhanced the bond durability.

Assessment of the molecular structure of an intermediate member of the triplite-zwieselite mineral series: A raman and infrared study

The mineral series triplite-zwieselite with theoretical formula (Mn2+)2(PO4)(F)-(Fe2+)2(PO4)(F) from the El Criolo granitic pegmatite, located in the Eastern Pampean Ranges of Córdoba Province, was studied using electron microprobe, thermogravimetry, and Raman and infrared spectroscopy. The analysis of the mineral provided a formula of (Fe1.00, Mn0.85, Ca0.08, Mg0.06)∑2.00(PO4)1.00(F0.80, OH0.20)∑1.00. An intense Raman band at 981 cm−1 with a shoulder at 977 cm−1 is assigned to the ν1 symmetric stretching mode. The observation of two bands for the phosphate symmetric stretching mode offers support for the concept that the phosphate units in the structure of triplite-zwieselite are not equivalent. Low-intensity Raman bands at 1012, 1036, 1071, 1087, and 1127 cm−1 are assigned to the ν3 antisymmetric stretching modes. A set of Raman bands at 572, 604, 639, and 684 cm−1 are attributed to the ν4 out-of-plane bending modes. A single intense Raman band is found at 3508 cm−1 and is assigned to the stretching vibration of hydroxyl units. Infrared bands are observed at 3018, 3125, and 3358 cm−1 and are attributed to water stretching vibrations. Supplemental materials are available for this article. Go to the publisher's online edition of Spectroscopy Letters to view the supplemental file.

Infrared and raman spectroscopic characterization of the silicate mineral gilalite Cu5Si6O17.7H2O

Gilalite is a copper silicate mineral with a general formula of Cu5Si6O17 · 7H2O. The mineral is often found in association with another copper silicate mineral, apachite, Cu9Si10O29 · 11H2O. Raman and infrared spectroscopy have been used to characterize the molecular structure of gilalite. The structure of the mineral shows disorder, which is reflected in the difficulty of obtaining quality Raman spectra. Raman spectroscopy clearly shows the absence of OH units in the gilalite structure. Intense Raman bands are observed at 1066, 1083, and 1160 cm−1. The Raman band at 853 cm−1 is assigned to the –SiO3 symmetrical stretching vibration and the low-intensity Raman bands at 914, 953, and 964 cm−1 may be ascribed to the antisymmetric SiO stretching vibrations. An intense Raman band at 673 cm−1 with a shoulder at 663 cm−1 is assigned to the ν4 Si-O-Si bending modes. Raman spectroscopy complemented with infrared spectroscopy enabled a better understanding of the molecular structure of gilalite.

Experimental Study of crack propagation in carbon steel using acoustic emission

Acoustic emission technique has become a significant and powerful structural health monitoring tool for structures. Researches to date have been done on crack location, fatigue crack propagation in materials and severity assessment of failure using acoustic emission technique. Determining severity of failure in steel structures using acoustic emission technique is still a challenge to accurately determine the relationship between the severity of crack propagation and acoustic emission activities. In this study three point bending test on low carbon steel samples along with acoustic emission technique have been used to determine crack propagation and severity. A notch is introduced at the tension face of the loading point to the samples to initiate the crack. The results show that the percentage of load drop of the steel specimen has a reciprocal relationship with the crack opening i.e. crack opening zones are influenced by the loading rate. In post yielding region, common acoustic emission signal parameters such as, signal strength, energy and amplitudes are found to be higher than those at pre-yielding and at yielding.

Surface engineering of reduced graphene oxide for controllable ambipolar flash memories

Tunable charge-trapping behaviors including unipolar charge trapping of one type of charge carrier and ambipolar trapping of both electrons and holes in a complementary manner is highly desirable for low power consumption multibit flash memory design. Here, we adopt a strategy of tuning the Fermi level of reduced graphene oxide (rGO) through self-assembled monolayer (SAM) functionalization and form p-type and n-type doped rGO with a wide range of manipulation on work function. The functionalized rGO can act as charge-trapping layer in ambipolar flash memories, and a dramatic transition of charging behavior from unipolar trapping of electrons to ambipolar trapping and eventually to unipolar trapping of holes was achieved. Adjustable hole/electron injection barriers induce controllable Vth shift in the memory transistor after programming operation. Finally, we transfer the ambipolar memory on flexible substrates and study their charge-trapping properties at various bending cycles. The SAM-functionalized rGO can be a promising candidate for next-generation nonvolatile memories.

One step closer into the design of fall protective device for individuals fitted with a bone-anchored prosthesis

The consequences of falls are often dreadful for individuals with lower limb amputation using bone-anchored prosthesis.[1-5] Typically, the impact on the fixation is responsible for bending the intercutaneous piece that could lead to a complete breakage over time. .[3, 5-8] The surgical replacement of this piece is possible but complex and expensive. Clearly, there is a need for solid data enabling an evidence-based design of protective devices limiting impact forces and torsion applied during a fall. The impact on the fixation during an actual fall is obviously difficult to record during a scientific experiment.[6, 8-13] Consequently, Schwartze and colleagues opted for one of the next best options science has to offer: simulation with an able-bodied participant. They recorded body movements and knee impacts on the floor while mimicking several plausible falling scenarios. Then, they calculated the forces and moments that would be applied at four levels along the femur corresponding to amputation heights.[6, 8-11, 14-25] The overall forces applied during the falls were similar regardless of the amputation height indicating that the impact forces were simply translated along the femur. As expected, they showed that overall moments generally increased with amputation height due to changes in lever arm. This work demonstrates that devices preventing only against force overload do not require considering amputation height while those protecting against bending moments should. Another significant contribution is to provide, for the time, the magnitude of the impact load during different falls. This loading range is crucial to the overall design and, more precisely, the triggering threshold of protective devices. Unfortunately, the analysis of only a single able-bodied participant replicating falls limits greatly the generalisation of the findings. Nonetheless, this case study is an important milestone contributing to a better understanding of load impact during a fall. This new knowledge will improve the treatment, the safe ambulation and, ultimately, the quality of life of individuals fitted with bone-anchored prosthesis.

Blast response of segmented bored tunnel using coupled SPH–FE method

Underground transport tunnels are vulnerable to blast events. This paper develops and applies a fully coupled technique involving the Smooth Particle Hydrodynamics and Finite Element techniques to investigate the blast response of segmented bored tunnels. Findings indicate that several bolts failed in the longitudinal direction due to redistribution of blast loading to adjacent tunnel rings. The tunnel segments respond as arch mechanisms in the transverse direction and suffered damage mainly due to high bending stresses. The novel information from the present study will enable safer designs of buried tunnels and provide a benchmark reference for future developments in this area.

Raman and infrared spectroscopic studies of phurcalite from Red Canyon, Utah, USA – Implications for the molecular structure

Raman and infrared spectra of the uranyl mineral phurcalite, Ca2(UO2)3O2(PO4)2⋅7H2O, from Red Canyon, Utah, USA, were studied and tentatively interpreted. Observed bands were assigned to the stretching and bending vibrations of (UO2)2+ and (PO4)3− units and to the stretching and bending vibrations and libration modes of water molecules. Approximate lengths of U–O in (UO2)2+ and O–H⋯O hydrogen bond lengths were inferred from observed stretching vibrations. The presence of structurally nonequivalent U6+ and P5+ was inferred from the number of corresponding stretching bands of (UO2)2+ and (PO4)3− units observed in the Raman and infrared spectra..

Characterization of the sulphate mineral coquimbite, a secondary iron sulphate from Javier Ortega mine, Lucanas Province, Peru – Using infrared, Raman spectroscopy and thermogravimetry

The mineral coquimbite has been analysed using a range of techniques including SEM with EDX, thermal analytical techniques and Raman and infrared spectroscopy. The mineral originated from the Javier Ortega mine, Lucanas Province, Peru. The chemical formula was determined as ðFe3þ 1:37; Al0:63ÞP2:00ðSO4Þ3 9H2O. Thermal analysis showed a total mass loss of 73.4% on heating to 1000 C. A mass loss of 30.43% at 641.4 C is attributed to the loss of SO3. Observed Raman and infrared bands were assigned to the stretching and bending vibrations of sulphate tetrahedra, aluminium oxide/hydroxide octahedra, water molecules and hydroxyl ions. The Raman spectrum shows well resolved bands at 2994, 3176, 3327, 3422 and 3580 cm 1 attributed to water stretching vibrations. Vibrational spectroscopy combined with thermal analysis provides insight into the structure of coquimbite.

A vibrational spectroscopic study of the borate mineral ezcurrite Na4B10O17·7H2O – Implications for the molecular structure

We have studied the boron containing mineral ezcurrite Na4B10O17·7H2O using electron microscopy and vibrational spectroscopy. Both tetrahedral and trigonal boron units are observed. The nominal resolution of the Raman spectrometer is of the order of 2 cm−1 and as such is sufficient enough to identify separate bands for the stretching bands of the two boron isotopes. The Raman band at 1037 cm−1 is assigned to BO stretching vibration. Raman bands at 1129, 1163, 1193 cm−1 are attributed to BO stretching vibration of the tetrahedral units. The Raman band at 947 cm−1 is attributed to the antisymmetric stretching modes of tetrahedral boron. The sharp Raman peak at 1037 cm−1 is from the 11-B component such a mode, then it should have a smaller 10-B satellite near (1.03) × (1037) = 1048 cm−1, and indeed a small peak at 1048 is observed. The broad Raman bands at 3186, 3329, 3431, 3509, 3547 and 3576 cm−1 are assigned to water stretching vibrations. Broad infrared bands at 3170, 3322, 3419, 3450, 3493, 3542, 3577 and 3597 cm−1 are also assigned to water stretching vibrations. Infrared bands at 1330, 1352, 1389, 1407, 1421 and 1457 cm−1 are assigned to the antisymmetric stretching vibrations of trigonal boron. The observation of so many bands suggests that there is considerable variation in the structure of ezcurrite. Infrared bands at 1634, 1646 and 1681 cm−1 are assigned to water bending modes. The number of water bending modes is in harmony with the number of water stretching vibrations.

A vibrational spectroscopic study of the arsenate minerals cobaltkoritnigite and koritnigite

Raman spectra of two well-defined types of cobaltkoritnigite and koritnigite crystals were recorded and interpreted. Significant differences in the Raman spectra of cobaltkoritnigite and koritnigite were observed. Observed Raman bands were attributed to the (AsO3OH)2− stretching and bending vibrations, stretching and bending vibrations of water molecules and hydroxyl ions. Both Raman and infrared spectra of cobaltkoritnigite identify bands which are attributable to phosphate and hydrogen phosphate anions proving some substitution of phosphate for arsenate in the structure of cobaltkoritnigite. The OH⋯O hydrogen bond lengths in the crystal structure of koritnigite were inferred from the Raman spectra and compared with those derived from the X-ray single crystal refinement. The presence of (AsO3OH)2− units in the crystal structure of cobaltkoritnigite and koritnigite was proved from the Raman spectra which supports the conclusions of the X-ray structure analysis.

A vibrational spectroscopic study of the silicate mineral plumbophyllite Pb2Si4O10⋅H2O

Raman spectroscopy complimented with infrared spectroscopy has been used to study the molecular structure of the mineral of plumbophyllite. The Raman spectrum is dominated by a very intense sharp peak at 1027 cm−1, assigned to the SiO stretching vibrations of (SiO3)n units. A very intense Raman band at 643 cm−1 is assigned to the bending mode of (SiO3)n units. Raman bands observed at 3215, 3443, 3470, 3494 and 3567 cm−1 are assigned to water stretching vibrations. Multiple water stretching and bending modes are observed showing that there is much variation in hydrogen bonding between water and the silicate surfaces. Because of the close similarity in the structure of plumbophyllite and apophyllite, a comparison of the spectra with that of apophyllites is made. By using vibrational spectroscopy an assessment of the molecular structure of plumbophyllite has been made.

A Raman and infrared spectroscopic characterisation of the phosphate mineral phosphohedyphane Ca2Pb3(PO4)3Cl from the Roote mine, Nevada, USA

Phosphohedyphane Ca2Pb3(PO4)3Cl is rare Ca and Pb phosphate mineral that belongs to the apatite supergroup. We have analysed phosphohedyphane using SEM with EDX, and Raman and infrared spectroscopy. The chemical analysis shows the presence of Pb, Ca, P and Cl and the chemical formula is expressed as Ca2Pb3(PO4)3Cl. The very sharp Raman band at 975 cm−1 is assigned to the PO43-ν1 symmetric stretching mode. Raman bands noted at 1073, 1188 and 1226 cm−1 are to the attributed to the PO43-ν3 antisymmetric stretching modes. The two Raman bands at 835 and 812 cm−1 assigned to the AsO43-ν1 symmetric stretching vibration and AsO43-ν3 antisymmetric stretching modes prove the substitution of As for P in the structure of phosphohedyphane. A series of bands at 557, 577 and 595 cm−1 are attributed to the ν4 out of plane bending modes of the PO4 units. The multiplicity of bands in the ν2, ν3 and ν4 spectral regions provides evidence for the loss of symmetry of the phosphate anion in the phosphohedyphane structure. Observed bands were assigned to the stretching and bending vibrations of phosphate tetrahedra. Some Raman bands attributable to OH stretching bands were observed, indicating the presence of water and/or OH units in the structure.

Vibrational spectroscopic characterization of the sulphate-carbonate mineral burkeite: Implications for evaporites

Burkeite formation is important in saline evaporites and in pipe scales. Burkeite is an anhydrous sulphate-carbonate with an apparent variable anion ratio. Such a formula with two oxyanions lends itself to vibrational spectroscopy. Two symmetric sulphate stretching modes are observed, indicating at least at the molecular level the nonequivalence of the sulphate ions in the burkeite structure. The strong Raman band at 1065 cm−1 is assigned to the carbonate symmetric stretching vibration. The series of Raman bands at 622, 635, 645, and 704 cm−1 are assigned to the ν4 sulphate bending modes. The observation of multiple bands supports the concept of a reduction in symmetry of the sulphate anion from T d to C 3v or even C 2v.

Vibrational spectroscopic characterization of the arsenate mineral barahonaite: Implications for the molecular structure

The mineral barahonaite is in all probability a member of the smolianinovite group. The mineral is an arsenate mineral formed as a secondary mineral in the oxidized zone of sulphide deposits. We have studied the barahonaite mineral using a combination of Raman and infrared spectroscopy. The mineral is characterized by a series of Raman bands at 863 cm−1 with low wavenumber shoulders at 802 and 828 cm−1. These bands are assigned to the arsenate and hydrogen arsenate stretching vibrations. The infrared spectrum shows a broad spectral profile. Two Raman bands at 506 and 529 cm−1 are assigned to the triply degenerate arsenate bending vibration (F 2, ν4), and the Raman bands at 325, 360, and 399 cm−1 are attributed to the arsenate ν2 bending vibration. Raman and infrared bands in the 2500–3800 cm−1 spectral range are assigned to water and hydroxyl stretching vibrations. The application of Raman spectroscopy to study the structure of barahonaite is better than infrared spectroscopy, probably because of the much higher spatial resolution.