Stiffness behaviour of injection moulded short glass fibre/impact modifier/polypropylene hybrid composites

The stiffness behaviour of injection moulded short glass fibre/impact modifier/polypropylene hybrid composites has been investigated in this work by theoretical predictions and experiments. Predictions from the self-consistent method were found to be in good agreement with test results for the impact modifier/polypropylene blends. By taking into account of the fibre orientation distributions in the skin and core layers, the values of Young's modulus for the skin and core layers were predicted by employing Eshelby's equivalent inclusion method and the average induced strain approach. The prediction of the values of Young's modulus for the whole sample was obtained by applying the simple mixture theory of laminated composites to the predicted results for the skin and core layers. Good correlation between predicted and experimental Young's modulus values were found.

A new model for the energy release rate of fibre/matrix interfacial fracture

On the basis of the well-known shear-lag analysis of fibre/matrix interface stresses and the assumption of identical axial strains in the fibre and matrix, a new model for predicting the energy release rate of interfacial fracture of the fibre pull-out test model is attempted. The expressions for stresses in the fibre, matrix and interface are derived. The formula for interfacial debonding energy release rate is given. Numerical calculations are conducted and the results obtained are compared with those of the existing models.

Micro- and macroscopic characterizations of the viscoelastic fracture of resin-based fibre composites

Micro- and macroscopic characterizations of the viscoelastic fracture of a unidirectional carbon-fibre-reinforced epoxy composite are presented. First, the micro-cracking behavior of the material is studied by the use of scanning electron microscopy; the in situ creep cracking process is observed and the crack propagation is measured. In order to obtain insight into the mechanisms of the observed creep cracking, macroscopic investigations were also carried out. Finite-element method simulations were carried out to calculate the stress distribution and the variation of stresses with time. A theoretical analysis of the orthotropy of viscoelastic fracture behavior of the material is also conducted.

Prediction of mixed-mode cracking direction in random, short-fibre composite-materials

The prediction of cracking direction in composite materials is of significance to the design of composite structures. This paper presents several methods for predicting the cracking direction in the double grooved tension-shear specimen which gives mixed-mode cracking. Five different criteria are used in this analysis: two of them have been used by other investigators and the others are proposed by the present authors. The strain energy density criterion proposed by G.C. Sih is modified to take account of the influence of the anisotropy of the strength on the direction of crack. The two failure criteria of Tsai-Hill and Norris are extended to predict the crack orientation. The stress distributions in the near-notch zone are calculated by using the 8-node quadrilateral isoparametric finite element method. The predictions of all the criteria except one are in good agreement with the experimental measurement. In addition, on the basis of the FEM results, the size of the zone in which the singular term is dominant is estimated.

Composite second-order performance improvement in optical fibre CATV transmission system using chirped fibre grating

Theoretically, we analyse the dispersion compensation characteristics of the chirped fibre grating (CFG) in an optical fibre cable television (CATV) system and obtain the analytic expression of the composite second-order (CSO) distortion using the time-domain form of the field envelope wave equation. The obtained result is in good agreement with the numerical simulation result. Experimentally, we verify the result by making use of the tunable characteristics of CFG to change the dispersion compensation amount and obtain an optimal CSO performance in a 125km fibre transmission link. Both the theoretical and experimental results show that the CSO performance can be improved by properly choosing the dispersion compensation amount for a certain fibre transmission link.

Design and analysis of a kind of large flattened mode optical fibre

In this paper, a refractive index pro. le design enabling us to obtain a. at modal field around the fibre centre is investigated. The theoretical approach for designing such multilayer large flattened mode (LFM) optical fibres is presented. A comparison is made between the properties of a three-layer LFM structure and a standard step-index pro. le with the same core size. The obtained results indicate that the effective area of the LFM fibre is about twice as large as that of the standard step-index fibre, but the LFM fibre has less effective ability to filter out the higher order modes than the standard step-index fibre with the same bending radius.

Single mode Er-doped pi-phase-shifted distributed feedback fibre grating laser

A novel method incorporating the shielded method and the post-processing method has been proposed to fabricate the pi-phase-shilted fibre grating. Then an Er-doped pi-phase-shifted distributed feedback fibre grating laser has been fabricated using the grating. The laser threshold is 20 mW. When pumped with 90 mW light at 980 nm, the laser gives an output of 1.1 mW. Its signal-to-noise ratio is better than 60 dB. It is demonstrated that the laser is single mode operation by means of a Fabry-Perot scanning interferometer.

Theoretical modelling of the effect of photon lifetime on the output dynamics of Er-doped distributed feedback fibre lasers

By employing a simple model of describing three-level lasers, we have theoretically investigated the effect of photon lifetime on the output dynamics of Er-doped distributed feedback fibre lasers. And based on the theoretical analysis we have proposed a promising method to suppress self-pulsing behaviour in the fibre lasers.

Phase-locking of two large-core fibre lasers with 60W of coherent output power

A phase-locking fibre laser array with up to 60 W of coherent output power based on two large-core fibre is reported. The slope efficiency of the in-phase mode is 37%. For two cases of spacings between the cores, steady high-contrast interference stripes are observed. When the whole system operates under a high pump power level, no thermal effects for the spatial filter have been observed, which means that we can increase the coherent output power further by increasing the individual fibre laser power.

Tm-doped fibre laser pumped Cr2+: ZnSe poly-crystal laser

Demonstrations of cw lasing in Cr2+:ZnSe poly-crystal are reported. The laser consists of a 1.7-mm-thick Cr2+:ZnSe poly-crystal disc pumped by a Tm-silica double-clad fibre laser at 2050nm. Using a concave high-reflection mirror with a radius of curvature of 500mm as the rear mirror, the laser delivers up to 1030mW of radiation around 2.367 mu m.

UV-blue upconverted emission from Nd3+-doped InF3-based heavy-metal fluoride glasses for blue upconversion fibre laser

We report spectral properties and thermal stability of Nd3+-doped InF3-based heavy-metal fluoride glasses. Fluoroindate glasses in the chemical compositions (in mol%) of (38-x)InF3-16BaF(2)-20ZnF(2)-20SrF(2)-3GdF(3)-1GaF(3-)2NaF-xNdF(3) (x = 0.1, 0.5, 1, 2, 3) have been prepared under a controlled atmosphere in a dry box. Strong UVblue upconversion emission from a green excitation wavelength has been observed and the involved mechanisms have been explained. Near-infrared emission occurs simultaneously upon excitation of the UV-blue upconversion emissions with a cw Ar(+)laser. The upconversion spectra have revealed four dominant emissions at 354, 380, 412 and 449 nm, which belong to the transitions of D-4(3/2) -> I-4(9/2), D-4(3/2) -> I-4(11/2) and P-2(3/2) -> I-4(9/2), D-4(3/2) -> I-4(13/2) and P-2(3/2) -> I-4(11/2), D-4(3/2) -> I-4(15/2) and P-2(3/2) -> I-4(13/2), respectively.

A novel hollow-core holey fibre with random hole distributions in the cladding

We provide a novel hollow-core holey fibre that owns a random distribution of air holes in the cladding. Our experiments demonstrate that many of the features previously attributed to photonic crystal fibres with perfect arrangement of air holes, in particular, photonic bandgap guidance, can also be obtained in the fibre. Additionally, this fibre exhibits a second guided mode with both the two-lobe patterns, and each pattern is in different colour.

High efficiency and broad bandwidth grating coupler between nanophotonic waveguide and fibre

A high efficiency and broad bandwidth grating coupler between a silicon-on-insulator (SOI) nanophotonic waveguide and fibre is designed and fabricated. Coupling efficiencies of 46% and 25% at a wavelength of 1.55 mu m are achieved by simulation and experiment, respectively. An optical 3 dB bandwidth of 45 nm from 1530 nm to 1575 nm is also obtained in experiment. Numerical calculation shows that a tolerance to fabrication error of 10 nm in etch depth is achievable. The measurement results indicate that the alignment error of +/-2 mu m results in less than 1 dB additional coupling loss.

Monolithically integrated transceiver with novel Y-branch by bundle integrated waveguide for fibre optic gyroscope

A novel Y-branch based monolithic transceiver with a superluminescent diode and a waveguide photodiode (Y-SDL-PD) is designed and fabricated by the method of bundle integrated waveguide (BIG) as the scheme for monolithic integration and angled Y-branch as the passive bi-directional waveguide. The simulations of BIG and Y-branches show low losses and improved far-field patterns, based on the beam propagation method (BPM). The amplified spontaneous emission of the device is up to 10mW at 120mA with no threshold and saturation. Spectral characteristics of about 30 nm width and less than 1 dB modulation are achieved using the built-in anti-lasing ability of Y-branch. The beam divergence angles in horizontal and vertical directions are optimized to as small as 12 degrees x 8 degrees, resulting in good fibre coupling.

Passive Q-switching modelocked Yb3+-doped fibre laser with GaAs absorber grown at low temperature

GaAs absorber was grown at low temperature (550degreesC) by metal organic chemical vapour deposition (MOCVD) and was used as an output coupler with which we realized Q-switching modelocked Yb3+-doped fibre laser. The shortest period of the envelope of the Q-switched modelocking is about 3mus. The modelocking threshold is 4.27W and the highest average output pulse power is 290 mW. The modelocking frequency is 12 MHz.