High strength, high fracture toughness fibre composites with interface control—A review

In this report we present the results from the second part of a study on the influence of fibre length and concentration on the properties of glass reinforced polypropylene laminates. The heat deflection temperature of these laminates is dependent on both fibre length and concentration. A maximum plateau level close to the polypropylene melting point was observed, longer fibres require a lower concentration to attain this plateau value. Elevated temperature stiffness retention was also enhanced by higher fibre concentration and longer fibres. The Cox—Krenchel equations gave a good prediction of the laminate stiffness over the temperature range —50 to 100°C. Both the in-plane and out-of-plane linear coefficients of thermal expansion were strongly dependent on fibre concentration but relatively insensitive to the fibre length. We obtained excellent correlation between experimental values of the in-plane linear coefficients of thermal expansion and theoretical predictions based on the shear lag theory. Out-of-plane linear coefficients of thermal expansion were found to be much larger than predicted by the equations used for continuous fibre reinforced composites. An approach based on the in-plane compression of the matrix due to the restriction of the matrix expansion by the reinforcing fibres was found to give good agreement with the experimental data. Good correlation of the experimental and predicted data was only obtained when the effect of voids was included in the calculations

The influence of fibre length and concentration on the properties of glass fibre reinforced polypropylene: 2. Thermal properties

Tensile behavior contrast of basalt and glass fibers after chemical treatment

RETRACTED: Environmental resistance and mechanical performance of basalt and glass fibers

The abrasive wear of short fibre composites

The fracture behaviour of thermoplastic poly(ethylene terephthalate) reinforced with short E-glass fibre was investigated using fractography and a fracture mechanics approach. The observed microstructures, crack propagation and the stress-rupture lifetime data indicate a sudden breakdown induced by far-field effectS. The critical damage appears to be correlated with a ductile-to-brittle transition of matrix fracture. The calculation of fracture toughness for various fibre orientations indicates that the fibre pull-out energy is the dominant term in the case in which the fibre orientation is perpendicular to the notch tip.

Fracture behaviour of collimated thermoplastic poly(ethylene terephthalate) reinforced with short E-glass fibre

The study of the stress-rupture lifetime of a PET/glass fibre system by means of fracture mechanics methods indicates the degradation of lifetime under an aggressive environment (10% HCl solution). The SEM-EDAX analysis reveals the depletion of calcium and aluminium elements from the fibre, and this is believed to be the cause of multiple fibre fractures. The fracture toughness is decreased because the role of fibre pull-out, which is the significant energy-consuming process, is negligible. A statistical analysis, from which the lifetime behaviour can be predicted, is carried out.

Chemically-assisted fracture of thermoplastic PET reinforced with short E-glass fibre

Stress corrosion testing of injection molded, short-fiber (E-glass) reinforced poly(ethylene terephthalate) (PET), in a 10 weight percent NaOH solution, indicated that a PET-matrix degradation mechanism was operating. This is in direct contrast to the fiber degradation observed in acidic (10 weight percent HCl solution) stress corrosion tests on this material. Stress-rupture lifetime in the alkaline solution was shorter than that in the acidic solution, suggesting that the alkaline attack on the PET matrix is more aggressive than the acidic attack on the E-glass fibers. In both environments, fiber/matrix interface deterioration was also observed. Alkaline lifetime versus toughness behavior has been analyzed by established statistical methodology, using the empirical lifetime expression and the Weibull distribution function.

Stress‐rupture lifetime of a poly(ethylene terephthalate)/glass composite under an alkaline solution environment

Microscopic observations of thermoplastic poly(ethylene terephthalate) reinforced with short E-glass fibers revealed a unique matrix microstructure influenced by the orientation of densely packed glass fibers. The observed platelets tend to surround a fiber in a cylindrical sheath pattern. This observation of the crystalline platelet morphology is possible by the combination of ion-etching and the shadowing effect of protruding fibers.

The matrix phase microstructure of a glass poly(ethylene terephthalate) injection-molding compound†

The voltage lifetime of a poly(ethylene terephthalate)/glass composite is measured for two different orientations of short fiber with respect to the applied electric field (perpendicular and parallel). The difference in the voltage lifetime between two configurations is attributed to the microstructural features at the (fiber/matrix) interface, particularly microvoids. The morphological observations by scanning and transmission electron microscopy (SEM, TEM), and optical microscopy reveal the presence of microvoids as well as the crazed matrix and consequent erosion channel. The tree initiation site is identified and the nature of tree propagation is explained. A theoretical model based on such microstructural features is constructed, which explains the voltage lifetime vs fiber orientation in a relative framework. It is concluded that the graseous discharge at microvoids is the main mechanism for electrical breakdown and the site of such gaseous discharge is the (fiber/matrix) interface. Therefore, the orientation dependence of the electrical breakdown is the geometrical effect of the interface voiding with respect to the direction of the applied electric field.

Chang Lhymn

Papers

Fracture behaviour of collimated thermoplastic poly(ethylene terephthalate) reinforced with short E-glass fibre

Chemically-assisted fracture of thermoplastic PET reinforced with short E-glass fibre

Stress‐rupture lifetime of a poly(ethylene terephthalate)/glass composite under an alkaline solution environment

The matrix phase microstructure of a glass poly(ethylene terephthalate) injection-molding compound†

Electric breakdown of a poly(ethylene terephthalate)/glass composite