Short Fiber-reinforced Thermoplastics Research Articles

Elastic behaviour of unidirectional short fibre-reinforced thermoplastics

The elastic behaviour of unidirectional short fibre-reinforced thermoplastics has been determined in terms of elastic modulus, relaxation and thermal coefficient of linear expansion. These properties can be derived from the properties of the components of the composite by using a simple constituent model. The reduced reinforcement of short fibres compared with that of continuous fibres is accounted for by an attenuation factor which depends on the aspect ratio of the fibres and the Young's modulus of the matrix.

Tensile and impact strengths of unidirectional, short fibre-reinforced thermoplastics

The tensile and impact strength behaviour of short glass fibre-reinforced thermoplastics (nylon 6, polypropylene and polymethylmethacrylate) have been studied by varying the matrix toughness and the interfacial shear strength. The fibre/matrix interface is found to have a strong influence on both the tensile and impact strengths. The critical fibre length concept was used to interpret experimental data. Scanning electron microscopy measurements were used to confirm the data.

Fracture in oriented short fibre-reinforced thermoplastics

Fracture mechanisms in a series of short fibre-reinforced thermoplastics made with controlled fibre orientation were investigated. The matrix materials used ranged from very ductile to brittle and the fibres from tough, relatively low modulus organic fibres to high modulus graphite. Examination of fracture surfaces using electron microscopy showed that, even when fibre length greatly exceeded the critical length, these composites fractured by fibres pulling out of the matrix with little fibre fracture. Cracks initiated at misaligned fibres, fibre ends, or other flaws tended to propagate through the matrix or along the fibre/matrix interface, depending upon the fibre-to-matrix adhesion.

Flow of short glass fibre-filled polymer melts

The quantitative description of the flow properties of non-newtonian thermoplastic melts in channels of various geometries is generally satisfactory for application to the design of plastics processing equipment. Mixtures of short glass fibres and non-newtonian thermoplastic melts have been shown to cause special flow problems; furthermore, the properties of short fibre-reinforced thermoplastics in the solid state are known to depend strongly on fibre orientation and fibre length which, in turn, are strongly influenced by the flow of the mixture in the molten state. A knowledge of the flow characteristics of short fibre-reinforced thermoplastics in the molten state as a function of the characteristics of the components is now very much needed. Two special rheometers have been constructed for investigating the flow of these composite melts in channels of rectangular and circular cross-section. They enable study of the effect of channel length, diameter, gap thickness and entrance conditions. Quantitative results illustrating the influence of fibres on the flow are discussed in view of their use for design purpose.