Technology and development of self-reinforced polymer composites

\u3cp\u3eIn recent years there has been an increasing amount of interest, both commercially and scientifically, in the emerging field of self-reinforced polymer composites . These materials, which are sometimes also referred to as single polymer composites , or all-polymer composites , were first conceived in the 1970s, and are now beginning to appear in a range of commercial products. While high mechanical performance polymer fibres or tapes are an obvious precursor for composite development, various different technologies have been developed to consolidate these into two- or three-dimensional structures. This paper presents a review of the various processing techniques that have been reported in the literature for the manufacture of self-reinforced polymer composites from fibres or tapes of different polymers, and so exploit the fibre or tape performance in a commercial material or product.\u3c/p\u3

Hybrid composites based on polyethylene and carbon fibres. Part 6: Tensile and fatigue behaviour

The tensile and fatigue behaviour of unidirectional carbon-high-performance polyethylene/epoxy hybrid composites has been studied, including the effect of hybrid design and surface treatment of the high-performance polyethylene ( ) fibres. Results indicated that the tensile behaviour of carbon- hybrids in both monotonic and fatigue testing can be interpreted, adopting the conventional ‘constant strain’ model for hybrid composites. Deviations from this constant strain model, so-called hybrid effects, were observed in monotonic tensile testing for those hybrid systems with the highest degree of fibre dispersion, incorporating either untreated or treated fibres, whereas only the latter displayed synergistic fatigue performance. Hybrid effects under tensile loading conditions were in reasonable agreement with calculations accounting for statistical effects and stress concentrations as determined by finite element analyses

Mechanical properties of flexible knitted composites

This study investigates the influence of the matrix material and the degree of prestretch of a knitted fibre structure on the mechanical properties of knitted composites with low fibre volume fractions. By embedding a flexible textile structure in an elastomeric matrix, composite materials are obtained that combine an interesting stress-strain behaviour with extreme extensibility and relatively high levels of energy absorption. Although this study focuses on the influence of the degree of prestretch of the knitted structure on composite properties based on rubbery matrices, reference materials based on highly cross-linked epoxy resins were also studie

Influence of applied stress and temperature on the deformation behaviour of high-strength poly(vinyl alcohol) fibres

The deformation behaviour of poly(vinyl alcohol) (PVA) fibres is studied using dynamic mechanical analysis, stress relaxation and uniaxial tensile experiments. Results indicate that the time and temperature dependences of these fibres decrease drastically under the influence of a statically applied stress or strain. These results are discussed in an attempt to relate the deformation behaviour of high-strength PVA fibres to events occurring on a molecular scale

Continuous-glass-fibre-reinforced polypropylene composites. 1. Influence of maleic-anhydride-modified polypropylene on mechanical properties

This study investigates the influence of maleic-anhydride-modified polypropylene (m-PP) on monotonic mechanical properties of continuous-glass-fibre-reinforced polypropylene (PP) composites. Maleic-anhydride-modified polypropylene was added to the PP homopolymer to improve the adhesion between the matrix and the glass fibre. Three-point bending tests were performed on 0Ý and 90Ý unidirectional glass-fibre/PP laminates with various weight fractions of m-PP in the PP matrix. These tests showed an increase in both longitudinal and transverse flexural strength up to 10 wt% m-PP, whereas at higher weight fractions of m-PP a decrease in flexural strength was observed. No significant influence of m-PP on composite stiffness was observed. Additional mechanical tests on unidirectional glass/PP composites with 0 wt% and 10 wt% m-PP showed only a small increase in fibre-dominated properties such as longitudinal tensile strength and strain, whereas composite properties that are governed by the interphase, such as transverse, shear and compressive strength, showed significant increases as a result of matrix modification and an enhanced interaction between the glass fibres and the PP matri

Mechanical properties of natural-fibre-mat-reinforced thermoplastics based on flax fibres and polypropylene.

Thermoplastic composites based on flax fibres and a polypropylene (PP) matrix were manufactured using (i) a film-stacking method based on random fibre mats and (ii) a paper making process based on chopped fibres. The influence of fibre length and fibre content on stiffness, strength and impact strength of these so-called natural-fibre-mat-reinforced thermoplastics (NMTs) is reported and compared with data for glass-mat-reinforced thermoplastics (GMTs), including the influence of the use of maleic-anhydride grafted PP for improved interfacial adhesion. In addition some preliminary data on the influence of fibre diameter on composite stiffness and strength is reported. The data is compared with the existing micro-mechanical models for strength and stiffness. A good agreement was found between theory and experiment in case of stiffness whereas in the case of strength the experimental values fall well below the theoretical predictions. Results indicated that NMTs are of interest for low-cost engineering applications and can compete with commercial GMTs when a high stiffness per unit weight is desirable. Results also indicated that future research towards significant improvements in tensile and impact strength of these types of composites should focus on the optimisation of fibre strength rather than interfacial bond strength

High strength and high modulus electrospun nanofibers

\u3cp\u3eElectrospinning is a rapidly growing polymer processing technology as it provides a viable and simple method to create ultra-fine continuous fibers. This paper presents an in-depth review of the mechanical properties of electrospun fibers and particularly focuses on methodologies to generate high strength and high modulus nanofibers. As such, it aims to provide some guidance to future research activities in the area of high performance electrospun fibers.\u3c/p\u3