Polymer fibres concept

The concept of a maximum shear strain is supported by the experimental relationship for the lifetime of a polymer fibre. For many polymer fibres the observed lifetime or the time to failure fb is given by... 

The exploitation of the inherent stiffness of polymer molecules to create strong and stiff polymer fibres or tapes has been in commercial practice for the past few decades. However, the commercial-scale application of these fibres and tapes as reinforcements in self-reinforced polymer composites is relatively new. After initial conception in the mid 1970s, numerous groups have investigated methods for scaling these concepts up into commercial products. With embodiments of these ideas now slowly appearing in the marketplace, further stimulation in process development as well as a move towards higher performance polymer systems is sure to follow. 

The concept of polymer reinforcement by monomolecular fibres is already old but many studies date from the last decade. The interest is particularly the very high aspect ratios and the levels of reinforcement with expected mechanical properties as high as ... 

From what has been stated above it is clear that there is a similarity in concepts over a considerable range of scale as between, on the one hand real crystals where the elements are atoms, through ordered phase materials such as copolymers, where the elements are amorphous but in a crystalline lattice, to macro-crystalline materials such as composites. Since a great deal of work has been done in recent years on the properties of composites, in particular fibre composites, it is worth examing the generality of the results obtained particularly in the respect of molecular composites such as semicrystalline polymers and copolymers. 

Commercially available non-oxide ceramic reinforcements are in three categories continuous, discontinuous, and whiskers. The great breakthrough in the ceramic fibre area has been the concept of pyrolysing polymers under controlled conditions, containing the desired species to produce high-temperature ceramic fibres. Silicon carbide fibre is a major development in the field of ceramic reinforcements. 

The concept Tie molecules" was introduced by Peterlin (1973), see Chap. 2. Tie molecules are part of chains or bundles of chains extending from one crystallite (or plate or lamella) to another in fibres they even constitute the core of the stretched filament. They concentrate and distribute stresses throughout the material and are therefore particularly important for the mechanical properties of semi-crystalline polymers. Small amounts of taut tie molecules may give a tremendous increase in strength and a decrease in brittleness of polymeric materials. 

Recently, much attention is being placed on fibres-reinforced/polymer systems as subjects of study. It was caused by increasing emphasis on high performance reinforced polymer composites. The concept of acid/base interactions across the fibre/polymer interface was noted particularly and the relevance of acid/base theories to the behaviour of po-... 

Two concepts from fibre-reinforcement theory are of general use in polymer mechanics. The first is the effect of inclusion shape on the anisotropic elastic moduli of a composite. Two rules control the effects of fibre reinforcement ... 

S.S. Selke and J. Childress in Wood-Fibre/Polymer Composites Fundamental Concepts, Processes and Material Options, Ed., M.P. Wolcott, Forest Products Research Society, Madison, WI, USA, Report No.l09, 1993. 

The patterns identified and measured within actual morphologies of many polymers do not readily conform to pre-existing conceptions based on extrapolation from optical observations. The key concept is that of the fibre, supposed to be generally a group of elongated lamellae with, in one theory, a cross-sectional dimension of order the characteristic length 6 = DIG where D is the diffusion coefficient... 

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