Abstract
Studies of deformation behaviour of short fibre reinforced thermoplastics are complicated by the facts that usually a wide range of fibre lengths are present in moulded test pieces and that the fibres are not systematically oriented with respect to any test direction. An equation has been derived for the stress/strain curve of such a material. This has been used to determine fibre/matrix bond strengths in two glass/nylon 6.6 and two glass/polypropylene composites from measured stress/strain curves and fibre length distributions.
It is concluded that major improvements in the properties of these materials will only be achieved by modifying processing to retain longer fibres.
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Abbreviations
- E c :
-
Modulus of composite
- E f :
-
Modulus of fibre
- E m :
-
Modulus of matrix
- V f :
-
Volume fraction of fibre
- σ c :
-
Stress in the composite
- σ f :
-
Peak stress in a fibre
- \(\bar \sigma _f\) :
-
Average stress in a fibre
- σ uf :
-
Ultimate strength of fibres
- σ m′:
-
Stress in matrix at fibre failure strain
- σ uc :
-
Ultimate strength of the composite
- ∈ c :
-
Strain in composite
- ∈ uc :
-
Ultimate strain of the composite
- τ :
-
Shear strength of the fibre matrix bond
- L :
-
Fibre length
- L ɛ :
-
Critical fibre length at a composite strain e
- L c :
-
Critical fibre length for fibre failure
- r :
-
Fibre radius
References
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H. L. Cox, Brit. J. Appl. Phys. 3 (1952) 72.
A. Kelly and W. R. Tyson, J. Mech. Phys. Solids 13 (1965) 329.
V. R. Riley and J. L. Reddaway, J. Mater. Sci. 3 (1968) 41.
P. Hancock and R. C. Cuthbertson, ibid 5 (1970)762.
J. H. Davis, private communication.
Brit. Pat. No. 950656.
A. H. Cottrell, “The mechanical properties of Matter” (Wiley, New York, 1964).
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Bowyer, W.H., Bader, M.G. On the re-inforcement of thermoplastics by imperfectly aligned discontinuous fibres. J Mater Sci 7, 1315–1321 (1972). https://doi.org/10.1007/BF00550698
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DOI: https://doi.org/10.1007/BF00550698