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Journal of Materials Science

, Volume 30, Issue 7, pp 1894–1901 | Cite as

Compressive strength of coated rigid-rod polymer fibres

  • U. Santhosh
  • K. E. Newman
  • C. Y. C. Lee
Papers

Abstract

One limitation to the use of high-strength/high-modulus rigid-rod polymer fibres like poly-(p-phenylene benzobisthiazole) (PBZT) and poly-(p-phenylene benzobisoxazole) (PBZO) in composite structures is their low compressive strength. Various theories have been developed to predict compressive strength of rigid-rod fibres. In this study the critical buckling stress for rigid-rod fibres with stiff external coatings has been theoretically modelled assuming that the failure mode in compression is the microbuckling of the fibrils in shear. Our model predicts that significant improvement in fibre compressive strength will occur only when relatively thick coatings, with thickness to diameter (t/D) ratios in excess of > 0.05, are used. Experimentally measured compressive strength of aluminium coated PBZT fibres shows values in good agreement to the theory at t/D ratios of 0.006 and below. Factors related to the selection of suitable coating materials and problems associated with establishing coating performance are identified.

Keywords

Polymer Aluminium Compressive Strength Fibril Failure Mode 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Nomenclature

P

axial compressive load

Pf

axial compressive load on the fibre

Pc

axial compressive load on the coating

Pcri

critical buckling load in the ith case

σcr

critical buckling stress

σco

compressive strength of the uncoated fibre

σc

compressive strength of the coated fibre

v(x)

lateral deflection of a buckled fibril or coating

Vm

amplitude of the lateral deflection in the mth mode

m

number of half-sine waves in the deflection mode

x

coordinate distance along axial direction

y

coordinate distance along radial direction

θ

coordinate distance along circumferential direction

l

length of the buckling unit

N

number of fibrils in the fibre

D

fibre diameter

d

fibril diameter

t

coating thickness

If

moment of inertia of the fibril

Af

cross-sectional area of the fibril

Ef

tensile modulus of the fibre

Ec

tensile modulus of the coating material

E

tensile modulus of the coated fibre

G

torsional shear modulus of the fibre

vc

Poisson's ratio of the coating material

ρf

density of the fibre

ρc

density of the coating material

ρ

density of the coated fibre

ΔUf

strain-energy change in the fibre

ΔUc

strain-energy change in the coating

ΔTf

external work done on the fibre

ΔTc

external work done on the coating

ξ

d/D

η

t/D

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Copyright information

© Chapman & Hall 1995

Authors and Affiliations

  • U. Santhosh
    • 1
  • K. E. Newman
    • 2
  • C. Y. C. Lee
    • 3
  1. 1.AdTech Systems Research Inc.DaytonUSA
  2. 2.Central Research and DevelopmentE.I. DuPont De Nemours & Co. Inc.WilmingtonUSA
  3. 3.AFOSR/NC, Air Force Office of Scientific ResearchBolling Air Force BaseUSA

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