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A Study of the Pull‐Out Performance of PPTA Fibres in Composites of Ethylene‐Type Ionomer Matrices/PPTA Fibres
Author(s) -
Sadiku Emmanuel R.,
Sanderson Ronald D.
Publication year - 2001
Publication title -
macromolecular materials and engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.913
H-Index - 96
eISSN - 1439-2054
pISSN - 1438-7492
DOI - 10.1002/1439-2054(20010901)286:9<535::aid-mame535>3.0.co;2-3
Subject(s) - materials science , composite material , kevlar , composite number , ultimate tensile strength , shear (geology) , delamination (geology) , shear stress , stress (linguistics) , adhesion , paleontology , biology , subduction , tectonics , linguistics , philosophy
The mean frictional shear stresses of six ionomer resins and sized Kevlar fibre were determined from fibre pull‐out tests. A study of the failure mechanisms occurring during pull‐out revealed that fibre delamination and fibre resin adhesion were factors which increased the measured frictional shear stresses and that there was a definite grouping of high and low frictional shear stress values. The low frictional shear stress values were used to calculate the mean frictional shear stress values, τ B , because these were uncomplicated by fibre delamination and fibre resin adhesion, since these factors (delamination and adhesion) are certainly not unexpected in an ionomer/Kevlar composite. From these shear stress values, it was determined that critical fibre lengths should be between 35 and 72 mm for the high tensile strength Kevlar fibres within an ionomer matrix, for the composite to be used effectively. The ratio of the debonding force ( F B ) to the frictional shear force ( F F ), θ , did not vary significantly with the lengths of the embedded reinforcing fibres. Both debonding and frictional forces indicate increasing trends with the interfacial contact areas. The ratio of the interfacial bonding strength ( τ B ) to the frictional shear stress ( τ F ), ϕ , for the resin PEA‐6 compared to the surface modified poly( p ‐phenylene terephthalamide) (PPTA) fibre ranged from 2 to 24. These ratios were grouped into two, viz: those where ϕ > 11 and those with ϕ < 7. Using only the τ F where ϕ > 11 provided a mean frictional shear stress of 0.94 MPa and a standard deviation, s , of 0.23 MPa (the number of test samples, n , was 9). This value is little different from the frictional shear stresses measured for sized PPTA (0.84 MPa). The decrease in the values of ϕ is attributed to the decrease in τ B , due to the surface modification reaction, without necessarily affecting the frictional shear stress, τ F .