Effect of quenching and annealing on fiber pull-out from crystalline polymer matrices

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Abstract
A single fiber pull-out test using a specimen suitable for optical microscopic observation of thermoplastic polymer matrices has been developed. By applying this test method, the effects of quenching and annealing on the pull-out of carbon fiber (CF) from polycarbonate (PC), poly(phenylene sulfide) (PPS), poly(ether ether ketone) (PEEK) and polypropylene (PP) matrices were investigated. Studies of pull-out specimens before and after the pull-out test were also performed using an optical microscope with crossed polaroids. With the CF-PC system, rapid quenching developed a localized birefringent region spreading to a wider area in the polymeric material of the fiber exit points of the matrix, and decreased the fiber pull-out resistance. With the CF-PPS and CF-PEEK systems, annealing developed the transcrystal of polymer matrix along the fiber surface, and significantly increased the fiber pull-out resistance. The fiber pull-out from the annealed PPS and PEEK matrices occurred as the result of adhesive failure in the matrix. With the CF-PP system, the fiber pull-out resistance decreased with increasing crystallinity of matrix. This extraordinary behavior is discussed in relation to the fast crystallization of PP and the specific configuration of the pull-out specimen.