SHORT FIBER-ELASTOMER COMPOSITES (3) THE MECHAICAL PROPERTIES OF SHORT FIBER-RUBBER COMPOSITES WITH VARIOUS RUBBERS

Abstract

The mechanical properties and swelling anisotropy of short fiber-elastomer composites were examined using two kinds of fibers; PET and carbon fiber, and matrix elastomers; EPDM, urethan rubber (UR), and CR. Those properties were affected by orientation of fibers, adhesion between fibers and matrix, and type of matrix.
Although PET fibers retained their original length after mixing, carbon fibers were broken to pieces of 150μm in length during mixing. Those fibers oriented unidirectionally in matrix rubber for the composites containing less than 10vol.% fibers. For non-polar EPDM with RFL-untreated PET fibers, the yield stress was the half of that of polar CR. In the case of RFL-treated fibers, the tensile stress of the composite increased almost linearlly till fracture with increasing strain. When the tensile stress of untreated PET-UR composite increased gradually, avoid was formed at the end of fiber and elongated longer with increasing strain. The tensile stress of PET-UR composite was increased a little by isocyanate treatment on PET surface. In the transeverse direction of fibers, the tensile stress of these cmposites with untreated PET gave the same values as that of matrix after breaking the adhesion between fibers and matrix. For carbon fiber-elastomer composite, the tensile stress and young's modulus in the longitudinal direction of fibers were much smaller than that of the composites with PET fibers. In the transeverse direction, the composite was not reinforced by carbon fibers because the interaction between carbon fibers and matrix were very weak.