The present study intends to study the ratcheting response of nylon fiber reinforced
natural rubber (NR)‐styrene butadiene rubber (SBR) composite samples
under asymmetric stress cycles. Uniaxial tests conducted on composite samples
have shown how influential the weight fraction of short nylon fibers on the
stress‐strain curves/loops under monotonic and cyclic loads is. NR/SBR composite
samples with various fiber contents of 0, 10, 20, 30, and 40 per hundred rubber
(phr) were tested under asymmetric stress cycles. In these tests, stress‐strain hysteresis
loops were progressively shifted over stress cycles resulting in progressive
plastic strain accumulation. Over stress cycles, ratcheting strain progressed
within the first few cycles with a relatively high rate, and as the number of cycles
increased, this rate decayed resulting in a plateau in strain accumulation (shakedown).
The ratcheting strain rate and magnitude resulting in shakedown were
highly affected by the nylon fiber content. The experimental observations
showed that this plateau (shakedown) occurred after a number of cycles in
NR/SBR composite samples where the widths of hysteresis loops stayed
unchanged. Samples with no fiber and that with 10 phr fiber content possessed
high ratcheting rates leading samples to failure after a few stress cycles. Fracture
surfaces in these samples were further analyzed through SEM investigation.