HYBRID EFFECTS ON MECHANICAL-PROPERTIES OF POLYOXYMETHYLENE

The present study investigated fracture and various mechanical propert ies of polyoxymethylene (POM) hybrids in tension and in flexure. The h ybrids examined consisted of short glass fibers (GF) and spherical gla ss beads (GB). Comparisons are made between experimentally observed va lues and predictions based on the rule-of-hybrid mixtures for hybrid s trength, modulus, Impact strength, fracture tough ness, and strain ene rgy release rates. Results indicated that tensile strength, flexural m odulus, and fracture toughness of POM/GB/GF hybrid composites can be e stimated from the following rule-of-hybrid mixtures P-H = P-POM/GF chi POM/GF + P-POM/GB chi POM/GB where P-POM/GB and P-POM/GF are the meas ured properties of the POM/GB and POM/GF composites, and chi(POM/GB) a nd chi(POM/GF) are the hybrid ratio (by volume) of the glass bead and that of glass fiber, respectively. In view of this, none of the aforem entioned properties show any signs of a hybrid effect. Flexural streng ths, impact strengths, and strain energy release rate ail showed the e xistence of a negative hybrid effect where negative deviation from the rule-of-mixtures behavior was observed. The latter was closer to the estimation based on the inverse rule-of mixtures.