IMPACT PROPERTIES OF SISAL-GLASS HYBRID LAMINATES

Work of fracture (WOF) of unidirectionally aligned sisal-glass hybrid laminates, especially glass core - sisal shell (SGS) laminates, have been studied using flat charpy test. Keeping the volume fraction of sisal at about 0.4, the WOF of SGS laminates linearly increased from 80.2 to 228 kJm-2 by varying the volume fraction of glass at the core (V(g) core) from 0 to 0.2. However, further enhancement in WOF has been observed when the glass core is shifted from the midline towards the tensile side of the laminate with respect to impact. The specific work of fracture (165 kJm-2) of SGS laminate at V(g) core 0.2 is identical to that of glass-reinforced polyester composites containing 0.6 volume fraction of glass. Addition of glass facings to SGS laminates increased its WOF by 20 to 30 kJm-2 when the volume fraction of glass in the facings (V(g) facings) was about 0.04. The increase in resistance to compressive yielding that occurs by placing glass facings above a critical size (V(g) facings congruent-to 0.04 in the present case) adversely affected the WOF of SGS hybrid laminates.