Preparation and Studying of Toughness and Fracture Characteristics for Fibrous Composites
Mays Sabah Mahdi
Abstract

Binary polymer blend was prepared by the mechanical mixing of epoxy resin (EP) with polycarbonate (PC) in different weight ratios of (0, 5, 10, 15 and 20%) of PC. Charpy impact test was carried out on these blends to determine the values of impact strength (I.S). It was found that the blend of the ratio of (20wt.%) of PC has the highest (I.S) compared with other ratios. For this reason, this percentage of mixing was selected to fabricate the composite material. Hand lay-up method was utilized to prepare the (single and hybrid) laminate composites with fiber volume fraction of (Ф=15%). Glass and Kevlar fibers were used to reinforce the epoxy and its blend with different sequences of skin and core layers of the composite where Kevlar fibers (K.F) used as skin layers and glass fibers (G.F) as core layers in the first hybrid composite and the opposite arrangement is right of the second hybrid composite. The values of Young's modulus (E), impact characteristics (I.S, Gc, Kc) and hardness were determined for these composites. It is found that the values of (E) and hardness decrease while the values of material toughness (Gc) increase with increasing the blending ratio of the polymer blend. It can also be noticed that the composites reinforced with Kevlar fibers (EP+K.F and blend+K.F) record the highest values of (Gc) compared with other composites. The fracture surfaces morphology of impact test samples of the blend and its composites have been examined using optical microscope. From differential scanning calorimetry (DSC) test, it is found that the sample (EP + G/K/G) gives the highest value of Tg which equal to (240°C). It is obtained that the sample (EP+K/G/K) gives the highest value of ultimate tensile strength (UTS) while the sample (EP+G.F) gives the highest value of compressive strength (C.S).