Effect of lay-up sequences on mechanical properties and fracture behavior of CFRP laminate composites

A long carbon fiber with 3.5 GPa in average tensile strength-reinforced epo xy plastic (CFRP) laminates has been studied to determine the effect of the lay-up sequences on the mechanical properties and fracture behavior of the advanced carbon fiber-reinforced plastics (CFRP) composite. The mechanical properties were evaluated by tensile, slow bend and instrumented Charpy im pact tests. Specimens with angles of 0 degrees, 45 degrees and 90 degrees b etween the fibers of the 0 degrees layers and the longitudinal direction of the specimen ((0 degrees), (45 degrees) and (90 degrees) specimens) were u sed. The unidirectional laminate (0 degrees /0 degrees ply-(0 degrees)) spe cimen exhibited high slow bend and Charpy impact fracture energy values as well as high strength, but they had a remarkable anisotropy for the mechani cal properties. The orthotropic laminates (0 degrees /90 degrees plies) had improved anisotropy for the properties compared with the 0 degrees /0 degr ees ply-(0 degrees) specimen. However, the tensile fracture stress of the 0 degrees /90 degrees ply-(0 degrees) and (90 degrees) specimens were about one-half that of the 0 degrees /0 degrees ply-(0 degrees) specimen and thei r slow bend and Charpy impact energies were about one-third those of the 0 degrees /0 degrees ply-(0 degrees) specimen. Although the tensile fracture stress of the 0 degrees /90 degrees ply-(45") specimen significantly decrea sed, its slow bend and Charpy impact energies drastically increased. There was a significant benefit in the mechanical isotropy for the quasi-isotropi c laminates (0 degrees /90 degrees/+/- 45 degrees plies). However, their me chanical properties were about 40% of that of the 0 degrees /0 degrees ply- (0 degrees) specimen. These results are described and discussed. (C) 2000 E lsevier Science Inc. All rights reserved.