In-situ damage sensing in intra-ply glass/carbon laminate composites under interlaminar shear loading

An experimental study is preformed to investigate the in-situ damage sensing capabilities of intra-ply hybrid carbon/glass laminate and epoxy composites under quasi-static interlaminar shear loading. A three-dimensional electrical sensory network is generated inside the composites through embedded carbon nanotubes (CNTs) in an epoxy matrix along with the carbon fibers in the intra-ply hybrid laminates. CNTs are dispersed in the epoxy matrix using a combination of ultrasonication and shear mixing techniques. Four circumferential ring probes are used to examine the electrical response under interlaminar shear load. The effect of four different intra-ply orientations (((0–90)_C, where carbon fibers are oriented along the loading direction), ((0–90)_G, where glass fibers are oriented along the loading direction), ((45/−45, where glass and carbon fibers are oriented at 45^o/−45^o and the laminates are repeated), and ((45/−45)_A, where glass and carbon fibers are oriented at 45^o/−45^o and the laminates are alternated)) on the shear constitutive behavior and the damage detection are discussed. Intra-ply orientations of (45/−45) and (45/−45)_A showed higher interlaminar shear strength and shear strain at break compared to (0/90)_C and (0/90)_G orientations. Out of all four orientations, (45/−45)_A provided a better resolution of electrical response for damage sensing applications.