Comparative dispersion degree and self-sensing of carbon nanotube (CNT)-phenol composites by electrical resistance measurements

Abstract

Self-sensing was investigated for single-carbon fiber/phenol and carbon nanotube (CNT)-phenol composites by electro-micromechanical technique. Comparative dispersion degree of CNTphenol solution was indirectly correlated with the uniform conductivity in solid CNT-phenol composites by measuring the electrical resistivity. In addition to tensile test, compressive strengths of neat phenol and CNT-phenol composites were measured using Broutman specimen. Buckling and kicking fiber breaks in neat phenol were observed due to the transversal tensile stress, which were correlated to compressive interfacial shear strength (IFSS). The contact resistivity between single-carbon fiber and CNT-phenol composite was measured by both twoand four-point methods using a gradient specimen. Dynamic contact angle by Wilhelmy plate technique of CNT-phenol composites were measured to obtain surface energy and work of adhesion, Wa between singe-carbon fiber and CNT-phenol surface. The IFSS result obtained from microdroplet test was consistent with thermodynamic work of adhesion. Since heterogeneous domains are formed at CNT-phenol surface, the advancing contact angle exhibited the hydrophobicity. CNT-phenol composite also exhibited a higher apparent modulus than neat phenol due to better stress transferring effect. The IFSS between single-carbon fiber and CNT-phenol increased than neat phenol case due to the added CNT. Micro-failure patterns of CNT-phenol composite under tensile and compressive loads were also evaluated by acoustic emission (AE).