PLA/Lignocellulosic Fiber Composites: Particle Characteristics, Interfacial Adhesion, and Failure Mechanism

Poly(lactic acid) (PLA) composites were prepared using six lignocellulosic fibers with widely varying particle characteristics. The composites were characterized by tensile testing, scanning electron (SEM), and polarization optical microscopy (POM). Micromechanical deformation processes during loading were followed by acoustic emission measurements. Interfacial adhesion was estimated by three independent methods. Contrary to most claims published in the literature, interfacial adhesion between PLA and natural fibers was found to be rather strong, a result confirmed by the quantitative estimation of adhesion strength, acoustic emission measurements, and SEM study. Strong interfacial adhesion results in weak dependence of the extent of reinforcement on the particle characteristics of the reinforcing fibers. Both acoustic emission measurements and microscopy indicated that the dominating micromechanical deformation process is the fracture of the fibers and close correlation was found between the initiation stress of fiber fracture, reinforcement, and the ultimate strength of the composites. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39902.