Micromechanical Simulations on Hygro-Mechanical Properties of Bio-fiber Plastic Composites
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1097-GG04-20
Micromechanical Simulations on Hygro-Mechanical Properties of Bio-fiber Plastic Composites Yibin Xue1, and Kunpeng Wang2 1 Mississippi State University, Starkville, MS, 39759 2 Dalian University of Technology, Dalian, China, People's Republic of Abstract The hygro-mechanical properties of bio-fiber composites comprise two aspects: the coupling between moisture diffusion and mechanical deformations and the coupling of moisture contents and the constitutive behaviors. Bio-fiber is hydrophilic, which absorbs water promptly when environmental moisture content increases; as the moisture content in the fiber increases, its mechanical properties decrease. This paper presents a series of micromechanical simulations to predict the hygro-mechanical behaviors of woodfiber-reinforced plastic composites considering the effects of fiber arrangements on the stress-strain relations and moisture-expansions on three progressively constructed constitutive configurations: 1) the fiber is elastic orthotropic and expandable under moisture variations; the plastic matrix is elastic isotropic and insensitive to environmental moisture variations, and the interface between fiber and matrix is perfectly bounded; 2) the plastic matrix is hyperelastic and expresses a certain degree of damage as deformation progresses; and 3) the interface has a pseudo adhesive layer that obeys Smith and Ferrante’s universal binding law implemented as a cohesive zone model in the micromechanical simulation. In configuration II, micromechanical simulations demonstrate significant reductions in the nominal elastic modulus of composites when a nonlinear elastic model for the polymer matrix is assumed. The prediction for stress-strain relationship is found to be comparable to the experimental measurements. A cohesive model in configuration III is introduced to evaluate the possible moisture degradation to the fiber-matrix interface, which results in a reduction in elastic modulus and failure strength of the composite s, as observed in experiments. The cohesive zone model parameters as a function of moisture content in the composites requires more attention in model correlation and guarantee more direct experimental observations. Keywords: Short fiber composite, fiber arrangement, moisture expansion, effective properties, micromechanical simulations, nonlinear behavior of matrix, imperfect interface 1. Introduction Bio-fiber-reinforced plastic composites have attracted attention from both academic and industrial fields, owing to the advantages of the bio-fibers against conventional reinforcement synthesis fibers (Nabi and Jog, 1999; Bledzki and Gassan, 1999). Nature fiber (NF)-reinforced plastic composites (NF-PCs) are low cost, low density, have high specific properties and increased durability, are low maintenance and recyclable, and offer ease of fabrication using traditional plastic and composite processing techniques, which have found many applications in civil structures and semi-structures (Rowell et al., 1998a, 1998b) as well as in automotive com
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