NONLINEAR MICROMECHANICAL MODELING OF HYGROTHERMAL EFFECTS ON STRUCTURAL BIOBASED COMPOSITE MATERIALS

Summary

Biobased composite materials fabricated from bacterial poly(β-hydroxybutyrate)-co-poly(β-hydroxyvalerate) (PHBV) resins reinforced with natural oak wood flour are being investigated as viable replacements to traditional, ecologically insensitive construction materials. The material properties achievable by these composites, which biodegrade anaerobically under specific conditions, are comparable to that of dimensional lumber; however, natural fiber composites remain particularly susceptible to hygrothermal degradation of the fiber–matrix interface because of the incongruent hydrophobicity of the biopolymer and the hydrophilicity of the cellulosic fibers.

A temperature-driven Fickian sorption-diffusion model is being employed to characterize the transient moisture absorption behavior of the wood flour composites. Constitutive models are being developed to incorporate volumetric swelling and fiber-matrix interfacial degradation due to moisture uptake. Simple, nonlinear micromechanical models using assumptions of isotropy can be employed to predict short-fiber composite stiffness and strength under combined environmental and mechanical loads. Preliminary experimental tests are being conducted to calibrate such models and to validate finite element simulations for combined mechanosorptive composite behavior.