Determination of in-plane elastic properties of rice husk composite

• In-plane mechanics of rice husk composite are analyzed in tensile and bending tests.
• The mechanics are modeled using a Mori–Tanaka model with orientation distribution.
• Results show that the composite responses can be captured with few limitations.

An approach to evaluate macroscopic elastic properties of rice husk composite from its morphology is demonstrated. Hard shells of rice husks were used as a low-cost reinforcing agent in thin polypropylene sheet. Composite samples containing 5–20% mass fractions of rice husks were formed by compression molding, and the orientation distributions of rice husks in the samples were evaluated from micrographs of the composite structure. Effective elastic properties of the composite were calculated from the Mori–Tanaka model that includes the effect of reinforcement orientation. The homogeneous Mori–Tanaka model was benchmarked against an equivalent composite model using explicit modeling of the reinforcements in a finite element simulation; good agreement between the in-plane moduli of the two models was confirmed. Predictive capabilities of the Mori–Tanaka model were demonstrated by matching the model responses to the composite response under uniaxial tensile tests and four-point bending tests. Predicted effective axial moduli compared favorably with the experimental values. However, discrepancy exists in the predicted flexural moduli due to the shortcoming of the Mori–Tanaka model in capturing the out-of-plane response. The comparisons show that the proposed approach is adaptable to predict the in-plane anisotropic elastic properties of compression-molded rice husk reinforced polypropylene composite.

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