Research PaperFrom lignocellulose to biocomposite: Multi-level modelling and experimental investigation of the thermal properties of kenaf fiber reinforced composites based on constituent materials

- The thermal conductivity of Individual kenaf fibers was measured.
- A multi-level constituent-based composite thermal conductivity model was developed.
- Effective thermal conductivity of a kenaf fiber reinforced composite was measured.

Natural fibers (such as kenaf) have garnered interest recently for use in composites because of their relatively high specific properties, low cost, and low environmental impact. Their thermal property information is limited, lacking experimental data on key properties such as thermal conductivity, specific heat, and CTE of the component fiber. This paper presents, for the first time, the thermal property data on kenaf fiber reinforced composites, and an approach to obtain the composite thermal properties based on constituent properties. Individual, plant-based fibers were measured independently and were then used to inform successful predictions of the effective thermal conductivity of the fiber reinforced composites. A unit cell model has been developed to predict the thermal properties of a planar, randomly oriented kenaf fiber-reinforced composite (near 22% volume fraction loading), which includes the effect of void content on the predicted thermal conductivity. A lower-level model is also developed for individual fiber thermal properties based on its constituents (lignin, cellulose, and hemicellulose). To validate this multi-level model, experimental measurements of the thermal diffusivity, coefficient of thermal expansion, and specific heat for the composite, the matrix, and the fibers were performed in the range from 30 °C to 160 °C, based on TMA, DSC, LFA, and transient electro-thermal (TET) techniques. Model results compare favorably with the experimental data, and are consistent with FEM modelling results based on fiber properties and fiber constituent materials (lignin, cellulose, and hemicellulose). This approach provides the basis for understanding component contribution to the fiber properties, as well as a technique to obtain fiber composite thermal property based on component properties. The composite thermal property data also fills an information gap and can be directly used in component design.

98