Fiber breakage/attrition

Another major factor effecting the performance of the biocomposites is the fiber attrition caused during processing. High shear rates experienced by lignocellulosic fibers during preprocessing as well as injection molding results in fiber twisting, bending, and breaking. All three modes of fiber damage reduces the effective fiber length of the lig- nocellulosic fibers available for load-bearing. Chaitanya and Singh (2016b) observed that long lignocellulosic fibers compared to short fibers are more prone to fiber attrition during processing. Also, the direct-injection molding process exhibits less fiber damage compared to the extrusion—injection molding process. To overcome these issues related to fiber—matrix—tooling interactions, some modifications in tool design are required. The nozzle diameter, sprue dimensions, gate dimensions, etc. should be increased to accommodate high lignocellulosic fiber reinforcement content. Modifying tool dimensions helps in reducing the shearing of fibers during processing.

Residual stresses

Residual stresses are generated within the developed biocomposites due to rapid solidification of the fiber—matrix mixture under high pressure. Residual stresses may result in warpage and stress cracking, resulting in permanent deformation of the product. However, these residual stresses can be kept under check by ensuring gradual and uniform cooling of the product in the mold. Proper mold design and careful selection of processing parameters like melt temperature and injection pressure can further help to reduce the residual stresses (Singh and Chaitanya, 2015).

 
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