Surface and Sub-surface analysis of hybrid polymer composites during machining operations

The present work is carried out to investigate the delamination defects and surface roughness during drilling on newly developed biodegradable hybrid composite laminates. The natural hybrid composite consists of Natural vetiveria zizaniodes (vetiver) and synthetic glass are used as reinforcements in vinyl ester resin to form four composite specimens based on varying the fiber compositions in each specimen while the resin content is kept as a constant. The specimens are subjected to drilling operations during which machining parameters like speed, feed rate, tool point angle and work sample are varied between four levels to form 44 D-optimal factorial design. After 28 runs the delamination factor at the entrance and exit of hole and machined subsurface roughness are measured as responses. The responses are analyzed using response surface method and non-linear regression equations are developed. Optimization on the data resulted in selection of best level of speed, feed and tool angle for the selected samples. Confirmatory runs have been conducted and the responses are measured. Average error between the model and confirmatory run was found minimal and hence the optimization was found to be satisfactory. (C) 2014 Elsevier Ltd.