Development of a Control Strategy for Monitoring the Delaminating Damage in Drilling Of Carbon Composite Laminates

Composite materials have attractive features, such as high strength to weight ratio and high stiffness to weight ratio. However, they are easily damaged during machining operations. A typical damage is delamination, which can occur when fiber reinforced composite laminates are drilled. Control of delamination is critical for the utilization of composite materials. This research seeks to develop a technique to control inter-ply delaminations during the drilling of laminated composites. A statistical factorial design technique is used to develop a model that relates the feed rate, cutting speed, and tool size to the acoustic parameters. A control algorithm is built from the model. The algorithm is used to modify the instantaneous feed rate in order to maintain the acoustic energy below a threshold value. This control strategy is effective in limiting the area of delamination. However, using high cutting speeds avoid the delamination of materials, but leads to high production costs due to excessive tool wear.Keywords: Composite Laminates, Drilling, Damage, Acoustic Emission

Vehicle regulations in Africa: Impact on used vehicle import and new vehicle sales

Mortality rates from outdoor air pollution in African have increased by 57% over three decades. Studies have shown that pollution from motor vehicles are a major cause. But at least 85% of Africa’s vehicle fleet are used vehicles, some of which are obsolete with outdated technologies. This paper examines the present and future vehicle regulations in various countries in Africa and their effect in curbing used vehicle import, new vehicle sales, and production. The investigation includes providing detailed data for used vehicle import into Africa from 2015 to 2019. The findings show that used vehicle imports continue to increase in countries like Nigeria and Libya. Where present, vehicle standards have neither translated to the increase in purchase nor production of new vehicles anywhere in Africa. The age restriction and ban on used vehicles has not led to an increase in new vehicle sales as many policymakers had hoped for. Growth of used vehicles dropped by 8.6% and new vehicles by 6%. The research discovered that though zero-rated new vehicles equipped with obsolete technology are sold in Africa, the policies have broadly overlooked their impact. Further recommendations have been made on the unified vehicle standards for Africa to adopt