Analysis Of Vacuum Failures During Curing Of Cfrp Composites.

ABSTRACT Carbon fiber reinforced Composite structures posses high strength and stiffness to weight ratios also exhibits good fatigue resistance and are less prone to deterioration caused by corrosion and cracking. Fabrication of these composite structures is highly process dependent. During curing process the physical mechanical and chemical properties are imparted to the components and are generally cured in autoclaves under controlled temperature pressure and vacuum. Any variation in these parameters leads to change in properties of a composite structure hence there is a need to analyse the effects of vacuum failures at during curing on mechanical and Ultrasonic Characteristics. Efforts are also made to analyze the root causes for the vacuum failures during curing process. Laminates made of Hexcel 913 carbon epoxy prepeg are prepared and cured in the autoclave by varying the vacuum levels at different salient points of cure process during curing. The specimens were prepared as per the DIN 29971 standards to evaluate the DT and NDT characteristics. The Experimental results shows that ILSS will not vary much if the vacuum fails after Tg Glass Transition point hence the vacuum can be maintained up to the Tg point and thereby it can be slowly reduced to zero. This shows that there is a scope to optimize the manufacturers recommended cure cycle so as to reduce the curing cost and time. This research work helps the designers in developing the tools and optimum cure cycles for carbon epoxy composite structures.