No abstract

Carbon fiber reinforced cyclic butylene terephthalate composites have been processed by vacuum infusion under two different non-isothermal processing routes starting from a one-component cyclic butylene terephthalate resin system. One of them was processed under a short cycle with fast cooling, and another one was processed under a long cycle with slow cooling. Both the micro-structure and low-energy impact properties of the composites have been investigated. On one hand, the fast cooling generates randomly dispersed voids and porosities in the resin-rich regions during the crystallization-induced shrinkage. On the other hand, the slow cooling generates a highly crystalline and brittle matrix without porosity. However, many micro-cracks appear in the resin-rich regions due to the combination of the brittleness and longitudinal shrinkage of the matrix. The critical delamination energy of the slow cooled composite is slightly higher than that of the fast cooled one, whereas this latter absorbs over 25% more energy before being penetrated, as well as performing in a less brittle way. The lower interlaminar shear strength of the fast cooled composite is suggested to be the origin of its higher energy absorbing capability and less brittle behavior.

Carbon fiber reinforced epoxy composites were successfully manufactured by a new compression resin transfer molding process. The main innovation is that the injection stage is vacuum assisted. The high fiber volume fraction and low void content are promising properties for structural applications. The samples were tested under instrumented falling weight impact loading. Based on the contact time and delamination plots, the damage initiation energy threshold has been found to be 1.42 J, and from the energy plot a 30.25 J penetration energy threshold is deduced. Damage propagation is more energy dissipative process than the initiation one, since the ductility index takes a value of 1.97.