A more subtle feature of the two cure cycles is shown in this figure, which displays the extent of cure at the surface and centerline for the two cure protocols.
		- Onset of gelation is expected to occur at a degree of conversion of 0.3- denoted by the horizontal line in the figure. - Recall that at gelation, the resin tends to become more rigid. - Notice that for the 65-degree cure, the extent of cure at the surface exceeds the gelation conversion of 0.3 prior to the centerline. In contrast, the centerline conversion of the 55-degree cure exceeds the gelation conversion prior to the surface. - The behavior of the progression of the cure fronts indicates that the 65-degree cure is progressing as an "outside-to-inside" cure; consequently, residual stresses may develop. - In contrast, the 55-degree cure follows an "inside-to-outside" cure, thereby reducing residual stress.