MORPHOLOGY ANALYSIS OF MICROVOIDS IN SMC - AGING EFFECTS

A quantitative morphological analysis of the porosity in sheet mouldin g compound (SMC) has been made by using image processing, especially f or the microvoids resulting from shrinkage compensation. The first res ult is that, for the virgin SMC, the microporosity is 5-8% in the exte rnal skin of the part and similar to 24% in its core. After hydrotherm al ageing the microvoids in the core are partially closed again, the t otal microporosity being reduced to similar to 5%. In the skin, the mi croporosity remains unaffected. Moreover, the size distribution is mod ified, as the largest microvoids are subdivided into smaller ones. In addition, the morphology of the microvoids has been studied through th eir fractal behaviour. The characteristic fractal dimension of their c omplex shape for the virgin material (D = 1.35) becomes Euclidean (D = 1) after ageing. Ageing for 6 and 2570 h and drying indicate the morp hology changes to be only partly reversible. In summary, swelling due to water occurs internally, and the irregular shape of the microvoids is smoothed. (C) 1998 published by Elsevier Science Ltd. All rights re served.