No abstract

A geometrical model generator for biological products is presented, which uses X-ray computed tomography images of quasi-axisymmetric biological products as input. It was tested with a dataset of 73 scanned Braeburn apples. For each sample, the generator constructed different cross sections. From these sections, contours were extracted and selected. The contours were expressed as a series of shape descriptors. For this purpose, elliptical Fourier descriptors were used. The obtained frequency distributions were transformed to standard normal distributions. On these transformed distributions, the covariance decomposition algorithm was applied. This algorithm generated new sets of descriptors, which opened up a large range of possibilities for generation of representative shape contours. After reverse transformation of the (generated) descriptor distributions, new contours were obtained from the new descriptors. These new contours were converted to 3D geometrical models of biological products by interpolation and revolving. By comparing the volumes of the generated models with those of the scanned fruit, it was shown that the resulting geometrical models have the same variability as the biological variability in the original dataset. This generator is a fast method, which requires minimal user intervention, and creates 3D models including the biological variability as observed in the scanned fruit. Because these 3D geometrical models are directly available as CAD models, they are useful for numerical modelling of transport phenomena in and around biological products.

Epoxidation of high-linolenic perilla oil was carried out in the presence of solid acidic ion-exchange resin at varying reaction temperatures for 8 h. A pseudo two-phase kinetic model that captures the differences in reactivity of double bonds at various positions in the fatty acid of a triglyceride molecule during both epoxy formation and cleavage was developed. The proposed model is based on the Langmuir-Hinshelwood-Hougen-Watson (L-H-H-W) postulates and considers the adsorption of formic acid on the catalyst as the rate-determining step. To estimate the kinetic rate constants of various reactions, genetic algorithm was used to fit experimentally obtained iodine and epoxy values of epoxidized perilla oil. A re-parametrized form of Arrhenius equation was used in the proposed model to facilitate the precise estimation of parameters with least computational effort. The obtainment of the least error between experimentally determined and theoretically predicted iodine and epoxy values indicates the robustness of the proposed model.

This paper first describes a curing process model comprised of the coupled cure-kinetics and thermal evolution in a cationic polymerization of a single layer of material and then extends it to multi-mode curing of multiple layers. The model is characterized as a switching multi-mode dynamic system that switches when the UV source is turned off and when a new layer is added to the existing layer. These two switching conditions are explicitly defined. The model is then used to determine the optimal mode switching times and the final process time which are considered as manipulated control variables. This is done by explicitly deriving the necessary conditions of optimality for the multi-mode switching system. The results are first illustrated for a two-layer composite laminate and then the results of five-layer curing are briefly discussed to show the versatility of the proposed approach. The optimal switching times and final time result in minimal cure level deviation across the thick composite material.

In this paper, we set to examine the inter-laminar shear strength of a fiber-reinforced composite part manufactured via a stepped-concurrent ultraviolet curing and layering process. This process was specifically proposed for making epoxy-based thick parts, whereby a layer-by-layer, model-based, optimal layering time and ultraviolet control scheme is set up with the objective of minimizing the degree of cure deviation across the final thick part. We focus on a cationic curing process wherein additional energy savings are possible by switching off the ultraviolet source after initiating the curing reaction with the ultraviolet source at each layer addition. Since the inter-laminar sheer strength of parts made via a layering process is often a concern, we consider the application of in-situ consolidation pressure in the layering process. We then characterize the inter-laminar shear strength by manufacturing samples with application of different in-situ consolidation pressures and measuring the inter-laminar shear strength of each sample by the short-beam shear test. The results showed that the inter-laminar shear strength of composite parts fabricated with the proposed stepped-concurrent curing, and layering process increases with the applied consolidation pressure up to a point. Scanning electron microscopy of samples cured at different in-situ consolidation pressure showed that the sample with optimum consolidation pressure has relatively uniform fiber to resin distribution and hence improved inter-laminar shear strength.