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UBC Theses and Dissertations

Effect of geometrical and process parameters on the quality of open moulded composite parts with sharp corners : a decision-based approach Torres, Juan David


The use of autoclaves and ovens in modern composite manufacturing processes has shown a potential to greatly control the geometry and structural properties of composite materials. The use of such manufacturing tools has been supported by numerical tools and optimization/statistical methods, in order to further improve the quality of composite products. However, the costs associated with these advanced manufacturing techniques are not always acceptable for all Fiber Reinforced Composite (FRC) manufacturers. In particular, for large products with low production rates (e.g., marine and automotive industries), open moulding are preferred as they typically offer the best compromise between the quality of the part and manufacturing production cost. The quality of open-moulded parts, however, is highly dependent on the skill of the operator, hence resulting in possible variations in part properties, particularly for geometrically complex parts. This variation often causes out-of-specification products, resulting in costly trial and error approaches to minimize the product defects. The purpose of this thesis was to study the FRC process conditions that have a statistically significant effect on the generation of defects in open-moulded parts with sharp corner (i.e., small radius) features. Samples with different geometrical, material and process parameters were manufactured. Defects such as void content, corner fiber bridging, fabric formability, fiber misalignment and bending resistance of the material were evaluated through different characterization techniques. The statistical analysis of the data has provided new means to determine the contribution of each parameter to the final quality of the composite part. The results suggest that the part radius and part thickness both have significant effects on the bending resistance of the FRC specimens. Also, it was observed that reinforcement orientation has a significant effect on the formability and surface defects around the part corners. Finally, a novel Multiple Criteria Decision Making (MCDM) approach has been developed using “signal to noise” ratios with subjective and objective weighting, in order to identify the optimum design parameters for both aesthetic and structural properties of the open moulded FRC parts with sharp corners.

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Attribution-NonCommercial-NoDerivs 2.5 Canada