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  • Influence of Cork Particle Incorporation on the Mechanical Behaviour of Glass Fibre Reinforced Polymer Laminates
    Publication . TAVARES, GABRIELA ISABEL GALIB; Magalhães, António Gonçalves
    This dissertation investigates the influence of cork particle incorporation on the mechanical behaviour and impact damage response of glass fibre-reinforced polymer laminates, assessing whether cork particles can improve low-velocity impact performance while identifying possible effects on static tensile properties. Composite laminates were manufactured using glass fibre reinforcement and polymer matrices, with cork particles incorporated at different contents. The manufacturing route comprised resin preparation, cork particle dispersion when applicable, manual impregnation and stacking of the glass fibre plies by hand lay-up, consolidation by manual compression between mould plates, and room-temperature curing under compression. The experimental programme included low-velocity impact tests, penetrant-enhanced radiographic inspection and tensile tests on selected configurations. The impact response was analysed through force, displacement and energy histories, while radiographic images were used to evaluate the apparent internal damage area after impact. Complementary laminate configurations were also considered to support the discussion of the influence of matrix system, reinforcement architecture and fibre orientation on the observed behaviour. The results showed that cork particle incorporation affected the impact response of the main laminate configurations. Compared with the cork-free reference, the cork-modified laminates generally reached higher maximum impact forces, increasing by approximately 37.7– 48.6%, and presented lower apparent radiographic damage areas, with reductions of approximately 47.1–78.4%. The most favourable response was obtained for the representative 5 wt.% cork configuration, which increased the maximum impact force from 1604.42 N to 2384.36 N and reduced the apparent radiographic damage area from 635.82 mm² to 137.08 mm². However, the response did not improve continuously with increasing cork content, since the highest cork content showed a reduction in impact performance when compared with the intermediate configuration. This behaviour was associated with possible processing-related limitations, mainly increased resin viscosity and reduced flowability, which may have affected fibre impregnation, particle dispersion and laminate homogeneity. The radiographic analysis confirmed that cork particle incorporation modified the damage response under the adopted impact conditions, although the method provided a two-dimensional projection of penetrantaccessible damage rather than a three-dimensional characterisation. The tensile results showed reductions of approximately 58.6% in tensile strength and 59.0% in Young’s modulus, while strain at failure increased by approximately 16.5%. These results indicate that, particularly in the unsaturated polyester-based laminate configurations, cork particle incorporation may improve the apparent impact damage response, although with a reduction in static tensile performance. Therefore, the use of cork particles as a dispersed phase in composite laminates requires an appropriate balance between impact damage tolerance, tensile properties, cork content, particle dispersion, matrix system and manufacturing quality. Overall, cork particles showed potential as functional modifiers for glass fibre-reinforced unsaturated polyester laminates subjected to low-velocity impact, while highlighting the need for optimisation of particle content and size, processing conditions and damage characterisation methods.
    2026-07-03Dissertação de mestrado Acesso aberto Ver mais