No abstract

The increasing use of fibre reinforced polymer composite materials in a wide range of applications increases the use of similar and dissimilar joints. Traditional joining methods such as welding, mechanical fastening and riveting are challenging in composites due to their material properties, heterogeneous nature, and layup configuration. Adhesive bonding allows flexibility in materials selection and offers improved production efficiency from product design and manufacture to final assembly, enabling cost reduction. However, the performance of adhesively bonded composite structures cannot be fully verified by inspection and testing due to the unforeseen nature of defects and manufacturing uncertainties presented in this joining method. These uncertainties can manifest as kissing bonds, porosity and voids in the adhesive. As a result, the use of adhesively bonded joints is often constrained by conservative certification requirements, limiting the potential of composite materials in weight reduction, cost-saving, and performance. There is a need to identify these uncertainties and understand their effect when designing these adhesively bonded joints. This article aims to report and categorise these uncertainties, offering the reader a reliable and inclusive source to conduct further research, such as the development of probabilistic reliability-based design optimisation, sensitivity analysis, defect detection methods and process development.

Composites of the polymer/® ller type, when the ® ller is a conductive material such as metal particles, exhibit electrical conductivity that increases with concentration of the conductive phase. These complex materials are considered to be chaotic mixtures of conductive particles randomly distributed in an insulating matrix. The conductivity of these materials in dc electric ® elds is studied in terms of percolation theory, where electrical conductivity s is rapidly increased at a critical concentration, de® ned as P c , of the conductive phase, according to s» (P P c ) a . In this work, various epoxy resin/conductive ® ller composites were prepared. The ® ller was metal powder of copper, aluminium, or zinc. The conductive behaviour of these materials was studied at temperatures varied from 20 to 140°C. Data obtained from these measurements are analysed using percolation theory and introducing new parameters b and s c into the above relation. A semiempirical algorithm is introduced for the determination of a, b, s c , and P c .MST/4657

The analysis and design of a novel flexible dielectric sensor, which can be integrated into a composite materials manufacturing process to measure the resin frontal flow, is presented in this paper. The proposed sensor consists of two parallel line electrodes and a ground plane covered by a dielectric material. The analytical description and the electrostatic modelling were considered for the design of the sensor and to enhance the understanding of the response of the sensor to the resin impregnation of a carbon fabric during the infusion phase. The optimization of the sensor’s response and the increase of its sensitivity with regards to the geometric characteristics and the materials used were the main objectives of this study. An experimental set-up for the vacuum infusion process which includes the proposed sensor was used to measure the capacitance and validate the derived resin flow against visual measurements. The results indicate that the sensor can provide information on the resin frontal flow within 2% accuracy against visual measurements, which make this technology promising for monitoring the liquid resin infusion processes.