Coupling agents are used in fibre-polymer composites to enhance the dispersion and adhesion of the fibres and to maximise the composite’s mechanical performance. This paper aims to review the existing approaches of selecting a coupling agent which will maximise the dispersion of randomly-oriented, discrete fibres in thermosetting polymer composites. Specialist insight, industrial sizing tables and trial-and-error testing are typical techniques currently used to select a coupling agent for a novel composite. The volume of potential coupling agents and the ambiguity in the sizing tables has made selecting the optimum coupling agent a current problem facing the composites industry. In this work, a range of functionalised Si3N4-fibre polymer composites was synthesised using a variety of silane coupling agents (SCAs) and commercial thermoset polymer resins. The tensile strength, Young’s modulus, toughness and shore D hardness of the composites were measured. It was determined that changing the SCA at the interface had a significant effect on the overall performance of the composite. Microstructural analysis of the interface was used to draw conclusions about the influence of the SCA on the extent of adhesion across the fibre-polymer phase boundary. The measured trends in composite tensile strength values were compared to the suggestions from typical sizing tables for each polymer to determine the effectiveness of the primary method used for selecting an SCA. There was a significant amount of deviation between the SCAs predicted to couple to the resin and the SCA which resulted in the greatest increase in tensile strength. It was concluded that current SCA selection methods are not efficient or robust techniques to develop a novel composite with maximum mechanical properties.
Journal: TechConnect Briefs
Volume: TechConnect Briefs 2019
Published: June 17, 2019
Pages: 53 - 56
Industry sector: Advanced Materials & Manufacturing
Topics: Advanced Materials for Engineering Applications, Materials Characterization & Imaging