Fused filament fabrication (FFF) is the most widely used additive manufacturing (AM) technique to produce fibre-reinforced polymer matrix composites, due to their low wastage, geometric flexibility and ease of use. Composite materials generally have superior properties such as being stiffer and more robust than conventional materials at a reduced weight leading to their application in a wide variety of sectors (aerospace, automotive etc). However, composites manufactured in this way are highly susceptible to defects such as high void content and poor bond quality at the fibre and matrix interfaces. These defects stop fibre-reinforced composite materials manufactured this way meeting industry standards and being used for structural applications. In the present work, a combination methodology of acoustic emission (AE) alongside tensile testing has been developed to investigate the structural integrity and mechanical performance of AM fibre-reinforced composites. Pure polymer samples and short carbon fibre reinforced composites were manufactured, and their mechanical properties were observed.
Fused filament fabrication (FFF) is the most widely used additive manufacturing (AM) technique to produce fibre-reinforced polymer matrix composites, due to their low wastage, geometric flexibility and ease of use. However, composites manufactured in this way are highly susceptible to defects such as high void content and poor bond quality at the fibre and matrix interfaces. In the present work, a combination method of Infrared Thermography, Acoustic Emission and micro-computerised tomography was developed for the monitoring of the FFF AM process. Both pure plastic and fibre-reinforced composites were manufactured, and the detection and development of defects created during the printing process were monitored. This combination of techniques allows for detection of defects such as porosity, voids and poor fibre-matrix bonding during printing and the verification of their presence after the printing without the need for destructive testing.
In the present work, a novel combination method of in-line monitoring and offline non-destructive evaluation was developed for the detection and monitoring of defects in additively manufactured specimen. The new methodology includes Infrared Thermography, Acoustic Emission and Micro-computerised Tomography to allow for the detection of anomalies during the printing process and the verification of their presence after the printing process without the need for destructive testing. It was found that the in-line monitoring can provide information on the efficacy of the printing process which is substantiated by the offline assessment.
Dense (1−x)KNbO3-x(Ba1/2Bi1/2)(Zn1/2Nb1/2)O3 (0 ≤ x ≤ 0.25) ceramics were prepared by the solid state reaction method. X-ray diffraction data show the average crystal structure to evolve from orthorhombic at x = 0 to pseudocubic at x = 0.25. Raman spectroscopy suggests the absence of polar order for x ≥ 0.25 ceramics. Polarisation versus electrical field measurements show a continuous decrease in the spontaneous polarisation with increasing x. Electrical-field-induced strain measurements reveal a piezoelectric-to-electrostrictive crossover. An electrostriction coefficient of 0.043 m4/C2 was measured for x = 0.15.
Every year millions of people seek dental treatment to either repair damaged, unaesthetic and dysfunctional teeth or replace missing natural teeth. Several dental materials have been developed to meet the stringent requirements in terms of mechanical properties, aesthetics and chemical durability in the oral environment. Glass-ceramics exhibit a suitable combination of these properties for dental restorations. This research is focused on the assessment of the thermomechanical behavior of bio-ceramics and particularly lithium aluminosilicate glass-ceramics (LAS glass-ceramics). Specifically, methodologies based on Infrared Thermography (IRT) have been applied in order the structure – property relationship to be evaluated. Non-crystallized, partially crystallized and fully crystallized glass-ceramic samples have been non-destructively assessed in order their thermo-mechanical behavior to be associated with their micro-structural features.
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