Revolutionising ceramics

Clay Technology magazine
,
17 May 2018

A new project aims to bring ceramics production up to date through the use of mechanical modelling and virtual prototyping, as Ellis Davies reports.

Methods aiming to revolutionise ceramic production have been developed by the Community Research and Development Information Service (CORDIS) – the European Commission’s distributor of information related to EU projects. The group has moved away from traditional means of production by adopting a more scientific approach based on advanced nonlinear mechanical modelling, which allows the modification of design through virtual prototyping.

Ceramic production can be traced back as far as 24000 BC, making clay one of the first materials humans manipulated. However, despite the long history, production ceramics is hampered by losses and defects.

The project, CERMAT2, finished in October 2017, and CORDIS recently produced the final report, detailing the improvements.

Improving the process

Ceramics are generally produced using a process known as forming – inorganic powders, such as metal oxides and clay, with or without water, are shaped into the final product – before being fired at temperatures of 1,000oC. Professor Andrea Piccolroaz, coordinator of CERMAT2, in a CORDIS press release said, ‘The consequence of this approach is an extremely high rate of rejects, which has an impact not only on manufacturing costs but also on the sustainability of the ceramic industry.’ It is one of the most energy intensive, highlighted Piccolroaz. ‘It is responsible for a large part of greenhouse gas and pollutants emissions.’

The new approach involves mathematical constitutive modelling, showing how a material reacts to different loads, of ceramic materials, experimental analysis, characterisation, and numerical simulation. This is done to optimise the design of the product with virtual prototyping, which allows the design to be validated using software, without the need for a physical model. 

An analysis method for the cold powder densification stage was introduced. This allows for the modelling of the nonlinear and anisotropic elastic response of the granulate/powdered materials, a physical property, such as strength or elasticity, that has a different value when measured in different directions. This removes problems related to large elastic deformation, such as the generation of false permanent strain, in which the final product can show signs of weakness where there may be none.

Researchers also overcame issues associated with the heating process. During this stage, the dimensions, or shape, of the final product can change dramatically, making the final form difficult to manage. A model was developed to predict the shape-change, allowing for the production of parts closer to the geometry set out in design. The model describes the mechanical state during and after the sintering process, predicting dimensions, porosity, and residual stresses, which can reduce the frequency of defects.

A better ceramic

The project also looked at enhancing the performance of ceramics. Models were developed to analyse crack propagation and interfacial cracks in ceramics by putting them under extreme mechanical loading conditions. The models are able to explain what can lead to crack appearance, so it can be avoided in production.

‘We successfully developed this method, and have now delivered the numerical routines and software for the optimal design of ceramic materials to our industrial partners,’ said Piccolroaz. ‘This is not only an advance in our knowledge of ceramic materials, but also a step forward in the design of ceramics.’

Aside from the development of new techniques, the project was conducted with an aim to train new researchers in model-led production methods. CORDIS reports that some of the trainees have branched out to a successful start-up, and look to spread the CERMAT2 process across the industry.

Read the final report summary at bit.ly/2vIsFTq