Mechanical testing

Characterising the mechanical properties and performance of advanced materials

Our research covers a wide range of test types and materials, developing new methods to characterise  advanced materials across the nano-micro-macro-structural scales, for both in-operando and ex-operando situations. We develop international standards to ensure our techniques are accepted by governing bodies to qualify materials for use in demanding environments, and understanding of the mechanisms which control the performance of the material.  

Macro scale testing - for polymer composite materials

We are carrying out research into new test methods and procedures, so that we have the capability to support industry to test new materials or for new applications. This includes:

• Evaluation of alternative geometries for through-thickness property characterisation in fibre-reinforced plastic composites
• Assessment of the suitability of existing mechanical property characterisation standards for 3D reinforced composites, and development of new methods where required.
• Continuation of international intercomparison exercise to generate precision data for the RARDE geometry and procedure for through-thickness property measurement (currently an ISO New Work Item).
• In-operando research focused on the development and validation of realistic accelerated ageing regimes and associated modelling approaches relevant to advanced materials systems. (This work associated with a collaborative Engineering Doctorate with Exova at Surrey University.)
• Optimisation of acid digestion techniques for characterising constituent fractions of composite materials and comparison to alternative methods.
• Initial scoping of test methodologies for rate dependence characterisation of advanced materials. 

• Installation of a new, state of the art mechanical test facility in collaboration with Instron using the latest static, high rate and fatigue test machines.

Micro scale testing - for metallic materials

We are understanding the microstructure of materials and the testing which is needed, including:

• Development of high temperature resistivity measurements using  the NPL Electro Thermo Mechanical Test System (ETMT) to enable improved quantification of strain measurement and phase changes in alloys, hard metals and nuclear graphite
• Comparison and validation of micro-mechanical tests against standard macro-mechanical tests for course grained and complex microstructured materials. This will help establish whether conventional test methods are appropriate for additively manufactured materials and to determine best practice for testing complex thin walled parts, when samples are machined directly from the finished component.
• Development of methods for the measurement of residual stress within a microstructure using ion beam hole or slot milling. This work supports an underlying theme of comparing surface residual stress values with subsurface measurements, comparing x-ray diffraction, FIB hole drilling, conventional hole drilling and conventional mechanical testing

Nano scale testing

We are developing a high temperature nanoindentation apparatus, in collaboration with a UK manufacturer, which will be to produce reliable procedures to determine the surface condition of materials at temperatures up to 900 °C and extend the understanding of their performance in harsh environments.

Test methods for the use of an in situ indenter apparatus within an electron microscope are being developed. Pillar and cantilever manufacture methods using focused ion beam milling are being studied with emphasis on structural damage due to ion implantation, true sample geometry variations, microstructural variation and substrate compliance.

Although some of these test methods have been developed for particular materials, they may also be applicable to other classes of material. 

Find out more about NPL's Mechanical testing services

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