15 June 2021
Sign up to our newsletterWant more news like this? Sign up to our newsletter.

Improved methods for failure prediction of hard foam components

Researchers at Germany’s Fraunhofer Institute for Structural Durability and System Reliability LBF have developed innovative test procedures and improved methods for the safe design of hard foam components

Today, a universally accepted procedure for multiaxial tests of hard foam components is missing. Some loading cases can hardly be realised experimentally. For example, plausible specifications for a hydrostatic tensile test are unknown and the balanced biaxial tensile test is costly to perform. To handle these problems, experts at the Fraunhofer Institute for Structural Durability and System Reliability LBF have established 2D and 3D balanced compression tests. The results of these experiments are clear and easy to interpret. In addition, with uniaxial tensile, compression, and torsion test, these test data ensure reliable modelling and plausible extrapolations, which allow for the estimation of the unavailable hydrostatic tensile data.

The equibiaxial compression loading is realised in a conventional tensile testing machine, applying a circular disc as specimen and a sheet steel loop for load application. The resulting effort is comparable to standard tensile tests. The 2D compression test represents an effective method for the first estimation of material behaviour. However, for precise modelling, a hydrostatic compression test is essential.

Two types of material behaviour under hydrostatic compression should be distinguished: destruction of the cells and hydrostatic collapse of the overall structure. Scientists at Fraunhofer LBF have implemented an innovative method for the testing of material behaviour under hydrostatic compression and applied it to several polymeric hard foams. They offer support on every level of the design process. As a result, the reliable solutions for optimised structures have been achieved.

They say that, for reliable modelling of materials which fail under hydrostatic compression (hard polymeric and ceramic foams, aerated concrete, soil, sintered and granular materials, etc.), the hydrostatic compression test is mandatory. The material properties from this test cannot be calculated from the tensile, compression, and torsion test data. Possible extrapolations, such as given above by the 2D compression test, may provide only estimates and should not be applied for critical applications.

They add that the hydrostatic (balanced 3D compression) test provides the necessary information for modelling of the elastic behaviour and failure at multiaxial compressive loadings. The results of the hydrostatic test lead directly to the required material model parameters, simplifying the fitting procedure significantly. Among others, the bulk modulus of the elastic behaviour is a result of these experiments.

With the new method, components containing hard foams can be designed more reliably and more cost-effectively. It allows designers take safe decisions about the choice of material for specific applications. The method also seems very promising for further materials like ceramic foams, aerated concrete, soil, sintered and granular materials, they point out.

Author
FAST magazine

Similar Articles

Condensation-free enclosure

An industrial enclosure that prevents condensation is being used to protect electrical distribution boards. Spelsberg’s AK Air enclosure system features an integrated ventilation ...

Die-cast aluminium enclosures

New from BCL Enclosures is a series of rugged, die-cast aluminium alloy enclosures designed specifically to protect electronic instruments.

Composite tank cladding

Product manager Sascha Oswald will report on GRP solutions for the tank container industry in a webinar scheduled for 10 August 2021. Free registration is available via the link ...

Specifying enclosures - advice

The design and specification of an enclosure can make or break an industrial application. While some projects require a standard enclosure for quick installation to keep costs ...

Technical glass introduction

Goodfellow introduces the uses and flexibility of technical glass.

Terraforming Mars - materials

Philip K. Dick’s 1964 science fiction novel, Martian Time-Slip, imagined a human colony on Mars reliant on waterways, allotments and robots. Today, such quaint sci-fi concepts are ...

Dispensing Made Easy with the

Fisnar, leading manufacturer of fluid dispensing equipment, is pleased to announce the launch of its DC50 Digital Dispense Controller. A new addition to their popular DC series ...

Added Choices for Zygology

Available now at Zygology, Southco’s new EM-05-4 and EM-05-05 Series Mini Electronic Slide Bolts further extend the successful Electronic Slide Bolt range with new and even more ...

New approach to the cure

UK adhesives supplier Techsil has launched a range of new adhesive products with low ion content that cure with UV, visible light or moisture.