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Vehicle seats and interior equipment put to the test

Vehicle designers and engineers, who place great importance on the design of the interior, and in particular the seats, are supported by the scientists from the Hohenstein Institute in Boennigheim, Germany.

18th December 2013

Innovation in Textiles
 |  Boennigheim

Medical/Hygiene, Transport/​Aerospace, Industrial, Interiors, Sustainable, Protective

Vehicle designers and engineers, who place great importance on the design of the interior, and in particular the seats, are supported by the scientists from the Hohenstein Institute in Boennigheim, Germany.

Comfortable seats – relaxed drivers

Optimally designed vehicle seats make an important contribution to road safety, researchers suggest. They support the driver's mental and physical performance, in particular on long journeys.

With regard to comfort properties, optimally designed vehicle seats can contribute to the vehicle driver being focused and relaxed even on long journeys. © Light Poet/

The researchers at the Hohenstein Institute have established four key characteristics which determine the physiological comfort of vehicle seats: initial heat flow, breathability, heat insulation and moisture buffering.

All these factors are evaluated in the Hohenstein Institute laboratories and they provide manufacturers with information for improving design and material selection.

All about hygiene

High temperatures combined with moisture make the interior of vehicles a potential breeding ground for bacteria and fungi, particularly in the summer. Microorganisms can lead to unpleasant odours, cause problems for allergy suffers and significantly reduce the durability of the interior equipment.

The abrasion resistance of textiles is tested using the Martindale device. A sample of the material to be tested is rubbed against a woollen standard material with a predefined weight load. The splitting value (measure: Martindale) resulting in the wear of two fibres is measured. © Hohenstein Institute

The Hohenstein experts conduct realistic tests on the effectiveness of antimicrobial finishes to determine how well textiles, plastics and other surfaces prevent the accumulation of microorganisms.

Standardised laboratory tests are also used to evaluate the effectiveness of antiviral finishes. To break chains of infection, products in the public sphere are already being used with an antiviral finish.

Excellent climate

The increasing number of allergy suffers and individuals with sensitivities is also posing new challenges for car manufacturers. The vehicle interior must be kept permanently free of harmful substances and allergens.

Therefore, the accumulation of microorganisms and the inflow from outside must be prevented. Within the framework of the harmful material tests in accordance with Oeko-Tex Standard 100, more than 100 parameters are investigated for the materials at the Hohenstein Institute.

The Skin Model is integrated in to a climate chamber to ensure constant testing conditions at all times. © Hohenstein Institute

The Institute offers effect-related tests on the biological safety of products, such as seat coverings. With the help of a simple in-vitro cell culture test, allergenic potential is recorded for the use of unknown dyes, dye components or other chemicals.

Investigations into sustainability

The combinations of crude-oil-based materials that are less biologically degradable, as well as the antimicrobial finishes that make good sense from a hygiene point of view, can become problematic at the end of a vehicle's life. They often prevent the rapid and non-residue decomposition of the interior equipment and add-ons.

To ensure a balance between these factors, material properties must be precisely analysed and optimised. In realistic models, the microbiologists at the Hohenstein Institute contaminate the test samples with voracious moulds. The material is then analysed to determine negative changes.

Keeping a cool head

To have an interior that is pleasantly cool in summer, but cosy and warm in winter, effective thermal insulation of the windows is particularly important, alongside the air conditioning.

Breathability and water vapour buffering of the seat are determined using a thermal regulation model of human skin – the Skin Model. It consists of a porous, heatable metal plate which can release a controlled amount of water vapour to simulate the formation of sweat as a function of different physical activity levels. © Hohenstein Institute

Based on standard DIN EN 410 ‘Glass in building’, the experts from the Hohenstein Institute therefore calculate the ‘g-value’ as the measure for the energy transmittance of materials.

Keeping ears open

The extent to which a textile material has a sound-absorbing effect and what sounds are caused by wind flow is tested at the Hohenstein Institute using acoustic test apparatus, which determines how well a material is able to reduce or absorb sound.

To recreate the body's heat output, an aluminium stamp in the shape of the human buttocks, the so-called Upholstery Tester, is pre-heated to skin temperature and pressed into the seat. Heat flow sensors integrated into the device record the level of heat insulation of the seat upon first contact and after reaching the temperature balance between body and seat. © Hohenstein Institute

The aero-acoustic test, on the other hand, examines the frequency spectra in which the materials themselves generate sound when they are subjected to air flow.

Advanced colour theory

Experts suggest that the majority of complaints from customers due to colour deviations could be avoided. The use of instrumental and visual colour analysis can ensure that the colour effect will correspond to the target values even on different materials and surfaces.

Instrumental colour measurement uses a ‘spectral photometer’ to determine the spectral reflection of test samples. This means the process examines which portions of white light are reflected by a material sample, establishing colour perception in the human eye.

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