Renault D42 1541 Flexible and Semi-Flexible Cellular Materials Compressive Strength

The standard "Renault D42 1541 Flexible and semi-flexible cellular materials compressive strength", developed by the French automobile company Renault, describes a method for characterizing the compressive strength of flexible and semi-flexible cellular materials made of rubber or flexible plastics (such as plasticized polyvinyl chloride, polyethylene), in the form of sheets, plates, strips, joints or molded parts, with locally open or closed cells formed by two parallel surfaces. The following are outside the scope of this standard:

• Cushioning parts (such as seat cushions and backs, upholstery sandwiches).
• Self-forming leather polyurethane foam pieces (in this case the test method described in the Renault D41 1003 standard is applied).
• Moving panel seals (door and trunk seals) (in this case the test method described in the Renault D41 1299 standard is applied.

The compressibility of the material is characterized by:

•  Generally, by “lift,” we mean the compressive stress per unit area of ​​surface required to compress the test specimen by 25 percent or 50 percent in the first or fifth compression cycle (lift force expressed in KPa).
• The compressive stress per unit length (linear lift force expressed in N/cm) required to compress the test specimen by 25 percent or 50 percent in the first or fifth compression cycle, possibly by “linear lift.”

Equipment used in this test method includes:

• Compaction machine: The machine must be equipped with a recording device that will give the load-deflection diagram. The speed of the moving crosshead must be set to a very low value (20 mm/min). The machine plates must be parallel, their surfaces must be larger than the surface of the test piece used. The plates must be parallel and have a hole network of 20 mm plus/minus 0,1 mm in diameter, with a distance of 6 mm plus/minus 1 mm between the axes (test method described in the Renault D45 1394 standard).
• Inertial testing machine which allows compression/decompression cycles to be carried out with a moving platen speed adjustable between 5 mm/min and up to 100 mm/min and equipped with a device which allows continuous recording of forces relative to the movement of the moving platen. The machine plates shall be parallel and shall be punctuated by a network of holes 20 mm plus/minus 1 mm in diameter, spaced 6 mm plus/minus 1 mm (axis to axis). In most cases a maximum force of 10 KN is sufficient. The absence of significant movement of the so-called “fixed” platen for the load range used is verified by making a control test at the lowest possible speed after placing a parallelepiped steel block of approximately 50 mm × 50 mm between the plates. If the displacement observed for the maximum load is negligible in relation to the thickness of the test piece, the determinations made on the recorded curve are made with reference to the inclined axis thus defined.
• Conditioned room at 23 degrees plus/minus 2 degrees temperature and 50 percent plus/minus 5 percent relative humidity.
• Test piece cutting equipment such as scissors, band saws and the like.
• Measuring equipment (ruler or caliper) for other dimensions of the test pieces.

The load-bearing test piece is a rectangular parallelepiped with a base of 50 mm × 50 mm and a thickness of 4 mm to 30 mm. This thickness can be obtained by superimposing two elements. If the room does not allow this test piece to be taken, the test piece used can have a smaller base, the smallest dimension of which must always be at least equal to the height. The dimensions of the test piece used are then stated again in the test report.

The existing moulding surfaces shall be retained on both sides of the test piece unless otherwise specified or substantially impossible. In either case, this shall be stated in the test report. The linear bearing test piece is a fixed element, 50 mm long, 4 mm to 30 mm thick, with a 10 per cent deviation from the part.

Three test tubes are prepared for each test. The test pieces are taken by measuring their heights so that they correspond to the direction of the pressure force applied during service. The test tubes are kept at room temperature for at least 3 hours.

When starting the tests, the base dimensions (load-bearing test pieces) or lengths (linear load-bearing test pieces) of the test pieces are precisely measured. The thickness of each test piece, after possible overlapping of its elements, is precisely measured with a compression machine, under the conditions described in the Renault D45 1394 standard, using the pressures (or loads) shown in the table given in the standard.

The moving speed of the moving platen is set to the specified speed. For samples with a thickness between 20 mm and 30 mm, the speed should be 100 mm/min. The test piece is placed in the middle of the bottom plate of the testing machine.

The compactor is adjusted according to these instructions:

• Exertion sensitivity scale compatible with prescriptions.
• Sensitivity: The sensitivity of the machine used and adapted according to the sensitivity of the measurement to be made.
• Speed: The speed of movement of the moving plate during compression and depressurization must be equal to the speed defined in this standard.

The moving platen is started and stopped when the compressive force is 50 N and 50 N, respectively, for the test piece carrying a load of 0,25 mm × 2,5 mm. The applied load on the linear bearing test specimen is 0,5 N. The position of the moving platen is determined.

At the selected speed, the distance between the plates is changed by 75 percent and the test piece is compressed and decompressed one or five times without interruption. At the same time, the effort/displacement curve is recorded at least for the first and fifth cycles.

After the final decompression, the moving plate is stopped in its starting position.

Our organization has a strong staff that closely follows the developments in the world in the field of science and technology and constantly improves itself. Among the numerous test, measurement, analysis and evaluation studies provided for businesses in various sectors, there are also test services in accordance with the "Renault D42 1541 Flexible and semi-flexible cellular materials pressure resistance" standard.