3.6  SMALL BALL IMPACT RESISTANCE 

3.6.1  Scope

This test measures the ability of laminate flooring to resist fracture due to impact by a small diameter ball. 

3.6.2  Test Apparatus

3.6.2.1       Impact apparatus as shown in Figure 3-5.

3.6.2.2       Impact dart weighing 25.0 g + 0.5 g.  It shall consist of a steel or brass dart tipped with a 5 mm (0.195 in) diameter steel ball.  The spherical surface of the ball shall have no damaged or flattened surface.  See Figure 3-5.

3.6.2.3       Dry graphite lubricant.

3.6.2.4       Overhead white fluorescent lights with bulb(s) positioned parallel to the line of sight and providing an intensity of 800 to 1100 lux (75 to 100 foot-candles) on the specimen surface.

3.6.2.5       Black, water washable marking pen (suitable for overhead transparencies).

3.6.2.6       Underlayment foam as a closed-cell foam with a thickness of 2.0 mm ± 0.5 mm (0.08 in + 0.02 in) and a density of 35 kg/m³ + 5 kg/m³ (2.2 lb/ft³ + 0.3 lb/ft³) or equivalent.

Figure 3-5

3.6.2.1       Environmental Chamber maintained at 23^oC + 3^oC (73^oF + 5^oF) and relative humidity of 50% + 5%.

3.6.2.2       Clean, soft, cloth. 

3.6.3  Specimens

3.6.3.1    Specimens shall be 200 mm x 200 mm x thickness (8 in x 8 in x thickness).  In cases where material is less than 200 mm (8 in) in one dimension of the face, the specimen shall measure 200 mm x nominal width x nominal thickness (8 in x nominal width x nominal thickness). 

3.6.4  Procedure

3.6.4.1       Condition the samples to constant weight (less than 0.1% deviation per 24 hours) in a conditioning chamber maintained at a temperature of 23^oC + 2^oC (73.4^oF ± 3.6^oF) and a relative humidity of 50 ± 5 percent.

3.6.4.2       Lubricate the inside diameter of the tube assembly with the dry graphite lubricant to minimize friction with the dart.

3.6.4.3       Place the specimen, face up, on underlayment foam of similar size as the specimen.

3.6.4.4       Place the specimen/underlayment assembly face up on a rigid horizontal surface.

3.6.4.5       Place the impact apparatus on the decorative surface of the specimen so that the edge of the round base is tangent to two edges of the specimen at one corner.  The bottom of the circular base shall be flush against the face of the specimen.

3.6.4.6       Position the dart at a height of 125 mm (5 in).

3.6.4.7       Release the dart and impact the face of the specimen.  Catch the dart when it rebounds so that multiple impacts do not occur.

3.6.4.8       Move the dart to the right 15 mm (5/8 in) while keeping the edge of the circular base tangent to one edge of the specimen.  See Figure 3-6.

3.6.4.9       Position the dart at a height of 150 mm (6 in).

3.6.4.10    Release the dart and impact the face of the specimen.  Catch the dart when it rebounds so that multiple impacts do not occur.

3.6.4.11    Repeat steps 3.6.4.9 and 3.6.4.10 while increasing the dart release height by 25 mm (1”) with each impact along the first edge of the specimen.

3.6.4.12    Use the marking pen to ink the impact points along edge 1 to accentuate the impact points.

3.6.4.13    Wipe the impact points with a clean, soft cloth to remove excess ink.

3.6.4.14    Cracks and fractures may appear as hairline cracks, concentric circles, or chips.  Dents without breaking the surface do not indicate failure.

3.6.4.15    Beginning with the impact point of lowest height, follow the impact point path of increasing impacts heights until 3 consecutive failures occur.  If 3 consecutive failures are not observed, continue with steps 3.6.4.11 through 3.6.4.14 along edge 2 of the specimen.

3.6.4.16    Edge 3 and edge 4 may be used as needed until failure is noted or the highest impact release point is achieved without failure.

3.6.4.17    The impact resistance is the height value immediately preceding the series of three consecutive failures. 

3.6.5    Report

3.6.5.1       Reference to this standard.

3.6.5.2       Description of the material under test.

3.6.5.3       Impact resistance as determined in 3.6.4.17.

3.6.5.4       Any deviation from the specified test method.

3.6.5.5       Date of the test.

Figure 3-6

3.6.6  Precision & Bias

3.6.6.1    Table 3-4 is based on interlaboratory studies conducted in 2001 involving 3 replicate tests of 12 materials tested by 6 laboratories. 

 Table 3-4

3.6.6.2    In Table 3-4, for the materials indicated:

3.6.6.2.1 Mean is the average of test results for all replicates from all labs.

3.6.6.2.2 S_r is the within-laboratory standard deviation of the mean and I_r = 2.83S_r (see 3.6.6.2.4 for application of I_r).

3.6.6.2.3 S_R is the between-laboratory standard deviation of the mean and I_R = 2.83S_R (see 3.6.6.2.5 for application of I_R).

3.6.6.2.4 Repeatability – In comparing two mean values for the same material obtained by the same operator using the same equipment on the same day, the means should be judged not equivalent if they differ by more than the I_r value for that material and condition.

3.6.6.2.5 Reproducibility – In comparing two mean values for the same material obtained by different operators using different equipment on different days, the means should be judged not equivalent if they differ by more than the I_R value for that material and condition. (This applies between different laboratories or between different equipment within the same laboratory.)

3.6.6.3    The judgments per 3.6.6.2.4 and 3.6.6.2.5 will have an approximate 95% (0.95) probability of being correct.