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Sample Sizes

MDF board samples were obtained from an Australian MDF plant. Phil asked for details of the plant - exactly what details Two types of board were chosen: a flooring grade MDF and HD3, which is the strongest and most moisture resistant of any commercially available MDF. This Australian produced MDF is composed of roughly 95% radiata pine and 5% of a eucalypt. The eucalypt, or other hardwood content can be modified to induce different properties in the final MDF.

The boards were obtained as 1200mm 1200mm sheets, 7.5mm thick. Blanks 20mm 100mm, 60mm 20mm and 15mm 15mm in size were cut on a table saw to a tolerance of 2mm. Four of the samples measuring 60mm 20mm were allocated for testing in a swellometer . Thirty-eight of the samples measuring 15mm 15mm were allocated for the tests of internal bond strength. Seventy six of the samples measuring 100mm 20mm were allocated for tensile testing and three point bend testing. Of each of these seventy six samples, half were chamfered on a mill to get the desired dog bone shape, necessary for reliable tensile testing, see Table .

Whenever possible the boards were stored in a Conditioning Room at 23 and 40% RH before testing. It is intended to do a complete repeat of the experiments undertaken and thus two boards of each type were obtained each from separate production runs. This ensures adequate replication of the experiment, for later statistical analysis.

  
Figure: The three sample sizes used in this experiment.

  
Table: The sizes, numbers, allocation and machining method of the MDF samples

One quarter of the total number of each size of sample are of the types; MDF heat treated, MDF untreated, HD3 heat treated and HD3 untreated. The same cuts were made for the replicate.