CORRELATION OF FRACTURE-TOUGHNESS OF BONDED JOINTS WITH QUALITY (ROUGHNESS) OF KNIFE-PLANED MDF SURFACES

Any wood or panel piece is planed before utilization. To obtain the be st surface quality in terms of roughness is generally the main objecti ve because everyone relates the final quality of any wood item to his sensitive perception of the surface brightness or roughness. Most ofte n, the surface is not kept in this primary stage. Sometimes, wood piec es are planed and calibrated to be jointed by glueing. The paper demon strates that the highest mechanical performance of the glued assembly is not obtained from the best surface quality defined as the lowest ro ughness. In a first step, different methods of surface roughness measu rement are described and compared. Then, surface quality is related to glueing (strain energy release rate) capability. At the same time, su rface quality is also studied in function of the planing or sanding fa ctors (cutting speed, feed speed, nature of tool,...). The existence o f optimal machining conditions to prepare a surface for glueing is dem onstrated on MDF.