Measurement of various properties of Southern pine and aspen as function of heat treatment

• Heat treatment reduced strength properties of the samples.
• Hardness of the samples reduced with increasing exposure time.
• Roughness of both species did not make any significant difference as a result of heat treatment.
• Shear strength of the samples reduced due to heat treatment.

The objective of this study was to investigate the influence of heat treatment parameters, namely temperature and exposure time on surface roughness, shear strength, hardness and density of Southern pine (Pinus echinata) and aspen (Populus grandidentata) samples. The specimens were exposed to two different temperature levels of 120–200 °C for time spans of 2–8 h. A stylus type portable profilometer was employed to evaluate the surface characteristics of the samples by taking measurements across the grain orientation. Average roughness (Ra), mean peak-to-valley height (Rz) and maximum roughness (Rmax) were used to evaluate surface roughness of the samples exposed to various heat treatment schedules. Comten testing unit was also used to determine shear strength and Janka hardness of the control and heat treated specimens. Based on the results of this study Southern pine samples had more enhanced surface quality but lower hardness values than those of aspen specimens with increased temperature and time of heat treatment schedules. It was found that heat treatment adversely affected hardness and shear strength properties of all types of samples. Reduction in shear strength values of Southern pine and aspen samples ranged from 23.31% to 68.59% and from 4.67% to 48.55%, respectively as compared to those of control samples. It appears that influence of heat treatment on all properties of the samples was more pronounced with increasing temperature and exposure time.