Influence of Microwave Power and Heating Time on the Drying Kinetics and Mechanical Properties of Eucalyptus gomphocephala Wood

The aim of this paper was to characterize through experiment the moisture and temperature kinetic behavior of Eucalyptus gomphocephala wood samples using microwave heating (MWH) in two scenarios: intermittently and continuously. The mechanical properties and surface appearance of the heated samples were also investigated. Continuous and intermittent microwave drying kinetic experiments were conducted at a frequency of 2.45 GHz using a microwave laboratory oven at 300, 500, and 1000 watts. Drying rate curves indicated three distinct phases of MWH. Increasing the microwave power with a shorter drying time led to rapid increases in internal temperature and water evaporation rates of the heated samples. Mechanical results indicated that samples heated under continuous MW (Microwave) power at 300 watts had a modulus of rupture (MOR) and modulus of elasticity (MOE) in three static bending tests higher than 29% and 36%, respectively, than samples heated at 1000 watts. Intermittent microwave heating (IMWH) of samples at 300 and 1000 watts produced the highest MOR and MOE values of 31% and 51%, respectively, unlike those heated under continuous microwave heating (CMWH). External qualitative observation showed that samples heated at high microwave power had severe surface checks. These defects were missing when using IMWH. An analysis of variance (ANOVA) showed that mechanical properties were linked to both microwave power level and the heating scenario, except for MOR in axial compression under CMWH.