Gravimetric measurements Clauses Exemplaires

Gravimetric measurements. Every specimen under hygrothermal conditioning was weighted at pre-determined intervals during the conditioning. Water was removed from the specimens’ surfaces using compressed air before weighting. The conditioning was stopped when effective moisture equilibrium was achieved, i.e., when the average moisture content of the specimens changed by less than 0.02% for two consecutive readings within a span of 7 ± 0.5 days as expressed by (2-1) in XXXX X0000 [50]: 𝑊𝑖 − 𝑊𝑖−1 < 0.02% (2-1) 𝑊𝑏 where 𝑊𝑖 is the measured weight; 𝑊𝑖−1 is the weight at the previous measurement and 𝑊𝑏 is the weight of the dry specimen. The specimens’ weights were plotted against time and the curves were fitted with a Fick law with the assumption that the composite is a single-phase Fickian material that behaves according to equation (2-2) with 𝑐 the specimen moisture concentration, 𝑡 the time, z the through-the-thickness direction and 𝐷𝑎 the apparent Fickian material diffusion constant. 𝜕𝑐 = 𝐷 𝜕²𝑐 𝜕𝑡 𝑎 𝜕𝑧² The initial and boundary conditions are stated in (2-3) and (2-4): 𝑐 = 𝑐0 𝑡 = 0 (2-3) 𝑧 = 0 𝑐 = 𝑐𝑎 ; 𝑧 = ℎ 𝑡 > 0 (2-4) The moisture content as a function of time was fitted using equation (2-5), 𝑀(𝑇, 𝑡) = 𝑀𝑚 × (1 − exp [−7.3 (