# Non-Destructive Infrared Evaluation of Thermo-Physical Parameters in Bamboo Specimens
## 1 Introduction  
Some properties make bamboo an excellent construction material; three of them are its high specific strength, fast growth, and abundance. Bamboo is stronger and denser than North American softwoods like pine, fir, and spruce. In the last years, these reasons have promoted an increment in the use of bamboo for construction in some Latin-American and Asian countries [1]. Guadua angustifolia kunth (Guadua a.k.) is a giant species of bamboo that not only grows fast, reaching its maximum strength after 3-4 years, but also decreases greenhouse effects, capturing 40 times more CO\({}_{2}\) than pine trees. The beneficial mechanical properties mentioned above, along with its ability to absorb CO\({}_{2}\), turns Guadua a.k. into an interesting construction material for sustainable development and an alternative to concrete and steel [2]. Previous works on bamboo characterization have concentrated their efforts on measuring its mechanical and thermal properties. In [3], authors have measured mechanical properties such as flexural properties and compressive strengths in bamboo culms of a commercial species in China named Moso. Compared to common North American construction woods loaded along the axial direction, Moso bamboo is approximately as stiff and substantially stronger in both flexure and compression, but denser. Additionally, the experimental results of mechanical characterization in glued laminated Guadua a.k. reveals higher strength and comparable stiffness compared to those of engineered timbers commonly used in the United States [4; 5]. The analysis of mechanical properties in bamboo species Kao Jue and Mao Jue usually used in Hong Kong and Southern China concluded thatthey are good construction materials with excellent mechanical properties against compression and bending [6]. In addition to the measurement of mechanical properties in bamboo samples, previous bamboo characterizations have also been oriented toward the estimation of thermal parameters. One approach evaluated the insulating properties of the PLA (poly lactic acid) bamboo fiber 'green' composites by determination of the thermal conductivity, which was measured using a hot-wire method. The thermal conductivity of PLA-bamboo fiber 'green' composites was significantly influenced by their density [7]. Another approach, instead characterizes thermal conductivity of bamboo fiber reinforced polyester composite using a guarded heat flow meter method [8]. The results of this study indicated that the developed composite is an insulating material. In [9], the authors evaluated the thermal conductivity of bamboo mat board (BMB) based on a steady-state guarded hot-plate method, and studied the effect of density on thermal conductivity of BMB. In [10], based on a photoacoustic technique in frequency configuration, [PERSON] et al. evaluated the thermophysical parameters of Guadua a.k. specimens such as thermal effusivity, thermal diffusivity, and thermal conductivity. The main findings show that thermal diffusivity is lower in the external region close to the bark surface, while this is kept constant along the stem. Even though these approaches successfully measure bamboo thermal properties, these parameters are not uniform in the same sample, and it is necessary to convert the cylindrical bamboo culm into a sample with specific dimensions and shape. This need for adaption renders these methods impractical when testing numerous specimens whose geometries are mostly cylindrical. Hence, it is important to analyze non-invasive methods that permit the estimation of thermal parameters in bamboo samples. Infrared thermography (IT) is a non-destructive technique that employs the heat emitted by bodies/objects to rapidly and noninvasively detect defects in specimens or estimate thermophysical parameters in materials [11; 12]. In active IT, it is necessary to apply heat to the specimen inspected in order to obtain significant temperature differences that prove the presence of anomalies.