Experimental Research On Properties On Parallel Strand Bamboo At High Temperature

Bamboo is a kind of renewable and biodegradable natural biomass materials, With the characteristic of fast growth and high-yield. Parallel strand bamboo (PSB), fabricated through industrial process by using raw bamboo, is a high strength bamboo-based composite. It has extensively potential prospective application as a structural material for building constructions. The mechanical properties and flame retardance are superior to those of lumber. The emission of carboxaldehyde is less than the requirement of E1 grade of EU standard. While PSB is combustible. At present, little study has been done on the performance of PSB under high temperature. Therefor it is of great importance for this thesis to study the fundamental performance of parallel strand bamboo in elevated temperature. The main research work and results in this paper are as follows:Based on the transient plane source method, the thermal conductivity and diffusivity at high temperature of PSB was measured by the Hot Disk. And the model between the thermal conductivity and the temperature was proposed. The TGA-DSC was used to test the heat capacity. Then the thermal stability of PSB was analyzed through the tested curve relationship between the mass change and the heated temperature by TGA.For the purpose of exploring the mechanical properties of the PSB at high temperatures, this thesis carried out the mechanical properties test including normal temperature specimens and high temperature steady-state specimens parallel to grain and perpendicular to grain for the uniaxial tensile test and the uniaxial compression test. Then the analysis of the failure mechanisms and failure criterion under various temperature conditions was done. The correlations between the target temperatures and the mechanical properties were investigated.In order to study the one dimensional charring rates of PSB, according to the standard ISO 834, a total of 48 specimens in 12 groups exposed to one side was tested. It was found that the charring rate was influnecd by the exposure time,moisture content and the ring orientation. A nonlinear time-location relation model is more accurately reflecting the location of the base of the char layer at a given time. With the increase of moisture content, both the charring rate parallel to rain and perpendicular to grain reduced. The charring rate perpendicular to grain is normally larger than that parallel to grain, and the ratio is between 1.1?1.3.At last the model describing the rate of char development was proposed. It is a function of exposure time,moisture content and the ring orientation.A total of 8 PSB beams in 4 groups exposed to four-side fire and 8 PSB beams in 4 groups exposed to three-side fire were tested to investigate the effect of corner rounding on charring rate. The results showed that the beam section area reduces due to charring. The corner turns to arc shape from original sharp edge. The great difference of charring rate was observed between the coner and the non-coner area. Based the one dimensional charring model, a new model applied to the charring rate of the beams considering the coner rounding effect was proposed.