漂珠聚氨酯复合泡沫力学特性及本构模型研究

以粉煤灰漂珠为主要组分的复合泡沫具有较高的比强度和比吸能,在轻质抗冲击结构设计和缓冲防护领域极具应用潜力。然而,漂珠尺寸和增强相等因素对材料力学性能和行为的影响机制尚不清楚,且当前研究尚未构建该类复合泡沫的力学模型,不利于开展结构设计中材料选型和数值仿真等工作。为此,该研究针对漂珠尺寸和蜂窝铝增强相对复合泡沫的力学性能和变形行为的影响规律进行系列准静态压缩实验研究,在此基础上采用Avalle理论构建该复合泡沫的力学模型。结果表明:①当相对密度小于0.29时,漂珠尺寸对复合泡沫的力学性能几乎没有影响;当相对密度大于0.29时,漂珠尺寸对复合泡沫力学性能的影响随密度的增大而增大;②对于含增强相的复合泡沫,含小尺寸漂珠的复合泡沫力学性能有明显提高,铝蜂窝的额外增强效果对包含小尺寸漂珠的复合泡沫更为明显,该增强机制主要是将材料的初始失效模式由剪切转变为轴向压溃;③使用Avalle理论构建的本构模型,其应力平台阶段和能量耗散特性的拟合与实验结果一致,可较为准确地预测该材料的基本力学性能。该研究可为粉煤灰的综合利用及其复合泡沫在轻质抗冲击结构设计中的应用提供理论参考和基本预测模型。

Mechanical characteristics and constitutive model of fly ash cenospheres polyurethane syntactic foam

Syntactic foam with fly ash cenospheres as the main component has high specific strength and specific energy absorption,showing its great application potential in lightweight impact resistant structures and buffer protection.However,the influence mechanism of the factors such as the fly ash cenosphere size and the reinforcement on the mechanical properties and behaviors is still unclear.In addition,the mechanical model of this kind of syntactic foam has not yet been constructed in current studies,which is not conducive to the material selection and numerical simulation related work in structural design.With regards to this,a series of quasi-static compression experimental studies were conducted about the influence of the fly ash cenospheres size and the honeycomb aluminum reinforcement on the mechanical properties and deformation behaviors of cenospheres polyurethane syntactic foams(CPSFs).Meanwhile,the mechanical model of CPSFs was constructed according to the Avalle theory.The results are as follows:①When the relative density is less than 0.29,the size of the cenosphere has little effect on the mechanical properties of the composite foam.When the relative density is greater than 0.29,the effect of the cenosphere size on the mechanical properties of the composite foam increases as the density increases.②For the composite foam containing reinforcing phase,the mechanical properties of the composite foam containing small-sized cenospheres are significantly improved.The additional reinforcement effect of the aluminum honeycomb is more obvious for the composite foam containing small-sized floating beads.This reinforcement mechanism is mainly to change the initial failure mode of the material from shear to axial crushing.③The results by the constitutive model constructed according to the Avalle theory,the fitting of the stress platform stage and the energy dissipation characteristics are consistent with the experimental results,and the basic mechanical properties of the material can be predicted more accurately.The study provides a theoretical reference and a basic prediction model for the comprehensive utilization of fly ash and promotes the application of its composite foam in the design of lightweight impact-resistant structures.