不同壳体材质头盔耐候性评估

Weather Resistance Evaluation of Helmet with Different Shell Materials

为评估不同壳体材质电动自行车头盔的耐候性能,利用3种人工加速老化试验[紫外、65℃热氧、双85(温度85℃、相对湿度85%)湿热]及大气暴露和室内保存等方式对定制的4种不同材质头盔样品进行处理,并对不同老化阶段头盔的安全防护性能进行测试,采用扫描电子显微镜、热重分析、动态力学分析等手段对样品的微观形貌、热性能进行分析。结果表明,经各加速老化处理后头盔的吸收碰撞能量加速度峰值均小于150g(g=9.80665 m/s^(2)),仍能在实际使用中发挥安全防护作用,这主要得益于头盔缓冲层的存在。依据老化后样品形貌变化、破裂情况及刚度性能,评估壳体材质显示,聚碳酸酯/丙烯腈-丁二烯-苯乙烯塑料合金料样品性能最优;评估老化方式显示紫外老化影响最小,65℃热氧老化次之,双85湿热老化后头盔变形严重且破裂情况增多,不符合实际的使用场景。经双85湿热老化后,样品微观形貌显示其断面微孔结构增加,而热稳定性变化不大。头盔壳体材质直接影响碰撞试验后样品是否破裂,头盔吸收碰撞能量加速度峰值受其缓冲层影响较大,刚度性能可以作为头盔壳体材质性能有效评估指标。

In order to evaluate the weather resistance of electric bicycle helmet with different shell materials,three accelerated aging tests[ultraviolet(UV)aging,65℃hot air aging,85/85(85℃,RH 85%)humidity-heat aging],atmospheric exposure and indoor storage methods were used for treating four customized helmet samples with different materials.The safety protection performances of helmets in different aging stages were tested,and the microscopic morphology and thermal properties of the samples were analyzed by scanning electron microscopy,thermogravimetric analysis and dynamic mechanics analyzer.The results show that the peak acceleration of the collision energy absorbed by the helmet after each accelerated aging treatment is less than 150g(g=9.80665 m/s^(2)),and it can still play a safety protection role in actual use,mainly due to the existence of the helmet buffer layer.According to the morphology change,rupture and stiffness performance of the sample after aging,the evaluation of the shell material shows that the PC/ABS alloy sample has the best performance.The evaluation of the aging method shows that the effect of UV aging is the smallest,followed by 65℃hot air aging,and the helmet is seriously deformed and has more cracking situations after 85/85 humidity-heat aging,which does not meet the actual use scenario.After 85/85 humidity-heat aging,the micromorphology of the sample shows that the cross-sectional microporous structure increases,but the thermal stability is not changed much.The helmet shell material directly affects whether the sample is broken after the crash test,and the peak acceleration of the collision energy absorbed by the helmet is greatly affected by its buffer layer,and the stiffness performance can be used as an effective evaluation index for the material performance of the helmet shell.