针对碳纤维头盔和超高分子量聚乙烯(PE)头盔,采用坠落式冲击试验台和基于冲击加速度及头部损伤指数(HIC)评价方法,系统研究了材料种类、缓冲垫密度和服役环境温度对头盔吸收碰撞能量的影响。结果表明:随着缓冲垫密度的增加,两种头盔在低温(-20℃)条件下的冲击加速度幅值均表现出增加趋势,在常温(20℃)及高温(50℃)下,碳纤维和PE头盔壳体的冲击加速度幅值均表现出明显的降低趋势。升高温度有利于降低头盔的加速度幅值,对于80g/L和90g/L的缓冲垫,两种头盔的冲击加速度幅值随温度升高都表现出降低趋势。缓冲垫密度和温度显著影响头部损伤指数,随着温度从-20℃升高至50℃,PE头盔的头部损伤指数均表现出增加趋势,然而,碳纤维头盔在50℃表现出与常温和低温相反的趋势,即随着缓冲垫密度增加,其头部损伤指数逐渐降低,但PE头盔的头部损伤指数数值低于碳纤维头盔。两种材料在冲击载荷下的损伤形貌不同:PE头盔有明显的基体凹陷形变特征但均无裂纹形成,而碳纤维头盔均表现出明显的基体开裂及纤维断裂。碳纤维由于其高刚度,在冲击力大于破坏强度后容易产生裂纹,无法通过结构系统塑性形变吸收冲击能量,是导致其在不同缓冲垫密度和不同温度条件下,头部损伤指数以及加速度幅值均高于PE的主要原因。PE具有较高的缓冲作用和吸收冲击能量能力,因此,虽然均表现出较大基体凹陷,但均无裂纹形成,采用PE头盔,头部损伤指数和加速度幅值都低于同等条件下的碳纤维头盔。

Regarding carbon fiber helmets and ultra-high molecular weight polyethylene (PE) helmets,using a drop impact test rig and evaluation methods based on impact acceleration and head injury criterion (HIC),the study systematically investigated the influence of material type,cushion pad density,and service environmental temperature on the helmet's ability to absorb collision energy.The results showed that with the increase of cushion pad density,the impact acceleration amplitudes of the two helmets at low temperature (-20℃) presented an increasing trend,while at room temperature (20℃) and high temperature (50℃),the impact acceleration amplitudes of carbon fiber and PE helmets exhibited an obvious decreasing trend.Increasing the temperature was conducive to reducing the acceleration amplitude of the helmets.For 80g/L and 90g/L cushion pads,the impact acceleration amplitude of both helmets showed a decreasing trend with increasing temperature.The density and temperature of the cushion pad significantly affected the head injury index.As the temperature increased from -20℃ to 50℃,the head injury index of the PE helmet showed an increasing trend.However,the head injury index of the carbon fiber helmet at 50℃ showed an opposite trend to the normal temperature and low temperature,that is,the head injury index of the carbon fiber helmet decreased gradually with the increase of the cushion pad density.However,the head injury index of PE helmet was lower than that of carbon fiber helmet.The damage morphology of the two materials under impact load was different:PE helmet had obvious matrix depression deformation characteristics but no crack formation,while carbon fiber helmet showed obvious matrix cracking and fiber fracture.Due to its high stiffness,carbon fiber material was prone to crack formation when the impact force was greater than the failure strength,and could not absorb the impact energy through the plastic deformation of the structural system,which was the main reason why the head damage index and acceleration amplitude of carbon fiber helmet were higher than that of PE helmet under different cushion pad densities and different temperatures.PE material had a high buffering effect and the ability to absorb impact energy.Therefore,although the matrix of PE showed a large depression,no cracks were formed.The head damage index and acceleration amplitude of the helmet made of PE were lower than that of the carbon fiber helmet under the same conditions.