聚乙烯自增强复合材料损伤过程的声发射特征

复合材料在承受外载时, 声发射可产生于基体破裂、纤维-基体界面脱粘和纤维断裂等。测定了U HMWPE/ HDPE 复合材料在拉伸载荷作用下的声发射(AE) 振幅信号。对特殊试样, 即预测到断裂有明确方式, 如纤维-基体界面脱粘、基体破裂、纤维断裂和分层等的试样, 实施加载直至破坏。用扫描电子显微镜(SEM) 观测试样的断裂表面, 对产生于若干特殊损伤类型的AE 信号进行了鉴别。在相同加载条件下, 完成了不同种类的U HMWPE/ HDPE 准各向同性层合板声发射检测。结果在特殊试样损伤类型与声发射信号事件振幅之间建立了对应关系, 揭示了上述各种准各向同性层合板损伤扩展过程的AE 特征与损伤破坏机制。各种准各向同性层合板试样的声发射事件累计数对拉伸应力关系曲线相异, 其相同损伤类型发生时所对应的拉伸载荷水平不等, 表明它们的铺设角度和铺设顺序对损伤演变过程有显著的影响。结果证实了它们的最终破坏由严重层间分层造成。 

Acoustic emission characteristics of damage processes inself-reinforced polyethylene composites

Upon being subjected to the external load,acoustic emission(AE) may occur from matrix cracking,interface debonding,fiber fracture,etc in composite materials.UHMWPE/HDPE composite materials were experimented to determine the event amplitude content of AE signals under tensile loads.Special specimens,designed to fail under well-defined modes such as matrix plastic deformation and cracking,fiber-matrix debonding,fiber breakage,delamination,etc were tested under the loads from zero to failure.The fracture surfaces of the specimens were observed by a scanning electron microscope(SEM).The AE signals were distinguished as being released from(several) special types of damage.AE measurements were performed subsequently for different types of UHMWPE/HDPE quasi-isotropic laminates under the same loading conditions.The correlations are established between the damage modes and acoustic emission events amplitude of special specimens which exhibit the dominant damage mecha-nisms.The AE characteristics of damage growth processes and the fracture mechanisms in UHMWPE/HDPE(quasi-isotropic) laminates are revealed.Accumulative numbers of acoustic emission events for different types of(UHMWPE/HDPE) quasi-isotropic laminates vs tensile stress curves are different from each other;the corresponding loading levels of their same type of damage occurrence are not equal.The results show that ply stacking angles and(sequences) affect remarkably the damage growth process of these laminates.It is verified that the final fracture of these materials is caused by severe interlaminar delamination.