复合材料开孔板拉伸损伤对剩余压缩强度的影响

Effect of tension damage on structures residual compression strength of open-hole composite laminates

通过试验和数值分析相结合的方式,探究含孔复合材料层合板拉伸损伤对其剩余压缩强度和失效模式的影响。试验方面,首先,通过开孔复合材料层合板拉伸试验引入两种程度的拉伸损伤,使用热揭层方法表征和量化其拉伸损伤程度。随后,开展含拉伸损伤的开孔复合材料层合板压缩试验,记录其载荷-位移曲线,并通过数字图像相关法(DIC)、应变片、微距相机等手段观察其变形和损伤演化特征。数值分析方面,构建基于LaRC失效准则的渐进损伤失效模型描述层内损伤演化,使用内聚力单元方法刻画复合材料层间分层损伤,基于此模型探究了开孔复合材料层合板损伤扩展规律。试验结果表明:拉伸载荷引起的孔边复合材料损伤以基体裂纹和分层损伤为主,在加载方向和纤维朝向夹角较小的层间,分层损伤程度更大。拉伸损伤会进一步加剧孔周应变集中,使孔邻域应变呈非对称,导致结构局部屈曲更早地发生,进而诱发结构整体破坏,相对于不含拉伸损伤开孔板,含拉伸损伤开孔板可使结构压缩承载能力下降25.8%。构建的数值计算模型可以准确预测拉伸载荷下孔周剪切应力引起的分层损伤和压缩阶段应变域场演化特征,也可揭示含不同程度拉伸损伤的开孔板压缩损伤扩展模式差异及探究纤维弯折失效、基体损伤和层间分层对结构承载能力的影响规律,为复合材料开孔板在变载荷作用下结构设计与剩余强度的确定提供支撑。

The influence of tension damage on residual compression strength and failure mode of open-hole composite laminates was investigated by tests and numerical analysis.In terms of test,firstly,two degrees of tension damage were introduced through the tension test of open-hole composite laminates,and the degree of tension damage was characterized and quantified by the thermal decal method.Then,the compression test of open-hole composite laminates with tension damage was carried out,the load-displacement curve was recorded.The damage evolution characteristics were observed by digital imaging correlation(DIC),strain gauge,macro camera and other means.In terms of numerical analysis,a progressive damage failure model based on LaRC failure criteria was constructed to describe the intralaminar damage evolution,and cohesive elements method was established to describe the interlaminar damage of composite materials.Based on this model,the damage expansion law of open-hole composite laminates was explored.The experimental results show that the damage caused by tensile load is mainly matrix crack and delamination damage,and the delamination damage is greater between layers with small angle between loading direction and fiber direction.Tension damage will further aggravate the strain concentration around the hole,resulting in an asymmetric strain in the neighboring region of the hole,leading to the local buckling of the structure earlier,and then inducing the overall failure of the structure.Compared with the open-hole composite laminates without tension damage,the open-hole composite laminates with tension damage can reduce the compressive bearing capacity of the structure by 25.8%.The constructed numerical calculation model can accurately predict the delamination damage caused by the shear stress around the hole under tensile load and the evolution characteristics of the strain field in the compression stage,and can also reveal the difference in the compression damage expansion mode of the open-hole composite laminates with different degrees of tension damage,and explore the effects of fiber bending failure,matrix damage and interlayer delamination on the structural bearing capacity.This work can provide support for structural design and determination of residual strength of openhole composite laminates under varying loading.