Experimental investigation of impacted multidirectional laminates under compressive static and cyclic loading

• Published in: Composite structures 2023-10, Vol.322, p.117335, Article 117335
• Main Authors: Jia, Zijiao, Garnier, Christian, Pastor, Marie-Laetitia, Rousseau, Jérôme, Gong, Xiaojing
• Format: Article
• Language: English
• Subjects: Engineering Sciences; Impact damage; Infrared thermography; Post-impact compression fatigue; QIQH laminates
• ISSN: 0263-8223
• DOI: 10.1016/j.compstruct.2023.117335

•The impact, compression after impact and post-impact compression fatigue properties of three QIQH laminates were investigated.•The thermographic method was applied to determine rapidly fatigue limit and S-N curves of post-impact fatigue CFRP laminates.•The difference in crack orientations and distributions of three stacking sequences have little influence on the residual compressive strength and post-impact fatigue properties. In this paper, the static and fatigue behaviors under compression of Multi-Directional (MD) Carbon Fiber Reinforced Polymer (CFRP) laminates with impact damage were investigated. After low-velocity impact performed on three 24-ply Quasi-Isotropic Quasi-Homogeneous (QIQH) laminates having different stacking sequences, the influence of the distribution of interfaces between two plies on the compression after impact and post-impact compression fatigue properties was evaluated. The damages on the surfaces and internal delamination were accessed via visual and optical observation and ultrasonic C-scan inspection. The thermographic approach, which has been developed and validated on numerous non-impacted composite materials, was applied for the rapid determination of the fatigue limit together with the S-N curves of post-impact fatigue specimens. Experimental results showed that with 5 J impact energy, the three stacking sequences gave similar impact results. The residual strengths measured by compression after impact tests were also similar to each other, so did the global damage modes. The determined fatigue limits of impacted specimens of different stacking sequences were nearly identical and the predicted S-N curves were also close to each other despite the exact crack propagation and orientation were not the same, under both compressive static and cyclic loads.