Damage progression and failure of single-lap thin-ply laminated composite bolted joints under quasi-static loading. (15th March 2020)

• Record Type: Journal Article
• Authors: Cao, Yuejie; Cao, Zengqiang; Zhao, Y.; Zuo, Duquan; Tay, T.E.
• Is Part Of: International journal of mechanical sciences. Volume 170(2020)
• Publication Date: 2020-03-15
• Subjects: Laminated composites -- Bolted joints -- Thin-ply -- Damage progression -- Failure; Mechanical engineering -- Periodicals; Génie mécanique -- Périodiques; Mechanical engineering; Maschinenbau; Mechanik; Zeitschrift; Periodicals; 621.05
• DOI: 10.1016/j.ijmecsci.2019.105360
• Languages: English
• ISSNs: 0020-7403

Abstract

Highlights: Detailed experimental failure analysis of single-lap thin-ply composite bolted joint is conducted. The interrupted observation of failed specimens is carried out by X-ray micro-CT and SEM. The bearing failure modes of the thin-ply laminates are similar to the conventional thickness composite. Furthermore, the fiber-matrix splitting is more serious although the delamination of the cross-section is near suppression. Mechanical test results show that the thin-ply laminate bolted joint has higher bearing capacity and longer progressive damage stages compared with the traditional thickness composite joints. Abstract: Composite bolted joints are widely used on primary and secondary load-bearing structures of aircrafts. However, investigating the damage progression and failure of composite bolted joints under high bearing loads is challenging due to the geometric, contact and material nonlinearities. In this work, an extensive experimental study has been carried out to investigate and understand the damage evolution and failure of single-lap thin-ply laminated composites bolted joints under quasi-static loading. Quasi-isotropic carbon/epoxy laminates with stacking sequence [45/0/-45/90]4s were selected for fabricating the test specimen. The specimens were observed using X-ray computed tomography (CT) scanning and SEM imaging at different stages of the loading process to evaluate internal damage and deformation characteristics. The results indicate that the bearing failure of composite bolted joints can be interpreted as an accumulated damage process with local compressing, and mainly includes four stages: damage initiation, damage evolution, non-linear softening and catastrophic failure. The major failure modes of the thin-ply laminates are found to be similar to those of traditional thickness composite, including fiber breakage, matrix cracking, delamination, fiber kinking and fiber-matrix splitting. However, the major difference is that the delamination growth in the bearing area in thin-ply composites is suppressed compared with the traditional thickness composites. Therefore, the obtained experimental data provides valuable information for developing mechanism-based failure models of single-lap thin-ply composite bolted joints. Graphical abstract: Image, graphical abstract