Authors: Yoshinobu Shimamura, Keiko Oda, Akira Todoroki, Hideo Kobayashi, Takaomi Inada
Abstract: Bolted joints are widely used for composite structures. As is well known, excessive bearing load gives rise to bearing failure at hole boundaries. Detecting bearing failure is important for assuring integrity of composite structures. Conventional nondestructive inspection methods are expensive, cumbersome, time-consuming, and not suitable for health monitoring, and a simple, low-cost inspection method for bearing failure must be developed. Authors have experimentally demonstrated detection bearing failure by an electrical resistance change method. In this study,
detectablity of remote damage, which includes bearing failure, using an electric resistance change method is investigated analytically. The results show that fiber breaking and delamination induce permanent increase in the electric resistance of the bolted composite joints, and that the proposed method, which involves measuring electric resistance, is effective for detecting bearing failure.
653
Authors: Yu Pu Ma, Xin Zhi Lin, Qing Fen Li, Zhen Li
Abstract: When stress is high, delaminate damage can be induced by transverse cracks. A complete
parabolic shear-lag damage model containing delamination induced by transverse cracks is
therefore proposed and applied to predict the stiffness reduction by transverse cracking in cross-ply
laminated composite materials. The predictions of the complete parabolic shear-lag analysis
model, the incomplete parabolic shear-lag analysis model, and the complete parabolic shear-lag
damage model containing delamination proposed in this paper have been compared. Results show
that the young’s modulus reduction values obtained by our analysis model are better agreement with
the experimental ones than other models.
43
Abstract: Failure process of laminated composites is performed by progressive failure analysis method. A modified form of Hashin’s failure criterion by Shokrieh is used to investigate the failure, where a sudden degradation model is proposed to reduce engineering material constants. The numerical study of laminated composites is implemented in ANSYS Parametric Design Language (APDL). The initiation and propagation of local damage and response of laminated composite structures from initial loading and ultimate failure are predicted. The model has been validated by comparing numerical results with existing experimental results. And then failure analysis of specimen fabricated from M40J/Ag80 on influence of the hole has been performed by the proposed model.
590
Authors: Vaibhav A. Phadnis, Farrukh Makhdum, Anish Roy, Vadim V. Silberschmidt
Abstract: The use of composite materials such as carbon fiber-reinforced plastic (CFRP) has grown considerably in recent years, especially in aerospace, automotive, sports and construction industries. The properties such as high strength and stiffness, low weight, excellent fatigue and corrosion resistance have made them a useful material for light-weight applications. Though parts made from CFRP are often manufactured to a near-net shape, various machining processes such as drilling, can be used to facilitate assembly of structures. Drilling CFRPs involve penetrating through several plies of laminate, which causes high stresses and strains in the vicinity of the drilled hole. Thus, the machining process not only affects the overall hole quality but also initiates discrete damage phenomena such as micro-cracking, matrix burning; delamination and fiber pull out in the specimen. Moreover, the cutting edges of a drill wear dramatically out due to presence of highly abrasive fibers in the matrix, resulting in increased thrust forces that can cause interply delamination.
150
Authors: Chun Hao Ma, Fei Xu
Abstract: This paper proposed a composite damage model including the damage initiation and evolution based on strain to predict the composite intralaminar damage under impact loading. In the numerical simulation, the user material subroutine VUMAT and the cohesive-zone model are chosen to describe the composite damage model and the delamination of interfaces between different plies. ABAQUS software is used to simulate the low-velocity impact of different thickness composite laminates. It is found that the delamination shape and area, the contact force and the deflection of the impactor obtained by the numerically simulation agree well with the experimental results.
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