Effects of ply thickness and 0-degree layer ratio on failure mode and strength of notched composite laminates: Experiment and high-fidelity simulation
Topic(s) : Special Sessions
Co-authors :
Ryo HIGUCHI (JAPAN), Xin LU (JAPAN), Ryoma AOKI (JAPAN), Tomohiro YOKOZEKI (JAPAN), Tomonaga OKABEAbstract :
Due to the recent development of the spread tow thin-ply technology [1,2], the design freedoms of ply thickness and stacking pattern per unit thickness in the composite laminated structure have been improved. Owing to this improvement, the nonconventional stacking sequence, which has never been applied to the aircraft structure so far, will be applicable. For instance, the extremely hard laminate with a high ratio of 0-degree ply can be used in the components where the loading direction is limited in a certain direction. This means that the excellent performance (specific stiffness and strength) in the fiber direction of unidirectional CFRP is able to be used more actively.
It is well known that the “in-situ” strength, which is defined as the stress and strain at ply failure within the laminates, depends on the ply thickness. Due to the high constraint from neighboring ply, the thin ply laminates have high in-situ transverse and shear strengths [3-5]. However, it was reported that superior in-situ strength doesn't always have a good effect on laminated strength [3]. Another disadvantage to thin-ply technology is that numerous candidate stacking patterns must be reviewed in the design process. Therefore, for the optimization of the future design of CFRP laminated structures by tailoring the ply thickness and orientation, the development of a high-fidelity simulation method, which was thoroughly verified by experiments in various ply thicknesses and stacking sequences, is necessary.
This study aims to experimentally investigate the influence of ply thickness and 0-degree ply ratio on the failure mode and strength of open-hole tensile tests and to develop a high-fidelity simulation method based on the experiments. In the experiment, we prepare the 6 types of CFRP laminates by changing the ply thickness from 0.05mm to 0.2mm and the 0-degree ply ratio from 10% to 67%. For all the layups, both the fracture tests and the interrupted tests are carried out to observe the progressive internal damage using X-ray radiography. These results are used to verify the prediction accuracy of the simulation scheme. In the numerical scheme, we develop a nonlinear extended finite element method that considers both geometric and material nonlinearity, including plasticity, damage, and non-Hookean behavior. Using the developed scheme, the open-hole tensile strengths of the CFRP laminates are evaluated in the cases of various ply thicknesses and layups. And the effects of each nonlinearity on the laminate strength are examined.
It is well known that the “in-situ” strength, which is defined as the stress and strain at ply failure within the laminates, depends on the ply thickness. Due to the high constraint from neighboring ply, the thin ply laminates have high in-situ transverse and shear strengths [3-5]. However, it was reported that superior in-situ strength doesn't always have a good effect on laminated strength [3]. Another disadvantage to thin-ply technology is that numerous candidate stacking patterns must be reviewed in the design process. Therefore, for the optimization of the future design of CFRP laminated structures by tailoring the ply thickness and orientation, the development of a high-fidelity simulation method, which was thoroughly verified by experiments in various ply thicknesses and stacking sequences, is necessary.
This study aims to experimentally investigate the influence of ply thickness and 0-degree ply ratio on the failure mode and strength of open-hole tensile tests and to develop a high-fidelity simulation method based on the experiments. In the experiment, we prepare the 6 types of CFRP laminates by changing the ply thickness from 0.05mm to 0.2mm and the 0-degree ply ratio from 10% to 67%. For all the layups, both the fracture tests and the interrupted tests are carried out to observe the progressive internal damage using X-ray radiography. These results are used to verify the prediction accuracy of the simulation scheme. In the numerical scheme, we develop a nonlinear extended finite element method that considers both geometric and material nonlinearity, including plasticity, damage, and non-Hookean behavior. Using the developed scheme, the open-hole tensile strengths of the CFRP laminates are evaluated in the cases of various ply thicknesses and layups. And the effects of each nonlinearity on the laminate strength are examined.