Eventos Anais de eventos
COBEM 2023
27th International Congress of Mechanical Engineering
Comparing DD and QUAD Laminates for Single Lap Joints
Submission Author:
Lucas Vignoli , RJ , Brazil
Co-Authors:
Glosdemberger Alves, Lucas Vignoli, RANULFO MARTINS CARNEIRO NETO
Presenter: Lucas Vignoli
doi://10.26678/ABCM.COBEM2023.COB2023-0292
Abstract
Design with composite is a challenge due to the large amount of variables from micro to macroscale. Regarding the macromechanical analysis, one of the most important design definitions for unidirectional laminates is the stacking sequence or layup, which is the orientation of each lamina. The most usual layup family, namely QUAD, has the plies oriented at 0°, 90°, +45° and -45° and follows the ten percentage rule. Basically, the ten percentage rule implies that laminate must be symmetric and it must have at least 10% of laminae in each orientation, i.e. 0°, 90°, +45° and -45°. Alternatively, Double-Double (DD) laminates were recently propose by Prof. Tsai and his group, where plies are oriented at ±Psi and ±Phi, where Psi and Phi are continuous variables ranging between 0° and 90°, improving the structural optimization. DD laminates have been demonstrated better structural response than QUAD for strength and buckling analysis, saving weight and cost. The present research is an effort to compare the response of QUAD and DD laminates in bonded joints, specifically single lap joints. The damage onset is evaluated using the commercial finite element software Ansys and considering the Drucker-Prager and Tsai-Wu damage criteria for the adhesive and the laminate, respectively. Considering the following QUAD laminate [45/90/-45/0]2s as reference, the proposed methodology is validated against experimental data from literature, resulting in an error of 0.47%. To obtain the stiffness equivalence according to the classical laminate theory, the DD family [±67.5/±22.5]4 is selected. The results indicate that all DD layups improve the joint damage onset. Additionally, there is an increasing on the damage onset forces up to 25% for the DD laminates [67.5/-22.5/22.5/-67.5]4 and [67.5/22.5/-22.5/-67.5]4 than for the equivalent QUAD [45/90/-45/0]2s. A very smooth stress distribution is realized for DD laminates due to the homogenization capability, decreasing the stress concentration from abrupt geometry variation in bonded joints.
Keywords
CFRP, SLJ, Unidirectional composite, double-double laminates, quad laminates
