Co-authors​ :

 P MAHESH (INDIA), Viswanath CHINTHAPENTA , Gangadharan RAJU , M RAMJI (INDIA) 

The aerospace and automotive industries have witnessed a significant increase in the usage of polymer matrix composites because of their excellent mechanical properties and higher strength-to-weight ratio. However, uncertainties in failure prediction become a deterrent to their optimal design. The strength and dominant damage modes of composite structures often depend upon the material system, stress concentration points, size of laminate, and loading conditions. For aircraft design certification of composite structures, the pyramid of tests approach is considered where coupon level to structural level experiments are carried out. Developing a numerical model capable of accurately predicting damage initiation to ultimate failure under various loading conditions, sizes, and materials will reduce the cost and time involved in aircraft design certification of composite structures. Although the strength and damage modes depend upon loading conditions and the size of the laminate, uniaxial open-hole tension (OHT) or compression (OHC) experimental data is commonly used to validate numerical models. However, damage modes and evolution patterns developed for various sizes of laminates under different combined loading cases may not be reflected in the OHT or OHC test scenario. So, the numerical models validated against OHT or OHC loading cases are incomplete and robust. Therefore, this work presents the mesoscale 3D continuum damage model to predict the effect of in-plane scaled laminate size on the open-hole strength and damage modes of CFRP laminates subjected to combined tension-shear loading scenarios. Later, the developed numerical model predictions are benchmarked against the experimental findings of in-plane open-hole CFRP Quasi-Isotropic (QI) laminates under combined tension-shear loading conditions, including the scaling phenomenon. Intra‐laminar damage is predicted based on the LaRC05 continuum damage model by considering the identification of matrix fracture, fiber kink band angle, and in-plane shear non-linearity. Further, intra-ply damage is modeled using the linear continuum damage method. Inter-laminar damage onset and evolution are predicted by ABAQUS inbuilt cohesive zone quadratic traction and Benzeggagh-Kenane (B-K) mixed mode fracture laws, respectively. A good agreement between numerical damage predictions and experimental Digital Image Correlation (DIC) and Acoustic Emission (AE) data is observed. Further, an error in the numerical open-hole strength predictions is within acceptable limits of corresponding experimental data.