Investigation & Simulation of Low Velocity Impact Induced Damage in Composite Overwrapped Pressure Vessel
Composite materials are used widely for aerospace and marine structures due to their superior mechanical properties, including high specific strength and stiffness, large damping, superior fatigue, corrosion resistance, etc. However, composite materials are susceptible to damage from impact loading due to their low toughness.
Especially, the damage due to low velocity impact does not clearly appear in its appearance and is difficult to detect. This barely visible impact damage reduces the strength of the structures and can cause unexpected accidents. Various low velocity impacts can occur on the composite structures during manufacturing, operation, and maintenance processes. Therefore, the impact damage and residual strength of the composite structures have been an important issue in the composite industries. The impact damage needs to be considered in the design stage and an efficient analysis tool is required to analyze the impact damage and residual strength of the composite structures.
In this study, a phenomenological composite damage model based on continuum damage mechanics (CDM) was used for the impact and residual strength analysis of composite structures. A damage variable considering the energy release rate of composite strength was derived to simulate the progression of the composite damage and it was employed in the damage model. The irreversible strain due to damage was also considered in the damage model. Also, nonlocal smeared cracking approach was considered to prevent the strain localization problem. Cohesive zone model was used to simulate the inter-laminar damage of composites. The damage model was implemented in the user material subroutine of Abaqus/explicit, VUMAT. This code can be used in both Abaqus/ Explicit & Ls-dyna software. The effect of the damages on the residual burst strength of the cylindrical composite pressure vessel was also investigated.
The analysis results such as the impact response, impact damage, and residual strength, were compared with the test data to verify the damage model and analysis methods.