A Kinematically Enriched Directed Continuum Damage Mechanics Approach to Model Low-Velocity Impact Damage in Composites
Topic(s) : Material and Structural Behavior - Simulation & Testing
Co-authors :
Manish KUMAR (INDIA), Supratik MUKHOPADHYAY (INDIA)Abstract :
Fibre-reinforced polymer (FRP) composites are highly used in aviation and automobile industries due to their combination of lightweight and impressive strength. In spite of numerous advantages, composite structures are prone to catastrophic failure due to their innate brittleness, which is a significant concern for aviation and transportation sector where passenger safety is paramount. One common damage event for composite structures is low-velocity impact (LVI). External aircraft components may experience unforeseen impact loads in diverse scenarios, ranging from ground operations to encounters with birds. This type of impact typically affects the interior of the laminate, leaving the exterior seemingly undamaged upon visual inspection. Therefore, it is also referred to as Barely Visible Impact Damage (BVID). Advanced structural health monitoring techniques are commonly required to identify the location and extent of this type of damage experimentally, which increases inspection cost and time. Computational realization of LVI events incorporating accurate damage models provides an alternate route to understand better this type of damage in a quick and inexpensive way.
In a Finite Element (FE) framework, modeling of damage under LVI commonly involves the utilization of continuum damage mechanics (CDM) framework at ply-level and cohesive zone models (CZM) for interface damage. However, the conventional CDM method degrades material stiffness over the entire element volume. This smeared damage approach results in an overall softening response but fails to represent the ‘discrete’ nature of ply cracks and crack-delamination interaction. Another drawback of the classical CDM is the mesh direction bias [1]. To circumvent these problems, a local fiber direction-oriented mesh is often employed for each ply [2], which increases meshing efforts significantly and causes mesh mismatch at ply interfaces. This necessitates the imposition of tie constraints to maintain assembly integrity which significantly increases computational time.
The present work employs a kinematically enriched directed CDM (D-CDM) approach [3, 4] to numerically simulate the onset and growth of damage under LVI in a multidirectional laminate. The D-CDM enhances traditional CDM by incorporating an accurate kinematic representation of the sharp crack topology of ply matrix cracks at the constitutive level. Additionally, a crack tracking algorithm is applied to eliminate mesh orientation bias in ply crack growth, reducing meshing efforts. The removal of tie constraints further contributes to a reduction in analysis time. This technique is implemented as a 3D user-defined material in Abaqus/Explicit. The numerical results obtained through this novel method are compared with experimentally obtained damage patterns reported in the literature [2], along with associated load-displacement curves, demonstrating excellent agreement.
In a Finite Element (FE) framework, modeling of damage under LVI commonly involves the utilization of continuum damage mechanics (CDM) framework at ply-level and cohesive zone models (CZM) for interface damage. However, the conventional CDM method degrades material stiffness over the entire element volume. This smeared damage approach results in an overall softening response but fails to represent the ‘discrete’ nature of ply cracks and crack-delamination interaction. Another drawback of the classical CDM is the mesh direction bias [1]. To circumvent these problems, a local fiber direction-oriented mesh is often employed for each ply [2], which increases meshing efforts significantly and causes mesh mismatch at ply interfaces. This necessitates the imposition of tie constraints to maintain assembly integrity which significantly increases computational time.
The present work employs a kinematically enriched directed CDM (D-CDM) approach [3, 4] to numerically simulate the onset and growth of damage under LVI in a multidirectional laminate. The D-CDM enhances traditional CDM by incorporating an accurate kinematic representation of the sharp crack topology of ply matrix cracks at the constitutive level. Additionally, a crack tracking algorithm is applied to eliminate mesh orientation bias in ply crack growth, reducing meshing efforts. The removal of tie constraints further contributes to a reduction in analysis time. This technique is implemented as a 3D user-defined material in Abaqus/Explicit. The numerical results obtained through this novel method are compared with experimentally obtained damage patterns reported in the literature [2], along with associated load-displacement curves, demonstrating excellent agreement.