# Effect of Cohesive Properties on Low-Velocity Impact Simulations of Woven Composite Shells
## 1 Introduction  
Low-velocity impact tests are commonly employed for assessing the damage resistance and tolerance of fibre-reinforced composite structures. The extensive research in this area focuses on experimental analysis, aiming to comprehend the intricate progressive degradation of the material, considering inter-related failure mechanisms [1, 2]. The intrinsic characteristics of the structure and of the impactor, and the prevailing environmental conditions collectively influence the structural response to low-velocity impact events. Visual inspection of the damaged area, measurement of dent depth, and a nondestructive evaluation, such as C-Scan, may be used to assess the damage extension in a structure that has experienced low-velocity impact(s) [3]. Typically, matrix cracking is the initial failure observed at the onset of the impact force. Subsequently, delaminations are induced by the matrix cracking and propagate further as the applied force continues to increase. A substantial decrease in force can frequently be used to detect the emergence of notable delaminations [4]. Depending on the amount of impact energy, there may be noticeable fibre breakage after the delamination has grown. Due to the flexibility of the matrix and the disorganisation of the broken fibres, persistent indentation may appear after the impact [5]. Understanding the phenomenon of impact damage in laminated composite structures presents a significant analytical challenge due to its intricate and complex nature. The numerical models built using the finite element (FE) method, on the other hand, are a powerful tool for predicting physical processes. Many different impact configurations and structures can be studied using FE models, especially in situations when experimental testing would be prohibitively expensive or complex [6; 7; 8; 9]. The computing requirements increase as the model's complexity increases. Hence, there is a need to dedicate efforts towards developing time-efficient FE models. Simulating low-velocity impact tests on composite structures poses a challenging problem due to the occurrence of contact and progressive degradation of the material. Consequently, it is crucial to accurately model the interlaminar and intralaminar failure mechanisms within an FE analysis. Additionally, defining several important parameters that can impact the precision of numerical predictions, such as material properties, element types, FE mesh discretization, assembly of the parts, and imposed boundary conditions, becomes imperative [10]. There is a scarcity of numerical studies focusing on the impact dynamics of cylindrical composite shells. Among the notable studies, [PERSON] et al. [11] conducted research that revealed a relationship between the curvature of composite shell and the contact force. They observed an increase in contact force with a higher shell curvature, accompanied by a decrease in deflection and the contact duration. Furthermore, they found that the velocity of the impactor had a more significant influence on the contact force compared to the mass of the impactor. Another noteworthy study by [PERSON] [12] demonstrated a similar contact force and deflection. [PERSON] and [PERSON] investigated the onset and evolution of impact damage in composite shells [13], while [PERSON] and [PERSON] established scaling relationships between impact energy, momentum, mass, and velocity [14]. In their investigation, [PERSON] et al. [15] employed an FE analysis to examine the impact behaviour of cylindrical composite shells. This paper aims to study the effect of the cohesive properties on the numerical predictions of low-velocity impact events on woven-fabric composite shells. This work is based on the FE modelling strategy presented in [16] and the experimental testing performed in [2]. The ABAQUS/Explicit [17] VUMAT subroutine specifically designed for fabric-reinforced composites was used to capture the intralaminar damage [18]. Simultaneously, a surface-based cohesive model (S-BCM) was implemented to account for the interlaminar damage.