# Failure Propagation Controlling for Frangible Composite Canister Design
## 1 Introduction  
A canister cover protects a missile from foreign object intrusion, shock, and weather effects such as rain and waves, and facilitates smooth ejection during missile launch. The first covers were represented from rigid doors [1] or covers that are ruptured by explosive means prior to missile launch [2]. [PERSON] [3] introduced a breakable cover using glass/epoxy laminae so that with the passage of the missile the cover would break, however, this solution didn't prevent the surface of the missile from being damaged during the launch, while [PERSON] et al. [4] numerically estimated the degradation of launch performance caused by the remnants of a missile canister cover with a sabot interface. An alternative solution aimed at ensuring the integrity of the missile during launch has been proposed by [PERSON] et al. [4]; this solution was validated by experimental tests and it consisted of a number of laminated composite canister covers fabricated and subjected to static burst pressure testing. Recently, the preferred canister cover is usually the rupture-type, which is easily manufactured and provides excellent handling, even though it could potentially compromise the adjacent structure if the missile canister cover does not break during launch. An innovative concept for a canister, consisting of a single carbon fiber composite laminate, is investigated, and by varying the geometric configuration, it is possible to optimize the fracture path and the contact force, as done with scaled panels subject to impact loads on the composite material [5, 6]. To trigger the fracture, some areas without fibers called carvings were formed to delineate triangular fragments, which were named petals. The approach used in this work is based on the Chang-Chang failure criterion [7], which was used for damage initiation and failure propagation controlling of the canister cover, the first-ply failure prediction of laminated composite plates was verified in several work comparing the experimental results [8, 9]. [PERSON] et al. in the work [10] applied the Chang-Chang criterion in analyzing the quasi-isotropic carbon/epoxy composite laminates underlow-velocity impact, conversely [PERSON] [11] used it for high velocities. Meanwhile, a failure analysis of a frangible cover was studied based on transient dynamics via the finite element method in comparison with the experimental results [5]. The aim is to design a suitable tailgate shape that improves reliability and ensures the safe launch and good protection during the life of the missile. The goal of this work is to develop a scientific and methodological approach to the study of the controlled fracture structure for the design and optimization of the missile tailgate. The state of the art with regard to the sea canister consists of the enclosure that contains the missile on the deck of the ship and is the only protection from external impact. The canister is usually made of metal, while the cover is made of polymer or ceramic materials, as shown in Figure 1. To prevent damage to the missile tip, in some cases a sabot is inserted between the missile and the cover to reduce the impact force. Usually, the tailgate type varies according to size, velocity envelopes and environment. Small size missile covers consist of flexible or breakable tabs, while medium and large size missile tailgates have a mechanical opening or are the rupture-type which have a programmed break. Common configurations have a four-pavilion dome, and the missile is placed on a trolley in the canister as shown in Figure 2 below. The Marte ER in Figure 3 is one of the most successful missiles produced by MBDA, and has a four-pavilion configuration with an internal stiffener at the tip which puts it in contact with the missile tip and the tailgate top. The stiffeners and the tailgate design provide a proper tailgate fragmentation, reducing contact force and accelerating the petals, as shown in Figure 4.  
Figure 1: Overview of a similar canister for a Harpoon missile [4].