Brittle Composite Material Design, Preparation Technology And Properties Of Experimental Research

In the structure of weapon industrial products fast developed recently, appeared a special kind of composites which have to have not only sufficient strength and stiffness to bear its working load but also ability to disintegrate in some specific triggering conditions. With this character of working mechanism this kind of composites are called "fragile composites" in this paper. For many fragile composite structures, such as the cover of missile launch canister etc., the function of disintegrating was implemented by explosive cut of blasting fuse. This method is reliable to ensure the structure disintegrating on time but there exist some drawbacks for it. The first one is that the electron component and initiating explosive device would be disabled after long-term deposition, and the second is that the blow wave of the explosive would hurt the electronic instrument inside the missile head. Therefore, to sought and develop new non-explosive fragmentation method is now becoming the focus of study on the fragile composites in weapon industry.According to the related literatures home and abroad, the working mechanism of fragile composites was proposed and some new fragile composites and structures were designed in this paper. Meanwhile, the design of material and its structure, and its preparation technology and fragmentation character were systematically studied.In this paper, the formula for calculating the strength of the short fiber reinforced composites was modified according to the tensile testing results of short glass fiber /191 resin composites. The failure criteria for short fiber fragile composites was established which provided a theoretical basis for the design of short fiber fragile composites. And also the testing database for short glass fiber /191 resin composites was established.The biomechanical property of eggs which can bear large uniform pressure was studied, and based on the failure criteria of short fiber fragile composites a short fiber/191 resin composite dome was designed as an application example. The results of the compressive test and the impact test showed that the fragile composite dome meets the requirements of its working mechanism.In this paper, a prestressed continuous fiber reinforced ejection fragile composite mortar case was designed based on the ejection propagation mechanism of the garden balsam seeds, and the mortar case model was prepared by filament winding process. The results of the compressive test and the impact test showed that the fragile composite mortar case can bear the air resistance to protect the biochemical substance in the shell and the mortar case will regularly fracture and release the biochemical substance under the impact. The numerical results agree well with the experimental results.According to the characteristics of unidirectional composites which tensile strength along the fiber direction is much higher than that along the direction vertical to the fiber a groove was made perpendicular to fiber direction, and then the orthotropic fragile composite laminate was prepared by these unidirection plies with grooves. The results of the compressive test and the impact test showed that the orthotropic fragile composite laminate can bear given uniform pressure, and will rapidly fracture along the pre-cast groove under impact.In this paper, based on a new concept of material design using regular assemblies of topologically interlocked elements proposed by Y. Estrin and A. V. Dyskin, and also based on the idea of "lu ban lock", a Chinese ancient educational toy, a new topologically interlocked fragile composite structure was proposed. As an application example, the model of water-resisting cover of deep sea missile launcher system was designed and its test specimen was prepared. The results of the simulation test showed that the topologically interlocked composite water-resisting cover can bear certain uniform water pressure, and will rapidly fracture under the reverse impact.In the last part of this paper, starting from fracture mechanics theory, a K_IC gradient composite plate which actively control the crack growth was designed and prepared with different material prescriptions in different layers. The crack propagation and the fracture morphology were observed by scanning electron microscopy （SEM）. Results showed that the crack propagated rapidly in the layers with lower value of K_IC, howether, the crack propagated difficultlyalong with the thickness direction.Summarily, some new development was made in this paper in the following aspects:1. The concept of "fragile composites" was firstly put forward based on their common character of working mechanism.2. The failure criteria of short fiber fragile composites was firstly established. The failure criteria provides a theoretical basis for the design of short fiber fragile composites.3. Starting from Bionics, the prestressed continuous fiber ejection fragile composite mortar case was designed and prepared based on the ejection propagation mechanism of the garden balsam seeds, firstly.4. A new topologically interlocked fragile composite structure was put forward and designed. This structure will enrich the non-explosive trigger fragmentation methods of the fragile composite structure.5. A K_IC gradient composite plate which actively control the crackgrowth was designed and prepared with different material prescriptions in different layers, firstly.