Macro-Micro Mechanical Behavior of a Highly-Particle-Filled Composite Using Digital Image Correlation Method

Particle reinforced composites represent a large group of materials used in a variety of applications, such as concretes and solid rocket propellant. The mechanical behavior of these materials depends on properties of constitutes and any microstructural changes that may occur in the body under loading. Generally, particles are applied to high stress in these composites. Heterogeneity plays an important role in composite fracture. Because the mechanical properties of dispersed phase and matrix differ from each other, any one of the following micro-damage nucleation mechanisms has been observed during the deformation process, including cracking of particles, debonding at the particle-matrix interface and fracture of the matrix. In addition, failure also depends on the volume ratio of particles to matrix. The polymer bonded explosive (PBX) is a highly filled composite material of crystalline high explosives (90%-95% by weight) in polymer binder. This matter is a kind of functionally energetic materials being used increasingly as energetic fillings in both civil and military applications when a very high performance is required. The mechanical properties of PBX subjected to a range of conditions are important criteria to determine a safe working life. The study on the mechanical properties and the failure mechanisms of PBX has drawn much attention in recent years [1-9]. Low strengths and safety concerns bring additional difficulties in preparing samples and conducting mechanical tests of PBX. Therefore, the fracture behavior and the failure mechanisms of PBX are not full understood, some beneficial works are still need to be done to bring some further insights into this issue. There are many techniques to measure the deformation in experimental test. Strain gauge and extensometer are widely used, while the microstructure deformation can not be provided by these techniques. Significantly, the strain gauge measures the deformation at a single point, which only gives information at one point, and the gauge may provide local reinforcement causing error in the displacement measure. Several high resolution and noncontact optical techniques do have the advantages that they can measure the whole displacement and strain field providing deformation information, and it is enough to follow strains until failure. In recent years, many beneficial works have been reported from Cavendish Lab. The quasi-static deformation fields were measured by this technique. The influence of particles microstructure was found to be significant for its fracture behavior