Dung D. Luong

A method for intermediate strain rate compression testing and study of compressive failure mechanism of Mg-Al-Zn alloy

Obtaining meaningful information from the test results is a challenge in the split-Hopkinson pressure bar (SHPB) test method if the specimen does not fail during the test. Although SHPB method is now widely used for high strain rate testing, this limitation has made it difficult to use it for characterization of materials in the intermediate strain rate range (typically 10−1000 s−1). In the present work, a method is developed to characterize materials in the intermediate strain rate range using SHPB setup. In this method, the specimen is repeatedly tested under compression at a given strain rate until failure is achieved. The stress–strain graphs obtained from each test cycle are used to plot the master stress–strain graph for that strain rate. This method is used to study the strain rate dependence of compressive response of a Mg-Al-Zn alloy in the intermediate strain rate range. A remarkable difference is observed in the failure mechanism of the alloy under quasi-static and intermediate strain rate comp...

High Strain Rate Compressive Behavior of Polyurethane Resin and Polyurethane/Al2O3 Hollow Sphere Syntactic Foams

Polyurethane resins and foams are finding extensive applications. Seat cushions and covers in automobiles are examples of these materials. In the present work, hollow alumina particles are used as fillers in polyurethane resin to develop closed-cell syntactic foams. The fabricated syntactic foams are tested for compressive properties at quasistatic and high strain rates. Strain rate sensitivity is an important concern for automotive applications due to the possibility of crash at high speeds. Both the polyurethane resin and the syntactic foam show strain rate sensitivity in compressive strength. It is observed that the compressive strength increases with strain rate. The energy absorbed up to 10% strain in the quasistatic regime is 400% higher for the syntactic foam in comparison to that of neat resin at the same strain rate.

Dynamic Response of Syntactic Foams and Sandwich Composites: Blast and High Strain Rate Loading

Syntactic foams are hollow particle filled composite materials containing closed-cell porosity. Reinforcement of porosity by the shell of the hollow particle results in high mechanical properties of these foams compared to foams containing gas porosity and enables their structural applications. The present work is focused on discussing dynamic properties of syntactic foams. More specifically, properties of syntactic foams under high strain rate compression and blast loading conditions are discussed for potential applications in lightweight armors and military structures. The wall thickness and volume fraction of hollow particles can be tailored to obtain high damping in these materials. Crushing of hollow particles and particle-matrix interfacial failure provide additional mechanisms of energy absorption, which can be used to develop syntactic foams with high energy absorption capabilities.