Impact Energy Absorption Capacity Research Articles

Impact response of aluminum foam core sandwich structures

Abstract Sandwich panels, comprised of metallic foam core and face sheets, are widely used to withstand impact and blast loadings. Based on the actual application requirements, the performance can be optimized with the proper combination of face sheets design. In this paper the impact responses of aluminum foams with various tailored face sheets, whose behavior represents elastic, elastic-ideally plastic and elastic–plastic strain work hardening, were investigated experimentally. The experiment was carried out using hemispherical indenters on blocks of aluminum foam with and without the face sheet. Competing failure modes for the initiation of failure are discussed based on comparison of energy absorption capacity. Results show that increase in thickness of foam and the use of face sheet enhances the impact energy absorption capacity. The type of face sheet not only affects the energy absorption capacity but also the failure mode for the foam blocks. Aluminum foam blocks with stainless steel sheet are strong enough to withstand the pre-designated impact loading without penetration damage. At the same time, this study also provides a comparison of the impact performance, in terms of impact energy and failure mode, among blocks with different face sheets under the low velocity impact.

Response of Foam- and Concrete-Filled Square Steel Tubes under Low-Velocity Impact Loading

This paper presents the results of experimental and numerical studies of the comparative behavior of square hollow section (SHS) tubes filled with rigid polyurethane foam (RPF) and concrete undergoing transverse impact loading. A series of instrumented drop hammer tests were performed on mild steel and stainless steel SHSs for both filled and unfilled constructions. The concrete-filled tubes had the highest impact resistance and energy absorption capacity, followed by the steel tubes filled with RPF, and then the hollow tubes. The results also show that RPFs can be used as an effective infill material in structural steel hollow columns when expedient enhancement of the energy absorption capacity is required, e.g., to increase blast and impact resistance of hollow structural elements. Nonlinear dynamic finite-element analyses were carried out to simulate drop hammer test conditions. The predicted impact forces, deformation histories, and failure modes were found to be in good agreement with the experimenta...

Impact resistance of poly(vinyl alcohol) fiber reinforced high-performance organic aggregate cementitious material

Poly(vinyl butyral) (PVB) which has many special engineering aggregate properties such as super lightweight, physical toughness, adhesion to a variety of surfaces and energy-absorbing characteristics is utilized as the sole aggregate in this study to develop a novel cementitious composite reinforced with Poly(vinyl alcohol) (PVA) fiber. Impact energy absorption capacity is evaluated based on the Charpy impact test. The results show that PVB composite material has lower density but higher impact energy absorption capability compared with conventional lightweight concrete and regular concrete. The addition of PVA fiber improves the impact resistance with fiber volume fractions. The remarkable change in the interfacial bond strength contributed by the non-covalent bond such as hydrogen bond and ether interactions at the interfaces between fiber, aggregate and matrix contributes to the improvement of the impact resistant capacity. A model based on fiber bridging mechanics and the rule of mixtures is developed to characterize the impact energy. A good correlation was obtained for the materials tested when experimental results are compared to those predicted by the developed model.

Low Velocity Impact Damage Characterization of Woven Jute—Glass Fabric Reinforced Isothalic Polyester Hybrid Composites

This study explores the effects of hybridization of glass fiber on low velocity impact behavior and damage tolerance capability of woven jute fabric composite. Laminates were fabricated by the hand lay—up technique using a mold and cured under light pressure at room temperature. Low velocity impact tests were conducted on jute and hybrid samples (150 × 150 mm) using an instrumented drop weight impact tower. All the samples were impacted at four different energy levels by changing the drop height, and load—energy—time plots were recorded using data acquisition software. Some of the samples were subjected to the non-destructive test (C-scan) to study the nature and extent of damage and to measure the delamination area. Post-impact tension tests were conducted to assess the damage tolerance capability of the composites. The results of the study indicated that jute laminates have better impact energy absorption capacity than jute—glass hybrid laminates; however their damage tolerance capability is less than jute—glass hybrid laminates.

Correlation between Charpy impact energy and J fracture toughness for thermally embrittled reactor pressure vessel steel

The Charpy impact energies of a reactor pressure vessel steel in the as received and several thermally embrittled conditions have been tentatively correlated to three J fracture toughness parameters derived under quasi-static loading regimen. Very good correlation has been achieved over the whole fracture resistance range of the structural steel, as obtained by the application of special heat treatments. It has been established that the parameters controlling the impact energy absorption capacity of the materials are the equivalent grain size of dual phase (ferrite/bainite) annealed microstructures and the bainite packet size of single phase quenched and tempered materials. The dependence of the Charpy impact energy of precracked, side grooved bend bars on the representative grain size of the microstructures tested has been disclosed as a Hall-Petch relationship.

Deformation and Fracture Mechanisms of Advanced Polymer Composites under Impact Loading

Instrumented drop weight impact testing has been used to study the impact performance of fiber reinforced polymer composites. Deformation processes and fracture mechanisms of thin-plate composite laminates were examined as a function of material parameters, plate thickness, stacking sequence, and impact loading rate. For the lami nates containing tough fibers, such as high-strength polyethylene, plastic deformation was found to be an important energy absorbing mechanism. High flexibility of these fibers allows the incident energy to be dispersed in a wider area and the impact load to be shared by a greater volume of material. A clean penetration crack was observed in the samples that contain primarily brittle fibers, such as graphite. This failure mode absorbed very lit tle incident energy. In addition, both matrix-fiber interfacial debonding and interlaminar cracking were shown to be effective in dissipating impact energy. Mechanistic study in dicated that the impact response of the laminates can be described by an initial stage of elastic deformation, followed by three stages of plastic deformation. Also, impact testing data showed that interlaminar hybridization with thermoplastic laminates was able to im prove the impact toughness of the otherwise brittle epoxy laminates. Fiber-matrix debon ding in thermoplastic laminates and interlaminar debonding between thermoplastic and epoxy laminates enhanced the impact energy absorption capacity of hybrid-matrix com posites. However, due to this poor interfacial adhesion, the result of post-impact three- point bending tests indicated an inferior damage tolerance for hybrid-matrix laminates. A simplified theory for impact failure mechanisms of composite laminates is proposed. It provides a mechanistic basis for the development of a practical model for the prediction of impact failure modes. This theory has proved to be useful in the studies on the impact penetration of more brittle composites.