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Specimen in a closed chamber. b High speed camera, c steel projectile inside a polystyrene foam, d specimen placed on top of a holder
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The present work aims to investigate experimentally the crack arrest capability and dynamic fracture mechanisms under impact loading of three commercial, rubber-toughened (RT) PMMA grades differing by their rubber nano-particle concentration and resulting Charpy impact toughness. For that purpose, Kalthoff and Winkler (KW)-like impact tests were pe...
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... diameter gas launcher was used. A gas pressure ranging typically between 0.5 and 10 bar allows for launching a 100 g-weight projectile at a speed ranging typically between 20 and 350 m/s. Various impact velocities were used in this study ranging between 20 and 100 m/s. Figure 6 shows the schematic view of the impact test experimental set-up and Fig. 7 some details. The specimen is loosely tightened on a specimen holder and then placed inside the closed chamber, see Fig. 7d. The projectile consists of a sub-calibrated, 25 mmlength and 20 mm-diameter steel projectile inserted in a 80mm length and 40 mm-diameter polystyrene foam guide, see Fig. 7c.The diameter of the steel projectile ...
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... projectile at a speed ranging typically between 20 and 350 m/s. Various impact velocities were used in this study ranging between 20 and 100 m/s. Figure 6 shows the schematic view of the impact test experimental set-up and Fig. 7 some details. The specimen is loosely tightened on a specimen holder and then placed inside the closed chamber, see Fig. 7d. The projectile consists of a sub-calibrated, 25 mmlength and 20 mm-diameter steel projectile inserted in a 80mm length and 40 mm-diameter polystyrene foam guide, see Fig. 7c.The diameter of the steel projectile is slightly lower than the distance between the two ...
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... view of the impact test experimental set-up and Fig. 7 some details. The specimen is loosely tightened on a specimen holder and then placed inside the closed chamber, see Fig. 7d. The projectile consists of a sub-calibrated, 25 mmlength and 20 mm-diameter steel projectile inserted in a 80mm length and 40 mm-diameter polystyrene foam guide, see Fig. 7c.The diameter of the steel projectile is slightly lower than the distance between the two ...
Citations
... The materials studied in this research are PMMA and RT-PMMA, both of which are transparent shock resistant materials. PMMA is a raw material without rubber addition while RT-PMMA65 and RT-PMMA 100 are rubber-added variants with the number signifies the percentages level of additives [11]. They are primarily made up of polymethyl methacrylate and a tough phase that is generally present as a core/shell dispersion. ...
The implementation of glass in various industries may cause some problems due to its brittleness characteristic. Its usage in the transportation sector has led to death and serious injuries to drivers and passengers in vehicles. It shows that the manufacturing process of the materials used requires an improvement in terms of brittleness to provide better protection to the consumer. Therefore, rubber toughened PMMA (RT-PMMA) was introduced as the rubber has the ability to increase the ductility of PMMA. PMMA and two different grades of RT-PMMA namely RT-PMMA65 and RT-PMMA100 were taken into consideration to investigate the effect of different rubber contents on the ductility of PMMA. Other than strain rate and temperature, humidity is also one of the factors that affect the ductile properties of PMMA. In this study, tensile tests at different humidity levels (11% and 98%) will be carried out by immersing the specimens in two different solutions which are lithium chloride (LiCl) and potassium sulfate (K 2 SO 4 ) beforehand. The output from the experimental works proved that the tensile properties of RT-PMMA are affected by the presence of humidity for all three grades of PMMA under consideration. It is also proved that RT-PMMA100 is more ductile compared to RT-PMMA65 on the tensile test.
... protection window, requires an evaluation of its crack arrest capability under impact loading. For that purpose, a series of Kalthoff and Winkler (KW)-type impact tests [2][3] has been carried on several grades of RT-PMMA evidencing the role of the rubber nanoparticles concentration, see [4,5]: the higher the nano-particles concentration the higher the resistance to crack propagation. ...
... Moreover, within the impact velocity range [20m/s;40m/s], cracks initiated from the notches tips are seen to arrest inside the specimen, with a crack advance depending on the impact velocity, see KW-type specimen and projectile used for the KW-type impact tests. After [5] 3 Numerical procedure Numerical simulations were conducted using the industrial computation code LS-DYNA employing the three-dimensional SPH-based spatial discretization and the explicit time integration scheme. ...
... Evidence of crack arrest inside the plate. After [5] In order to be as close to the experimental conditions as possible, all the parts interacting during the impact were modeled. Both RT-PMMA doubly-notched plate and steel sub-calibrated projectile were discretized using particles (SPH), and the polyethylene foam projectile guide (sabot) using finite elements, see Fig.3b. ...
The use of shock resistant RT-PMMA in engineering structures potentially subject to accidental overloading requires an evaluation of its crack arrest capability under impact loading. Based on experimental results obtained from a series of Kalthoff and Winkler (KW)-type impact tests, the present study aims at numerically reproducing the conditions for brittle-like crack initiation and propagation in impact-loaded RT-PMMA. For that purpose, three-dimensional SPH numerical simulations were conducted and the performance of various failure criteria was evaluated. The numerical model together with a combination of stress- and strain- dependent failure criteria were shown to fairly reproduce the experimental results in terms of finite crack advance and orientation.
The objective of the present work is to propose an engineering-oriented numerical methodology capable of reproducing crack initiation and arrest in semi-brittle structures under high loading rate. With this aim in view, the SPH-based method implemented in LS-DYNA is employed to reproduce the three-dimensional crack initiation, propagation and arrest in a rate- and temperature-dependent grade of RT-PMMA under Kalthoff and Winkler-type impact loading. The ability of critical maximum principal stress- and critical plastic strain-controlled failure criteria, first individually and then combined to reproduce the crack arrest was evaluated by comparison with experimental results. In spite of the overall brittle nature of the PMMA matrix, it was shown that the most pertinent criterion for the material of interest is the one expressed in terms of critical plastic strain, as a consequence of the gain in ductility brought by the embedded rubber nanoparticles. In pratice, the real crack pattern can be reproduced only if the two criteria are used together. Following a design of experiment, an optimised set of values for the critical maximum principal stress and plastic failure strain were found. A good agreement in terms of crack advance (as a function of the impact velocity) and propagation angle is seen between the experimental and numerical results.
The discrete element model (DEM) has attractive advantages in expressing multiple cracks propagation problem in continuum, but the description of material plastic characteristics by current DEM is restricted by the connection model, which is the core procedure in DEM modeling process. A Godunov‐type continuum‐based DEM model is proposed to solve the dynamic response of materials under high‐speed impact, in which there is a state transition of material model from continuous to discontinuous. In this paper, under the framework of DEM, the contact discontinuity between adjacent elements is analyzed with the Godunov method, and a connection model derived from the physical process is established. Firstly, the numerical solution of the Riemann problem, which is equivalent to the plane wave collision operator, is solved by an iterative method, and an explicit time‐marching integral format for the dynamic impact problem in elastic‐viscoplastic materials is derived. Then, the numerical model is validated by comparing the calculation results with theoretical results, using a wave propagation example in plate. In addition, the capacity of simulating material property discontinuity and multiple cracks are validated by cases of stress wave transmission and reflection at the materials interface and the cracks capture in Kalthoff dynamic shear test, respectively.
