Polylactic acid (PLA) is a widely used biomaterial in medical applications as a biodegradable and renewable aliphatic polyester type of material. This material is often subjected to different defects and damages from in-service and manufacturing conditions, and the increasing demand for PLA for different applications requires a thorough understanding of its fracture behavior. In this work, a numerical and experimental study of the mixed-mode fracture behaviors of three-dimensional (3D)-printed PLA samples with a zigzag pattern of different filling ratios was performed using a recently developed special loading fixture. The 3D-printed samples were produced with a 200°C nozzle at 60°C bed temperature and 50 mm/s printing speed. Mixed-mode fracture tests from pure tensile to pure shear loading were performed by varying the loading angle, α, from 0 to 90°. Finite-element analyses were conducted by using the Abaqus software program, and geometrical factors were obtained at different loading angles. As a result, the fracture toughness values of pure tensile loading, pure shear loading and mixed modes were determined.

Metal–polymer–metal hybrid sandwich panels are gaining importance in civil, automotive and aerospace applications due to their light weight and damping properties. Compared with composite materials, hybrid materials consisting of separate metal and thermoplastic parts can be recycled much more easily. Besides their applications as covering material on buildings as well as general insulation material, recycled aluminum (Al)–low-density polyethylene (LDPE)–aluminum hybrid panels yield a potential usage of light ballistic protection. In this study, a standard hybrid panel of 3·2 mm polyethylene filling and two 0·4 mm aluminum metal sheets was experimentally tested under ballistic impact. A finite-element model was used with a commercial software program and validated against the experimental results. The finite-element results show that stacking of multiple layers of panels absorbs more energy than an equivalent single-layer panel. Six layers of stacked hybrid aluminum–LDPE–aluminum panels are capable of absorbing the impact energy of a 9 mm pistol projectile, and they can be utilized as recyclable inexpensive ballistic protection materials.

Metal-polymer-metal hybrid sandwich panels are gaining importance in various industrial applications due to their light weight and damping properties. When compared with composite materials, hybrid materials consisting of separate metal and thermoplastic parts can be recycled more easily. In addition to their applications in civil engineering, the aluminum-low density polyethylene-aluminum (Al-LDPE-Al) sandwich panels yield a potential use as light ballistic protection material. In this study, a standard hybrid panel of 3.2 mm polyethylene filling and 0.4 mm of two aluminum metal sheets was experimentally tested under ballistic impact. A finite element model was constructed via commercial software and validated through shooting experiments with a rifle under real conditions. The finite element model was used to simulate the oblique impact behavior of Al-LDPE-Al sandwich panels as a single layer, as 5 layers stacking and as a single layer equivalent of the stacked 5 layer. Results showed that the oblique impact does not have a significant effect on the single layer panel. Stacked layers, however, and the equivalent single layer of a stacked layer have the highest energy absorption under a 30° hitting angle.

Metal-polymer-metal hybrid sandwich panels are gaining importance in various industrial applications due to their light weight and damping properties. When compared with composite materials, hybrid materials consisting of separate metal and thermoplastic parts can be recycled more easily. In addition to their applications in civil engineering, the aluminum-low density polyethylene-aluminum (Al-LDPE-Al) sandwich panels yield a potential use as light ballistic protection material. In this study, a standard hybrid panel of 3.2 mm polyethylene filling and 0.4 mm of two aluminum metal sheets was experimentally tested under ballistic impact. A finite element model was constructed via commercial software and validated through shooting experiments with a rifle under real conditions. The finite element model was used to simulate the oblique impact behavior of Al-LDPE-Al sandwich panels as a single layer, as 5 layers stacking and as a single layer equivalent of the stacked 5 layer. Results showed that the oblique impact does not have a significant effect on the single layer panel. Stacked layers, however, and the equivalent single layer of a stacked layer have the highest energy absorption under a 30° hitting angle.