This paper investigates size effects on the mechanical response of additively manufactured lattice structures based on a commercially available polylactic acid (PLA) polymer. Initial attention is focused on investigating geometrical effects in the mechanical properties of simple beams and cubes. Following this, a number of geometrically scaled lattice structures based on the body-centered cubic design were manufactured and tested in order to highlight size effects in their compression properties and failure modes. A finite element analysis was also conducted in order to compare the predicted modes of failure with those observed experimentally. Scaling effects were observed in the compression response of the PLA cubes, with the compression strength increasing by approximately 19% over the range of scale sizes investigated. Similar size-related effects were observed in the flexural samples, where a brittle mode of failure was observed at all scale sizes. Here, the flexural strength increased by approximately 18% when passing from the quarter size sample to its full-scale counterpart. Significant size effects were observed following the compression tests on the scaled lattice structures. Here, the compression strength increased by approximately 60% over the four sample sizes, in spite of the fact that similar failure modes were observed in all samples. Finally, reasonably good agreement was observed between the predicted failure modes and those observed experimentally. However, the FE models tended to over-estimate the mechanical properties of the lattice structures, probably as a result of the fact that the models were assumed to be defect free.

In recent, the efforts to reduce environmental pollution by developing biodegradable material has received wide interest. The aim of this paper is to investigate the effect of durian skin fiber (DSF) on the properties of thermoplastic cassava starch (TPCS) matrix as the biodegradable material. The composites were prepared by using hot press technique to convert the starch into thermoplastic starch polymer. The effects of incorporating different amount of DSF (0-50 wt.%) on the matrix was evaluated using several testings, i.e., water absorptions, water solubility, thickness swelling, moisture content, biodegradation analysis and density measurement. The results show that incorporation of DSF has reduce the water absorption characteristic of the material. Thickness swelling of the sample were increase following the addition of DSF into the TPCS matrix, indicating improve environmentally friendly properties. Water solubility of the composites showed a decreasing trend with increasing DSF content. The morphology of the samples shows adhesion of fiber and matrix which indicates good compatibility between this component. Meanwhile, there is no apparent changes on the density of the composites following the incorporation of fiber. Overall, this finding shows that DSF has potential to improve the functional characteristics of TPCS matrix as alternative green material.

The aim of this paper is to investigate the effect of cogon grass fiber (CGF) on the thermal and mechanical properties of thermoplastic cassava starch (TPCS)/beeswax matrix. The alteration of TPCS/beeswax reinforced with cogon grass fiber was performed by incorporating various amount of CGF (0,10,20,30,40 wt.%) into the polymer matrix. The samples were then evaluated using thermogravimetric analysis and tensile test. The findings showed that the thermal properties of the composite were slightly improved as the CGF content increase. The mechanical test showed that the tensile strength and tensile modulus increased with the addition of the CGF. However, the elongation at break showed a decreased pattern following the increasing content of CGF compared to the 0% of fiber content. In general, the findings from this study have shown that the TPCS/beeswax reinforced with the CGF composite has improved the functional properties of the composites compared to the TPCS matrix.

Recently, ceramics and metal-armed structures have been replaced by ceramics combined with ultra-high molecular weight polyethylene (UHMWPE) composite laminated structures for NIJ level III and level IV body armor applications. This shift is due to the superior specific energy absorption capabilities of the ceramics/UHMWPE composites compared to traditional ceramics and metal armor; however, it comes at a higher cost. Manufacturing body armor that offers higher specific energy absorption at a lower cost is challenging. As the thickness of UHMWPE increases, both the specific energy absorption and the overall cost of the body armor increase. Additionally, there is limited experimental data to evaluate the thickness of ceramics and UHMWPE to explore the performance of NIJ level III body armor, indicating that further research is needed. In this study, six different types of ballistic plate configurations were manufactured. Following that, high velocity impact tests were conducted to investigate the effects of front and back layer thicknesses of UHMWPE (Type 1 to Type 3 plates), the effects of foam material (Type 4 plate), and the effects of different thicknesses of boron carbide (B ₄ C) ceramic strike face (Type 5 and Type 6 plates) on the back face signature (BFS) of the ballistic plate. It was found that the BFS of Type 5 and Type 6 ballistic plate configurations is lower by 12% and 8.5%, respectively, compared with that of the Type 4 UHMWPE/polyvinyl chloride low-density foam ballistic plate. However, the Type 5 option is cost-effective and easy to manufacture, making it the preferred choice over the Type 6 variant.

Ultra-high molecular weight polyethylene (UHMWPE) laminate composites are widely used in impact-resistant structures due to their high specific strength and exceptional energy absorption capabilities. However, previous studies encountered challenges in characterizing the tensile properties of UHMWPE composites, including specimen slippage, stress concentrations, and failures outside the gauge length. This work presents the design and development of an interchangeable clamp for the tensile testing of UHMWPE composites. This clamp guarantees secure gripping and uniform load transfer across the UHMWPE specimens. The developed clamp can be used interchangeably in quasi-static and high-strain-rate devices, facilitating the evaluation of a broad range of strain rates. The tensile properties of two UHMWPE composites were subsequently assessed using this clamping system, with strain measured through three-dimensional digital image correlation (3D-DIC). The effectiveness of a 3D-DIC technique for measuring strain in the UHMWPE composite is demonstrated. The tests reveal that the designed clamp enables reliable measurements, with tensile strength values reaching approximately 1300 MPa. The measured tensile properties are useful for the input data of numerical simulations, providing valuable insights for developing highly efficient protective structures.