Experimental Evaluation of Shear Properties of Lightweight PVC Core for Marine Application Using Digital Image Correlation System

Abstract

Sandwich structures are well-known and frequently used solutions in marine applications, especially when structural stiffness is required. An important part of the sandwich structure is the core, which usually carries shear loads. Therefore, choosing a reliable test method and knowing the exact shear properties of the particular core used in the structural design is beneficial for every engineer. Shear properties of the FlexyFoam M-55, a closed-cell, lightweight PVC foam with an apparent density of 60 kg/m3, have been investigated according to the ASTM C273 standard, using the tensile and compressive loading of metal supporting plates glued to the PVC foam sample. A digital image correlation (DIC) technique was used to monitor the crack propagation, and the appearance of secondary stresses at the foam-adhesive interface and strain field for the representative sample was presented. Displacement was measured using the testing machine sensors and compared to the measurements from the DIC technique. Specimen manufacturing details, surface preparation, and the gluing sequence were described, and measuring equipment and experiment settings were presented. Stress-strain curves have been presented and shear modulus and ultimate shear strength of the foam were compared for each test approach. The results were discussed and compared with the manufacturer’s data, as well as with foams of similar densities. The well-established approach in testing the core material was discussed, and recommendations were given to improve the testing procedure.

Recent Advancements in Design Optimization of Lattice‐Structured Materials

“…Discussing the mathematical background and methodologies of ML is out of scope of the present review; the interested readers are referred to the following studies for detailed descriptions. [160][161][162][163] Challapalli and Li [164] proposed an optimization process composed of data generation, training and testing an ML model to predict the compressive properties of newly generated dataset outperforming the conventional octet truss lattice material (Figure 13a). Initially, an RVE made of several points was constructed in MATLAB, in which various types of unit cells were generated by connecting different points using permutations and combinations commands.…”

“…Moreover, due to their high strength-to-weight ratio and high energy absorption, lattice-structured materials are also utilized in aerospace, [184,185] automotive, [162,186,187] and marine applications. [160,161,188,189] Particularly, in aerospace missions, the main function of a satellite frame is to support all other subsystems and protect them from the launching loads and the space environment. [190] This however is constrained by the strict lightweight requirements of a spacecraft.…”

“…[197,198] However, further research on the choice of core lattice structures is conducted to provide lighter structures with better mechanical behavior using AM. [160,161,188,189] Taking into consideration different loading conditions, additively manufactured lattice-filled structures provide a more favorable tool to enhance the durability of civil and military ships. In this regard, Jia et al [196] investigated the potential of using a designed central symmetric lattice structure in compressor impeller or as shells of underwater vehicles.…”

“…Discussing the mathematical background and methodologies of ML is out of scope of the present review; the interested readers are referred to the following studies for detailed descriptions. [ 160–163 ]…”