Evaluation of Flexural Stiffness For The Lightweight Polymer Foam Core Sandwich Structures
Composite sandwiches are the multi-layer structural members that can be designed with vast variety of materials to obtain desired physical and mechanical properties. Very high strength to weight ratio, good impact and corrosion resistance, heat and acoustic insulation are the main advantages of the composite sandwich structures. Besides these, depending upon the core and face sheet materials it also provides superior flexural stiffness. However, the evaluation of the flexural stiffness of the sandwich structures is not based on a common standard and the calculations have been carried out according to the sandwich handbooks’ formulations which are related to cumulative summation of each layer stiffness. In this study, the flexural stiffness of a sandwich having lightweight polymer foam core (48 kg/m3 PVC) and carbon fiber facings (3K woven plain, 200 g/m2) was evaluated with the aid of ASTM D7250/D7250M – 06 Standard. The composite sandwiches manufactured by vacuum bagging method were tested considering two different loading configurations as indicated in ASTM Standard under three-point bending loading. The span length was first determined as 150 mm and then 200 mm, respectively. The use of ASTM D7250 Standard approach eliminates additional tests for determining the young modulus of the core and facings and directly helps to calculate flexural stiffness considering two different loading configurations.
Index Terms: Sandwich structures, flexural stiffness, three-point bending test, ASTM D7250 Standard.