Strength Of Sandwich Beams Research Articles

Influence of Rigid Inserts on Shear Modulus and Strength of Sandwich Beams with Polyurethane Foam as Core

In the present work, core shear modulus and flexural rigidity of sandwich panels with three different densities ranging from 100 to 300 kg/m3 and with two different thicknesses (8 and 6 mm) of polyurethane foams separated by glass fiber bi-woven impregnated with epoxy resin as facings have been experimentally determined as per ASTM C 393 and analyzed in the light of data obtained by other researchers. The influence of different volume fractions (0.1 and 0.2) of rigid inserts made of polyurethane foam of 900 kg/m3 density between facing and core at beam center on core shear modulus have been examined. The results have also been analyzed with core shear modulus obtained from direct shear test. Also, the failure modes of the sandwich panels and the corresponding strengths of the sandwich panels tested have been analyzed in detail. The influence of rigid inserts on the failure mode and strength of the sandwich panel has also been investigated.

Performance of Sandwich Structures with Composite Reinforced Core

Sandwich panels with a foam core reinforced with composite laminates were investigated. The effective material properties of the reinforced core were obtained by homogenization. The general equations of equilibrium for sandwich plates were derived and used for parametric studies of the behavior of the sandwich plates. Three Point Bending tests were performed to experimentally measure the bending stiffness along with the strength of sandwich beams. The test results were also used to verify the analytical solution obtained by using the sandwich plate theory. It was found that local indentation must be included in the theoretical model. Static punching tests (SPT) and low velocity impact (LVI) tests were performed to investigate the behavior of sandwich plates under static and dynamic point loads. The force-displacement relations were modeled based on indentation data. The damage modes, effects of the core reinforcement, and effects of the foam were investigated. A second manufacturing method for constructing the reinforced core was presented, and its properties were compared with those obtained using the original manufacturing method.

Performance of Sandwich Structures with Composite Reinforced Core

Sandwich panels with a foam core reinforced with composite laminates were investigated. The effective material properties of the reinforced core were obtained by homogenization. The general equations of equilibrium for sandwich plates were derived and used for parametric studies of the behavior of the sandwich plates. Three Point Bending tests were performed to experimentally measure the bending stiffness along with the strength of sandwich beams. The test results were also used to verify the analytical solution obtained by using the sandwich plate theory. It was found that local indentation must be included in the theoretical model. Static punching tests (SPT) and low velocity impact (LVI) tests were performed to investigate the behavior of sandwich plates under static and dynamic point loads. The force-displacement relations were modeled based on indentation data. The damage modes, effects of the core reinforcement, and effects of the foam were investigated. A second manufacturing method for constructing the reinforced core was presented, and its properties were compared with those obtained using the original manufacturing method.

Strength of sandwich beams with interface debondings

The adhesive joint bonding the faces to the core material in a sandwich structure ensures that the loads are transferred between the components. However, debondings may arise either during the manufacturing process or due to overloading. These will reduce both the stiffness and the load bearing capacity of the structure. In the present paper, debondings in foam core sandwich beams are investigated assuming that cracks in the interface between the face and core are present. Stress intensity factors are found from an analytical model and compared to solutions from several finite element calculations. Fracture toughness values, determined from simple specimens, are used to predict the fracture loads for beams with simulated debondings subjected to four-point bending.

Strength of sandwich beams with mid-plane debondings in the core

Sandwich beams containing cracks in the mid-plane of the core are investigated. The cracked part is subjected to a constant remote shear stress field. Beams with different cross-section geometries and materials were analyzed by the finite element method (FEM) in order to compute the stress intensity factors at the crack tips. An analytical approach for estimation of the energy release rate, based on a potential energy calculation, is presented that agrees well with results from the FE analyses. Results from four-point bending tests with cracked beams show that the fracture load can be accurately predicted. The simplicity of the analytical model makes it possible to compute critical crack lengths and safety factors for various types of sandwich beams.