Response of syntactic foam core sandwich structured composites to three-point bending

Use of syntactic foams as core materials gives several distinct advantages over traditionally used core materials. Syntactic foams have an excellent combination of compressive strength, low density, low radar detectability and low moisture absorption coefficient among others. The present work aims at studying the behavior of sandwich-structured composites containing syntactic foam as core material under three-point bending conditions. Flexural and short-beam shear tests are conducted, where large (16: 1) and small (5: 1) aspect ratio (span length/thickness ratio) specimens are tested, respectively. It is observed that the specimen failure mode changes completely with the change in the aspect ratio. Specimens are found to fracture under the effect of shear stresses in the smaller aspect ratio specimens, whereas compressive stresses lead to the fracture in higher aspect ratio specimens. The observations of fracture features are correlated with the test data and the load-displacement curves obtained in the tests. A method of analysis is also presented for syntactic foams and the sandwich structures containing syntactic foam as core material.