Load Bearing Properties of Three-Component Polymer Composites Ahsan Ahmed, 1 Atef Fahim, 1 Hani E. Naguib 2 1 Department of Mechanical Engineering, University of Ottawa, Ottawa, Ontario, Canada 2 Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario, Canada Metal or solid polymer anchors are used as the load transfer components for foam and foam composites when they are used as the structural elements in design. The traditional method of fixation of these components is by fastening and adhesion. In this study, anchors were created in the form of inserts and were imbedded in the sandwich composite during the foaming process, resulting in the manufacture of three- component composite. Flexure tests were conducted to study the effect of different geometries (rectangular, cylindrical, tapered/wedge shaped) and lengths of metal inserts on the strengths of sandwich compo- sites. The stress strain response, mode of fracture of sandwich composite with metallic anchors was eluci- dated. The results showed that long tapered inserts imbedded in sandwich composite provide better load bearing and adhesion properties than other geome- tries. A model is presented that describes the relation- ship between stiffness reduction and progressive crack length of sandwich composite. Finite element analysis (FEA) of the interactions between the inserts and sand- wich composites under different loads were carried out. FEA modeling and experimental results were in good agreement, thus validating the model. POLYM. COMPOS., 31:1731–1737, 2010. ª 2010 Society of Plastics Engineers INTRODUCTION The application of sandwich composites in load-bear- ing components is rapidly increasing. Sandwich structures usually employ two thin, stiff and high performance lam- inate face sheets, bonded to a relatively thick low-density foam core. The structure through its increased moment of inertia transforms a bending load to tension and compres- sion in the face sheets. The core connects the face sheets and resists shear. The primary purpose of sandwich struc- tures is to produce load-bearing parts with a high bend- ing stiffness-to-weight ratio. The main drawback of poly- mer-based composites is their inability to withstand con- centrated load. Joints, hinges, and anchors used in polymer structures invariably are made of nonfoamed materials, primarily metals, and the interface between the two materials become the weakest link of the sandwich structures. The most common problem hindering even more wider use of such sandwich panels has been deciding how to attach them to each other or to other components of the structure. Gluing panels together can work, but it is diffi- cult and time consuming, as special fixtures and tools must be made in order to hold everything in place while the glue sets. Inserts glued into the panels have been the preferred method, but they present a different set of prob- lems, as they are applicable mostly to the metallic foams [1]. Therefore, this research presents a methodology to redesign the metallic insertion inside sandwich composites with foam core based on the superior benefits of compo- sites. Studies have been conducted on the mechanical properties of foams and composites. Daniel and Abot [2] studied the flexural properties of sandwich composite beams. It was reported that the face sheets govern the bending behavior of the beams. Theulen et al. [3] con- ducted bending tests on sandwich structures with foam cores and glass fiber reinforced epoxy facings. An opti- mum core to face weight ratio was found for both bend- ing strength and stiffness. Flexural, shear and compressive properties of sandwich composites were reported [4-6]. The primary damage mode observed was the formation of shear cracks in the core at a measured strain value. Fatigue response characteristics of sandwich composites were studied [7-9], and it was reported that both Mode I and Mode II cracking was observed in the core and along the interface between core and face sheets. Research on the experimental, numerical results for bending and inden- tation of rectangular sandwich plates and panels were car- ried out [10-13]. A computer-based modeling technique to assist the development of a novel-bending test on simple supported sandwich plates was also presented. Indentation Correspondence to: Hani E. Naguib; e-mail: naguib@mie.utoronto.ca DOI 10.1002/pc.20963 View this article online at wileyonlinelibrary.com. V V C 2010 Society of Plastics Engineers POLYMERCOMPOSITES—-2010