SANDWICH COMPOSITE BEAMS for STRUCTURAL APPLICATIONS de Aguiar, José M. , josemaguiar@gmail.com Faculdade de Tecnologia de São Paulo, FATEC-SP Centro Estadual de Educação Tecnológica Paula Souza. CEETEPS Praça Coronel Fernando Prestes, 30 - Bom Retiro - São Paulo-SP - CEP 01124-060  de Aguiar, João B. , joaobdaguiar@gmail.com Universidade Federal do ABC Centro de Engenharia, Modelagem e Ciências Sociais Aplicadas.  Av. dos Estados, 5501 Bangu 09090-400 - Santo Andre, SP - Brasil  

Structural Sandwich Composite Beam Special laminated composite type produced by bonding thin stiff skins (two) to lightweight thick core; Sandwich beam made of: Core material : modified phenolic (endure harsh weather, resists chemical and corrosion, extreme temperatures, low humidity absorption) Skin material : bi-axial glass fiber Advantage: elevated bending stiffness/weight ratio; high impact strenght and corrosion resistance; high strength core can hold mechanical connectors ( compared to honeycomb and trussed core options) high strength core holds compressive load compared to traditional soft cores. Structural beam sections can be formed by gluing sandwiches beam modules due to limited thicknesses availability: Horizontal skins Vertical skins H H

Four point bending test Property Skin Core Young´s Module (MPa) 14280 1150 Maximum tensile stress (MPa) 242 14 Maximum compressive stress (MPa) 211 21 Thickness (mm) 1.92 16.16

Rectangular beam – Horizontal position Rectangular beam – Horizontal position. Vertical displacements (1LSW_F) Load P=4550 N H Dimensions B H L Horizontal 50 mm 20 mm 400 mm Core material W 298.82 mm

Core material: Tensile stress less than 5 % of max core tensile stress Tension cracks appear at bottom of core material Mechanical Property Compressive Tensile Core max stress 21 MPa 14 MPa

Bottom skin layer: Tensile stress less then 15% of max tensile skin stress Mechanical Property Skin Core Max tensile stress 242 MPa 14 MPa

Failure Mode: compressive skin failure Compressive skin stress less than 1% of max compressive stress “Specimen 1LSW-F failed due to compressive failure of the fibre composite skin followed by delamination between the core and the skin.” A.C.Manalo Mechanical Property Skin Core Max compressive stress 211 MPa 21 MPa

Rectangular beam – Vertical position. Vertical displacements (1LSW_E) Load P=5000 N “The load capacity of specimen 1LSW-E increased linearly with deflection but showed reduction in stiffness at a load of around 5000 N due to the tensile cracking of the core.” A.C.Manalo H Skin Core Young´s Module 14280 (MPa) 1150 MPa Vertical Position B=20 (mm) H=50 (mm) Thickness 1.92 (mm) 16.16 (mm)

Core material: Tensile stress exceeds core max tensile stress “Tensile core cracks were also observed in specimen 1LSW-E. The presence of non-horizontal skin prevented the premature failure of the core” A.C.Manalo Dimensions B H L Horizontal 20 mm 50 mm 400 mm Mechanical Property Skin Core Max tensile stress 242 MPa 14 MPa H

Failure Mode: Progressive compressive failure of non-horizontal skins “The specimen 1LSW-E failed due to progressive compressive failure of the skin followed by tensile failure of the skins. “ A.C. Manalo Mechanical Property Compressive Stress Tensile Skin 242 MPa 211 MPa

Conclusions FEM results permits to infer the failure scenario shown on flexural testing of structural composite beams; Fem models for glueded laminated sandwiches : side by side and piled up cross-sections can be developed to speculate about failure modes; The beam strength depends on the number and combination of laminated skins; The effect of load-distribution of the gluing certainly needs to be taken into account into the failure scenario. Lack of information on non-linear effects as well as number and fiber orientation limits considerably the fem modeling simulations.