Answer: Laminar composites are stacks of bonded sheets (laminae) with different fibre orientations; sandwich panels have two strong, thin face sheets bonded to a thick, light core.
Structural composites are made of layers whose properties depend on both the material and the geometric arrangement of the parts.
1. Laminar composites
- Made of two-dimensional sheets or panels (laminae), each with a preferred high-strength direction (e.g. aligned fibre-reinforced plastic or wood veneer).
- The layers are stacked so that the strong direction changes from layer to layer (e.g. 0°/90°/±45°) and are bonded together.
- Result: fairly high strength in many directions in the plane.
- Examples: plywood (wood veneers with grains at right angles), carbon-fibre laminates in aircraft parts, laminated safety glass.
2. Sandwich panels
- Two thin, strong and stiff outer face sheets (Al alloy, fibre-reinforced plastic, steel, plywood) bonded to a thick, lightweight core.
- Core materials: rigid polymer foams, balsa wood, or honeycomb (thin foils formed into hexagonal cells, perpendicular to the faces).
- Faces carry bending (tensile and compressive) loads; the core keeps the faces apart, resists shear and gives stiffness with very low weight.
- Applications: aircraft floors, wings and doors, building panels and roofs, boat hulls, refrigerated trucks; they also give heat and sound insulation.
