A fiber-reinforced composite's stiffness follows the rule of mixtures, weighted by how well the fibers
are aligned with the load direction (angle θ).
E_composite = Vf·Ef·cos⁴θ + Vm·Em
δ_max = F·L³ / (48·E·I)
σ_fiber = E_fiber·ε · Vf
- Fiber angle — orientation of reinforcing fibers relative to the load axis; 0° is stiffest.
- Fiber volume fraction — proportion of fiber vs. matrix resin; more fiber usually means stiffer, stronger material.
- Applied bending load — force applied at the beam tip, driving visible deflection and stress.
- Unidirectional / Cross-ply — switches between all-fibers-one-way and alternating 0°/90° layers, which resist bending differently along each axis.
This layered fiber-matrix model is exactly how real carbon-fiber and glass-fiber composites are engineered
for aircraft wings, wind-turbine blades and racing car chassis.