Aerospace Composites — Laminate Design & FEA

Introduced composite material systems — fiber types, resin systems, and performance trade-offs versus metallic structures. Covered failure modes, damage tolerance, and when composites are and aren't the best choice. Included an introductory FEA exercise applying stress, strain, and deformation analysis to composite structural components.

Examined the testing procedures used to verify prepreg material properties before manufacturing — including chromatography, DSC, and viscosity tests. Analyzed cure cycle stages, failure modes at each stage, and the effect of temperature excursions on resin advancement. Applied stress analysis frameworks to evaluate cured laminate performance.

Derived and applied Classical Laminate Theory (CLT) to multi-ply composite laminates — developing the ABD stiffness matrix, computing ply-level stresses and strains, and applying failure criteria (Tsai-Wu, max strain). Covered constitutive relationships, transverse shear, and bending-extension coupling for unsymmetric laminates.

Applied composite plate theory to model thin and thick laminates using midplane reference assumptions. Covered transverse shear, Kirchhoff-Love plate kinematics, and bending/in-plane coupling. Performed FEA using Abaqus to extract ply-level strains, interlaminar stresses, and first-ply failure loads across a range of laminate stacking sequences.

Optimized composite laminate stacking sequences using FEA-driven optimization in Abaqus. Applied gradient-based and GRG (generalized reduced gradient) methods to minimize weight while meeting strength constraints. Iterated fiber angle and ply thickness combinations to achieve maximum structural efficiency under combined loading conditions.

Performed extensive Abaqus FEA on composite sandwich structure panels — modeling face sheets, core materials, and adhesive interfaces. Extracted section forces from Abaqus to feed into hand calculations verifying margin of safety. Analyzed failure under bending, shear, and combined loading with fiber strain constraints applied at the ply level.

Modeled a composite laminate cylinder (h=50in, r=30in) with a 10in access hole cutout in Abaqus CAE using 3D shell elements. Partitioned the geometry, assigned laminate layup properties, meshed with shell elements, and applied internal pressure loading. Post-processed stress concentrations around the cutout and compared failure indices across multiple laminate configurations.