# Multiscale Compressive Failure Analysis of Wrinkled Laminates Based on Multiaxial Damage Model

## TL;DR

This paper studies how wrinkles in composite materials affect their strength and failure under compression, using experiments and a new simulation model.

## Contribution

The paper introduces a novel multiscale model combining a generalized method of cells with multiaxial Hashin failure criteria to predict compressive failure in wrinkled composites.

## Key findings

- Wrinkles reduce the ultimate load capacity of composite laminates.
- The multiscale model accurately predicts failure modes and load-displacement curves.
- Wrinkles promote local buckling and alter damage distribution.

## Abstract

The waviness defect, a common manufacturing flaw in composite structures, can significantly impact the mechanical performance. This study investigates the effects of wrinkles on the ultimate load and failure modes of two Carbon Fiber Reinforced Composite (CFRC) laminates through compressive experiments and simulation analyses. The laminates have stacking sequences of [0]10S and [45/0/−45/90/45/0/−45/0/45/0]S. Each laminate includes four different waviness ratios (the ratio of wrinkle amplitude to laminate thickness) of 0%, 10%, 20% and 30%. In the simulation, a novel multiaxial progressive damage model is implemented via the user material (UMAT) subroutine to predict the compressive failure behavior of wrinkled composite laminates. This multiscale analysis framework innovatively features a 7 × 7 generalized method of cells coupled with stress-based multiaxial Hashin failure criteria to accurately analyze the impact of wrinkle defects on structural performance and efficiently transfer macro-microscopic damage variables. When any microscopic subcell within the representative unit cell (RUC) satisfies a failure criterion, its stiffness matrix is reduced to a nominal value, and the corresponding failure modes are tracked through state variables. When more than 50% fiber subcells fail in the fiber direction or more than 50% matrix subcells fail in the transverse or thickness direction, it indicates that the RUC has experienced the corresponding failure modes, which are the tensile or compressive failure of fibers, matrix, or delamination in the three axial directions. This multiscale model accurately predicted the load–displacement curves and failure modes of wrinkled composites under compressive load, showing good agreement with experimental results. The analysis results indicate that wrinkle defects can reduce the ultimate load-carrying capacity and promote local buckling deformation at the wrinkled region, leading to changes in damage distribution and failure modes.