# Stress Analysis and Stiffness Degradation of Open Cracks Composite Laminates Subjected to External Loads

## TL;DR

This paper studies how open cracks in composite laminates affect stress distribution and stiffness under external loads.

## Contribution

A new method is proposed to analyze stress distribution and stiffness degradation in cracked composite laminates using equilibrium differential equations and complementary energy minimization.

## Key findings

- Fiber orientation and material properties significantly affect stress distribution in symmetric composite laminates.
- Structural parameters influence the reduction of cross-layer shear modulus in laminates with transverse matrix cracks.
- The results have practical implications for engineering applications involving composite materials.

## Abstract

Composite laminated structures have extensive applications in the field of bionic engineering. Proficient comprehension of the mechanical properties of these structures is instrumental in the advancement of bionic composite materials. The objective of this study is to investigate the stress distribution and degradation of stiffness in composite laminates exhibiting open smooth surface cracks under varying external loads and structural parameters. Utilizing the general series function of the laminate’s axial stress, the general expression for the stress components of the damaged laminate is derived by integrating the equilibrium differential equation, boundary conditions, and stress continuity conditions. The influence of fiber orientation and material properties on the stress distribution within each layer of symmetric composite laminates was examined. Thereafter, the reduction in cross-layer shear modulus was assessed by employing the principle of complementary energy minimization. The impact of structural parameters on shear modulus reduction was explored. The findings indicate that structural and material parameters of symmetric laminates featuring transverse matrix cracks exert a notable influence on the stress distribution and degradation of stiffness within each layer, imparting practical significance to the research outcomes in engineering applications.