# Presentation: 128361

## Large Deformation Non-Linear Response of Composite Structures

- C.C. Chamis
- NASA Glenn Research Center
- Cleveland, OH
- L. Minnetyan
- Clarkson University
- Potsdam, NY

- Invited Presentation for Innovative  Solutions to Challenging Problems
- NASA Workshop on FEM & FEA
- Goddard Space Flight Center
- Greenbelt, MD - May 18, 2000

## Presentation Outline

- Background
- Objective
- Approach
- Applications
- Composite panel fracture
- Composite shell-burst
- Composite containment
- Composite pre-forms manufacturing
- Summary

## Progressive Fracture Under Cyclic Load(Experimental Data:  Mandel, et al)

## Objective

- Describe a non-traditional computational simulation method/computer code to a variety of non-linear structural responses

## What is This Non-Traditional Computational Method?

- Bottoms-up synthesis for structural behavior/response
- Telescoping composite mechanics
- Top-down decomposition for local effects
- Progressive substructuring
- Nodal-base finite element formulation
- Progressive structural fracture
- Incremental linear updating
- Multi-factor interaction material behavior model
- Node(s) - by - node(s) un-zipping
- Integrated into a seamless computer code (CODSTRAN)

## COMPOSITE DURABILITY STRUCTURAL ANALYSIS (CODSTRAN)

## Multi-Scale Hierarachical SimulationComputational Simulation: Recursive A;;lication of Laminate Theory

## CODSTRAN Damage Tracking - Representative Points
1. Equilibrium - no damage
2. Initial damage: degrade properties
3. Damage accumulation: more degradation
4. Damage stabilization: no additional damage
5. Damage propagation

- 1. Equilibrium - no damage
- 2. Initial damage: degrade properties
- 3. Damage accumulation: more degradation
- 4. Damage stabilization: no additional damage
- 5. Damage propagation

## Composite Structural Performance Evaluation Summary

- Structural Analysis Model (SAM)
- Where:
- Solution of SAM:

- Structural Integrity
- Fatigue and Life
- Structural Durability
- Structural Reliability

## Overall CODSTRAN Simulation

## Stiffened Composite Panel

## Compressive Load with End DisplacementAS-4/HMHS[[0/±45/90]s]6

## Predicted and Measured Ultimate Loads for Compression Tests

## Pressurized Cylindrical ShellsGraphite/epoxy laminated compositeVf = 0.60;  Vv = 0.01;  Tcu = 177°C (350°F)

- In all cases damage initiation was my matrix cracking due to transverse tensile stresses in 0° plies.
- For the defect-free shells, fiber fractures did not occur until the burst pressure was reached.

## Damage Progression With Pressure

## Damage Progression With Pressure

## Composite Shell Burst Pressure (PSI) Summary

## Failure of the (90/0/+75/-75)s Laminate at 104psi

## Composite Containment Structure - Finite Element Model

## Effect of the Shell Thickness on the Damage

## Woven, Knitted, Braided & Non-woven Fabric Structures

## Traction Test

- Traction Test of a soft matrix fiber-reinforced Composite under tension:
- 2 plies of initial angles +/- 50 degrees
- Initial geometry of 2 in. x 0.01 in.
- Length of the ends of the specimen do not change
*Traction Test Specimen*
*Initial Finite Element Mesh*
*Finite Element mesh at 30% Elongation*

## Traction Test

## Traction Test

- Remarks:
- The deformations must be monitored to prevent elongation of the fibers
- The computation of the local fiber angle provides valuable information on the process
*Fiber angle at 30% elongation*
*Finite Element mesh at 30% elongation*

## Tube Manufacturing Process Geometry

- Simulation of a Tube Manufacturing Process:
- Cylindrical fiber weaves and mold of same diameter
- The bases are fixed to coincide with each other

*Fiber Weaves:*
*Cylinder of 5 in. diameter and 18 in. long*

*Mold:*
*Bent Cylinder of 5 in. diameter and radius of curvature of 11 in.*

*Result:*
*Fiber Weaves fitted over the mold*

## Summary

- A non-traditional computational simulation method with a seamless computer code for non-linear structural response/behavior was described
- It is bottoms-up synthesis; top-down decomposition with incremental linear updating
- Its versatility was demonstrated by presenting simulating results from
- Composite panel fracture
- Composite burst
- Composite containment
- Composite pre-forms manufacturing
- The method/computer code is unique
- Only one of its kind