INTRODUCTION

Motivation
• Improving through-thickness thermal conductivity in laminated composites could lead to increased use of composites in many thermal applications

Goal
• Developing the fundamental understanding of the effect of microstructure on thermal properties would allow optimization based on functional requirements

Approach
• Evaluate effect of fiber tow shape, orientation, volume fraction and stacking sequence on thermal properties
• Implement various FE models to correlate the microstructure with thermal conductivity

FE MODEL IMPLEMENTATION

Finite Element model assumptions
• Assume isotropic and homogeneous material properties for fiber and matrix
• Specify constant temperature on the top and bottom; insulated on sides.
• Apply a thin resin layer on top and bottom of the laminates
• Numerically: to avoid singularities < 10% thickness of fiber tow layer
• In reality: resin rich surface layer does exist for class A surface finish

FIBER TOW CROSS-SECTION SHAPE EFFECT

STACKING SEQUENCE STUDY

HEAT FLUX OBSERVATION

GEOMETRIC PARAMETER

SUMMARY

• Fiber volume fraction is the dominant factor determining thermal conductivity.
• Models containing elliptical fiber tows with major axis through the thickness show larger thermal conductivity than those with circular shape or major axis within the plane.
• UD-ply all in the same direction always exhibit higher through-thickness thermal conductivity than cross-ply and general stacking sequence.
• A geometric parameter is proposed to better understand and correlate effective thermal conductivity variation with fiber tow orientation.
• These microstructure effects can be further extended to tailor composite thermal conductivity.

ACKNOWLEDGEMENT

This work is supported by National Science Foundation (CMMI-0970002).