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SAE Alabama

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Kurt Wagner

on 9 April 2013

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Transcript of SAE Alabama

By Kurt Wagner
2013 Auburn University Formula SAE
Chassis Engineer Physical Testing Build Up Method for
Monocoque Chassis Analysis Design Philosophy Design Parameters The Racecar Chassis Requirements:
Contain and protect the driver

Carry the structural loads of the suspension

Provide a mounting point for all other necessary parts AU FSAE 2011 Car Monocoque: Single Shell Stresses outer skin rather than triangulated steel tube structure

Originated in aircraft design

Adopted by Formula 1 in 1981 for its specific strength and stiffness Sandwich Composites Flat panels have low bending stiffness

Nomex and aluminum core is added to separate two carbon panels

Analogous to I-Beam Flexural Modulus 2013 Car Design Goals Weight: 35lb

Improve torsional rigidity to greater than 2600ft-lb/deg

Maintain reliability: “To finish first you first must finish”

Modify existing molds to reduce manufacture time and increase track testing Safety Considerations Minimum requirements:

Side impact stiffness and strength

Shear strength perpendicular to laminate

Driver safety harness attachment Auburn FSAE 2012 Car Team's first monocoque

Finished 4th in endurance event 12th overall at FSAE-Lincoln

2012 monocoque weight: 68lb

2012 total chassis stiffness: 1400ft-lb/deg Testing Testing Approach Computer Simulation:

Holistic view

Test complex geometry

Rapid iteration Physical Testing:

Most accurate results

Provides failure mode (9 types for side impact)

Some tests required by rules Physical Testing: 3-Point Bending Dictates layup of: side impact structure, front roll hoop support, front bulkhead support, and front bulkhead

Purpose: meet safety requirements with minimal weight

Composite: epoxy matrix, fabric, number of plies
Core: material, density, thickness Minimum Load Physical Testing: Perimeter Shear Required minimum 13kN puncture strength for 1” diameter bar Physical Testing: Seatbelt Attachment Minimum 13kN tensile load requirement
Multiple nut plates tested
Selection based on specific strength Physical Testing: Hard Points Reinforcement for point loads (suspension, chassis and engine attachment)

Compressive strength for bolt pretensioning

Additional shear area

Materials tested: G10 phenolic, Hysol adhesive, balsa wood, and solid carbon Shear Stress: Hard Point Test Sample: Core G-10 Hard
Point Tesile Testing Shear Testing Tensile Testing Shear Testing FEA/Shape Optimization FEA was used to tie together physical testing and identify highly stressed areas A topological shape optimization aided in developing where a thicker laminate was needed Manufacturing Lay up Schedule: Core Red: 1.25” thick (side impact structure)

Yellow: 0.375” thick

Green: 0.25” thick

White: No core Lay up Schedule: Carbon Plies Purple: 14-ply (side impact structure)
Red: 10-ply
Yellow: 8-ply
White: 6-ply Validation Weight 48lb painted chassis weight

29.5% savings versus 2012 chassis Torsional Stiffness Measured torsional stiffness: 3280ft-lb/deg

134% greater than 2012 Chassis Reliability Questions
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