## End Compression of Sandwich Columns

Toolbox to calculate the axial strength for a sandwich laminate as well as the optimal core thickness for a given load

Free

• ### Short description

  Due to their light weight capabilities sandwich colums consisting of two stiff, strong face sheets and a light weight core are used in whide rage of applications. To a good approximation, the face sheets carry the bending and in-plane loads whilst the core carries transverse shear. Under axial compression failure is due to Euler macrobuckling, core shear buckling, face wrinkling or face sheet mircobuckling depending upon the material combination and geometrz of column.    

### References

Details to the calculation as well as experimental results can be found in N.A. Fleck, I. Sridbar / Composites: Part A 33 (2002) 353-359

### Details

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Latest update

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08.01.2016

08.01.2016

1.0

Free

MIT-Licence

English

Pictures

### Screenshots

Toolbox setup

Exemplaric result of the sensitivity analysis - Influence of the layer stiffness on the sandwich fracture load

• ### Analytical formulae

Under in-plane compression at least four failure modes exists

### Elastic buckling in bending (Euler Buckling)

For the case with build in ends, the Euler Buckling load results to

$P_{ Euler }=\frac{ 4\pi^{ 2 } }{ l^{ 2 } }\frac{ btc^{ 2 }E_{ Skin } }{2 }$

with young's Modulus of the Skin E_Skin, width of the sandwich b, face sheet thickness t and core thickness c

### Elastic buckling in shear (core shear buckling)

The core shear buckling is set by the shear stiffess of the core

$P_{ S}=bcG_{ core }$

### Plastic microbuckling of the face sheets

Plastic microbuckling of the face sheets occurs when the axial compressive stress within the face sheets attains the plastic microbuckling strength

$P_{ Skin}= 2tb\sigma_{ cr }$

with the microbuckling strength sigma_cr

### Face Wrinkling

WRinkling is the short-wavelangth elastic buckling of the shace sheets. Upon assuming that the face sheets buckle as elstic beams upon a linear elastic foundation the compressive stress for wrinkling is given conservatively by

$P_{ fw}= 2tb *0.5\sqrt[3]{E_{ Skin } E_{ Core }G_{ Core } }$

### Minimum weight design for a given axial strength

Typically, in the design of a sandwich column, it is required to select the column geometry which minimises the overall mass for a given load carring capacity.

The optimal core thickness c_opt is obtained by equating the microbuckling load to the macrobuckling lad, to give

$c_{ opt }= \frac{ l }{ -\frac{ \pi^{ 2 }\sigma_{ cr }E_{ Skin } P}{ 2G_{ Core } } +\sqrt{ \left( \frac{ \pi^{ 2 }\sigma_{ cr }E_{ Skin }P }{ 2G_{ Core } } \right)^{ 2 } +\pi^{ 2 }\frac{ E_{ Skin } }{\sigma_{ cr } }}}$

with

$P=\frac{ Applied Load }{ lb\sigma_{ cr } }$

• ### Name

engidesk GmbH

Since the company’s formation as RWTH Aachen university spin-off in 2012, engidesk GmbH represents a modern and dynamic software house based in Aachen, Germany. The highly committed team of young professionals around the founders Dr. Lars Lambrecht and Marc Branscheid constantly enhances its uniquely innovative development environment for research and development engineers. The engidesk software enables companies & research facilities to make better use of their technical know-how by harmonising and standardising complex calculations across work groups and entire companies. Unique and easy-to-use interfaces allow for the seamless combination and merger of any calculation know-how to single, directly applicable modules – regardless of the original developing system. Above that, the engidesk market place provides knowledge holders with the possibility to commercialise valuable know-how by putting up problem oriented – all compatible – calculation sequences for sale.