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# Composite Materials/Safety factor for composite structures

Question
Hello and good day.

I am a master student in the field of mechanical engineering. I have a project which requires me to determine the strength of a laminated composite structure. What I would like to know is how do I evaluate the strength of this composite structure.

I've read a few composite books and found out on these laminated composites failure criteria such as Tsai-Hill, Hoffman, Tsai-Wu, etc. However, these failure criteria are used to evaluate the strength of laminated composite plates.

What I am analysing is an aircraft hinge made of laminated composite. As you know, the hinge is not a plate. So, I was wondering how do I evaluate the structural integrity of this hinge. How do I know that the composite material is capable of withstanding the applied load.

For a monolithic metal, I can easily calculate the factor of safety of the hinge and decide whether or not the hinge can withstand the applied load. Since, laminated composite are orthotropic in nature, how do I calculate the factor of safety of the composite hinge?

Is there any other method to evaluate the structural integrity of the composite hinge beside calculating the factor of safety?

For the stress analysis, I am using FEA software (MSC Nastran).

This is a complex question, if I want to answer it in detail. To begin, if you do Nastran on Aluminum, how do you evaluate the safety factor? You compute the von Mises stress. Well, that is a failure criterion. The same for composites. You evaluate a failure criterion. Please dont use Tsai-Wu. It´s not good. You need to read my textbook.

Composite Materials

Volunteer

#### Ever Barbero

##### Expertise

Structural Mechanics, Mechanics of Materials, Structural Analysis, Material Modeling (numerical, analytical), Testing (mechanical, aging, etc.) of Composites and Polymers, mainly Polymer Matrix and to lesser extent Materials Science and Processing of same. See http://mysite.verizon.net/everbarbero/

##### Experience

Working with Composites since 1983, two patents.

Organizations
Fellow, Society for the Advancement of Materials Process Engineering SAMPE
Fellow, American Society of Mechanical Engineers ASME
Member, American Society for Testing Materials ASTM
Member, American Institute of Aeronautics and Astronautics AIAA
Member, American Society of Engineering Education ASEE

Publications
100+ peer reviewed papers on every major journal on composites and mechanics
Introduction to Composite Materials Design, ISBN: 1-56032-701-4, http://www.mae.wvu.edu/barbero/icmd/
Finite Element Analysis of Composite Materials, ISBN: 1-4200-5433-3, http://www.mae.wvu.edu/barbero/feacm/

Education/Credentials
PhD Engineering Science, 1989, Virginia Tech.
BSME, BSEE, 1983, UNRC.

Education/Credentials
PhD Engineering Science, 1989, Virginia Tech.
BSME, BSEE, 1983, UNRC.

Awards and Honors
SAMPE Fellow (2006).
ASME Fellow (2003).
Best Overall Paper Award, Combined Composite Expo’99 and ASCE Materials Conference’99, Cincinnati, OH.
Best Paper Award, 1999 ASME J. of Composites for Construction, Vol. 4, No. 4, p. 185-191.
MAE Alumni Academy Award for Outstanding Teaching, 1999.