Model reduces stress and warpage in polymer composite structures

August 31, 2000

CHAMPAIGN, Ill. - Fiber-reinforced composites are strong and lightweight, but suffer from hidden stresses that can warp the final product or degrade its performance. Modifying the process variables through trial and error is expensive and time consuming. Now, a model developed at the University of Illinois promises to improve both the quality and reliability of these polymeric parts.

"The warpage of composite structures during the manufacturing process is a direct consequence of residual stress development,² said Philippe Geubelle, a professor of aeronautical and astronautical engineering at the UI. "These stresses arise because of thermal expansion, chemical shrinkage and non-uniform curing. The ability to predict the residual stresses and their effects is crucial to the manufacture of dimensionally accurate composite structures."

Geubelle and his colleagues - professors Charles Tucker and Scott White, and graduate students Qi Zhu, Min Li and Daniel O'Brien - have assembled a model that simulates the heat transfer, pressure, curing and residual stress development that occurs during the manufacturing cycle of thermoset composite parts. "When working with metals, you can carve, bend or stamp the material into the desired shape; but with composites, you actually make the material as you make the part," said Tucker, the W. Grafton and Lillian B. Wilkins Professor of Mechanical and Industrial Engineering at the UI. "The manufacturing process is complicated, with many interacting physical phenomena that can affect the final form. Our model allows us to explore those phenomena and to perform our 'trial and error' on a computer instead of on a factory floor."

Often, improving one processing variable only makes the overall problem worse because another variable that had previously been offset becomes more prominent, Geubelle said. "This points out the need for a thorough and fundamental approach to the issues that control the manufacturing process." By simulating the mechanical effects of process variables, the model allows engineers to predict accurately the final dimensions and residual stresses in polymer-matrix components - including the tendency of parts to change shape and "spring forward" when removed from their molds.

"Combining the simulation with special optimization methods creates a powerful and versatile analytical tool that can help reduce product defects and improve dimensional accuracy," Tucker said. "We can tell the software which parameters we are willing to change, and the program runs multiple simulations to find the best manufacturing solution that satisfies all of our requirements."
-end-
Zhu presented the model at the International Congress of Theoretical and Applied Mechanics, held Aug. 27 to Sept. 2 in Chicago. A paper describing the model will appear in the Journal of Composite Materials. Another paper in which the model is used to optimize the curing process will appear in the journal Polymer Composites. Funding was provided by the National Science Foundation.

University of Illinois at Urbana-Champaign

Related Composites Articles from Brightsurf:

Researchers prove titanate nanotubes composites enhance photocatalysis of hydrogen
In a paper published in NANO, researchers from National Taiwan University examined the photocatalytic performances of titanate nanotubes (TNTs) against commonly-used titanium dioxide (TiO2) and discovered superior performance of TNTs.

Scientists propose multifunctional liquid metal nanocapsules
Prof. LI Chaoxu and his coworkers from the Institute of Bioenergy and Bioprocess Technology (QIBEBT) of the Chinese Academy of Sciences (CAS) have proposed multifunctional liquid metal nanocapsules.

Nanocrystals from recycled wood waste make carbon-fiber composites tougher
In a new study, Texas A&M University researchers have used a natural plant product, called cellulose nanocrystals, to pin and coat carbon nanotubes uniformly onto the carbon-fiber composites.

Machine learning reveals vulnerabilities in 3D-printed carbon-fiber composites
Components made of glass- and carbon- fiber reinforced composites, soaring in high-performance applications, can be 3D printed.

Titanium oxide-based hybrid materials promising for detoxifying dyes
Photoactive materials have become extremely popular in a large variety of applications in the fields of photocatalytic degradation of pollutants, water splitting, organic synthesis, photoreduction of carbon dioxide, and others.

Self-assembling, biomimetic composites possess unusual electrical properties
Sometimes, breaking rules is not a bad thing. Especially when the rules are apparent laws of nature that apply in bulk material, but other forces appear in the nanoscale.

IKBFU Physicists keep improving 'smart' composites for biomedical sensors
The new composites are related to the multiferroic-class materials which have mutually controlled magnetic and electric properties.

New study presents stretchable and colorless solar cells, using Si microwire composites
A recent study, affiliated with South Korea's Ulsan National Institute of Science and Technology (UNIST) has introduced a flexible and transparent solar cell, using silicon microwire composites.

KIST researchers develop high-capacity EV battery materials that double driving range
Dr. Hun-Gi Jung and his research team at the Center for Energy Storage Research of the Korea Institute of Science and Technology have announced the development of silicon anode materials that can increase battery capacity four-fold in comparison to graphite anode materials and enable rapid charging to more than 80% capacity in only five minutes.

New nano-barrier for composites could strengthen spacecraft payloads
The University of Surrey has developed a robust multi-layed nano-barrier for ultra-lightweight and stable carbon fibre reinforced polymers (CFRPs) that could be used to build high precision instrument structures for future space missions.

Read More: Composites News and Composites Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.