Integration of Process Parameter Control and Digital Image Correlation Methods in an Investigation of the Variability of Marine Polymer Matrix Composite Material Properties

The nature of continuous fiber composite materials, with their combination of layered
and interwoven fibers bound together by a polymer resin matrix, lead to an inevitable variability
in mechanical properties. This is especially true if the fabrication process is not well controlled.
Unlike fabricating components with metals, where the properties of the material are known
beforehand, the final properties of the composite material are determined during the process of
fabricating the composite part. The research described herein was undertaken to better enable the
use of polymer matrix composites in the marine construction industry by developing a
knowledge base on the relationships between manufacturing parameters and the material
properties of the finished parts.
 

Professionals from the marine composite fabrication industry were consulted to obtain
insight into the process parameters of concern for today’s composite materials manufacturing
methods. The survey of industrial marine designers and fabricators was intended to identify
potential sources of variability and to characterize processing issues. In addition to the survey, a
thorough literature review was conducted to identify current research areas for manufacturing of
composites.
 

The research was broken up into two distinct phases; A Round-Robin Study and a
Laboratory Study. The Round-Robin Study was intended to investigate the variability in
material properties encountered when different manufacturers fabricate identical composite parts
with identical base materials, while the Laboratory Study investigated the effects of various
manufacturing variables during the fabrication of composite laminates under controlled
conditions.
 

A three-dimensional digital image correlation (DIC) system was implemented throughout
this research. The DIC method uses photogrammetry to measure full-field strain and position
over the entire visible imaging area of the test specimen. Statistical analysis of the test results
was performed to characterize the variability in material properties in accordance with the
guidelines set forth in Composite Materials Handbook-17, which is the composite industry’s
standard for composite materials testing and analysis.
 

This integrated research will contribute to advance scientific understanding on the
relationships between process parameters and mechanical property variability of composite
materials. The impact of the research is to enable the development of rational composites
fabrication methods and reliable engineering design procedures.