SAMPE Journal - September/October 2012 - (Page 52)

Tech Tidbits Dr. Scott W. Beckwith SAMPE Technical Director swbeckwith@aol.com Manufacturing Defects in Composite Structures Dr. Scott W. Beckwith SAMPE International Technical Director and President, BTG Composites Inc., Taylorsville, UT The design and analysis of functioning, high performance, safe composite structures depends upon numerous decisions that the structural design engineer, the materials engineer and the manufacturing engineer must make over the course of getting a composite product into the marketplace. Theoretical design processes rely upon a firm understanding of the physics and material aspects generally of three important materials in a composite: the reinforcement fiber, the resin matrix (for polymer composites), and, that region defined as the “interface” between the fiber-resin. The latter often contributes a lot – but often is ignored in the generation of theoretical structural models1-2. To the designer/analyst the governing mathematical equations defining how the material and structure responds to loads is typically governed by a number of physical assumptions. Whether one relies upon “micromechanics”, “macromechanics” and “laminated plate theory – LPT”, the assumptions often are pretty universal in developing failure criteria. They usually mean assuming: •Fiber and resin are perfectly bonded together •Plies (individual layers) are perfectly bonded together •Plies are homogeneous in nature Consequently, failure criteria are developed in the absence of the presence of manufacturing defects which can be a significant contributor to early failure of a structural part. One then asks “what types of manufacturing defects might exist in a composite product?” In essence, the manufacturing of composite structural parts over time has often been a combination of engineering science as well as a manufacturing labor involving carefully controlled process steps and technical skills on the shop floor. Environmental and processing conditions (temperature, moisture, shelf-life, out-time, contamination and various other factors) can often create manufacturing Figure 1. Effect of Void Content Upon Short Beam Shear Strength (Carbon/Epoxy) 52 Figure 2. Effect of voids upon fatigue strength in carbon/epoxy composite. SAMPE Journal, Volume 48, No. 5, September/October 2012

Table of Contents for the Digital Edition of SAMPE Journal - September/October 2012

SAMPE Journal - September/October 2012
Contents
President’s Message
SAMPE Journal Editorial Calender
Technical Director’s Corner
Prepreg Non-Autoclave Manufacturing Technology: Program Overview and Co-Cure Enablers for Disruptive, Pervasive Use
Welcome SAMPE’s Newest Members
Materials & Products
SAMPE Tech 2012|Charleston, SC
Perspectives
SAMPE Proceedings
Perspectives- Taking Material Science To The Next Frontier: Models Of Past Material Innovations And How They May Impact The 21st Century
Europe News & Views
SAMPE Europe’s SETEC 2012, Lucerne, Switzerland
SAMPE Europe’s SEICO 2013, Paris, France
SAMPE 2013|Long Beach Call for Papers
Industry News
Approach to Optimizing a Combined Out-of-Autoclave (OOA) Prepreg/Liquid Composite Molding (LCM) Process for Integrated Structures
SAMPE LinkedIn Communities
Corporate Partners
The SAMPE Foundation
Tech Tidbits
SAMPE Upcoming Events
Face-Sheet Quality Analysis and Thermo- Physical Property Characterization of OOA and Autoclave Panels
Advertiser’s Index
Resource Center
SAMPE Membership Application
SAMPE Books & CD’s Order Form
Industry Events Calendar
Chapter Meetings Dates and Contacts

SAMPE Journal - September/October 2012