Session: 03-12-01: Testing and Characterization

Paper Number: 120908

120908 - Impact of Stacking Sequence and Size Effects on Open Hole Compressive Performance 

Open hole compression testing is one of the most common evaluations of aerospace-grade composite materials and serves as an important allowable design value. The test utilizes quasi-isotropic laminates, with associated vulnerabilities to ply count and stacking sequence changes. Previous studies have focused on the impact of ply vs sub-laminate scaling on notched specimen size effects and resulting strength predictions. Works characterizing OHC and other compressive testing with stress intensifications have observed the impacts of 0- & 90- degree ply location, however only when considering one thickness of specimen. Resulting in a reference base where altered locations of 0- & 90-degree plies within the laminates are not considered simultaneously to size effects. This study focused evaluating both size and center ply effects on OHC performance using the Toray T1100G/3960 toughened prepreg system. Quasi-isotropic laminates of [+45/0/-45/90]NS and [+45/90/-45/0]NS, with N ranging from 1-4, were chosen to create varied thicknesses still commonly seen in test campaigns. Each laminate type had four panels manufactured for testing two sets of specimens at two test conditions. The first set for each laminate type was tested to full failure. The second sample had a specimen tested to increasing percentages of the average failure load for that laminate type. Interrupted test coupons were analyzed to evaluate damage propagation for test condition, ply count and stacking sequence variations. Using both the compressive strength results from complete testing and damage area analysis from interrupted testing, a deeper understanding of size and stacking sequence effects can be gained. The repetition of tests for both room temperature ambient and elevated temperature wet conditioned coupons expands the observation of stacking sequence and size effects is to the most common test conditions. The data collected provides an important overall evaluation of these factors on past test campaigns as choices in ply count and stacking sequence choices varied over time. 

Presenting Author: Joseph McDonald Toray Composite Materials America

Presenting Author Biography: Joseph McDonald is a Research Scientist at Toray Composite Materials America in Tacoma Washington. After completing a Master's at the University of Massachusetts Lowell focusing on composite repair of wind turbine blades, he joined Toray in 2022. His research focuses on supporting the development of new prepreg systems for aerospace and sports grade materials from a composite mechanics view.