Session: 16-01-01: Government Agency Student Poster Competition

Paper Number: 140937

140937 - Experimental Method to Determine the Mode-I In-Situ Bond Strength-Toughness Development During Automated Placement of Uncured Thermoset Carbon/epoxy Tows 

In-situ bond strength toughness (IBST), commonly referred to as tow tackiness, is a first order property affecting the adherence quality and defect formation (e.g., wrinkles, folds) during automated tow placement (ATP) processing of uncured thermoset polymer matrix composite (PMC) tows. Tow-tow IBST develops over a characteristic millisecond timescale (t_c <= 50 ms) due to the rapid tow placement velocity of ~ 1 m/s, under the application of temperature and pressure. In this poster, an experimental method is presented to determine the short millisecond timescale tow-tow mode-I IBST in terms of fracture mechanics-based traction-separation behavior.  The test specimen consists of two tows bonded to rigid platens with a pre-crack between them to induce crack initiation. Experiments are performed using IM7-G/8552 carbon/epoxy prepregs for both long and short timescales at a constant debonding rate of 5 mm/s, contact pressure of 0.23 MPa and bonding temperature at 40° C. In addition, high-speed two-dimensional digital image correlation (2D-DIC) is used to image and measure tow-tow interfacial deformation during debonding. The peak traction and apparent energy release rate are found to significantly decrease at the short millisecond timescale contact hold times compared to longer (i.e., second) timescale.  For a 1 s contact hold time, the peak traction is determined as 0.232 MPa, which reduces to 0.099 MPa at 50 ms and further to 0.087 MPa at 30 ms. This represents a substantial decrease of 62.5% from 1 s to 30 ms. For a 1 s contact hold time, the apparent critical energy release rate is determined as 72.0 J/m², which decreases to 30.75 J/m² at 50 ms and to 28.40 J/m² at 30 ms. This represents a substantial decrease of 60.6% from 1 s to 30 ms.

Presenting Author: Debrup Chakraborty University of South Carolina

Presenting Author Biography: Debrup is currently pursuing his Ph.D. in Mechanical Engineering at the University of South Carolina. He is a graduate research assistant at the McNair Center for Aerospace Innovation and Research, and is passionate about developing cutting-edge solutions for the aerospace industry using advanced composite materials and automated tow placement (ATP) technology. He recently established a novel experiment to emulate a real-time ATP process and optimize the process parameters using various engineering tools and methods, such as troubleshooting, root cause analysis, and digital image correlation in aid of high-speed imaging techniques. He also hold a Master of Science in Mechanical Engineering with Management from Queen's University Belfast in the United Kingdom where he developed a 3D model of a fixture prototype to inspect the crashworthiness of composite laminate bolted joint as per ASTM D5961 by executing Design for Manufacturing and Assembly with the Pugh decision-matrix method and also performing Finite Element Analysis to validate the effective material selection, product reliability, and durability. Debrup is born and brought up in Kolkata, India and pursued his undergraduate education in Mechanical Engineering from the SRM Institute of Science and Technology in Chennai, India.

Authors:

Debrup Chakraborty University of South Carolina
Karan Kodagali University of South Carolina
Sreehari Rajan Kattil University of South Carolina
Dennis Miller University of South Carolina
Subramani Sockalingam University of South Carolina
Michael A Sutton University of South Carolina