TITLE:
Quasi-Static Flexural Properties of a Pultruded Glass Fiber/Unsaturated Polyester Square Pipe
AUTHORS:
Yuri Imai, Gabriel Fortin, Badin Pinpathomrat, Keigo Nishitani, Anin Memon, Yuqiu Yang, Akio Ohtani, Hiroyuki Hamada
KEYWORDS:
Automotive Composites, Flexural Testing, Pultruded Pipe, Mechanical Strength, Fracture Behavior
JOURNAL NAME:
Open Journal of Composite Materials,
Vol.9 No.3,
July
10,
2019
ABSTRACT: This paper explores quasi-static flexural properties
and fracture behavior of a pultruded glass fiber/unsaturated polyester square pipe
for automotive structural applications. Three-point flexural testing is performed
in an Instron Universal Testing Machine with steel jigs supporting the top and bottom
surfaces of the pipe. Acoustic emission (AE)
measurements are recorded during flexural testing to evaluate initial fracture in
the pipe structure. After final fracture, five cross-sections of the pipe are cut
at 50-mm intervals along the longitudinal axis, with the first cut located at the mid-span
of the pipe. Cross-sections of a pipe from an interrupted test where initial fracture is
detected from the AE method are also prepared. Damage locations and behavior on
each cross-section are observed. The flexural testing results
show that the cumulative AE counts increase rapidly from 2.5 kN, that final failure
occurs at a maximum load of approximately 13 kN, and that corresponding initial
and final failure occurs in the two corner regions on the compressive side of flexural
loading. Failure initiates by stress concentrations due to the upper jig on the
top surface during bending. The cross-sectional observations
also reveal clear deformation behavior of the pipe where failure is present, marked
by inward bending of the top surface and upper corners located on the compressive
side, near the jig. The locations of maximum stresses and deformations obtained
from finite element analysis of this pipe structure are in very good agreement with
the experimental observations.