JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - 48

TECHNOLOGY

OPLC

54
56

Draping

Flock fibre-reinforced laminar composites
for improved Mode I fracture toughness
Temperature-sensitive joints
for water-soluble braiding mandrels
Damping

An innovative composite damping solution

TECHNOLOGY OPLC

Flock fibre-reinforced laminar composites
for improved Mode I fracture toughness

YONG K. KIM, Chancellor Professor,
Bioengineering Dpt., JOHN M. RICE, Professor
Emeritus, Mechanical Engineering Dpt.,
VIJAY CHALIVENDRA, Associate Professor,
Mechanical Engineering Dpt.
ARMAND F. LEWIS, Adjunct Professor,
Bioengineering Dpt.
College of Engineering,
University of Massachusetts-Dartmouth

Interfacially flocked Z-axis oriented reinforcing fibres can dramatically
improve the interlaminar shear strength of organic polymer laminar composites (OPLC). To this end, three flock process methodologies were developed: "wet flocking", "dry flocking" and "pre-flocking". As the pre-flocking
methodology was found to produce the composite panels with the highest
interlaminar shear strength, it should be further developed as the most
"user-friendly" way of introducing flocked fibre reinforcement technology
into OPLC applications.

tudies related to improving the interlaminar shear
strength of multilayer organic polymer engineering
composites have been ongoing since the widespread
commercial use of composite materials commenced in the
1950's and 60's. Since then, various techniques have been introduced to enhance the interlaminar strength of layered composite materials [1-4]. During this time, it was concluded that
the source of this poor interlaminar shear strength lies in the
lack of Z-direction inter-ply fibre reinforcement between the
assembled layers of fibrous composite layers. Techniques were
needed to re-arrange or place reinforcing fibres so that they
can bridge across these contiguous laminar plies. This would
tend to create a more structurally isotropic laminar structure.
In pursuing this goal, special preform fabrics were fabricated
using advanced textile technologies such as multi-directional knitting, 3D weaving or through-the-fabric stitching and
pinning processes [5, 6]. While these methods were found to
be tedious and restrictive, they certainly resulted in the de-

sired 3D orientation of yarn fibres in the reinforcing fabric's
structure. Unfortunately, these 3D textile processing methods
were found to be very expensive as well as design restrictive;
they also have scalability difficulties. Furthermore, these 3D
fibre orientations were not conducive to optimized strength
utilization of the parent yarn due to the obliqueness at the
yarn structure's interlacing points. Therefore, some of these
3D structures were prone to stress concentrations under mechanical service, leading to poor fatigue resistance. All these
approaches perform in their special application areas but, in
many cases, they would often degrade the composite's inplane properties. This is especially true for the through-thickness textile stitching methods [7-9].
Reviewing the inadequacies of all of these cumbersome,
high-cost, design-limited techniques, it was obvious that one
must search for other inter-ply laminar fibre placement reinforcement methodologies. In response to this challenge, procedures were sought for developing a means of positioning
Z-axis oriented fibres at the interfacial ply-layers of organic
polymer laminar composites (OPLC). To this end, the University of Massachusetts at Dartmouth (UMD) research team
developed a novel processing technique for Z-axis fibre-rein-

jec composites magazine / No110 January-February 2017

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017