Influence of Milled Glass Fiber Fillers on Mode I &amp; Mode II Interlaminar Fracture Toughness of Epoxy Resin for Fabrication of Glass/Epoxy Composites

Kannivel Saravanakumar,Rotte Souhith,Vellayaraj Arumugam,Carlo Santulli

doi:10.3390/fib8060036

Abstract

The present work is focused on improving mode I and mode II delamination resistance of glass/epoxy composite laminates (50 wt.% of glass fibers) with milled glass fibers, added in various amounts (2.5, 5, 7.5 and 10% of the epoxy weight). Including fillers in the interlayer enhances the delamination resistance by providing a bridging effect, therefore demanding additional energy to initiate the crack in the interlaminar domain, which results in turn in enhanced fracture toughness. The maximal increase of mode I and mode II fracture toughness and of flexural strength was obtained by the addition of 5% milled glass fiber. The mechanism observed suggests that crack propagation is stabilized even leading to its arrest/deflection, as a considerable amount of milled glass fiber filler was oriented transverse to the crack path. In contrast, at higher filler loading, tendency towards stress concentration grows due to local agglomeration and improper dispersion of excess fillers in inter/intralaminar resin channel, causing poor adhesion to the matrix, which leads to reduction in fracture toughness, strength and strain to failure. Fractured surfaces analyzed using scanning electron microscopy (SEM) revealed a number of mechanisms, such as crack deflection, individual debonding and filler/matrix interlocking, all contributing in various ways to improve fracture toughness.

Highlights

Fiber reinforced plastic (FRP) composites are extensively used in aerospace, automobile, marine, civil construction and wind turbine industries, where they are competitive for some properties, such as in-plane strength-to-weight ratio and fatigue resistance, with conventional metals
This paper focuses on improvement of mode I and mode II delamination resistance by employing milled glass fiber fillers as filler particles in glass/epoxy composite laminates, discussing the effect of interface modification by appropriate microscopic observation and linking it to the flexural behavior of laminates
The glass fiber reinforced plastic (GFRP) composite laminates of dimension 300 × 300 mm2 were fabricated with a stacking sequence of [0◦ ]16 by hand lay-up technique

Summary

Introduction

Fiber reinforced plastic (FRP) composites are extensively used in aerospace, automobile, marine, civil construction and wind turbine industries, where they are competitive for some properties, such as in-plane strength-to-weight ratio and fatigue resistance, with conventional metals. Interlaminar failure, usually referred to as delamination, occurs as key failure mechanism within the interplay–resin domain, which is activated by out-of-plane stresses [3,4]. Several techniques, such as through-thickness stitching (TTS), Z-pinning, 3D weaving, were employed to enhance the strength of the interlaminar region. These techniques may on the other side cause a reduction in in-plane mechanical properties, fiber volume loss, and cause increased production cost [5,6,7]

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