Low-Velocity Impact Behavior of Foam Core Sandwich Panels with Inter-Ply and Intra-Ply Carbon/Kevlar/Epoxy Hybrid Face Sheets.

Stanley Samlal,R Santhanakrishnan

doi:10.3390/polym14051060

Abstract

Sandwich composites are extensively employed in a variety of applications because their bending stiffness affords a greater advantage than composite materials. However, the aspect limiting the application of the sandwich material is its poor impact resistance. Therefore, understanding the impact properties of the sandwich structure will determine the ways in which it can be used under the conditions of impact loading. Sandwich panels with different combinations of carbon/Kevlar woven monolithic face sheets, inter-ply face sheets and intra-ply face sheets were fabricated, using the vacuum-assisted resin transfer process. Instrumented low-velocity impact tests were performed using different energy levels of 5 J, 10 J, 20 J, 30 J and 40 J on a variety of samples and the results were assessed. The damage caused by the modes of failure in the sandwich structure include fiber breakage, matrix cracking, foam cracking and debonding. In sandwich panels with thin face sheets, the maximum peak load was achieved for the inter-ply hybrid foam core sandwich panel in which Kevlar was present towards the outer surface and carbon in the inner surface of the face sheet. At an impact energy of 40 J, the maximum peak load for the inter-ply hybrid foam core sandwich panel was 31.57% higher than for the sandwich structure in which carbon is towards the outer surface and Kevlar is in the inner surface of the face sheet. The intra-ply hybrid foam core sandwich panel subjected to 40 J impact energy demonstrated a 13.17% higher maximum peak load compared to the carbon monolithic face sheet sandwich panel. The experimental measurements and numerical predictions are in close agreement.

Highlights

Foam core sandwich composites are used in industries such as aerospace, automobile, wind turbines, marine functional materials and even in home appliances because of their high strength to weight ratio, good buckling resistance and tailorable design which remains dimensionally stable across a wide temperature range [1–5]
The low-velocity impact-resistant properties of the carbon fiber face sheet sandwich composites are improved with the addition of the intra-ply and inter-play hybrid Kevlar face sheets
The inter-ply carbon/Kevlar sandwich panel shows a considerable increase of peak load when the Kevlar-ply is placed as the outer lamina in the incident face sheet

Summary

Introduction

Foam core sandwich composites are used in industries such as aerospace, automobile, wind turbines, marine functional materials and even in home appliances because of their high strength to weight ratio, good buckling resistance and tailorable design which remains dimensionally stable across a wide temperature range [1–5]. Sandwich foam core structures have distinct advantages which make them the preferred choice for numerous applications involving bending, buckling and energy absorption applications such as dynamic loading, high- and low-velocity impacts, blasts, crashes, etc. Impact failure is a common problem that affects the strength and structural integrity of sandwich composites [10,11]. This issue is usually caused by the degradation of energy absorption competence and structural stiffness. Hybrid composites are designed and developed to improve different properties such as impact resistance, thermal conductivity, dielectric breakdown strength, flexural and environmental degradation resistance [14–16]

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