Residual properties of composite plates subjected to impact fatigue

Abstract

This work deals with post-impact residual mechanical behavior of composite plates made with glass fiber cloth and two different thermosetting resins (epoxy and polyester). It is well known that damages induced by multiple impacts greatly reduce the residual properties. How are the residual strength or stiffness affected by the impacts? How does impact energy and number of impacts contribute to the degradation of mechanical properties? What kind of supports induces more damages and consequently a larger reduction in residual properties? These are some questions that we attempt to clarify in this paper. To investigate and assess the effect of the energy level and number of impacts on the total induced damage and residual properties, impact fatigue tests were carried out at selected energy range of: 3 J, 4 J, 5 J, and 6 J. Then, coupons containing the damaged area are cut out, in order to estimate the tensile, compressive, and shear residual properties, particularly residual strength. The energy level and number of impacts are major factors influencing the loss of stiffness and strength. However, stiffness is more affected than strength by the repeated impacts. A clear decrease of compressive residual strength with the number of impacts for the two fixture conditions (clamped on two opposite sides and a circular clamp) is demonstrated. The drop in the case of the circular clamping is more visible, confirming a greater extent of damages. A three-parameter damage model is proposed and applied, with some conclusions are withdrawn in this investigation.

Tensile post-impact behaviour of thin carbon/epoxy and glass/epoxy hybrid woven laminates – Part I: Experimental study

“…Indeed, the impact generates local delamination that induces micro-buckling of the bundles of fibres that can lead to a total failure. Studies on post-impact tensile behaviour on woven fabric laminates are more recent [12,13,14,15]. Most of them are conducted on carbon with layers oriented at 0 • /90 • .…”

Rupture by impact-induced fatigue of a copper foil strip embedded in a multifunctional composite material

“…The impactor has a hemispherical head, 15 mm in diameter, and a mass M of 5.7 kg. This machine was used in previous works by Ouroua et al, 25 Azouaoui et al 2,4 and Mouhoubi et al 5,6 A description of the experimental setup is given in (Figure 2). The assembly used for holding the test samples is generally used for the evaluation of puncture strength in plastic materials.…”

“…Previous research studies were focused on non-hybrids composite materials. [2][3][4][5][6][7][8][9] The study of damage phenomena of these composite materials is more complex than the study of their elastic or viscoelastic properties. In fact, during a repeated impact load, micro cracks appear in the composite matrix with ruptured fibers, and non-cohesive structures appear at interfaces, which make the prediction of the behavior of damaged structures difficult.…”

“…The behavior of these materials under cyclic dynamic loads such as repeated shocks has always been a center of interest to designers and researchers. [2][3][4][5][6][7][8][9]11,25 Tests of shock-driven fatigue allow the study of the effects of the number of impacts and the accumulated impact energy on the damage of composite materials. Studies of the effect of impact energy on the life span of layered glass-polyester materials, where plots of fatigue curves showed a classical fatigue behavior, were reported in Refs.…”

Development and characterization of structural adhesives for aerospace industry with alumina nanoparticles under shear and thermo-mechanical impact loads

“…Epocast 50-A1/946 epoxy has been extensively used for bonded joints in composite structures [1][2][3][4] as well as for laminating system in aeronautical applications, as recommended by the Boeing Company, owing to their low-viscosity and good flame-retardant property. [5][6][7][8][9] To the best of the authors' knowledge, this is the first work, to date, to present the characterization of modified Epocast epoxy with different weight percentage (wt%) of nano-alumina under shear and thermo-mechanical impact loads. The improvement in the mechanical properties of the Epocast epoxy may lead to improvement in their applications, which will be investigated in the following papers.…”