Tensile behavior of glass/epoxy laminates at varying strain rates and temperatures
Introduction
Composite materials based on polymeric matrix are often used over the past decades in aircraft, aerospace structures, automotive and petrochemical industries. Composite products such as pressure vessels, gas pipes, containers and aircraft components became popular and acceptable by most of the engineers and users. Static and dynamic mechanical loading and also temperature behavior have to be taken into consideration for the design of composite structures. However, the mechanical response of fiber-reinforced polymeric composites is sensitive to the temperature and to the rate at which they are loaded [1]. Unlike metals, which have been studied extensively over a wide range of strain rates and temperatures, only limited amount of information is available on the effects of strain rate and temperature on the response of fibrous composites.
Many researchers have performed tensile tests at different strain rates in composite materials. Others have studied the tensile behavior at different temperatures. To achieve the high performance required in the material’s projected applications, a good understanding of the mechanics of GFRP tensile specimens under different temperatures and strain rates is essential.
It is well known that temperature affects the strength and stiffness of polymer matrix composite structures. The mechanical performance of glass fiber-reinforced polymer (GFRP) composite materials under elevated temperature is characterized by a significant decrease of stiffness and strength when the glass transition temperature of the resin is approached and exceeded [2], [3], [4], [5]. Nevertheless, the strain rate sensitivity is still a controversial subject. Some studies have reported that strain rate did not significantly affect tensile behavior [6], [7], [8], [9], [10], [11], whereas others affirm that strain rate influences mechanical response of this type of composite materials [12], [13], [14], [15], [16], [17], [18].
In some papers [8], [9], [12], [13], higher ultimate tensile strength and Young’s modulus are measured for higher strain rates. Nevertheless, others reported that any increase in the test velocity decrease the tensile strength and stiffness of composites [12], [18]. These differences can be explained by matrix and reinforcement, test conditions, specimen type and manufacture and experimental procedures and equipment, which can imply in the behavior of such composite materials.
The main goal of the present paper is to analyze the coupled effect of temperature and strain rate on the composite behavior. Initially experimental results are presented in order to illustrate the effect of strain rate and temperature on the mechanical response for GFRP under a wide range of strain rates and then analytical expressions are proposed for the elasticity modulus and the ultimate strength as functions of the loading rate and temperature. The predicted properties are compared with experiments showing a good agreement.
Section snippets
Materials and experimental procedures
The apparatus and procedure used to obtain the tensile properties in the GFRP laminates are described below.
The tensile tests were performed according to the method prescribed in ASTM D3039 [19]. The test specimens were cut from hand lay-up sheets. The glass was a cross-ply plain weave e-glass [0/90] fabric with 326 g/cm2 weight. The composite had a fiber weight fraction of 70% with eight layers of glass. The epoxy resin system used was RR515 from SILAEX® based on a diglycidyl ether bisphenol A
Experimental results
Experimental data determining the dynamic response of a composite structure loaded at different strain rates is limited by the range of strain rates, which can practically be applied for a particular test method. It is desirable to obtain information about strain rates outside the range that can be achieved experimentally, in order to predict the behavior of materials over very long loading times.
Fig. 3 presents the typical stress vs. strain results of GFRP at 20 °C, 40 °C, 60 °C and 80 °C and at
Conclusions
The mechanical response of a cross-ply glass fiber reinforced plastic (GFRP) composite was experimentally measured for temperatures ranging from 20 to 80 °C at three different strain rates (1.6 × 10−5, 1.6 × 10−4, 1.6 × 10−3 s−1) and predicted based on the fundamental properties of its constituents using an analytical and approach. These results showed that GFRP is strongly affected by strain rate and temperature. In particular the ultimate tensile strength is only dependent from strain rate and
Acknowledgements
The financial support of FAPERJ (Rio de Janeiro State Funding), CNPq (Research and Teaching National Council) and CAPES (Coordination of Improvement of Higher Level Personnel) are gratefully acknowledged.
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2022, Composites Part B: EngineeringCitation Excerpt :A similar trend was observed for GFRP laminates by Ou et al. [18] and Reis et al. [16]. Although there are a number of studies [16,17,22] on the dynamic tensile properties of FRP laminates, but little attention has been paid to FRP bars. The current investigations on the deterioration of FRP composites in SWSSC and marine environments were mainly conducted by measuring static tensile properties, the study on their dynamic properties is quite limited.