Effect of thermal‐oxidative aging on carbon fibre‐bismaleimide composites

Abstract

Purpose -The purpose of this paper is to investigate the effect of thermal-oxidative aging at 1508C on the mechanical properties of carbon fibre reinforced bismaleimide composites. Design/methodology/approach -Composites specimens after thermo-oxidative aging at 1508C for various times (up to 1,000 h) were investigated by scanning electron microscopy (SEM) for fracture morphology, Fourier transform infrared (FTIR) spectroscopy for chemical structures, and flexural strength test and inter-laminar shear strength (ILSS) test for mechanical properties. Findings -The results indicated that the mechanical properties of carbon fibre/BMI composites were affected significantly by testing temperature rather than by aging time. SEM results showed that the good adhesion of fibre and matrix resulted in the better mechanical properties. The composites showed lower flexural strength and ILSS at 1508C due to the viscoelastic behaviour of matrix resin. The FTIR spectra confirmed the decomposition of crosslinked maleimide occurred just on the surface of composites during various aging times. Research limitations/implications -Results indicated that carbon fibre/BMI composites had excellent heat resistance and aging resistance. Practical implications -Due to their excellent thermal and mechanical properties, the carbon fibre/BMI composites show greater potential for their applications in some extreme fields such as aerospace and machine. Originality/value -The paper investigates the relationships of the fracture morphologies of composites and chemical structures of matrix resin to the mechanical properties after thermo-oxidative aging.

The Effect of Thermooxidative Aging on the Durability of Glass Fiber-Reinforced Epoxy

“…These changes may be attributed to the increase in the crosslinking density of the epoxy matrix as a result of simultaneous postcuring and physical aging during thermooxidative degradation [15,41]. To be more precise, by increasing cross-linking density, the cross-linked network within the epoxy matrix will bear the majority of the induced loads in the composite material [13]. Consequently, the tensile strength and modulus of elasticity rose significantly over the prolonged aging period.…”

“…Thermal-oxidative aging may irreversibly change the chemical structure of polymer matrix composites [13,14]. Alterations to the chemical structure during thermooxidative [1,9,13,[15][16][17][18][19][20][21][22], loss of volatiles [2,[23][24][25][26][27], dehydration [13,28,29], chain scission [25,[30][31][32][33][34], additional cross-linking [1,13], and carbonyl growth [19,29]. The initial chemical changes are accompanied by dehydration of secondary alcohols and the release of low molecular weight gaseous species due to random chain scission.…”

“…However, at moderate heat exposures (24 ∘ C-177 ∘ C), chain cross-linking is the dominant chemical change in the matrix compared to chain scission [14]. Indeed, the increase in the cross-link density of the cured matrix primarily occurs during the initial aging period and is caused by postcure reactions [13,17,35,36], which result in the excessive brittleness of the matrix [37]. As aging proceeds in the presence of oxygen, susceptible chemical structures in the resin are oxidized to various carbonyl containing groups.…”

Properties of novel bismaleimide resins and thermal ageing effects on the ILSS performance of their carbon fibre–bismaleimide composites

“…With the passage of aging time, especially at high temperature in the presence of oxygen, the matrix resin on surface layer of composites experiences the decomposition which may lead to the debonding or interfacial damage. Many researchers have investigated the effects of thermal aging on mechanical properties of carbon fibre–bismaleimide composites , but few discussed how the properties under high test temperatures changed.…”

“…Aging studies are long‐term process, and often need decades to fully assess the long‐term performance of composites. Therefore, various approaches have been made to accelerate ageing, such as hygrothermal ageing , vacuum thermal cycling , thermal aging , proton irradiation , and electron irradiation . Thermal aging is considered to be the most effective and common method for simulating the real conditions.…”