Thermal, rheological, and mechanical properties of a polymer composite cured at different isothermal cure temperatures

Abstract

Thermal, rheological, and mechanical properties of a commercial carbon fiber epoxy prepreg, Cycom 977-2 UD, were obtained for isothermal cure temperatures ranging from 149 C to 182 C. For each cure profile, an encapsulated-sample rheometer (ESR) was used to measure the storage modulus. Each ESR cure profile was followed by the glass transition temperature (T g ) test. The degree of cure () during cure and the heat of reaction of the prepreg were obtained using a differential scanning calorimeter (DSC). Combined loading compression (CLC) and short-beam shear (SBS) tests were performed to obtain compressive properties and SBS strength, respectively. It was observed that the compressive properties did not vary significantly for the studied isothermal cure temperatures; likewise, the compressive failure mode was the same for all the CLC specimens. However, the SBS strength for the specimens cured at 149 C was approximately 10% less than that of those cured at isothermal cure temperatures ranging from 160 C to 182 C. Further, the failure mode of the SBS specimens cured at 149 C was also different from other specimens. The storage modulus of the ESR sample cured at 149 C also showed a 10% decrease compared to other ESR samples. The SBS strength exhibited a good correlation with the storage modulus and a weak correlation with T g and .

Characterization of shear stress at the tool‐part interface during autoclave processing of prepreg composites

“…According to ASTM D4473, the gel point is defined as the maximum value of Tan(δ). In agreement with the results presented by Alavi‐Soltani et al,20 gelation of the prepreg IM7/977‐2 UD occurred at the 74th min, which corresponded to point C showed in previous results. Therefore, point C related the gel point to the starting point of the shear stress plateau when release film was used [Figure 5(a)].…”

Effects of postcure temperature variation on hygrothermal‐mechanical properties of an out‐of‐autoclave polymer composite

“…For autoclave composites, the curing involves time, temperature, external pressure, and vacuum pressure where the external pressure and vacuum pressure variation are known to have significant effects on void content and mechanical properties of the final part . The effects of cure temperature and state of cure variation were also studied by several researchers . Lee and Springer investigated the effects of curing on mechanical properties for a wide range of degree of cure ranging from 0.6 to 1 for Fiberite T300/976 graphite‐epoxy composite.…”

Composite materials – modelling, prediction and optimization

“…The position of this system could be adjusted with an axial slider (8). As can be seen, all of these components were mounted on a common foundation (9).…”

“…Both aspects induce local viscosity variations, infl uencing the evolution of both saturated and unsaturated resin fl ow fronts [5]. Temperature and degree of cure are also extremely important in relation to process-induced stresses and strains, infl uencing fi rst of all the state of the material (liquid, gelled solid or vitrifi ed solid) and, as a consequence, its mechanical properties [9]. It is generally accepted that stresses and deformations in composite laminates are related to the interaction between the tool and the part [10], and to gradients in the temperature and degree of cure through the thickness of the composite [11].…”

“…at each location in the composite material undergoing processing, all the constituents experience the same temperature), the whole temperature fi eld can be established by solving a unique non-linear equation using lumped (homogenized) material properties [4][5][6][7][8][9][10][11][16][17][18], which can be written as Streamlines of resin fl ow in the tapered region of the die Figure 5.21 [5.46] where T is the temperature; t is the time; ρ c is the density; c p ,c is the specifi c heat capacity; k x ,c , k y ,c and k z ,c are the thermal conductivities of the composite material along the x (pull), y and z directions, respectively; and V r is the resin volume fraction. The source term q in Eq.…”