The effect of matrix cracking on mechanical properties in FRP laminates

Abstract

Background: Fiber Reinforced Polymer (FRP) laminates have properties, which are highly dependent on the ply fiber orientations and which can be designed for optimum laminate performance. The purpose of this study is to investigate the effect of matrix cracking on the mechanical properties of FRP laminates with various off-axis angles, and to provide a critical test for an analytical solution using variational stress analysis. Methods: Carbon and glass fiber reinforced polymer laminates (CFRP and GFRP) are tested. FRP prepregs are cured by using autoclave method to form laminates with layups [θ m / φ n ] s . The laminates are then loaded monotonically and cyclically to obtain their mechanical properties and the effect of matrix cracks on the properties. Some of the effects include reduction of laminates' stiffness and residual strains after unloading. In order to obtain higher crack densities in specimens, artificial cracks method was introduced in this study, where notches were made at the edges of some specimens before tested in tension. Cracks observation for CFRP laminates is done by using the X-ray technique, while for GFRP laminates a DSLR camera is used.

Application of DIC to deformation measurement around damages in CFRP cross-ply laminates

“…In order to make sure matrix cracks uniformly occur on the specimen for easier damage observation by X-ray radiography and DIC system, the artificial crack method is induced in this study. This method is explicitly explained in Fikry et al (2018) where artificial crack method can be done by making notches at both edges of the specimen by using a knife before pulling it in a tensile test machine with cross head speed of 1mm/min to a specific load. Then the specimen is unloaded back to zero and the notched edges are cut by using composite material cutting machine mentioned above at ±5mm from the edges.…”

Analytical model for determining effective stiffness and mechanical behavior of polymer matrix composite laminates using continuum damage mechanics

“…Nonlinear stress-strain response of GFRP cross-ply laminates Figure 12. Comparison of (a) transverse crack density, (b) stiffness reduction, and (c) stress-strain response of T700SC/2592 ½0=90 8 =0 predicted using the present model with experimental results (Fikry et al (2018)).…”

“…Ultimate fiber failure strain e fc (%) 1.77 1.83 This result implies that the ultimate failure strength of CFRP laminates with 0 plies can be determined using the strain-based fiber criterion, and the ultimate fiber failure strain used in this criterion can be predicted through SEM simulations. The nonlinear stress-strain behavior of the T700SC/2592 ½0=90 8 =0 laminate was predicted using the present model, and the results were compared to the experimental result obtained by Fikry et al (2018). We denote T700SC/2592 as CFRP-II.…”

“…The nonlinear stress-strain response of CFRP cross-ply laminates resulting from transverse cracking was calculated using the present model and compared to the experimental results obtained in this study. We also applied our model to the results reported by Fikry et al (2018). The stress-strain Table 2.…”

Interlaminar Shear Behavior of Laminated Carbon Fiber Reinforced Plastic from Microscale Strain Distributions Measured by Sampling Moiré Technique

“…First, 8 layers were alternately stacked with the stacking sequence of +45° and −45°. Then, another 8 layers were symmetrically stacked with the stacking sequence of −45° and +45° from the 9th layer to the bottom layer ( Figure 3 b), to form a balanced structure with less coupling effect [ 35 ]. The prepregs were cured in an autoclave at a preheating temperature of 90 °C for 1h followed by heating at 130 °C at a pressure of 0.2 MPa for 3.5 h, and the cured laminate was cut to the specimen with the desired size using a composite material cutting machine (AC-300CF, Maruto Testing Machine Co., Tokyo, Japan) [ 35 ].…”