The Influence of Fiber, Matrix, and Interface on Transverse Cracking in Carbon FiberReinforced Plastic Cross-Ply Laminates

Abstract

The transverse tensile strength of a unidirectional laminate is generally accepted as a material property. The transverse strength of a single ply in angle-ply laminates is influenced by the neighboring layers (effect of constraint) and is for this reason not a material property. In the present investigation of four different carbon fiber-reinforced plastics (CFRP) this influence of constraint and the effect of fiber, matrix, and interface on transverse cracking are investigated. An intermediate ductile resin system proved to increase the transverse strength significantly (if the fiber matrix bond is good) in comparison with a brittle resin system. A highly ductile matrix (polyetheretherketone—PEEK), however, did not further or additionally improve the transverse strength significantly. The intermediate ductile resin system proved to be sensitive to the formation of voids under the cure conditions applied. The inhomogeneous distribution of voids disturbed the expected constraining effect.

Effect of Matrix Ductility on Elastic—Plastic Interlaminar Stresses in Thermoplastic AS4/PEEK Composite Laminates

“…[AE] s laminate has four plies with thickness h. The laminate has three resin-rich layers (RRLs) included between different plies of lamina. According to the research given by Peters [21], each resin-rich area between plies with thickness of 2d is twice the fiber diameter. For each ply with h, PEEK in resin-rich layers is considered to be a homogenous, isotropic, and elastic-plastic material; the material in the middle part with h-2d is a homogenous, orthotropic, and elastic continuum, and its first material principal axis x 1 is the ply fiber orientation (the stacking sequence).…”

“…A progressive damage 3D finite element model with resin-rich layers included was used by Gamble et al [20] to predict matrix damage and interlaminar delamination in carbon/fiber composite materials. Considering the influence of fiber, thermoplastic matrix, and their interface on transverse cracking in CFRP, the resin-rich layer model between plies was also used by Peters [21], and the resin layer was suggested to be a resin-rich area of twice the fiber diameter.…”

Prediction of Microcracking Distributions in Composite Laminates Using a Monte-Carlo Simulation Method

“…Some of the simpler strength-based models use CLPT to describe the stresses [6][7][8][9]. Shear lag solutions [10][11][12][13][14] have also been used to obtain stresses. Cracking in the strength-based methods is determined by comparing the derived stress-state with a material failure property.…”

“…Researchers who have used probability functions, such as in strength distributions, have adjusted the parameters such that they reflect the desired characteristics. Examples of these adjustments can be seen in strength-based studies for fatigue loads [11][12][13][14][40][41][42][43]. From experimental data,…”

Transverse cracking in CFRP cross-ply laminates with interlaminar resin layers

“…Predictions of the transverse crack density were also conducted by Laws and Dvorak [3], Han et al [4] (a combination of the shear-lag analysis and the energy criterion), Fukunaga et al [5], Lee and Daniel [6] (a combination of the shear-lag analysis and the strength criterion), Nairn [7] (a combination of the variational stress analysis and the energy criterion), Peters et al [8] and Takeda and Ogihara [9][10][11] ] by considering the statistical characteristics of 90° ply strength. In recent years, interlaminar-toughened laminates have been developed in which resin-rich layers are placed in interlaminar regions in order to enhance the interlaminar fracture toughness of CFRP laminates.…”