Failure of fiber-reinforced composite laminates under longitudinal compression

Abstract

A micro-mechanics approach is put forward to predict the fiber kink inclination angle and the strength of a unidirectional composite under longitudinal compression. Internal stresses of constituent materials in the kink-band are calculated through Bridging Model; thus, only the constituent fiber and matrix properties of the composite are needed. Considering the non-uniform stress distribution caused by the embedded fiber, the homogenized stresses of the matrix are converted into true values with stress concentration factors before being used for failure analysis. The definition and application of stress concentration factors are introduced. A failure criterion based on Mohr’s theory is established to determine the orientation of potential failure surface and the failure situation of matrix, whereas a maximum normal stress failure criterion is used to detect the fiber breakage. The longitudinal compressive strength of a laminate is defined as the applied load at the moment when a failure of whichever constituent materials occurs first. The practicability and accuracy of the theory have been verified with a comparison between the predictions and the measurements obtained from the worldwide failure exercises and some other literatures.

Splitting failure of a composite under longitudinal tension

“…Fiber volume friction 2560 5180 4167 90 0.6 longitudinal compression, as θ f ,1 c shown in Figure 3, can be found in our previous research. [42,43] For the composite in Figure 4A, the general deformation and fiber rotation are plotted in Figure 4B or Figure 5. Let us analyze the determination of fiber rotation angle.…”

True Stress Theory of Matrix in A Composite: A Topical Review

“…It is evident that the load share of the fiber attains the highest when a continuous fiber composite is subjected to a longitudinal load, and thus a fiber fracture can occur most possibly. Even in such a case, however, a fiber splitting failure is often seen at a longitudinal tension ( Figure 2 a), and a fiber kinking failure occurs most frequently at a longitudinal compression ( Figure 2 b [ 12 ]), both of which are caused by a matrix shear failure [ 13 , 14 ]. Due to an inevitable fiber misalignment in a composite fabrication, a longitudinal load generates a shear stress component in the misaligned coordinate system ( Figure 2 c).…”

“…Using the true stress concept, a number of long-standing and challenging problems in composite failures are resolved satisfactorily and easily. They include a necessary and sufficient condition for a fiber and matrix interface debonding to occur given a composite subjected to an arbitrary load [ 8 ], a fiber splitting [ 13 ] or kinking [ 14 ] failure versus a fiber fracture, and a large shear deformation of the composite induced from relative slippage displacements between debonded fiber and matrix interfaces [ 15 ]. All of these failures are analyzed with no iteration.…”

Tensile failure prediction of a short fiber or particle composite

“…We have already obtained all of the SCFs of the matrix in a continuous fiber composite, 26,27,30 and various kinds of failures can be estimated based on the true stress concept and with a minimum number of input. 31,32 For a failure analysis of a SFRC, the critical step is still in determination of the matrix SCFs. However, only a longitudinal SCF of the matrix in the SFRC needs to be determined since all of the other directional SCFs are the same as those in a continuous fiber composite.…”

“…Otherwise, a SCF would be infinitely large when a crack occurs on the fiber and matrix interface as the matrix stresses at the crack tip are singular. We have already obtained all of the SCFs of the matrix in a continuous fiber composite, 26,27,30 and various kinds of failures can be estimated based on the true stress concept and with a minimum number of input 31,32 …”