Katleen Vallons

Intra-Laminar Damage in Carbon Fiber-Reinforced Composites: Experimental Observations and Model Validation

The intra-laminar damage during quasi-static loading of Carbon Fiber-Reinforced Plastics (CFRPs) leads to degradation of ply mechanical properties. The possible intralaminar damage mechanisms are fiber failure, matrix cracking, and fiber/matrix debonding. In addition to experimental investigation of these mechanisms, modeling methodologies have been developed to predict the degradation of ply properties, accounting for (some of) these mechanisms. One of these methodologies is proposed by Ladeveze and LeDantec [1]. This model requires a set of input parameters, which are obtained through mechanical tests on laminates with prescribed lay-ups. In the current study, we extract these input parameters for an aerospace-grade CFRP, with detailed explanations. Beside the conventional parameter identification procedure, the parameters are linked to the physical progression of damage (in terms of crack densities), which is measured in the in situ images taken during the tests.

4 – Databases for fatigue analysis in composite materials

Abstract Large amounts of fatigue data for composite materials have been generated over the years. This type of data can be extremely useful for researchers or designers. Unfortunately, many of the fatigue studies have only been published as conference and journal papers. Some larger-scale initiatives, however, do exist, and several publicly accessible databases collecting fatigue data for composites are discussed in this chapter: the European FACT database, which was later absorbed into the OptiDat database, and the American SNL/MSU/DOE database. An overview is given of the contents of these databases, as well as their general structure, and how one can access them.

Fatigue in non-crimp fabric composites

Because of the many benefits they can offer, non-crimp fabrics (NCFs) have quickly gained a firm position in many composite production processes. This type of fabric, however, has some unique features that distinguish them from other textiles, and significant differences in mechanical behaviour have been observed. The present chapter gives an overview of experimental fatigue findings for both glass and carbon NCF composites, focussing not only on the fatigue life but also on the evolution of damage and stiffness during the fatigue process. The influence of the NCF parameters on the fatigue life is also treated.

Damage Behaviour of Ncf Carbon / Epoxy Laminates Under Tension

Composites reinforced by non-crimp fabrics (NCF) reach stiffness level close to the ideal cross-ply laminates with unidirectional plies, but damage behaviour of NCF-composites exhibit significant differences from the behaviour of the laminates with unidirectional plies (non-stitched laminates). The paper presents results of experimental studies of the initiation and development of damage in NCF-composites. Some of the observed phenomena can be explained and predicted using FE modelling of the composite deformation. Others are difficult to explain; they present a challenge for understanding the behaviour of NCF-composites. The materials are carbon/epoxy composites, reinforced by biaxial NCF 0°/90° and ±45°. Two different sets of fabrics (different producers) were used for the reinforcement, and the fibre volume fraction of the plates had two different levels: about 45% and about 55%. The samples were loaded in different directions in tension. Damage initiation and development was studied using acoustic emi...