Compliant interlayer

It is shown in Section 7.2 that the PVAL coating applied onto Kevlar and carbon fibers is potentially beneficial for improving the transverse fracture toughness of the composites made therefrom. Encouraged by this promising result, further studies were conducted on the effects of the compliant interlayer on the stress distributions. 

The microductile/compliant layer concept stems from the early work on composite models containing spherical particles and oriented fibers (Broutman and Agarwal, 1974) in that the stress around the inclusions are functions of the shear modulus and Poisson ratio of the interlayer. A photoelastic study (Marom and Arridge, 1976) has proven that the stress concentration in the radial and transverse directions when subjected to transverse loading was substantially reduced when there was a soft interlayer introduced at the fiber-matrix interface. The soft/ductile interlayer allowed the fiber to distribute the local stresses acting on the fibers more evenly, which, in turn, enhanced the energy absorption capability of the composite (Shelton and Marks, 1988). 

Exposure to 70 °C gives similar results for the surface treated fiber (Fig. 24). That is, a complete reversibility in noted. The finished fiber (i.e. the fiber with the interphase consisting of the amine deficient brittle interlayer) experiences a nonrecovery of interfacial shear strength after moisture exposure and dehydration. Parallel surface spectroscopic investigation of the fiber surfaces show that under these conditions the fiber surface chemistry is not permanently altered by this exposure. Model studies of epoxies with the amine deficient composition of the interphase show that, the wet Tb of this material is about 70 °C. Therefore, the interphase is at or above its wet Tg and therefore because of the compliant nature of this material, stresses cannot be transfered efficiently and the interface is permanently distorted. 

Each of these steps depends on the process before. The software suite starts with the material selection, in which also an individual material can be dehned. Fiber orientations and the number of plies can be selected in a following step. All material parameters must be chosen before the analysis can start. Six structural analysis modules can be differentiated with the CDS software suite. These solid mechanic modules are thick-walled cylinder, thin plate, thin plate impact-fastener modeling, thick plate, discontinuous tile modeling and compliant beam interlayer analysis. The CDS software suite allows changing the parameters of the manufacturing process or the laminate structure in real time. Four result sections for those parameter changes are provided by the software the effective properties, thermal-processing response, stress-strain results and the failure response. The CDS software suite is a complete analysis tool kit which is easy to use for the client. The software also allows export into an external simulation tool. 

Metai/glass interlayer compliant in 3-D seals off interfaces... 

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