Computational Implementation of a Thermodynamically Based Work Potential Model For Progressive Microdamage and Transverse Cracking in Fiber-Reinforced Laminates

A continuum-level, dual internal state variable, thermodynamically based, work potential model, Schapery Theory, is used capture the effects of two matrix damage mechanisms in a fiber-reinforced laminated composite: microdamage and transverse cracking. Matrix microdamage accrues primarily in the form of shear microcracks between the fibers of the composite. Whereas, larger transverse matrix cracks typically span the thickness of a lamina and run parallel to the fibers. Schapery Theory uses the energy potential required to advance structural changes, associated with the damage mechanisms, to govern damage growth through a set of internal state variables. These state variables are used to quantify the stiffness degradation resulting from damage growth. The transverse and shear stiffness of the lamina are related to the internal state variables through a set of measurable damage functions. Additionally, the damage variables for a given strain state can be calculated from a set of evolution equations. These evolution equations and damage functions are implemented into the finite element method and used to govern the constitutive response of the material points in the model. Additionally, an axial failure criterion is included in the model. The response of a center-notched, buffer strip-stiffened panel subjected to uniaxial tension is investigated and results are compared to experiment

Seawater effect on pin-loaded laminated composites with two parallel holes

The aim of this study was to investigate the effects of seawater on the failure mode, first failure load and bearing strength behaviour of the pinned joint of fibreglass-reinforced woven epoxy composite prepregs. The specimens were kept in seawater for 3- and 6-month periods. After each period, their mechanical properties were examined. The edge distance-to-upper hole diameter (E/D), the two hole-tohole centre diameter (K/D), the distance from the upper or the lower edge of the specimen to the centre of the hole-to-hole diameter (M/D), and the width of the specimen-to-hole diameter (W/D) ratios were selected as parameters. Moreover, the finite element models of the specimens were developed using ANSYS software, and the Tsai-Wu criterion was used to obtain the first failure load. The numerical and experimental results were compared and were found to be in good agreement for the first failure load