Mechanical failure around pin-loaded hole in an elastically orthotropic or quasi-isotropic plate is investigated using a contact stress analysis method. The plate considered is made of laminated fiber-reinforces composite material and is loaded by an elastic pin. The contacting surface is assumed unbonded and frictionless.
A minimization problem formulation is used for the contact stress analysis. The finite element method is adopted for numerical evaluation. The resulting quadratic programming problem which is dual to the original problem is then solved by Lemke's algorithm, obtaining the contact angle and detailed contact stress distribution.
The failure strength and mode is predicted based on the Yamada-Sun failure criterion using the stress calculated along the characteristic curve for each lamina.
The procedure is applied to several different geometries and laminate arrangements.
Contact angle and stress distribution depend on the material construction and geometry. However, the contact angle remains unchanged for a given material and geometry. This behavior greatly simplifies the failure analysis since a load scaling is possible in this case. When there is nonzero clearance or interface, the contact angle changes with loading.
Among the geometric parameters considered, the failure mode is more sensitive to the width-to-diameter ratio than to the edge-to-diameter ratio. The net-tension failure mode is dominant when the width-to-diameter ratio is about 3, while the shear-out failure mode is when it is 5. Failure strength increases according as the width and edge distance increase. In the case of clearance fit, bearing failure mode are predicted and failure strength decreases as a pin-hole clearance increases. The predicted failure modes and strengths are in good agreement with the experimental results.
