Richard A. Scott

Strength of Mechanically Fastened Composite Joints

A method is presented for predicting the failure strength and failure mode of mechanically fastened fiber reinforced composite laminates. The method in cludes two steps. First, the stress distribution in the laminate is calculated by the use of a finite element method. Second, the failure load and the failure mode are predicted by means of a proposed failure hypothesis together with Yamadas failure criterion. A computer code was developed which can be used to calculate the maximum load and the mode of failure of joints involving laminates with different ply orientations, different material properties, and dif ferent geometries. Results generated by the present method were compared to data and to existing analytical and numerical solutions. The results of the pres ent method were found to agree well with those reported previously. Parametric studies were also performed to evaluate the effects of joint geometry and ply orientation on the failure strength and on the failure mode.

Failure of Composite Laminates Containing Pin Loaded Holes—Method of Solution

A method is presented for predicting the failure strength and the failure mode of fiber reinforced composite laminates containing one or two pin loaded holes. The method involves two steps. First, the stress distribution in the laminate is calculated by the use of a finite element method. Second, the failure load and failure mode are predicted by means of a proposed failure hypothesis together with the Yamada-Sun failure criterion. A computer code was developed which can be used to calculate the maximum load and the mode of failure of laminates with different ply orientations, different material properties, and different geometries. Tests were also conducted measuring the failure strengths and failure modes of Fiberite T300/1034-C laminates containing a pin-loaded hole or two pin-loaded holes in parallel or in series. Com parisons were made between the data and the results of the model. Good agreement was found between the analytical and the experimental results.

Failure Strength of Nonlinearly Elastic Composite Laminates Containing a Pin Loaded Hole

A method is presented for calculating the failure strengths and failure modes of composite laminates containing a pin loaded hole for materials exhibiting nonlinearly elastic behavior. The analysis follows that proposed by Chang, Scott, and Springer for linearly elastic composites with two notable exceptions: a) the shear stress-shear strain relation in each ply is taken to be nonlinear with the form proposed by Hahn and Tsai, and b) the Yamada-Sun failure criterion is modified to include nonlinear effects. Numerical results, generated using a nonlinear finite element scheme, were compared to data. These comparisons show that for laminates exhibiting nonlinear behavior the present analysis provides the failure strengths and failure modes more accurately than the previous method employing a linear stress-strain analysis.

Dispersive elastodynamics of 1D banded materials and structures : analysis

Abstract The elastodynamics of 1D periodic materials and finite structures comprising these materials are studied with particular emphasis on correlating their frequency-dependent characteristics and on elucidating their pass-band and stop-band behaviors. Dispersion relations are derived for periodic materials and are employed in a novel manner for computing both pass-band and stop-band complex mode shapes. Through simulations of harmonically induced wave motion within a finite number of unit cells, conformity of the frequency band structure between infinite and finite periodic systems is shown. In particular, only one or two unit cells of a periodic material could be sufficient for “frequency bandedness” to carry over from the infinite periodic case, and only three to four unit cells are necessary for the decay in normalized transmission within a stop band to practically saturate with an increase in the number of cells. Dominant speeds in the scattered wave field within the same finite set of unit cells are observed to match those of phase and group velocities of the infinite periodic material within the most active pass band. Dynamic response due to impulse excitation also is shown to capture the infinite periodic material dynamical characteristics. Finally, steady-state vibration analyses are conducted on a finite fully periodic structure revealing a conformity in the natural frequency spread to the frequency band layout of the infinite periodic material. The steady-state forced response is observed to exhibit mode localization patterns that resemble those of the infinite periodic medium, and it is shown that the maximum localized response under stop-band conditions could be significantly less than in an equivalent homogenous structure and the converse is true for pass-band conditions.

Non-planar, non-linear oscillations of a beam--I. Forced motions

Abstract Large amplitude whirling motions of a simply supported beam constrained to have a fixed length are investigated. Equations of motion taking into account bending in two planes and longitudinal deformations are developed. Using the method of harmonic balance, response curves for certain planar and non-planar steady state, forced motions are obtained. Another approximate scheme is used to study the stability of these motions. Stable regions corresponding to non-planar motions are found, thus confirming the existence of whirling motions. Numerical results are presented and discussed for several specific cases.

Design of Composite Laminates Containing Pin Loaded Holes

Methods are presented for sizing composite laminates containing one, two, or several pin loaded holes, the holes being arranged either in a single row or in two parallel rows. It is shown how the design parameters (number of holes, hole diameter, hole positions) can be found, which result in the maximum failure load and in the max imum failure load per unit weight.

The effect of laminate configuration on characteristic lengths and rail shear strength

Tests were performed measuring the characteristic lengths in tension and in com pression and the rail shear strength of Fiberite T300/1034-C graphite epoxy com posites. The results show the effects of geometry on the characteristic lengths. The results also indicate the variability of rail shear strength with the volume fraction of zero degree plies in the laminate.

Particulate allogeneic bone grafts into maxillary alveolar clefts in humans: A preliminary report

The purpose of this study was to determine the ability of particulate allogeneic bone graft to adequately bridge unilateral maxillary alveolar clefts in humans. Twenty patients with unilateral alveolar clefts and oronasal fistula underwent alveolar cleft grafting with a clinically appropriate amount of particulate allogeneic bone. The grafted cleft area was followed radiographically for three to six months postsurgery. Although it was difficult to quantitate, it was both clinically and radiographically apparent at three months that bone bridging and filling of the cleft had occurred in 100% of the cases. From this study, it appears that allogeneic bone is a viable alternative for repairing alveolar clefts and that its use has a significant benefit to the patient by eliminating the morbidity of a second operative site.

Extension of eigenfunction-expansion solutions of a fokker-planck equation--I. First order system

Ah&met-The work is concerned with eigenfunction-expItnsion solutions to the forward FokkerPlanck equation associated with a specific, non-linear, first-order system subject to white noise excitation. Using a digital computer, a substantial number of new terms in the expansions have been generated. With this new information, inverted Domb-Sykes plots revealed a pattern in the coefficients for certain ranges of values of the parameters. Through this pattern, Dingle’s theory of terminants was used to recast the series into a more favorable computational form.

An unusual complication after excision of a recurrent mucocele of the anterior lingual gland

A case report of a recurrent mucous extravasation phenomenon in the anterior lingual gland is presented. Multiple surgical procedures were necessary to eradicate the lesion. Alginate impression material was used during one of the surgical procedures to aid in defining the margins of the lesion. A foreign-body reaction arose in the tongue as a result of residual alginate within the tissues, necessitating further surgery. The use of this technique cannot be recommended in areas where extension into surrounding tissue planes is possible.