Super Mic-Mac – a new preliminary design tool for composites

Super Mic-Mac (SMM) combines the traditional laminated plate theory with Boeing's Strain Invariant Failure Theory (SIFT) and Accelerated Testing Methodology (ATM) of Prof. Yasushi Miyano. With this wide ranging platform, we can determine not only the static strength but creep and fatigue strengths as well. Included in the features of SMM are the hygrothermal stress from curing and moisture absorption. The effect of moisture on the strength is covered in a master curve so hot-wet condition can be quantitatively determined.

SMM has many input/out options. Among the inputs, are multiple load sets as well as spectral loading condition. So multiple load that a point in a structure can encounter can be determined using a laminate ranking (LamRank) procedure from which the critical load for each laminate is calculated. The same multiple load set can be applied to different positions in a structure that can be covered by the best laminate. All the loads within a set can have different temperature and time-varying magnitude simulating creep and fatigue environment.

Finally the output options include traditional carpet plots, a profile showing the region of best laminate in a phase diagram plot based on either the highest strength ratio or lowest laminate thickness. The critical load for each laminate is indicated in a laminate ranking option. So the lightest laminate may not be the best option. The ranking routine let engineer look over a series of potential laminates and pick the most suitable one for a variety of practical considerations.

All the descriptions above can be applied to laminates with or without a circular hole. The stress concentration calculation is useful as a basis for damage tolerance assessment; i.e., the presence of holes and their effect on laminate performance. Design for safe life and fail safe can be rationally established instead of a series of knowdown factors.

In short, with SMM an engineer can quickly find the best laminate(s) for designing composite components and structures not possible without SMM. We have run many test cases and found that many composites can perform better than aluminum on a weight basis by 50 percent. That is twice the traditional claim of 25 percent advantage in favor of composites. Thus with a simple tool like SMM composites can be designed with far more effectiveness than ever before.