推荐回答（4个）
首先解释一下抗压强度的概念，抗压强度，代号σbc，指材料在外部压力作用时的极限强度。金属材料分为塑性材料（如低碳钢）和脆性材料（如铸铁）。塑性材料受压发生变形时只会越压越扁，没有抗压强度，只有许用挤压应力，但脆性材料受压时是会压坏或压裂的，它有抗压强度，且它的抗压强度比抗拉强度高。
Q235B钢材抗压许用应力，只能通过许用挤压应力计算：
[β]=（1.5-2.5）*[σ]----适用于塑性材料
[β]=（0.9-1.5）*[σ]---- 适用于脆性材料
[σ]为材料许用应力。
Q235机械性能：
弹性模量（E/Gpa）：200~210
泊松比（ν）：0.25~0.33
抗拉强度（σb/MPa）：375-500
伸长率（δ5/%）：
≥26（a≤16mm）
≥25（a>16-40mm）
≥24（a>40-60mm）
≥23（a>60-100mm）
≥22（a>100-150mm）
≥21（a>150mm）
其中 a 为钢材厚度或直径。
在板材里，是最普通的材质，属普板系列。过去的一种叫法为：A3。
执行标准：外部标准为：GB/T709-2006《热轧钢板和钢带的尺寸、外形、重量及允许偏差》，内部标准为：GB/T3274-2007 《碳素结构钢和低合金结构钢热轧厚钢板和钢带》许用应力是有标准的，许用应力是根据不同场合、环境温度等等一个值，具体可参考材料力学表。在计算工作应力，当工作应力小于许用应力时，该况运行时安全的。 机械设计或工程结构设计中允许零件或构件承受的最大应力值。
建筑结构补强I级规定的碳纤维强度：3500MPa，这是指最大抗拉强度，实际设计上要比这个低很多，《混凝土结构加固设计规范》中有详细介绍。
碳纤维有一个名义厚度，比如说300g/平方米的单向纤维，日本东丽原丝，厚度为0.167mm，实测强度接近4700MPa，有一些则会低一些。
不一而足。
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